我的 ListPreference 在运行时不会更改应用程序主题

Question

当我在ListPreference 中选择一个项目来更改我的应用程序的主题时，如何让我的Activity 重新创建自己并保持特定主题？出于某种原因，无论选择 ListPreference 中的哪个项目，我的应用都停留在浅色主题上。我不确定我在这里做错了什么。

styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light"/>

    <style name="MyDarkSettingsTheme" parent="Theme.AppCompat"/>

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

</resources>

活动

class SettingsActivity : AppCompatActivity(), SharedPreferences.OnSharedPreferenceChangeListener {
    // Declaring initial value for applying appropriate Theme
    private var mCurrentValue: Boolean = true // True is the default value

    override fun onCreate(savedInstanceState: Bundle?) {
        // Checking which Theme should be used. IMPORTANT: applying Themes MUST called BEFORE super.onCreate() and setContentView!!!
        val mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
        mCurrentValue = mSharedPreferences.getBoolean("light", true)
        if (mCurrentValue) setTheme(R.style.MyLightSettingsTheme)
        else setTheme(R.style.MyDarkSettingsTheme)

        super.onCreate(savedInstanceState)
        setContentView(R.layout.settings_activity)
        supportFragmentManager
            .beginTransaction()
            .replace(R.id.settings, SettingsFragment())
            .commit()

        val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
        sharedPreferences.registerOnSharedPreferenceChangeListener(this)
    }

    // In order to recreate Activity, we must check the value here. Because, when we come back from another Activity, the onCreate isn't called again.
    override fun onStart() {
        super.onStart()

        setContentView(R.layout.settings_activity)
        supportFragmentManager
            .beginTransaction()
            .replace(R.id.settings, SettingsFragment())
            .commit()

        val mFrameLayout = findViewById<FrameLayout>(R.id.settings)

        val mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
        val mNewValue = mSharedPreferences.getBoolean("light", true)
        // If value differs from previous Theme, recreate Activity
        if (mCurrentValue != mNewValue) recreate()

//        if (mNewValue) {
//            mFrameLayout.setBackgroundColor(Color.WHITE)
//        }
//        else {
//            mFrameLayout.setBackgroundColor(Color.BLACK)
//        }

        // ... do other stuff here

    }

    class SettingsFragment : PreferenceFragmentCompat() {
        override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
            setPreferencesFromResource(R.xml.root_preferences, rootKey)
        }
    }

    override fun onDestroy() {
        val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
        sharedPreferences.unregisterOnSharedPreferenceChangeListener(this)
        //...
        super.onDestroy()
    }

    override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences, key: String) {
        when (key) {
            "list_theme" -> {
                if (sharedPreferences.getString(key, "light") == "light") {
                    setTheme(R.style.MyLightSettingsTheme)
                    recreate()
                }
                else if (sharedPreferences.getString(key, "dark") == "dark") {
                    setTheme(R.style.MyDarkSettingsTheme)
                    recreate()
                }
            }
        }
    }
}

1) 活动打开

2) ListPreference 点击

3) 选择深色偏好

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }


    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        return when (item.itemId) {
            R.id.action_settings -> {
                val intentSettings = Intent(this, SettingsActivity ::class.java)
                startActivity(intentSettings)
                true
            }

            else ->
                super.onOptionsItemSelected(item)
        }
    }
}

Answer 1

首先，您需要在 styles.xml 文件中添加更多颜色/主题。

例子：

<!-- Base Light application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

<!--Dark Theme Default-->
<style name="AppThemeDark" parent="Theme.AppCompat">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

在我的 Base Application 类中，我添加了这 3 个方法。我的应用程序有 3 个主题，如果您有更多主题，您可以相应地编辑代码。

@Override
public void onCreate() {
    super.onCreate();
    PreferenceManager.setDefaultValues(this, R.xml.pref_main, false);
    Context context = this;
    context.setTheme(getUserTheme());
    mInstance = this;
    res = getResources();
    shared = PreferenceManager.getDefaultSharedPreferences(context);
}

public static int getTheme(Context context, int light, int dark, int amoled) {
    String darkTheme = context.getString(R.string.dark_mode_theme);
    String amoledTheme = context.getString(R.string.amoled_mode_theme);
    shared = PreferenceManager.getDefaultSharedPreferences(context);
    String theme = shared.getString(Constants.PREFERENCE_THEME, darkTheme);
    //Able to access these values outside the class!
    if (theme.equals(darkTheme)) {
        return dark;
    } else if (theme.equals(amoledTheme)) {
        return amoled;
    } else {
        return light;
    }
}

private int getUserTheme() {
    return getTheme(this, R.style.AppTheme, R.style.AppThemeDark, R.style.AppThemeAMOLED);
}

如果您没有扩展 Application 的类，请创建它，然后将此行放入 <Application> 标记中，然后将其添加到 AndroidMainfest

 android:name="App"

我还在Base Activity Class 中添加了以下方法。我所有的活动都扩展了这门课。如果您的应用程序只有一个活动，那么这与您的相关性较低。

protected abstract int getAppTheme(); //has to be implemented in anything that extends this class

protected void setAppTheme(int id) {
    super.setTheme(id);
    themeId = id;
}

 protected void onResume() {
        super.onResume()
        if (themeId !== getAppTheme())
        {
            recreate();
        }
    }

更改主题后，您需要重新创建活动以激活更改。

recreate();

很遗憾，您不能从静态方法调用它。我还建议检查 onCreate 中的主题，如果当前主题与用户选择的主题不匹配，则更改主题，然后调用 recreate();。

接下来，在扩展基本活动类的常规活动中，我添加了这个。确保在任何地方都保持相同的顺序。否则，主题将不匹配。

 public int getAppTheme() {
        return App.getTheme(this, R.style.AppTheme, R.style.AppThemeDark, R.style.AppThemeAMOLED);
    }