在“firstUse”之后onCreate不会一致地报告Android偏好设置 - 我的错，但是如何？

Question

编辑我忘记了一大堆代码。 在这里插入。

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    Log.w("Before switch", (String) item.getTitle());
    switch (item.getItemId()) {
      case R.id.menu_settings:
        Log.w("Before intent","\n");
        Intent intent = new Intent(this, SettingsActivity.class);
        startActivity(intent);
        Log.w("back from intent", "\n");
        preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);
        focusAtClue = preferences.getBoolean("focus",true);
        screenSaver = preferences.getBoolean("screen",true);
        Log.w("after intent", focusAtClue + " " + screenSaver);
        return true;

      default:
        Log.w("onOptItemSel","default");
        return super.onOptionsItemSelected(item);
    }
  }
}

这里的onCreate代码用于创建首选项，如图所示。 preferences.xml的xml作为注释插入。 它也包含在下面，完好无损。

首选项存储在键focus和screen 。 对？

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);
    boolean firstUse = preferences.getBoolean(FIRST_USE, true);
    if (firstUse){
      Toast helloMessage = Toast.makeText(getApplicationContext(), "Hello First Time User",Toast.LENGTH_LONG);
      helloMessage.show();
      editor = preferences.edit();
      editor.putBoolean(FIRST_USE, false);
      editor.putBoolean  ("focus", false);
/*NOTE THE MATCHED STRING  vvvvv
      <CheckBoxPreference
              android:key="focus"   android:title="@string/focusAfterShow" android:summary="Always place the cursor" android:defaultValue="false"/> */
      editor.putBoolean  ("screen", false);
/*NOTE THE MATCHED STRING  vvvvvv
      <CheckBoxPreference
              android:key="screen"  android:title="@string/screenSaver" android:summary="Keep screen on" android:defaultValue="false" /> */
          editor.commit();
    }
    else {
    ///////////////////// problems here *******************
      SharedPreferences preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);
      focusAtClue = preferences.getBoolean("focus",focusAtClue);
      screenSaver = preferences.getBoolean("screen",screenSaver);
      Log.w("oncreate:", focusAtClue + " " + screenSaver);
    ///////////////////// problems 
    }
  }

preferences.xml ：

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory
        android:title="Screen options">
        >
        <CheckBoxPreference
            android:key="focus"
            android:title="@string/focusAfterShow"
            android:summary="Always place the cursor at the 'clue' (sum) after tapping 'Show'."
            android:defaultValue="false"
            />
        <CheckBoxPreference
            android:key="screen"
            android:title="@string/screenSaver"
            android:summary="Keep screen on at all times while running this app."
            android:defaultValue="false"
            />
    </PreferenceCategory>
</PreferenceScreen>

离开主屏幕的应用程序然后返回到它之后，prefs没有变化，如logcat所示。

然后我通过选中它的框来更改第一个pref。 logcat正确显示。 涉及的代码在SettingsFragment.java ：

package com.bffmedia.hour11app;

import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.PreferenceFragment;
import android.util.Log;

public class SettingsFragment extends PreferenceFragment implements OnSharedPreferenceChangeListener {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
  @Override
    public void onResume() {
        super.onResume();
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
    }
  @Override
    public void onPause() {
        super.onPause();
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
    }
    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {    
       //SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(getActivity());
       Log.w("onSharedPrefChgd", sharedPreferences.getBoolean("focus",false) + " " + sharedPreferences.getBoolean("screen",false));
       }
    }

然后我从内存中的应用程序列表中删除该应用程序，然后从应用程序图标运行它。

onCreate说两个值都是FALSE，但只有第一个值。

这是logcat ，只有我通过Log.w写的行。 有3个组可供查看：创建prefs并更改第一个pref，工作正常。 然后是第二个onCreate ，其中两个值都被认为是false ，这是错误的 - 首先是真的 - 但是设置屏幕显示我确实检查了第一个框。

