greenrobot/android-tips-tricks

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Cheatsheet about tips and tricks for Android Development

This is a simple set of tips and tricks regarding Android Development which I have gathered from various sources. It helps me direct other android devs in my community regarding stuff each android dev should know about. It is also there for me to keep track of anything I either learn on my own or from other sources now and then when browsing the internet.

Contributions are always welcome, hoping people will help me in growing this. To contribute, simply open up a PR with the changes.

Index

• Know Your Tools
  • Android Studio
  • Emulator
  • Vysor / scrcpy
  • DeskDock
  • ADB Shell
• Make better choices while coding
• Tips regarding UI/UX
• Tips if you use Kotlin
• Extra : Android Libraries built by me
• Translations

Know Your Tools

Android Studio

• Code faster by using keyboard shortcuts

  Description	Mac	Linux/Win
  Lookup IDE commands / Actions	Cmd Shift A	Ctrl Shift A
  Open Class	Cmd O	Ctrl O
  Open File	Cmd Shift O	Ctrl Shift N
  Open recently edited file	Cmd Shift E	Ctrl Shift E
  Open Symbol	Cmd Opt O	Alt Shift N
  Open recently used file	Cmd E	Ctrl E
  Last Edited Location	Cmd Shift Backspace	Ctrl Shift Backspace
  Find Usage in persistent window	Opt F7	Alt F7
  Find Usage in floating window	Cmd Opt F7	Ctrl Alt F7
  Format the code with proper Indentation	Cmd Opt L	Ctrl Alt L
  Surround With	Opt Cmd T	Alt Ctrl T
  Open Terminal	Opt F12	Alt F12
  Generate Setter/Getters	Cmd N	Alt Ins
  Find Class	CMD O	Ctrl N
  Refactor/Rename	Shift F6	Shift F6
  Quick Fix	Opt Enter	Alt Enter
  Goto Definition	Cmd B	Ctrl B
  Show parameters for selected method	Cmd P	Ctrl P
  Refactor This	Ctrl T	Ctrl Alt Shift T
  Stop Process	Cmd F2	Ctrl F2
  Search Everywhere	Shift Shift	Shift Shift
  Select Methods to Override	Ctrl O	Ctrl O
  Delete Line	Cmd Backspace	Ctrl Y
  Duplicate Line	Cmd D	Ctrl D
  Grow/Shrink selection from cursor	Opt Up/Down Arrow key	Shift Ctrl W
  Multicursor Selection	Ctrl G	Alt J

  Complete Keymap Guide : Linux/Win | MacOSX

• Use plugins to become more efficient

  1. KeyPromoter X

     The plugin basically will annoy the hell out of you by showing you a big screen overlay with the key combination you should have used, if you used your mouse to execute some command to a level when you basically would start using the key combination just to avoid KeyPromoter annoying you all the time. It also has some useful features, like it will prompt you to create a key binding for a command whenever an action does not have a key binding and you have used it 3 times using your cursor. [ Old Version: KeyPromoter]

  2. String Manipulation

     Provides actions for text manipulation such as Toggle case, encode/decode, sorting,

  3. Lines Sorter

     Add Sort Lines action in Edit menu to sort selected lines or whole file if the selection is empty.

  4. Findbugs

     Provides static byte code analysis to look for bugs in Java code from within Android Studio

  5. Sonar Lint

     The plugin that provides on-the-fly feedback to developers on new bugs and quality issues injected into Java, JavaScript and PHP code.

  6. Checkstyles

     The plugin provides both real-time and on-demand scanning of Java files from within Android Studio.

  7. ADB Idea

     The plugin that adds ADB commands to Android Studio and IntelliJ such as ADB Uninstall App, ADB Kill App, ADB Restart App, etc

  8. Exynap

     The plugin which helps you find and implement the code you require in an instant.

  9. Dagger IntelliJ Plugin

     The Dagger IntelliJ plugin creates visual connections between a @Inject object and the @Provides method that creates it.

  10. JVM Debugger Memory View

      This plugin extends the built-in JVM debugger with capabilities to explore objects in the JVM heap during a debug session.

  11. Android Parcelable code generator

      Plugin which generates Android Parcelable boilerplate code for you.

• Use Live Templates in Android Studio
  • newInstance - Generates the static newInstance function inside a Fragment
  • Toast - Generates Toast.makeText(context, "", Toast.LENGTH_SHORT).show();
  • fbc - findViewById with cast
  • const - Define a android style int constant
  • logd - Generates Log.d(TAG, "");
  • logm - Log current method name and its arguments.
  • logr - Log result of the current method
  • logt - static logtaf with current classname
  • psf - public static final
  • sout - Prints a string to System.out
  • soutm - Prints current class and method names to System.out
  • soutp - Prints method parameter names and values to System.out
  • visible - Set view visibility to VISIBLE
  • gone - Set view visibility to GONE
  • noInstance - private empty constructor to prohibit instance creation

Comprehensive list of all Live Templates in Android Studio

• Postfix code completion in Android Studio

  Android Studio/IntelliJ havea special kind of code completion which allows you to write code specific to a field

  • <expr>.null will auto complete to if(<expr> == null)
  • <expr>.notnull will auto complete to if(<expr> != null)
  • <expr>.var will auto complete to T name = <expr>
  • <expr>.field will auto complete to create a global field variable field = <expr>
  • <ArrayExpr>.for will auto complete to for(T item : <Arrayexpr>)
  • <ArrayExpr>.fori will auto complete to for(int i = 0; i < <Arrayexpr>.length; i++)
  • <ArrayExpr>.forr will auto complete to for(int i = <Arrayexpr>.length - 1; i > 0 ; i--)

  Complete list of available postfix code completion can be found at Settings → Editor → Postfix Templates

• Use the Darcula Theme in Android Studio

  Ok, I know its more like a preference, but trust me using that keeps your eyes less strained as they would be if you used the Default Light theme.

