我想寻求一些帮助：在我的应用程序，我只有一个活动，一个preferenceActivity（不需要其他的，它只是一个简单的背景同步的应用程序，所以prefsActivity是主/启动）。用户设置preferences后，检查一个复选框preference，并启动（或停止）的服务。在起点，一个对话框显示。 但现在的问题是：如果用户preSS背面（离开活动），再次启动了，比试图选中该复选框preF，在prefsactivity崩溃。对话框不会显示。我不知道为什么，以及如何解决它。

I'd like to ask for some help: In my app, I have only one activity, a PreferenceActivity (don't need other, it's just a simple background-sync app, so the PrefsActivity is the Main/Launcher). After the user setup preferences, checks a checkBoxPreference, and that starts (or stops) a service. At starting, a dialog shows. But here is the problem: if the user press back (leave the activity), start it again, and than tries to check the checkBoxPref., the prefsactivity crashes. Dialog doesn't shows. I have no idea why, and how to fix it.

这code是exsactly同那一部分，是什么给了我这个问题：

This code is exsactly same with that part, what gives me the problem:

prefsActivity.java：

PrefsActivity.java:

   package is.it.works;

   // imports .....

   public class PrefsActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener {
SharedPreferences prefs;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    addPreferencesFromResource(R.xml.prefs);
    prefs = PreferenceManager.getDefaultSharedPreferences(this);
    prefs.registerOnSharedPreferenceChangeListener(this);
}// onCreate

@Override
public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
    if (key.equals("checkTest")) {
        showDialog(1);
    }
    if (key.equals("cancel")) {
        dismissDialog(1);
    }
}// onSPC

@Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
    case 1: {
        ProgressDialog dialog = new ProgressDialog(this);
        dialog.setMessage("press back twice, start the app again, and click checkbox...");
        dialog.setIndeterminate(true);
        dialog.setCancelable(true);
        dialog.setOnCancelListener(new OnCancelListener() {

            @Override
            public void onCancel(DialogInterface dialog) {
                prefs.edit().putBoolean("cancel", false).commit();
            }
        });
        return dialog;
    }// case
    }// switch
    return null;
}// onCreateDialog
}// PrefsActivity

prefs.xml：

prefs.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">

    <CheckBoxPreference android:key="checkTest" android:title="test" />

</PreferenceScreen>

和清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="is.it.works" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="4" />

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".PrefsActivity" android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>
</manifest>

LogCat中的错误：

LogCat error:

09-14 10:34:34.472: ERROR/AndroidRuntime(281): Uncaught handler: thread main exiting due to uncaught exception
09-14 10:34:34.502: ERROR/AndroidRuntime(281): android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@43756de8 is not valid; is your activity running?
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.view.ViewRoot.setView(ViewRoot.java:456)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:177)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.view.Window$LocalWindowManager.addView(Window.java:409)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.app.Dialog.show(Dialog.java:238)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.app.Activity.showDialog(Activity.java:2413)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at is.it.works.PrefsActivity.onSharedPreferenceChanged(PrefsActivity.java:27)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.app.ApplicationContext$SharedPreferencesImpl$EditorImpl.commit(ApplicationContext.java:2727)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.Preference.tryCommit(Preference.java:1199)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.Preference.persistBoolean(Preference.java:1404)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.CheckBoxPreference.setChecked(CheckBoxPreference.java:155)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.CheckBoxPreference.onClick(CheckBoxPreference.java:143)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.Preference.performClick(Preference.java:811)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.preference.PreferenceScreen.onItemClick(PreferenceScreen.java:190)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.widget.AdapterView.performItemClick(AdapterView.java:284)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.widget.ListView.performItemClick(ListView.java:3246)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:1635)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.os.Handler.handleCallback(Handler.java:587)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.os.Handler.dispatchMessage(Handler.java:92)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.os.Looper.loop(Looper.java:123)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at android.app.ActivityThread.main(ActivityThread.java:4203)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at java.lang.reflect.Method.invokeNative(Native Method)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at java.lang.reflect.Method.invoke(Method.java:521)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
09-14 10:34:34.502: ERROR/AndroidRuntime(281):     at dalvik.system.NativeStart.main(Native Method)
09-14 10:34:34.522: INFO/Process(52): Sending signal. PID: 281 SIG: 3
09-14 10:34:34.532: INFO/dalvikvm(281): threadid=7: reacting to signal 3
09-14 10:34:34.592: INFO/dalvikvm(281): Wrote stack trace to '/data/anr/traces.txt'
09-14 10:34:38.533: DEBUG/dalvikvm(107): GC freed 437 objects / 21560 bytes in 136ms
09-14 10:34:39.183: INFO/global(175): Default buffer size used in BufferedReader constructor. It would be better to be explicit if an 8k-char buffer is required.
09-14 10:34:44.632: INFO/global(175): Default buffer size used in BufferedReader constructor. It would be better to be explicit if an 8k-char buffer is required.
09-14 10:34:47.412: INFO/Process(281): Sending signal. PID: 281 SIG: 9
09-14 10:34:47.472: INFO/ActivityManager(52): Process is.it.works (pid 281) has died.
09-14 10:34:47.492: INFO/WindowManager(52): WIN DEATH: Window{4394f638 is.it.works/is.it.works.PrefsActivity paused=false} 

googleing了很多之后，我觉得，错部分是ProgressDialog对话框=新ProgressDialog（本）;。原因这一变化。但量变到质变为getApplicationContext（），或prefsActivity.this犯规的帮助，这个问题仍然存在。 请告诉我它为什么会发生，什么可能是解决方案！谢谢！ 我stucked，现在我不知道......

After googleing a lot, I think, the wrong part is the "ProgressDialog dialog = new ProgressDialog(this);". Cause "this" changes. But changeing it to "getApplicationContext()", or "PrefsActivity.this" doesnt help, the problem is still on. Please, tell me why is it happens, and what could be the solution! Thank You! I'm stucked, and now I have no idea...

推荐答案

我有一个非常类似的问题（其中落在我在这里），并发现了一个很简单的解决它。虽然我的code是不同的，它应该很容易适应。这是我的修正：

I had a very similar issue (which landed me here) and found a very simple fix for it. While my code is different, it should be easy to adapt. Here is my fix:

public void showBox() {
    mActive = true;
    if (! ((Activity) mContext).isFinishing()) {
        mDialogBox.show();
    }
} 

因此​​，在样品code中的问题，修复将是（在猜测）：

So, in the sample code in the question, the fix would have been (at a guess):

@Override
public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
    if (key.equals("checkTest")) {
        if (! this.isFinishing()) {
            showDialog(1);
        }
    }
    if (key.equals("cancel")) {
        dismissDialog(1);
    }
}// onSPC