Google I/O 2016: Android notes

Ashish on May 19, 2016

General

  1. Multitasking – multi-window mode and picture-in-picture mode. This includes the ability to launch window in adjacent activity, and drag and drop between activities.
  2. Notifications – Custom quick settings tile for an activity
  3. Multi-locale – users can specify locale beyond their primary locale
  4. ScopedDirectoryAccess for the shared storage
  5. New file-level encryption mode (as opposed to block-level encryption) and the corresponding Direct Boot
  6. Java 8, Jack, and ndk support in Gradle
  7. GCC deprecated in favor of Clang

TechTalk on Image size/compression

  1. PNG – Get image down to 256-bit palette (if possible) or compress them using Zopfli. Test the difference with butteraugli
  2. Convert PNG to Vector drawable using Potrace. Vector drawable are natively supported on Android 5.0 and above. Use compat to use them on the older versions. Or generate PNG for the older versions (not recommended)
  3. WebP is another option (Note: Speaker failed to mention that WebP is natively supported only on Android).
  4. Avoid JPEGs. They are usually larger in size.

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My rm -rf moment

Ashish on May 5, 2016

Yes, it did happen, and no, I am not stupid enough to execute rm -rf *. It was a bit more convoluted than that. I was trying to prepare a customized SD card image for the Android emulator. The fastest way to do that was to mount the SD card on my GNU/Linux machine and modify the files. The files on the SD card have root as the owner. Therefore, the easiest way to maintain a clean state was to make all modifications using sudo. My script included a command rm -r ${base_dir}/${old_file}. While executing the script, due to an error, both the variables were not set. It took me a few hours to recover; I never committed the broken script, so, I did not harm anyone else. But since then, my bash scripts have always included set -o nounset.

Android command-line: gradle and testing

Ashish on January 3, 2015

For android projects, some engineers use Android Studio (new), some use Eclipse with ADT (old), few like me still savor command line, this blog post is about handling (building, installing and testing) android projects from command line.

  1. To create android project 
    $ android create project --target 4 --name TestAndroidApp --path ./test_android_app --activity Main --package net.ashishb.TestAndroidApp --gradle --gradle-version 1.0.+ 
  2. After changing to directory test_android_app (cd test_android_app), fix a bug 
    # Replace "runProguard" with "minifyEnabled" in build.gradle
$ sed -i '' 's/runProguard/minifyEnabled/' build.gradle

     

  3. Some useful gradle commands 
    $ gradle tasks  # Lists all tasks.
$ gradle assembleDebug  # Assemble debug build
$ gradle installDebug  # Install debug build
$ gradle assembleRelease  # Install release build
  4. The code will be in src directory, eg. for the Main activity, code is in src/main/java/net/ashishb/TestAndroidApp/Main.java and test is in src/androidTest/java/net/ashishb/TestAndroidApp/MainTest.java
  5. For testing, modify the Main class and add square method, 
    public static int square(int x) {
      return x * x;
}

    And in MainTest

    public void testSquare() {  // Tests must start with test prefix.
   this.assertEquals(100, Main.square(10));
}
  6. Modify build.gradle to add a testing config 
    android {
    ...

    defaultConfig {
      testApplicationId "net.ashishb.TestAndroidApp.test"
      testInstrumentationRunner "android.test.InstrumentationTestRunner"
      testHandleProfiling true
      testFunctionalTest true
    }

    ...
}

     

  7. Run the test(s) 
    $ gradle installDebug installDebugTest && adb shell am instrument -w -e class net.ashishb.TestAndroidApp.MainTest#testSquare net.ashishb.TestAndroidApp.test/android.test  # Runs the testSquare test.

$ gradle installDebug installDebugTest && adb shell am instrument -w  net.ashishb.TestAndroidApp.test/android.test.InstrumentationTestRunner  # Runs all tests.
  8. Complete code can be seen at https://github.com/ashishb/android_gradle_demo

Android, Gradle and compile-time only dependencies

Ashish on August 8, 2014

Android plugin for Gradle does not support Java-style compile time only dependencies.

After spending a few hours on trying to build android app targeted for Amazon SDK (without using Amazon’s Android specific plugin but just their jar stubs for maps, ADM and Home widget), I finally found that the one way to support compile-time dependencies is following.

For application project

configurations {
    provided
}

dependencies {
    // ...
    provided fileTree(dir: "${project.rootDir}/path_to_libs_dir", include: '*.jar')
}

// Android's version of sourceSets.main.compileClasspath
android.applicationVariants.each { variant ->
    variant.javaCompile.classpath += configurations.provided
}

For the library project

configurations {
    provided
}

dependencies {
    // ...
    compile fileTree(dir: 'libs', include: '*.jar')
    provided fileTree(dir: "${project.rootDir}/patch_to_libs_dir", include: '*.jar')
}

android.libraryVariants.all { variant ->
    // Exclude the jar files from making its way into the final apk.
    // Irrespective of what the path_to_libs_dir is the final jar files end up in libs dir.
    variant.packageLibrary.exclude('libs/lib1.jar')
    variant.packageLibrary.exclude('libs/lib2.jar')
    // ...
}

References

  1. https://stackoverflow.com/questions/16613722/gradle-configurations-not-working-as-expected-in-new-android-build-system
  2. http://stackoverflow.com/a/24157721