• Don't use a small font

  Preferably use a font in Android Studio that's easy to read and is at a font size which does not forces you to strain your eyes. My primary font is FiraCode and secondary font is Menlo font

• Use a code style

  You should use a standard codestyle, so possible contenders can be

  • AOSP Codestyle
  • Square IntelliJ Codestyle
  • Grandcentrix Codestyle

• Use the Embedded Terminal inside Android Studio

• Use the Memory/Network/CPU Monitor inside Android Studio to profile your code/app

• Configure Android Studio

Back to Index

Emulator

Apart from using physical devices, one should use emulators as they are as of now easy to manage and equivalently powerful.

• Genymotion
• Intel Emulator bundled in SDK Manger

Back to Index

Vysor

This one needs special mention due to how useful it is. It basically is a window to your device i.e it streams and allows you to interact with your physical device on your laptop. Very useful when you are demoing your app during a presentation. You can interact with your physical device and it will be shown right in your laptop screen. It has a paid/free version, paid version is totally worth buying.

scrcpy

It is basically used to display and control your Android device and is the open source equivalent of Vysor. The good folks at Genymotion built this tool and then open sourced it (Open Source FTW).

Back to Index

DeskDock

Yes, vysor was great, but if you want to share your keyboard and mouse directly to your Android device, then this app is for you. It enables you to control your Android device as if it was part of your desktop computer. The FREE version includes the use of computer mouse, while the PRO version includes features such as use of keyboard. This is useful where you can test your app without your hands ever leaving your keyboard.

Back to Index

ADB SHELL

Few handy commands you can use to interact with emulator/device, through terminal.

• Learn about various techniques involved when using ADB

Back to Index

Make better choices while coding

• Setup handy adb aliases for your terminal [Ref Link]

  Append the below Aliases to your ~/.bashrc or ~/.zshrc file, save and restart the terminal. Once saved, use them as show in Usage column

  # Take a screenshot
  # Usage: screenshot
  alias screenshot="adb exec-out screencap -p > screen-$(date -j "+%s").png"
  
  # Fire an intent
  # Usage: startintent https://twitter.com/nisrulz
  alias startintent="adb devices | tail -n +2 | cut -sf 1 | xargs -I X adb -s X shell am start $1"
  
  # Install Apk
  # Usage: apkinstall ~/path/to/apk/App.apk
  alias apkinstall="adb devices | tail -n +2 | cut -sf 1 | xargs -I X adb -s X install -r $1"
  
  # Uninstall an app
  # Usage: rmapp com.example.demoapp
  alias rmapp="adb devices | tail -n +2 | cut -sf 1 | xargs -I X adb -s X uninstall $1"
  
  # Clear all data of an app
  # Usage: clearapp com.example.demoapp
  alias clearapp="adb devices | tail -n +2 | cut -sf 1 | xargs -I X adb -s X shell pm clear $1"
  
  # Launch your debug apk on your connected device
  # Execute at the root of your android project
  # Usage: launchDebugApk
  alias launchDebugApk="adb shell monkey -p `aapt dump badging ./app/build/outputs/apk/debug/app-debug.apk | grep -e 'package: name' | cut -d \' -f 2` 1"
  

• Use OkHttp over HttpUrlConnect

  HttpUrlConnect suffers from quite some bugs. Okhttp solves them in a more elegant manner. [Reference Link]

• Reference local aar files as below [Stackoverflow Ref]

    dependencies {
       implementation(name:'nameOfYourAARFileWithoutExtension', ext:'aar')
    }
    repositories {
       flatDir {
          dirs 'libs'
       }
    }
  

• Use Pidcat for a better log reading experience

• Use some Version Control System(VCS) like Git

• Use ClassyShark

  It is a standalone tool for Android Devs used to browse any Android executable and show important info such as class interfaces and members, dex counts and dependencies

• Use Stetho

  Debug your android apps using Chrome Dev Tools. Includes tools like Network Monitor, Shared Preference explorer etc.

• Use Battery Historian

  A tool to analyze battery consumers using Android "bugreport" files.

• Always use a constant version value like "1.2.0"

  Avoid using + when specifying the version of dependencies.

  • Keeps one secured from unexpected API changes in the dependency.
  • Avoids doing an extra network call for the checking latest version of each dependency on every build.

• Use Handler instead of a TimerTask

• Do not use your own personal email for Google Play Developer Account

• Use Vectors instead of PNG

  If you do have to use png, compress them. Take a look at TinyPNG.

