java - 在 "firstUse"之后 onCreate 报告的 Android 首选项设置不一致——我的错，但是怎么样？

Question

EDIT 我忘记了一大块代码。在此处插入。

  @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);
    }
  }
}

此处的 onCreate 代码用于创建首选项，如图所示。 preferences.xml 中的 xml 作为注释插入。它也完整地包含在下面。

首选项存储在键focus 和screen 下。对吧？

  @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>

离开应用程序进入主屏幕然后返回主屏幕后，偏好设置没有变化，如 logcat 所示。

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

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 表示两个值都是 FALSE，但只有第一个是。

这是 logcat，其中只有我通过 Log.w 编写的行。有 3 个组要看:创建首选项和更改第一个首选项，效果很好。然后是第二个 onCreate，这两个值据说都是 false，这是错误的——第一个是 true——但是设置屏幕显示我做了选中第一个框。

我对自己做错了什么一无所知。

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

这里的问题是您没有查看正确的首选项 xml 文件。 PreferenceFragment 中的首选项被保存到默认首选项 xml 文件中，并且在您的 MainActivity 中，因为您正在使用 getSharedPreferences(SETTINGS, MODE_PRIVATE)，这会创建一个新文件除了默认的首选项 xml 文件。

为了修复它，只需将该代码更改为 PreferenceManager.getDefaultSharedPreferences(this)，然后您将查看与 PreferenceFragment 相同的首选项 xml 文件用途。

更多信息 here....还有here.....

这就是您需要做的所有修复工作，我刚刚测试过它，它可以工作!

    @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，下面这段代码看起来不会像您想象的那样运行。这段代码的执行不会在调用 startActivity() 时暂停，它会继续执行。因此，此处的日志将反射(reflect)设置 Activity 打开之前 SharedPreference 的状态，而不是之后。

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;