15

首先，我的应用程序的结构如下：

 SpashActivity -> MainActivity -> switching between many fragments

我的应用程序使用SlideMenu在片段之间切换。我必须使用attach而不是replace保持片段状态。它看起来像：

  public void switchContent(int index, String fragmentTag) {                
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction transaction = fragmentManager.beginTransaction();
    if (fragmentManager.findFragmentByTag(fragmentTag) != mContent) {
        if (!mContent.isDetached()) {
            transaction.detach(mContent);
        }
        if (null == fragmentManager.findFragmentByTag(fragmentTag)) {
            switch (index) {
            case 0:
                mContent = new CategoryFragment();
                break;
            case 1:
                mContent = new BookFragment();
                break;
            case 2:
                mContent = new BookDetailFragment();
                break;
             // etc
            }
        } else {
                mContent = fragmentManager.findFragmentByTag(fragmentTag);              
        }

        if (mContent.isDetached()) {
            transaction.attach(mContent);
        } else if (!mContent.isAdded()) {
            transaction.add(R.id.content_frame, mContent, fragmentTag);
        }

        transaction.addToBackStack(null);
        transaction.commit();
        fragmentManager.executePendingTransactions();
    }
    Handler h = new Handler();
    h.postDelayed(new Runnable() {
        public void run() {
            getSlidingMenu().showContent();
        }
    }, 50);
}

当后台堆栈倒数为零时，我的应用程序必须退出：

 @Override
public void onBackPressed() {
    if (0 == getSupportFragmentManager().getBackStackEntryCount()) {
        // show confirm exit dialog.
        // If user press ok, try to exit, the splash activity will call finish()  
         // if(dialog == ok){ 
           Intent intent = new Intent(MainActivity.this, SplashActivity.class);
           intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
           intent.putExtra(SplashActivity.EXIT_KEY, true);
           startActivity(intent);
         // }  
    } else {
        super.onBackPressed();
    }
}

但有时（并非总是）我遇到异常并在用户多次按下时使我的应用程序崩溃（即使确认退出对话框也没有出现 - 意味着返回堆栈计数大于零）：

  09-30 20:32:53.419: E/AndroidRuntime(796): Uncaught handler: thread main exiting due to uncaught exception
  09-30 20:32:53.470: E/AndroidRuntime(796): java.lang.RuntimeException: Unable to pause activity {com.org.scgroup/com.org.scgroup.MainActivity}: java.lang.IllegalStateException: Failure saving state: active BookDetailFragment{43e7e0d8} has cleared index: -1
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3162)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3119)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3102)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.access$2400(ActivityThread.java:119)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1870)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.os.Handler.dispatchMessage(Handler.java:99)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.os.Looper.loop(Looper.java:123)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.main(ActivityThread.java:4363)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at java.lang.reflect.Method.invokeNative(Native Method)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at java.lang.reflect.Method.invoke(Method.java:521)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at dalvik.system.NativeStart.main(Native Method)
  09-30 20:32:53.470: E/AndroidRuntime(796): Caused by: java.lang.IllegalStateException: Failure saving state: active BookDetailFragment{43e7e0d8} has cleared index: -1
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.support.v4.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1716)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.support.v4.app.FragmentActivity.onSaveInstanceState(FragmentActivity.java:532)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at com.actionbarsherlock.app.SherlockFragmentActivity.onSaveInstanceState(SherlockFragmentActivity.java:126)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at com.jeremyfeinstein.slidingmenu.lib.app.SlidingFragmentActivity.onSaveInstanceState(SlidingFragmentActivity.java:51)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at com.org.scgroup.MainActivity.onSaveInstanceState(MainActivity.java:324)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.Activity.performSaveInstanceState(Activity.java:1022)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1180)
  09-30 20:32:53.470: E/AndroidRuntime(796):    at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3144)
  09-30 20:32:53.470: E/AndroidRuntime(796):    ... 12 more

onSaveInstanceState方法：

  @Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    try {
        Ln.d("onSaveInstanceState");
        outState.putInt(CURRENT_FRAGMENT_KEY, currentFragment);

        if (0 < getSupportFragmentManager().getBackStackEntryCount()) {
            getSupportFragmentManager().putFragment(outState, "mContent", mContent);
        }
    } catch (Exception ex) {
        Ln.e(ex);
    }
}

你能告诉我我哪里错了吗？提前致谢。

4

3 回答 3

1

您的片段状态会自动保存和恢复，无需在您的onSaveInstanceState方法中执行任何操作。不要在您的活动中保留对您的片段的任何引用（在您的情况下currentFragment，mContent），如果您需要某个片段，请从FragmentManager例如获取它findFragmentByTag。

于 2016-05-28T14:11:38.910 回答
1

在分离和附加之间读取片段统计可能存在问题。

尝试使用这样的东西：

FragmentTransaction ft = fragmentManager.beginTransaction();

//ft.detach(fragment).attach(fragment).commitAllowingStateLoss(); // crashing

ft.replace(getView().getId(), fragment).commitAllowingStateLoss(); // not crashing
于 2017-01-03T05:47:56.823 回答
0

尝试改变

 @Override
public void onBackPressed() {
    if (0 == getSupportFragmentManager().getBackStackEntryCount()) {

至

 @Override
public void onBackPressed() {
    if (getSupportFragmentManager().getBackStackEntryCount() < 1 ) {

我希望这有效

于 2015-10-28T06:16:14.397 回答