• Use proguard

  android {
    ...
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
  }
  

  [Read more from the manual here]

• Use shrinkResources

  android {
    ...
    buildTypes {
        release {
            shrinkResources true
            minifyEnabled true
            ...
        }
    }
  }
  

• Follow the below rule to have faster gradle builds

  Gradle memory >= Dex memory + 1Gb
  

• Split your apk using gradle when using Native code, do not bundle all of em together and ship!.. coz that will make you evil

  defaultConfig {
      ...
  
      ndk {
        abiFilters "armeabi", "armeabi-v7a", "mips", "x86"
      }
    }
  
  //Split into platform dependent APK
  splits {
    abi {
      enable true
      reset()
      include 'armeabi', 'armeabi-v7a', 'mips', 'x86' //select ABIs to build APKs for
      universalApk false //generate an additional APK that contains all the ABIs
    }
  }
  
  // map for the version code
  project.ext.versionCodes = ['armeabi': 1, 'armeabi-v7a': 2, 'mips': 5, 'x86': 8]
  
  // Rename with proper versioning
  android.applicationVariants.all { variant ->
    // assign different version code for each output
    variant.outputs.each { output ->
      output.versionCodeOverride =
          project.ext.versionCodes.get(output.getFilter(com.android.build.OutputFile.ABI), 0) *
              1000000 +
              android.defaultConfig.versionCode
    }
  }
  

• Learn about some architecture such as MVP or Clean

• Try to understand and follow TDD (Test Driven Development)

• To force re-download of dependencies

  ./gradlew --refresh-dependencies
  

• To exclude a certain task from being run by gradle

  Suppose you want to exclude the task javaDoc then use -x option followed by the task name, i.e javaDoc in this case.

  ./gradlew clean build -x javaDoc
  

• To have the each subproject script name match that of the project name

  Then add this line in settings.gradle

  rootProject.children.each{
    it.buildFileName = it.name + '.gradle'
  }
  

  Checkout more gradle tips here

• Follow the DRY principle DRY = Do not Repeat Yourself

• Package by Feature, not layers

• Learn about Dependency Resolution

  With the speed android dependencies update, sooner or later you are going to encounter some sort of dependency conflict. The solution is making use of Dependency Resolution. Official Reference

• Use different package name for non-release builds

    android {
        buildTypes {
            debug {
                applicationIdSuffix '.debug'
                versionNameSuffix '-DEBUG'
            }
  
            release {
                // ...
            }
        }
    }
  

• Find and STOP leaking memory in your android app

• If you’re creating a gradient in xml with a part being completely transparent, be really careful when using @android:color/transparent

• Follow a standard naming convention for your resources

• Make use of custom gradle tasks in your build.gradle files

  Android uses Gradle as its build system, which actually allows one to make a lot of things easy by creating tasks to automate things. This reddit post enlists a lot of such useful gradle scripts

• Use a proper .gitignore in your Android Projects, Check it here

• Use LeakCanary to detect memory leaks in your app - Its a memory leak detection library for Android and Java.

• Speed up your gradle builds in Android Studio 2.3+

  • Switch to gradle 3.4.1

    Run this inside your project folder to update your gradle wrapper

    ./gradlew wrapper --gradle-version 3.4.1 --distribution-type all
    

  • Set the below property in your global gradle.properties file

    android.enableBuildCache=true
    

• Stop a running gradle build process

  ./gradlew -stop
  

• Enable gradle to automatically download missing platforms in android sdk

  Set the below property in your global gradle.properties file

  android.builder.sdkDownload=true
  

  This is an experimental option and it only downloads build tools and platforms, but doesn't actually update Google or Support repository [Bug Ref]

• Donot include both jcenter() & mavenCentral() in your build.gradle file

  JCenter is a superset of MavenCentral. [Ref tweet]

• Clear your gradle cache if you think that bundled support and google play services lib in android sdk are inconsistent

  • Goto ~/.gradle/caches/ and delete everything inside the cache folder.
  • Open SDK Manager and resync all support libs and google play services
  • Next re-sync your project
  • Everything should become consistent and functional.

• Setup Android Studio to fail build if code contains //STOPSHIP [Ref Link]

  To enable the //STOPSHIP lint check, in your build.gradle

  android {
  ...
      lintOptions {
          abortOnError true
          fatal 'StopShip'
      }
  }
  

  If you have a //STOPSHIP comment in your code, this will cause an error to be thrown when a release apk is generated.

  You can turn on //STOPSHIP highlighting in Android Studio (isn't enabled by default) in

  Preferences > Editor > Code Style > Inspections.

  Search for STOPSHIP to find the correct setting.

• Use alfi to find the gradle dependency statement for a library

  Its basically the command line version of Gradle, Please which is a web hosted.

  • Run

    alfi name_of_library
    

  • Copy the desired library

  • Paste in your build.gradle

• Use dryrun to test a library directly

  • Just Run

    dryrun REMOTE_GIT_URL
    

• Output unit tests directly to the console [Ref Link]

  A small neat trick to see Android unit tests logging results as they happen in the terminal.

  android {
      ...
      testOptions.unitTests.all {
        testLogging {
          events 'passed', 'skipped', 'failed', 'standardOut', 'standardError'
          outputs.upToDateWhen { false }
          showStandardStreams = true
        }
      }
    }
  

• Make your builds faster by building offline [Ref Link]

  The --offline flag tells gradle to always use dependency modules from the cache, regardless if they are due to be checked again. When running offline, gradle will never attempt to access the network to perform dependency resolution. If required modules are not present in the dependency cache, build execution will fail.

  • Assembling develop debug at full speed:

    ./gradlew assembleDevelopDebug --offline
    

  • Running your unit tests at full speed:

    ./gradlew test --offline
    

• Use an abtracted Logger class

• If you want to automatically initialize your library, use a Content Provider [Read how Firebase does it - Ref Link]

• Reduce installed app size with "android:extractNativeLibs:false" in <application> [Ref Link]

  This will essentially prevent the system from creating a second copy of the .so files and fix the System.loadLibrary call so it’s able to find and open native libs straight from the APK, no code changes on your part required.

