TabActivity 切换到后台遇到的问题

//这是有问题的代码，多关闭打开几次就会报如下异常
/**

09-18 10:47:21.225 8617-8617/derlinp.com.appsearch E/InputEventSender﹕ Exception dispatching finished signal.
09-18 10:47:21.225 8617-8617/derlinp.com.appsearch E/MessageQueue-JNI﹕ Exception in MessageQueue callback: handleReceiveCallback
09-18 10:47:21.235 8617-8617/derlinp.com.appsearch E/MessageQueue-JNI﹕ java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1377)
at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:504)
at android.support.v4.app.FragmentActivity.onBackPressed(FragmentActivity.java:178)
at android.app.Activity.onKeyUp(Activity.java:2204)
at android.view.KeyEvent.dispatch(KeyEvent.java:2694)
at android.app.Activity.dispatchKeyEvent(Activity.java:2447)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:49)
at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:258)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1977)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.widget.TabHost.dispatchKeyEvent(TabHost.java:324)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:2050)
at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1514)
at android.app.Activity.dispatchKeyEvent(Activity.java:2442)
at derlinp.com.appsearch.activity.MainActivity.dispatchKeyEvent(MainActivity.java:98)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1977)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:3963)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3937)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3530)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3431)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3587)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3431)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3563)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3726)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2028)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1722)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1713)
at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2005)
at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:138)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:5111)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797)
at com.android.internal.os.ZygoteInit.main(Zyg
09-18 10:47:21.245 8617-8617/derlinp.com.appsearch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: derlinp.com.appsearch, PID: 8617
java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1377)
at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:504)
at android.support.v4.app.FragmentActivity.onBackPressed(FragmentActivity.java:178)
at android.app.Activity.onKeyUp(Activity.java:2204)
at android.view.KeyEvent.dispatch(KeyEvent.java:2694)
at android.app.Activity.dispatchKeyEvent(Activity.java:2447)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:49)
at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:258)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1977)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.widget.TabHost.dispatchKeyEvent(TabHost.java:324)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1408)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:2050)
at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1514)
at android.app.Activity.dispatchKeyEvent(Activity.java:2442)
at derlinp.com.appsearch.activity.MainActivity.dispatchKeyEvent(MainActivity.java:98)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1977)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:3963)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3937)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3530)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3431)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3587)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3431)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3404)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3454)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3423)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3563)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3726)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2028)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1722)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1713)
at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2005)
at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:138)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:5111)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(Zygote

*/
//意思就是说在某个Activity被系统销毁的时候系统框架调用onSaveInstanceState方法后还执行程序就会报IllegalStateException异常，这本就是android本身的问题，在这里我刚好试到一种方法可以避免这个异常，就在执行跳转命令后返回false，不往下传，返回事件就在这里终止。就没有再报错，还有一种解决方案就是在TabActivity下的每个Activity分别重写onBackPressed()来切换到后台。这样写不会报之前的异常，只是同样的代码要写几遍，很烦

最开始的代码
 1   public boolean dispatchKeyEvent(KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN
                && event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
                ResolveInfo launcherResolve=queryCurrentLauncher();
                Intent intent=new Intent();
                intent.addCategory(Intent.ACTION_MAIN);
                ComponentName componentName=new ComponentName(launcherResolve.activityInfo.packageName,launcherResolve.activityInfo.name);
                intent.setComponent(componentName);
                startActivitySafely(intent);
            Toast.makeText(this, "要开始切换了", Toast.LENGTH_SHORT).show();
        
        }
        return super.dispatchKeyEvent(event);
    }
    private void startActivitySafely(Intent intent){
        try{
            startActivity(intent);
            Toast.makeText(this, "切换到后台成功", Toast.LENGTH_SHORT).show();
        }catch (Exception e){
            Toast.makeText(this, "切换到后台失败", Toast.LENGTH_SHORT).show();
            e.printStackTrace();
        }
    }

    private ResolveInfo queryCurrentLauncher() {
        Intent launcherIntent = new Intent(Intent.ACTION_MAIN);
        launcherIntent.addCategory(Intent.CATEGORY_HOME);
        launcherIntent.addCategory(Intent.CATEGORY_DEFAULT);
        List<ResolveInfo> launcherInfoList = getPackageManager().queryIntentActivities(launcherIntent, PackageManager.MATCH_DEFAULT_ONLY);

        ResolveInfo launcherResolveInfo = null;
        ActivityManager activityManager = (ActivityManager) getSystemService(Service.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> tasks = activityManager.getRunningTasks(30);
        Iterator<ActivityManager.RunningTaskInfo> itInfo = tasks.iterator();
        while (itInfo.hasNext()) {
            ActivityManager.RunningTaskInfo info = itInfo.next();
            for (ResolveInfo resolveInfo : launcherInfoList) {
                String name1 = info.topActivity.getClassName();
                String namme2 = resolveInfo.activityInfo.name;
                if (name1.equals(namme2)) {
                    //获取当前使用的桌面
                    launcherResolveInfo = resolveInfo;
                    return launcherResolveInfo;44                 }
            }
        }
        return launcherResolveInfo;
    }

修改后的代码

    public boolean dispatchKeyEvent(KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN
                && event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
                ResolveInfo launcherResolve=queryCurrentLauncher();
                Intent intent=new Intent();
                intent.addCategory(Intent.ACTION_MAIN);
                ComponentName componentName=new ComponentName(launcherResolve.activityInfo.packageName,launcherResolve.activityInfo.name);
                intent.setComponent(componentName);
                startActivitySafely(intent);
            Toast.makeText(this, "要开始切换了", Toast.LENGTH_SHORT).show();
            return false;
        }
        return super.dispatchKeyEvent(event);
    }
    private void startActivitySafely(Intent intent){
        try{
            startActivity(intent);
            Toast.makeText(this, "切换到后台成功", Toast.LENGTH_SHORT).show();
        }catch (Exception e){
            Toast.makeText(this, "切换到后台失败", Toast.LENGTH_SHORT).show();
            e.printStackTrace();
        }
    }

    private ResolveInfo queryCurrentLauncher() {
        Intent launcherIntent = new Intent(Intent.ACTION_MAIN);
        launcherIntent.addCategory(Intent.CATEGORY_HOME);
        launcherIntent.addCategory(Intent.CATEGORY_DEFAULT);
        List<ResolveInfo> launcherInfoList = getPackageManager().queryIntentActivities(launcherIntent, PackageManager.MATCH_DEFAULT_ONLY);

        ResolveInfo launcherResolveInfo = null;
        ActivityManager activityManager = (ActivityManager) getSystemService(Service.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> tasks = activityManager.getRunningTasks(30);
        Iterator<ActivityManager.RunningTaskInfo> itInfo = tasks.iterator();
        while (itInfo.hasNext()) {
            ActivityManager.RunningTaskInfo info = itInfo.next();
            for (ResolveInfo resolveInfo : launcherInfoList) {
                String name1 = info.topActivity.getClassName();
                String namme2 = resolveInfo.activityInfo.name;
                if (name1.equals(namme2)) {
                    //获取当前使用的桌面
                    launcherResolveInfo = resolveInfo;
                    return launcherResolveInfo;
                }
            }
        }
        return launcherResolveInfo;
    }

这样就避免了再TabActivity下的每个Activity中分别写切换到后台的代码。