如何从 Preferences 子屏幕移回到 PreferenceFragmentCompat 中的主屏幕？

Question

我正在尝试使用 PreferenceFragmentCompat 实现设置屏幕。我的偏好 xml 有一个像这样的偏好子屏幕：

preferences.xml

    <CheckBoxPreference
        android:defaultValue="false"
        android:key="@string/pref_sound_key"
        android:summary="@string/pref_sound_summary"
        android:title="@string/pref_sound_title" />

    <PreferenceScreen android:title="Inner Screen">
        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_1"
            android:title="@string/title_1" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_1"
            android:title="@string/title_1" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_2"
            android:title="@string/title_2" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_3"
            android:title="@string/title_3" />
    </PreferenceScreen>

</PreferenceScreen>

Preference Main Screen

现在，在应用程序中，子屏幕不会打开，直到我在父 activity 中实现 PreferenceFragmentCompat.OnPreferenceStartScreenCallback 接口，如 PreferenceFragmentCompat 文档中所指定。

MainActivity.java

public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat,
 PreferenceScreen preferenceScreen) {    
    preferenceFragmentCompat.setPreferenceScreen(preferenceScreen);
    return true;
}

问题就出在这里。在实现界面时，子屏幕打开，但我无法找到返回第一屏幕的方法。

Preference Subscreen

按返回键关闭应用程序。

有什么办法可以在应用栏上放一个后退箭头，这样按下它就会返回主屏幕吗？

Answer 1

通过使用 setPreferenceScreen，您可以将根首选项屏幕设置为子首选项屏幕，这会阻止您使用首选项屏幕的层次结构来返回导航。

我建议您将每个 PreferenceScreen 视为一个 Fragment，并在导航到子屏幕时添加一个新的 Fragment。

@Override
public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat,
                                       PreferenceScreen preferenceScreen) {
    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    MyPreferenceFragment fragment = new MyPreferenceFragment();
    Bundle args = new Bundle();
    args.putString(PreferenceFragmentCompat.ARG_PREFERENCE_ROOT, preferenceScreen.getKey());
    fragment.setArguments(args);
    ft.add(R.id.fragment_container, fragment, preferenceScreen.getKey());
    ft.addToBackStack(preferenceScreen.getKey());
    ft.commit();
    return true;
}

MyPreferenceFragment

public class MyPreferenceFragment extends AppPreferenceFragment {

   public static final String FRAGMENT_TAG = "my_preference_fragment";

   public MyPreferenceFragment() {
   }

   @Override
   public void onCreatePreferences(Bundle bundle, String rootKey) {
       setPreferencesFromResource(R.xml.preferences, rootKey);
   }
}

AppPreferenceFragment

public abstract class AppPreferenceFragment extends PreferenceFragmentCompat {

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    // Set the default white background in the view so as to avoid transparency
      view.setBackgroundColor(
              ContextCompat.getColor(getContext(), R.color.background_material_light));

  }
}

这样，当您按下后退按钮时，每个片段都会从堆栈中弹出。

有关详细信息，请参阅此 GitHub 项目

Answer 2

我已经添加了一个带有屏幕截图和代码片段的完整工作示例here in this post，希望这对某人有所帮助。

它涵盖以下场景：-- 1) 一个带有两个复选框和一个子屏幕标题的主设置屏幕。 2) 点击子屏幕标题，新的首选项子屏幕打开。 3) 按下后退键，控制进入主设置屏幕。所以背压处理得当

MainActivity 看起来像这样（重写的 onPreferenceStartScreen 方法处理新 window 中新子屏幕的打开）：--

  public class MainActivity extends AppCompatActivity implements PreferenceFragmentCompat.OnPreferenceStartScreenCallback {

    private static final String TAG = MainActivity.class.getName();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FragmentManager fragmentManager = getSupportFragmentManager();
        Fragment fragment = null;
        if (savedInstanceState == null) {
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragment = new AdvancedSettingsFragment().newInstance("Advanced Setting");
            fragmentTransaction.add(R.id.fragment_container, fragment);
            fragmentTransaction.commit();
        }
    }

    @Override
        public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat,
                                           PreferenceScreen preferenceScreen) {
        Log.d(TAG, "callback called to attach the preference sub screen");
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        AdvancedSettingsSubScreenFragment fragment = AdvancedSettingsSubScreenFragment.newInstance("Advanced Settings Subscreen");
        Bundle args = new Bundle();
        //Defining the sub screen as new root for the  subscreen
        args.putString(PreferenceFragmentCompat.ARG_PREFERENCE_ROOT, preferenceScreen.getKey());
        fragment.setArguments(args);
        ft.replace(R.id.fragment_container, fragment, preferenceScreen.getKey());
        ft.addToBackStack(null);
        ft.commit();
        return true;
    }

最后是子屏幕片段setPreferencesFromResource(R.xml.preferences, rootKey)；处理子屏幕到根密钥的附件。

public class AdvancedSettingsSubScreenFragment extends PreferenceFragmentCompat {
    private static final String TAG = AdvancedSettingsSubScreenFragment.class.getName();
    public static final String PAGE_ID = "page_id";

    public static AdvancedSettingsSubScreenFragment newInstance(String pageId) {
        AdvancedSettingsSubScreenFragment f = new AdvancedSettingsSubScreenFragment();
        Bundle args = new Bundle();
        args.putString(PAGE_ID, pageId);
        f.setArguments(args);
        return (f);
    }

    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        // rootKey is the name of preference sub screen key name , here--customPrefKey
        setPreferencesFromResource(R.xml.preferences, rootKey);
        Log.d(TAG, "onCreatePreferences of the sub screen " + rootKey);
    }
}

如何从 Preferences 子屏幕移回到 PreferenceFragmentCompat 中的主屏幕？

How to move back from Preferences subscreen to main screen in PreferenceFragmentCompat?

android

preference-v7