• Selectivily execute a specific method in Android Studio [Ref Link]

  

• Did you get one of these Google Play Developer Policy Violation Emails? Worry not, generate a Privacy Policy for your android app [Ref ink]

  • Take a look at App Privacy Policy Generator, a web app to generate a generic privacy policy for your app.

• Define a variable at build time In your build.gradle

  android{
    defaultConfig {
      ...
      buildConfigField "String", "SERVER_ENDPOINT", '"http://www.myendpoint.com"'
      buildConfigField "int", "FOO", "52"
      buildConfigField "boolean", "LOG", "false"
      ...
    }
  }
  

  and then use it in code as BuildConfig.SERVER_ENDPOINT, BuildConfig.FOO,BuildConfig.LOG

• Calculate the version code and version name in your build.gradle manually, based of version values In your app's build.gradle

  versionMajor = 0
  versionMinor = 0
  versionPatch = 0
  versionBuild = 1
  
  verCode = versionMajor _ 1000000 + versionMinor _ 10000 + versionPatch \* 100 + versionBuild
  verName = "${versionMajor}.${versionMinor}.${versionPatch}"
  
  // Use
  android{
    defaultConfig {
          ...
          versionCode verCode
          versionName verName
          ...
    }
  }
  

• Calculate the version code and version name in your build.gradle automatically, based on git information

  Note: These functions go specifically inside the app's build.gradle and cannot be used with ext.

  In your app's build.gradle

  // Version code is calculated as the number of commits from last commit on master
  def getVersionCode = { ->
    try {
      def code = new ByteArrayOutputStream()
      exec {
        commandLine 'git', 'rev-list', 'HEAD', '--count'
        standardOutput = code
      }
      return Integer.parseInt(code.toString().trim())
    } catch (exception) {
      return "1";
    }
  }
  
  // Version name is Last Tag Name + No. of commits form last Tag +  short git sha
  def getVersionName = { ->
    try {
      def stdout = new ByteArrayOutputStream()
      exec {
        commandLine 'git', 'describe', '--tags', '--dirty'
        standardOutput = stdout
      }
      return stdout.toString().trim()
    } catch (exception) {
      return "0.0.0.1";
    }
  }
  
  // Use
  android{
    defaultConfig {
      ...
      versionCode getVersionCode()
      versionName getVersionName()
      ...
    }
  }
  

• Get the date of build as a variable In your app's build.gradle

  // Get the date of build
  def getDateOfBuild = { -> // ISO 8601 time format
    return new Date().format("yyyy-MM-dd'T'HH:mm'Z'").toString().trim()
  }
  
  // then use it as a variable in BuildConfig
  android{
    defaultConfig {
      ...
      buildConfigField "String", "DATE_OF_BUILD", "\"${getDateOfBuild()}\""
    }
  }
  

• Get the Git SHA as a variable In your app's build.gradle

  // Get the last Git Short Hash
  def getGitHash = { ->
    def stdout = new ByteArrayOutputStream()
    exec {
      commandLine 'git', 'rev-parse', '--short', 'HEAD'
      standardOutput = stdout
    }
    return stdout.toString().trim()
  }
  
  // then use it as a variable in BuildConfig
  android{
    defaultConfig {
      ...
      buildConfigField "String", "GIT_SHA", "\"${getGitHash()}\""
    }
  }
  

  Have a look at the Paperwork Project, which generates build info for your Android project without breaking incremental compilation

• Activity LifeCycle [Ref Link]

  

• Tip about onSaveInstanceState()
onSaveInstanceState() is called only when the OS decides to kill the Activity instance. It will not be called when Activity is explicitly killed i.e User pressed back button or finish() is called from code.

• If you are into building Android Libraries, then read here for more tips

• Read about whats in an APK here

• Input some text in an editfield in a running emulator from your keyboard

  adb shell input text "keyboard text"
  

• Use areNotificationsEnabled() from NotificationManagerCompat to detect whether your users blocked your Notifications [Ref Link]

• Don't hard-code encryption keys, a simple grep for "Ljavax/crypto" reveals them in bytecode [Ref Link]

• Intents have a limited payload size (1Mb), don't serialize and attach entire file to it [Ref Link]

• Always copy a file before sending it as intent URI. Receiving app could edit it & send a canceled result [Ref Link]

• Use http:// as scheme for app deeplinks, they are more universal & when app not installed drive users to a domain you own [Ref Link]

• Use below to display your app launch time [Ref Link]

  adb shell am start -W <packagename>/. <activityname>
  

• Use Java 8 features by adding sourceCompatibility & targetCompatibility to your build.gradle file

  android {
    ...
    compileOptions {
      sourceCompatibility JavaVersion.VERSION_1_8
      targetCompatibility JavaVersion.VERSION_1_8
    }
  }
  

