Migrating to the AppCompat Library

Overview

The AppCompat support library enables the use of the ActionBar and Material Design specific implementations for older devices down to Android v2.1. Currently, new projects created through Android Studio incorporate this library by default. You can confirm by looking at the build.gradle file to see the AppCompat library being set:

dependencies {
    compile 'com.android.support:appcompat-v7:22.2.0'
}

Note that the AppCompat library has an implicit dependency on the support-v4 library. It does not necessarily need to be declared.

Search and replacing changes

Older projects may not include this library, so migrating requires changing the theme references and many of the main imports described in this blog post. Because the class declarations are not compatible, you need to make sure you are using the support library definitions entirely. Otherwise your app is likely to crash.

The simplest is often to do a search-and-replace to start changing the following statements to start using the support libraries.

Activities Changes

• import android.app.Activity -> import android.support.v7.app.AppCompatActivity
• extends Activity -> extends AppCompatActivity

Fragment Changes

• extends FragmentActivity -> extends AppCompatActivity
• import android.support.v4.app.FragmentActivity -> import android.support.v7.app.AppCompatActivity
• import android.app.Fragment -> import android.support.v4.app.Fragment
• getFragmentManager() -> getSupportFragmentManager()

ActionBar Changes

• import android.app.ActionBar -> import android.support.v7.app.ActionBar
• getActionBar() -> getSupportActionBar()

Theme XML Changes

If you were migrating from the Holo theme, your new themes.xml would inherit from Theme.AppCompat instead of android:Theme.Holo.Light:

-    <style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
+    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

Menu XML Changes

For your menu/ layout files, add an app: namespace . For menu items, the showAsAction must be from the app namespace instead of android namespace. It is considered a custom attribute of the support library and not supported in the main Android framework.

-<menu xmlns:android="http://schemas.android.com/apk/res/android">
+<menu xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto">
 <item android:id="@+id/myMenuItem"
       android:title="@string/select"
-      android:showAsAction="ifRoom"
+      app:showAsAction="ifRoom"

If you are using widgets such as the SearchView, you must also use android.support.v7.widget.SearchView instead of android.widget.SearchView. Note that the app namespace must also be used.

+<menu xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <item android:id="@+id/contentSearch"
           android:orderInCategory="2"
           android:title="@string/search"
-          android:showAsAction="ifRoom"
-          android:actionViewClass="android.widget.SearchView">
+          app:showAsAction="ifRoom"
+          app:actionViewClass="android.support.v7.widget.SearchView">

Changing targetSDKVersion

In addition, setting the targetSdkVersion to the latest SDK version ensures that the AppCompat library will attempt to apply the Material Design assuming the device itself can support it. In other words, targetSdkVersion only is used as an extra check to determine whether the SDK version should even be supported or not. The support library will still check to see if the minimum SDK version is being used on the device.

android {
    targetSdkVersion 21

References

• http://www.androidauthority.com/goodbye-menu-button-hello-action-bar-48312/
• http://android-developers.blogspot.in/2013/08/actionbarcompat-and-io-2013-app-source.html
• http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-pre.html
• https://chris.banes.me/2015/04/22/support-libraries-v22-1-0/