对于我做错了什么，我一无所知。

05-16 13:25:20.290  18778-18778/com.bffmedia.hour11app W/Before switch? Settings
05-16 13:25:20.291  18778-18778/com.bffmedia.hour11app W/Before intent? [ 
05-16 13:25:20.292   438:0x1a07 I/ActivityManager ]
    START u0 {cmp=com.bffmedia.hour11app/.SettingsActivity} from pid 18778
05-16 13:25:20.449  18778-18778/com.bffmedia.hour11app W/back from intent? 
05-16 13:25:20.450 18778:0x495a W/after intent ]
    false false ***************************** CORRECT ************************



05-16 13:35:16.717  18778-18778/com.bffmedia.hour11app W/onSharedPrefChgd? 
     true false *********************************** CORRECT



05-16 13:37:21.185  20014-20014/com.bffmedia.hour11app W/Before switch? Settings
05-16 13:37:21.186  20014-20014/com.bffmedia.hour11app W/Before intent? [ 
05-16 13:37:21.188   438:0x2ef I/ActivityManager ]
    START u0 {cmp=com.bffmedia.hour11app/.SettingsActivity} from pid 20014
05-16 13:37:21.245  20014-20014/com.bffmedia.hour11app W/back from intent? [ 
05-16 13:37:21.245 20014:0x4e2e W/after intent ]
    false false *************************************** WHY? *******************************************

Answer 1

这里的问题是你没有查找正确的首选项xml文件。 PreferenceFragment将保存到默认首选项xml文件中，并保存在MainActivity中，因为您使用的是getSharedPreferences(SETTINGS, MODE_PRIVATE) ，除了默认首选项xml文件外，还会创建一个新文件。

为了解决这个问题，只需将该代码更改为PreferenceManager.getDefaultSharedPreferences(this) ，然后您将查找PreferenceFragment使用的相同首选项xml文件。

这里有更多信息......还有......

以下是修复它所需要做的所有事情，我只是对它进行了测试并且有效！

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);
        //use this instead:
        preferences = PreferenceManager.getDefaultSharedPreferences(this);

        boolean firstUse = preferences.getBoolean(FIRST_USE, true);
        if (firstUse){
            Toast helloMessage = Toast.makeText(getApplicationContext(), "Hello First Time User",Toast.LENGTH_LONG);
            helloMessage.show();
            editor = preferences.edit();
            editor.putBoolean(FIRST_USE, false);
            editor.putBoolean  ("focus", false);
/*NOTE THE MATCHED STRING  vvvvv
      <CheckBoxPreference
              android:key="focus"   android:title="@string/focusAfterShow" android:summary="Always place the cursor" android:defaultValue="false"/> */
            editor.putBoolean  ("screen", false);
/*NOTE THE MATCHED STRING  vvvvvv
      <CheckBoxPreference
              android:key="screen"  android:title="@string/screenSaver" android:summary="Keep screen on" android:defaultValue="false" /> */
            editor.commit();
        }
        else {
            ///////////////////// problems here *******************
            //no need to create another preferences, it's already defined above
            //SharedPreferences preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);

            //This should work now!!!!!!
            focusAtClue = preferences.getBoolean("focus",focusAtClue);
            screenSaver = preferences.getBoolean("screen",screenSaver);
            Log.w("oncreate:", focusAtClue + " " + screenSaver);
            Toast helloMessage = Toast.makeText(getApplicationContext(), "Hello Returning User " + focusAtClue + " " + screenSaver,Toast.LENGTH_LONG);
            helloMessage.show();
            ///////////////////// problems
        }
    }

还有一点需要注意，看起来下面这段代码不会像你想象的那样表现。 执行此代码不会在调用startActivity()暂停，它将继续执行。 因此，此处的日志将反映“设置活动”打开之前的SharedPreference的状态，而不是之后的状态。

此外，您还应该在此处使用默认的共享首选项。

Intent intent = new Intent(this, SettingsActivity.class);
startActivity(intent);
Log.w("back from intent", "\n");
//preferences = getSharedPreferences(SETTINGS, MODE_PRIVATE);
preferences = PreferenceManager.getDefaultSharedPreferences(this);
focusAtClue = preferences.getBoolean("focus",true);
screenSaver = preferences.getBoolean("screen",true);
Log.w("after intent", focusAtClue + " " + screenSaver);
return true;