• Setup a gradle task to archive apks and proguard files on build, for backup purposes

  task deployApks(type:Copy) {
      description = "Copies APKs and Proguard mappings to the deploy directory"
      def appName = "<app_name>";
      def versionDir = android.defaultConfig.versionName+"_"+android.defaultConfig.versionCode;
  
      println("Copies APK and Proguard to " + versionDir)
  
      from 'build/outputs/mapping/release/'
      include '**/mapping.txt'
      into '../.admin/deploy/' + versionDir
      rename ('mapping.txt', "${versionDir}-mapping.txt")
  
      from ('.') {
          exclude '**/build', '**/src'
      }
  
      include '*.apk'
      into '../.admin/deploy/' + versionDir
      rename ('app-release.apk', "${appName}-${versionDir}.apk")
  }
  

• Use activity-alias or your launcher icons will disappear when renaming/moving your MainActivity

• To enable aapt2 set below in gradle properties

  android.enableaapt2=true
  

• To testout doze mode, trigger it using adb [Ref Link

  adb shell dumpsys deviceidle force-idle
  

• Thumb rule regarding setting compileSdkVersion, minSdkVersion and targetSdkVersion

  minSdkVersion (lowest possible) <= targetSdkVersion == compileSdkVersion (latest SDK)

• Google released an option to include OSS license activity in your app, use that to attribute credits to the OSS libs in your app [Ref Link]

  Checkout a working example here

• Make Android Studio render <merge> layouts correctly by specifying the layout type with the tools:parentTag attribute [Ref Link]

  

• Checkout the Background Execution Limits on Android Oreo and update your app to work with the restrictions [Ref Link]

• To take good screenshots with clean status bar use the Demo Mode in Android [Ref Link]

  • Steps

    1. Enable Demo Mode

       adb shell settings put global sysui_demo_allowed 1
       

    2. Enable/disable icons by running the right command

       // display time 12:00
       adb shell am broadcast -a com.android.systemui.demo -e command clock -e hhmm 1200
       
       // Display full mobile data without type
       adb shell am broadcast -a com.android.systemui.demo -e command network -e mobile show -e level 4 -e datatype false
       
       // Hide notifications
       adb shell am broadcast -a com.android.systemui.demo -e command notifications -e visible false
       
       // Show full battery but not in charging state
       adb shell am broadcast -a com.android.systemui.demo -e command battery -e plugged false -e level 100
       

    3. Run app and take screenshots

    4. Exit demo mode once you are done

       adb shell am broadcast -a com.android.systemui.demo -e command exit
       

• To record video of your android device [Ref Link]

  adb shell && screenrecord /sdcard/download/fileName.mp4
  

  Hit Ctrl+C to exit/stop recording

  Recorded video file is saved at the location mentioned in the command on the device itself.

• Use Dao inheritance to reduce the amount of boilerplate code [Ref Link]

• Instead of using getActivity() in fragment, keep a habit of getting context from onAttach(). [Ref Link]

• Avoid setting a background in every view/fragment as it likely causes overdraw. [Ref Link]

• View.getWidth() = 0? That's because your view hasn't been layout yet, use globallayoutListener to know layout done. [Ref Link]

• Android never kills activities, it only kills processes. When low memory the lowest priority ranked will be killed.[Ref Link]

• Use .([filename].java:[line]) in your log statements to make them clickable in Android Studio and Intellij IDEA.

• Use -whyareyoukeeping class com.jeroenmols.MyClass to figure out why certain a class wasn't removed.[Ref Link]

• Use certificate pinning to resist impersonation by attackers using mis-issued or otherwise fraudulent certificates, when making requests from your app. [Ref Link]

• Do download the latest emulator using CLI

  cd <android_sdk>/tools/bin
  ./sdkmanager --channel=3 emulator
  

  To check the version of emulator, use ./sdkmanager --channel=3 emulator

• Checkout some tricks when using Android Strings in XML

• Cleanup your Gradle caches by deleting files not accessed within the last month [Ref Link]

  find ~/.gradle -type f -atime +30 -delete
  find ~/.gradle -type d -mindepth 1 -empty -delete
  

  To check the size of your gradle cache, run: du -sh ~/.gradle

• Checkout some cool tricks when using tools: attribute in your android layouts, such as sample data and recyclerview item layout previews

• Remove all debug log statements from the release build using the below proguard rules. (app's build.gradle should have minifyEnabled true set for this to work)

  # Remove all debug logs
  -assumenosideeffects class android.util.Log {
      public static *** d(...);
  }
  

  The above snippet is usually appended to contents of app/proguard-rules.pro file

• Should I use Enums in Android?

  tl;dr

  • If you need code to be very performant integer constants may be the way to go

    public class Operator {
        public static final int ADD = 1;
        public static final int SUBTRACT = 2;
        public static final int MULTIPLY = 3;
        public static final int DIVIDE = 4;
    }
    

  • Use Enums because

    • Are type-safe, so you can only use valid enum types
    • Provide better code readability
    • Can implement interfaces
    • Support polymorphic behavior
    • In some really trivial cases, Proguard can optimize Enums into integer constants for you [Ref Link]
    • Performance difference rarely makes a difference.

    public enum Operators {
        Add, Subtract, Multiply, Divide
    }
    

• The string resource android.R.string.yes doesnot yield string "Yes" instead it yields "Ok". Similarly the string resource android.R.string.no doesnot yield string "No" instead it yields "Cancel" [Ref Link]

  

• Don’t want generated files in your AS search results? Go to Preferences -> File Types -> Ignore files and folders and add the pattern to ignore - e.g. *.dex;*.class; [Ref Link]

• If you uncheck “Suspend” and check “Evaluate and Log” in breakpoint menu, the breakpoint will print evaluated statement into the uncluttered “Console” window. No need for recompile due to added Log.d statements anymore [Ref Link]

