Android Studio: resolving duplicate AndroidX and support classes errors

While migrating an Android project from the support libraries to use the AndroidX libraries, I encountered the following errors regarding "duplicate class android.support.v4.app xxxx found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:26.1.0)"; even though all the Java/Kotlin/XML source code files have been replaced with the AndroidX versions and the old support libraries have been removed from the app's build.gradle file.

The screenshot below illustrates the error.


The solution I found was to set project wide gradle properties.

1. In Android Studio, open up the project's gradle.properties file.
   
2. Insert the following two lines:
   
   android.enableJetifier=true
   android.useAndroidX=true
   
   
3. Save the file, select Build | Clean Project. Then select recompile again.
   
   The duplicate classes error messages no longer appear.|

Set Android system bar to be transparent when Navigation drawer is opened

While developing Android apps, a lot of times I broke the code and made the Android system bar opaque when the Navigation drawer is opened, as shown in the screenshot below.

Then I had to waste precious time hunting down the cause. So I am putting down the requirements to enable the Android system bar to be transparent over the Navigation drawer.

1. In Android Studio, open up the XML layout file e.g. activity_main.xml for the activity with the Navigation Drawer. In the AndroidX DrawerLayout widget, make sure the property fitsSystemWindows is set to true.
   
   
   
   
2. Next, create a "no action bar" style e.g. AppThem.NoActionBar in styles.xml to be used by the activity with the Navigation Drawer. In the example below, the style inherits the theme Theme.AppCompat.DayNight.DarkActionBar style for day and night mode styling.
   
   
   
3. Set the properties windowActionBar to false and windowNoTitle to true.
   
4. Then create the same "no action bar" style for Android API 21 and above e.g. /path/to/res/values-v21/styles.xml. Set the properties windowDrawsSystemBarBackgrounds to true and statusBarColor to "@android:color/transparent" as shown below.
   
   
   
5. Compile and run the application. The system bar should be transparent over the Navigation Drawer now.
   
   

Resolving Android Studio "Cannot fit requested classes in a single dex file" error

After I added an additional library to an Android app, this error "null, Cannot fit requested classes in a single dex file (# methods: 66445 > 65536)" occurred while trying to build the application in Android Studio, as shown in the screenshot below.
 
The solution to this is to enable multi dex support in the Android app. The following steps show how to do this:

1. In Android Studio, add in a new dependency to the androidx.multidex:multidex library to the app's build.gradle file.
   
   dependencies {
   ...etc...
   implementation 'androidx.multidex:multidex:2.0.1
   ...etc...
   }
   
2. Then in the same app build.gradle file, toggle true the multiDexEnabled property.
   
   android {
     defaultConfig {
       ...etc...
       multiDexEnabled true
       ...etc...
     }
   }

Now, compiling the Android application should no longer result in the dex error.

Android Studio: Resolving PreferenceFragment is deprecated warning

I encountered the following warning message in Android Studio while converting some Android Java code to Kotlin:
'PreferenceFragment' is deprecated. Deprecated in Java

Some digging through the Android documentation resulted in a solution; the android.preference.PreferenceFragment class is being deprecated and can be replaced with the new Jetpack androidx preference classes. So I needed to do the following:

1. Add a new dependency to the new Androidx preference library in the app's build.gradle file
   
   implementation "androidx.preference:preference:1.0.0"
   
2. In the Kotlin source code, remove the following namespace import statement:
   
   import android.preference.PreferenceFragment
   
3. Insert the following namespace import statement:
   
   import androidx.preference.PreferenceFragmentCompat
   
4. Then override the abstract onCreatePreferences method.
   

override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
//        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

Migrating Android support library Renderscript code to AndroidX

Android is deprecating the Support compatibility libraries  and replacing them with the new AndroidX libraries. To aid in the migration of Android projects using the deprecated support libraries, Android Studio has a Refactor to AndroidX tool. I used that to migrate an old Android project and while it works for the most part, it did not manage to migrate the files using the support renderscript classes; I presume that is because the AndroidX namespace does not have the equivalent renderscript classes.

To complete the migration to AndroidX, I had to do the following by hand:

1. In all the code files using the android.support.v8.renderscript.* classes, replace them to android.renderscript.* as shown below.
   
   
2. In the app's build.gradle file, upgrade the renderscriptTargetApi level to 17 and turn off the renderscript support mode (renderscriptSupportModeEnabled to false) as shown below.
   
   
   
3. Save all the files and rebuild the project.
   
   The project should manage to sync and build successfully.

Note: At the time of writing, Android can only compile android.renderscript.* classes into 32 bit *.bc files. This may be a problem in future as Google Play is moving to apks that support 64 bit files.