//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: handleReceiveCallback09-18 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(Zyg09-18 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) { 2 if (event.getAction() == KeyEvent.ACTION_DOWN 3 && event.getKeyCode() == KeyEvent.KEYCODE_BACK) { 4 ResolveInfo launcherResolve=queryCurrentLauncher(); 5 Intent intent=new Intent(); 6 intent.addCategory(Intent.ACTION_MAIN); 7 ComponentName componentName=new ComponentName(launcherResolve.activityInfo.packageName,launcherResolve.activityInfo.name); 8 intent.setComponent(componentName); 9 startActivitySafely(intent);10 Toast.makeText(this, "要开始切换了", Toast.LENGTH_SHORT).show();11 12 }13 return super.dispatchKeyEvent(event);14 }15 private void startActivitySafely(Intent intent){16 try{17 startActivity(intent);18 Toast.makeText(this, "切换到后台成功", Toast.LENGTH_SHORT).show();19 }catch (Exception e){20 Toast.makeText(this, "切换到后台失败", Toast.LENGTH_SHORT).show();21 e.printStackTrace();22 }23 }24 25 private ResolveInfo queryCurrentLauncher() {26 Intent launcherIntent = new Intent(Intent.ACTION_MAIN);27 launcherIntent.addCategory(Intent.CATEGORY_HOME);28 launcherIntent.addCategory(Intent.CATEGORY_DEFAULT);29 List launcherInfoList = getPackageManager().queryIntentActivities(launcherIntent, PackageManager.MATCH_DEFAULT_ONLY);30 31 ResolveInfo launcherResolveInfo = null;32 ActivityManager activityManager = (ActivityManager) getSystemService(Service.ACTIVITY_SERVICE);33 List tasks = activityManager.getRunningTasks(30);34 Iterator itInfo = tasks.iterator();35 while (itInfo.hasNext()) {36 ActivityManager.RunningTaskInfo info = itInfo.next();37 for (ResolveInfo resolveInfo : launcherInfoList) {38 String name1 = info.topActivity.getClassName();39 String namme2 = resolveInfo.activityInfo.name;40 if (name1.equals(namme2)) {41 //获取当前使用的桌面42 launcherResolveInfo = resolveInfo;43 return launcherResolveInfo;44 }45 }46 }47 return launcherResolveInfo;48 } 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 launcherInfoList = getPackageManager().queryIntentActivities(launcherIntent, PackageManager.MATCH_DEFAULT_ONLY); ResolveInfo launcherResolveInfo = null; ActivityManager activityManager = (ActivityManager) getSystemService(Service.ACTIVITY_SERVICE); List tasks = activityManager.getRunningTasks(30); Iterator 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。