  

• To measure how long a method took to execute, you can use TimingLogger class. [Ref Link]

  • Typical Usage

    TimingLogger timings = new TimingLogger(TAG, "methodA");
    // ... do some work A ...
    timings.addSplit("work A");
    // ... do some work B ...
    timings.addSplit("work B");
    // ... do some work C ...
    timings.addSplit("work C");
    timings.dumpToLog();
    

  • Output

    D/TAG     ( 3459): methodA: begin
    D/TAG     ( 3459): methodA:      9 ms, work A
    D/TAG     ( 3459): methodA:      1 ms, work B
    D/TAG     ( 3459): methodA:      6 ms, work C
    D/TAG     ( 3459): methodA: end, 16 ms
    

• If you're working with Android Things and you don't have an extrenal screen for your device, install scrcpy and use it to see what's going on your Android IoT device. It works a charm over wireless adb. [Ref Link]

• Android Studio has this weird behaviour that it allows to edit its default code style, which leads to a weird side-effect. If you open your pre-setup project(with set codestyle and copyright configs) in Android Studio it will delete all pre-setup codestyle and copyright profile in this project. This is every much evident if you checked in your configs into git for sharing purpose, which is lost immediately as soon as you open the project

  deleted:    .idea/codeStyles/Project.xml
  deleted:    .idea/codeStyles/codeStyleConfig.xml
  deleted:    .idea/copyright/profiles_settings.xml
  deleted:    .idea/copyright/copyright.xml
  

  To fix that please follow along as below: [All thanks to Said Tahsin Dane for the solution]

  • We first need to verify that your Default codestyle isn't modified. To check that please open Android Studio with any project except your pre-setup(with set codestyle and copyright configs) project. Then navigate to Preferences>Edior>Codestyle and check if your code scheme has Default in BLUE color (this means it is modified).

    

  • However if it is not colored BLUE, you are good and you can go ahead to open your pre-setup(with set codestyle and copyright configs) project and everything should be pre-setup for you.

  • If it is modified (colored BLUE), then click on the cog icon and select Restore Default

    

  • After you hit that option, simply accept the change

    

  • Once done, you will see your Default is no more colored BLUE or modified, which means you are good

    

  • Now simply go ahead and open your pre-setup(with set codestyle and copyright configs) project and everything should be pre-setup for you.

• If you add android:sharedUserId to an already published app, the app data will be cleared for all users that install your upgrade (because Android changes the process). So if you ever intend to use it, you must add it before publishing your app [Ref Link]

• When opening up methods for testing, use otherwise to still hide it from code complete.[Tweet Link, Ref Link]

  

• You can group your recent Android Studio projects, and add icons to them [Ref Link]

  

• Only build a single configuration to speed up debug builds. [Ref Link]

  

• Avoid the annoying jump to Design tab while editing XML. Prefer XML editor under Settings [Ref Link]

  

• Reduce installed app size with android:extractNativeLibs="false" in [Tweet Link, Ref Link]

  

• Run a single unit test from the command line using the --tests option e.g: ./gradlew testDebugUnitTest --tests "*.MainPresenterTest" . Use * to avoid typing the entire package name. [Ref Link]

• Improve Android Studio code inspections with Thread annotations [Tweet Link, Ref Link]

  

• Use adb to put a phone into doze mode for testing [Tweet Link, Ref Link]

  

• Get faster gradle builds by only using one resource configuration for your development builds [Ref Link]

  android {
    ...
    productFlavors {
      dev {
        ...
        // The following configuration limits the "dev" flavor to using
        // English stringresources and xxhdpi screen-density resources.
        resConfigs "en", "xxhdpi"
      }
      ...
    }
  }
  

• Use areNotificationsEnabled() from NotificationManagerCompat to detect whether your users blocked your Notifications [Tweet Link, Ref Link]

  

• Activity.runOnUiThread is just a convenient wrapper of Handler.post; don't pass around Activity just so you can use it. [Ref Link]

• Define your interfaces with the highest possible option that will suffice. Don't use an Activity when a Context will do. [Ref Link]

• If you're not building a replacement for the dialer, use ACTION_DIAL not ACTION_CALL to initiate a call. [Ref Link]

• Specifying buildToolsVersion in your build.gradle files is optional when using Android plugin 3.0.0 or later. By default the plugin uses the minimum version of the build tools required by the version of the plugin you're using. [Tweet Link, Ref Link]

  

• You can insert variables into AndroidManifest defined in build.gradle [Tweet Link, Ref Link]

  

• Requesting updates from a system service may drain battery, so register for updates in onResume and unregister in onPause. [Ref Link]

• Hierarchy Viewer won’t run on prod devices, if however u want to run it then follow below steps [Tweet Link, Ref Link]

  

• Variable and init block declaration order in Kotlin, actually matters :) if you want to use a variable inside init {} initialize it before it.

