支持Android Pie中的明暗主题

Question

Android Pie added the ability to toggle light/dark theme in the Settings -> Display -> Device Theme menu.

I want my app to apply the correct theme according to the Device Theme set in the device settings.

According to the Styles and Themes Android guide, for dark mode the app should use a theme that extends Theme.AppCompat , and for light mode the app should use a theme that extends Theme.AppCompat.Light .

So I created two themes in my app:

<style name="AppTheme.Dark" parent="Theme.AppCompat">
  ...
</style>

<style name="AppTheme.Light" parent="Theme.AppCompat.Light">
  ...
</style>

However in AndroidManifest.xml when I declare the application with the <application> tag I can only specify one theme in the android:theme attribute:

<application
    android:name=".MyApplication"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher"
    android:supportsRtl="true"
    android:theme="@style/AppTheme.Light"
    tools:replace="android:name">

How do I declare my application in AndroidManifest.xml to dynamically pick @style/AppTheme.Light or @style/AppTheme.Dark according to the Device Theme set in the device settings?

Answer 1

If you want to change theme of an already existing activity, call recreate() after setTheme().

Note: don't call recreate if you change theme in onCreate(), to avoid infinite loop.

  protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Call setTheme before creation of any(!) View.
         setTheme(android.R.style.Theme_Dark);

        // ...
        setContentView(R.layout.main);
    }

Answer 2

You may want to try Theme.AppCompat.DayNight instead of defining two themes. Its implementation in this video Cost of a Pixel Color .

However, when I test this on an emulator, toggling Settings -> Display -> Device Theme menu doesn't work. I have to toggle Developer Options -> Night Mode -> Always On and dark theme is picked automatically.

Since I don't own an Android Pie device, I'm not sure if this is a bug of emulator.