• When comparing intents it does not compare any extra data included in the intents [Tweet Link, Ref Link]

• To show a ringtone picker to the user, use the ACTION_RINGTONE_PICKER intent to launch the picker as a subactivity. [Ref Link]

• Want to remove focusState on an item in GridView? Try: android:listSelector="#00000000" [Ref Link]

• You can generate the proguard keep rules via the APK Analyzer inside Android Studio. [Ref Link]

  

• When viewing an Android Manifest, there is a tab at the bottom that allows you to see the merged manifest. Use this to inspect the merged manifest and find conflicts. [Ref Link]

  

• In the APK analyzer in Android Studio, classes/members listed in italic are only references, not definitions. If it's in italics, it's defined in another DEX file (or the SDK). [Ref Link]

  

• To be able to write multiline Todo comments, simply indent by 1 tab from second line onwards. [Ref Link]

  

• You can get rid of a lot of noise in the Logcat, by Right Clicking a selected text > "Fold lines like this" option!. [Ref Link]

  

• There is a quick way to surround your layout with a Linear Layout via using a Live Template. You can create one called wrapll by setting it up [Ref Link]

  

  ...and use it as below

  

  You can create more based on your usecase :smile:

Back to Index

Tips regarding UI/UX

• Motion

  • Material Design uses real-world metaphors as its foundation. Objects in the real world don't move linearly, they move in curved paths and accelerate and decelerate according to the motion's properties.
  • As such, motion should also use such properties and animate objects so that the motion feels natural rather than forced
  • For example, a car leaving the screen in a movie starts off slowly, then accelerates till it's out of the frame. Similarly, views should be interpolated using classes like AccelerateInterpolator, FastOutSlowInInterpolator, etc. [More Info]
  • When changing the visibilities of views, if you add android:animateLayoutChanges="true" to the parent, you get a nice little animation for free. [Ref Link]

• Typography

  • While custom typefaces can be used for branding, it is essential to stick to Roboto and Noto if possible, especially for body text, due to their clarity and optimistic nature.
  • Roboto covers Latin, Greek and Cyrillic extended scripts, with Noto filling in for other language scripts [More Info]
  • Weight balancing is an important aspect of typography, the fundamental concept of which is that the larger a typeface is, the less its weight should be so that it doesn't appear too thick and balances its weight with smaller typefaces of higher weights
  • Typography should align to a 4dp baseline grid, and maintain a minimum contrast ratio of 4.5:1 based on luminance values, with a recommended ratio being 7:1.
  • The ideal reading length for large blocks of text is 40 to 60 characters per line. Anything less is too narrow and anything more is too wide.

• Icons

  • Icons should be designed at 48dp, with 1dp edges, which equates to
    • 48px by 48px at mdpi
    • 72px by 72px at hdpi
    • 96px by 96px at xhdpi
    • 144px by 144px at xxhdpi
    • 192px by 192px at xxxhdpi
  • An additional icon of 512px by 512px should be designed for use on Google Play
  • Material icons, in addition to the base icon, should contain the following important elements
    • 1dp tinted edge at the top
    • 1dp shaded edge at the bottom
    • Contact shadow - a soft shadow around all edges of raised elements
    • Finish - a soft tint to provide surface lighting, fading from upper life to lower right [More Info]

• Ripples

  • When implementing Ripple Effect use ?attr/selectableItemBackground instead of ?android:attr (Ref)

  • When implementing Ripples contained within the view like Button, use (Ref)

    android:background="?attr/selectableItemBackground"
    

  • When implementing Ripples that extend beyond the view's bounds like ImageView: (Ref)

    ?attr/selectableItemBackgroundBorderless
    

• Other Points to Note
  • Views should be aligned to Material Design's 8dp baseline grid and the keylines when possible. This gives the UI a sense of structure and hierarchy. [More Info]
  • If you plan on keeping a reference to any ViewGroup (LinearLayout, FrameLayout, RelativeLayout, etc.), and you don’t want to use any methods specific to this particular type of Layout, keep it as a ViewGroup object. [More Info]
  • While picking an accent color (if the brand already has one), pick a color complementary to the primary color so that the contrast is high enough

Back to Index

Tips if you use Kotlin

• Checkout From Java to Kotlin

  Cheatsheet when you come from Java to Kotlin. Very nice resource to compare the two languages.

• Checkout Kotlin Style Guide by Google

Back to Index

Other Resources

• Adhere to the coding guidelines

• Google's Maven Repository

• Listen to podcasts

  1. Fragmented
  2. Android Developers Backstage

  There are others too, but the above two are the popular ones, you can lookup more using tag android on sites offering Podcast Services.

  P.S : I use Player.fm to listen to these podcasts. They even have an Android Client, all for FREE.

• Checkout Android Dialogs Short byte sized android interview videos with experts.

• Checkout Google's Udacity Android courses

  Free courses and (paid) Nanodegree programs aimed at beginners up to advanced Android developers taught by professionals.

• Checkout CodePath Android Cliffnotes

  It is the central crowdsourced resource for complete and up-to-date practical Android developer guides for any topic.

• Take care about copyright

• Checkout new android libraries

  Android Arsenal - Android developer portal with tools, libraries, and apps

• Checkout android example apps

  • Android Examples - Simple basic isolated apps, for budding android devs.
  • Google Samples - Various sample apps provided by Google
  • Google Android Codelabs
  • Google Android Codelabs
  • QualityMatters
  • Android-Testing
  • Espresso-Samples

• Follow on Twitter

  • #AndroidDev

• Create a List on Twitter

  • Android List

• Read the Effective Java by Joshua Bloch

  • Cheatsheet/Summary

• Subscribe to Caster.io

  Bite-sized Android development videos

• Bookmark these sites for staying upto date

  • Android Developers - Youtube Channel
  • Android Niceties - UI Showcase
  • Material Design Specs
  • Material Components
  • Everything About Material Design
  • Platform Version Distribution
  • Android Studio Release Notes
  • Android Developers Blog
  • AndroidDev-Reddit
  • Github Trending Java Projects
  • Stackoverflow-Android tag
  • Support Library History
  • Android Conferences
  • Android Dev Docs
  • Material Up - DesignShowcase
  • Dribbble - MaterialDeisgnShowcase
  • UltimateAndroidReference

• Bookmark these sites for keeping track of Android Support Libs(AOSP AndroidX)

  • File a bug/issue for Android KTX
  • Info regarding sending a PR to AOSP AndroidX Libs
  • Stuff worked on for AOSP AndroidX

• Checkout the Testing guide

• Use freely available mockable api points

  • Mockey - A tool for testing application interactions over http, with a focus on testing web services, specifically web applications that consume XML, JSON, and HTML.
  • JSON Placeholder - Fake Online REST API for Testing and Prototyping
  • API Studio - a playground for API developers
  • Mocky - Mock your HTTP responses to test your REST API
  • Mockbin - Mockbin allows you to generate custom endpoints to test, mock, and track HTTP requests & responses between libraries, sockets and APIs.

• Subscribe to newsletters to stay upto date

  • Android Weekly - Free newsletter that helps you to stay cutting-edge with your Android Development
  • AndroidDevDigest - A Handcrafted Weekly #AndroidDev Newsletter
  • Infinium #AndroidSweets - Fresh news from Droid zone
  • Kotlin Weekly - Free newsletter to stay uptodate with Kotlin Development

• ADB/Fastboot Tools made available as a separate package by google, download latest version for

  • MacOSX
  • Linux
  • Windows

• Some other awesome utility tools

  • Android SVG to VectorDrawable - One VectorDrawable to rule all screen densities
  • SQLite Viewer - View sqlite file online
  • Android 9-patch shadow generator - Tool that makes fully customizable shadows possible
  • APK method count - Tool that outputs per-package method counts
  • Material Palette - Easily generate the color pallete based on material design
  • Color Tool - Create, share and apply color palettes to your UI
  • Javadoc Themer - Give your boooring javadocs a splash of colors!
  • Method Count - Use this tool to avoid the dreaded 65K method limit of the DEX file format!
  • Gradle, please - Lookup dependency reference name to include as your gradle dependencies
  • jsonschema2pojo - Generate Plain Old Java Objects from JSON or JSON-Schema
  • Android Asset Studio - A web-based set of tools for generating graphics and other assets that would eventually be in an Android application's res/ directory.
  • Device Art Generator - Quickly wrap app screenshots in device artwork
  • Google Translator Toolkit - Translate strings.xml files to any language and download as XML
  • JSONViewer - Awesome JSON formatter
  • ShapeShifter - SVG path morphing animation editor.
  • App Privacy Policy Generator - Generate a generic privacy policy for your app for the playstore.
  • gnirehtet - Reverse tethering for Android.
  • Adaptive Icons - Try out the new Adaptive Icons in your browser
  • Android Starters - Handcrafted starter projects, optimized for simplicity and ease of use.
  • Language Switcher Tile - An android plugin that allows you to easily change your device language.
  • Flipper - Flipper is a platform for debugging mobile apps on iOS and Android. Visualize, inspect, and control your apps from a simple desktop interface.

• Awesome android libraries

  • StorIO - Beautiful API for SQLiteDatabase and ContentResolver
  • Retrofit - Type-safe HTTP client for Android and Java by Square, Inc.
  • Picasso - A powerful image downloading and caching library for Android
  • LeakCanary - A memory leak detection library for Android and Java.
  • AndroidViewAnimations - Cute view animation collection.
  • Calligraphy - Custom fonts in Android the easy way.
  • Alerter - Android Alerting Library

Back to Index

Extra : Android Libraries built by me

• EasyDeviceInfo - Enabling device information to be at android developers hand like a piece of cake!
• Sensey - Android library to make detecting gestures easy
• PackageHunter - Android library to hunt down package information
• Zentone - Easily generate audio tone in android
• RecyclerViewHelper - RecyclerViewHelper provides the most common functions around recycler view like Swipe to dismiss, Drag and Drop, Divider in the ui, events for when item selected and when not selected, on-click listener for items.
• StackedHorizontalProgressbar - Android Library to implement stacked horizontal progressbar
• QREader - A library that uses google's mobile vision api and simplifies the QR code reading process
• ScreenShott - Simple library to take a screenshot of the device screen, programmatically!
• EvTrack - Android library to make event and exception tracking easy
• OptimusHTTP - Android library that simplifies networking in android via an async http client
• ShoutOut - Android library for logging information in android
• Lantern - Android library handling flashlight for camera and camera2 api. Added support for handling display/screen light.

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Translations

If you would like to contribute by translating this doc, please do so by sending a PR which follows the below points

• Make sure the filename is README-language.md i.e README-English.md, README-Greek.md, etc.
• The original content/formatting is retained in the translated doc.
• Check for grammar and spelling mistakes before hand.

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Credits

This curated cheatsheet includes tips and tricks that I have been following in my workflow as well as those being suggested/followed by other android devs worldwide.I have tried to add direct links wherever I could remember, giving people due credit who have explained the concepts. If you think I have missed any, then either send a PR or open an issue and I will fix it asap.

If you appreciate my work, consider buying me a cup of :coffee: to keep me recharged :metal: [PayPal]

License

Copyright 2016 Nishant Srivastava

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.