应用程序在导航抽屉内的片段内按下返回按钮时退出

Question

当我尝试从子片段移动到父片段时，我的应用程序退出（它不会崩溃）。这里 LandingActivity.java 是我调用片段 ChannelGrid.java 的主要活动，它调用片段 GridMain.java。当我在片段GridMain应用程序退出而不是移动到ChannelGrid.java中按下移动设备的后退按钮。我已将addToBackStack（“tag”）添加到片段并尝试使用onKey（）..我也在不同设备上测试了我的应用程序..我检查了找出具有相同问题的其他解决方案并尝试了它们，但没有任何效果..

导航抽屉-LandingActivity.java-ChaanelGrid.java(Fragment)-GridMain.java(Fragment)

LandingActivity.java

   currentFragment = new ChaanelGrid();

                currentFragment.setArguments(args);
                frgManager = getFragmentManager();

                frgManager.beginTransaction().add(R.id.content_frame, currentFragment).addToBackStack("tag")
                        .commit();

ChaanelGrid.java

Fragment currentFragment = new GridMain();



                    FragmentManager frgManager;
                    frgManager = getFragmentManager();
                    frgManager.beginTransaction().add(R.id.content_frame, currentFragment).addToBackStack("GridMain")
                            .commit()

GridMain.java（我也试过不使用 onKey() 方法但没有用）

rootView.setOnKeyListener(new View.OnKeyListener() {


   @Override
        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if (keyCode == KeyEvent.KEYCODE_BACK)
            {
                Fragment currentFragment = new ChaanelGrid();


                FragmentManager frgManager;
                frgManager = getFragmentManager();
                frgManager.beginTransaction().replace(R.id.content_frame, currentFragment)
                        .commit();
                return true;
            }

logcat 详细

   10-31 21:46:57.954  24452-24452/D/ActivityThread﹕ ACT-AM_ON_PAUSE_CALLED ActivityRecord{41eb8b98 token=android.os.BinderProxy@41bb9828 {xyz/xyz..activity.LandingActivity_}}
10-31 21:46:57.971  24452-24452/ D/ActivityThread﹕ ACT-PAUSE_ACTIVITY_FINISHING handled : 0 / android.os.BinderProxy@41bb9828
10-31 21:46:58.007  24452-24452/ V/InputMethodManager﹕ focusOut: android.widget.GridView@41f06f40 mServedView=android.widget.GridView@41f06f40 winFocus=false
10-31 21:46:58.297  24452-24452/ I/SurfaceTextureClient﹕ [0x5143bc58] frames:44, duration:1.002000, fps:43.883736
10-31 21:46:58.350  24452-24452/ D/OpenGLRenderer﹕ Flushing caches (mode 0)
10-31 21:46:58.432  24452-24452/ D/OpenGLRenderer﹕ Flushing caches (mode 0)
10-31 21:46:58.753  24452-24452/ D/OpenGLRenderer﹕ Flushing caches (mode 0)
10-31 21:46:58.754  24452-24452/ D/OpenGLRenderer﹕ Flushing caches (mode 0)
10-31 21:46:58.755  24452-24452/ D/OpenGLRenderer﹕ Flushing caches (mode 2)
10-31 21:46:58.879  24452-24452/ D/ActivityThread﹕ ACT-DESTROY_ACTIVITY handled : 1 / android.os.BinderProxy@41bb9828

我尝试在 LandingActivity.java 中添加以下内容

@Override

public void onBackPressed() {
    FragmentManager frgManager;
    frgManager = getFragmentManager();

    Fragment fragment = fragmentManager.findFragmentByTag("GridMain");
    if (fragment != null) {
        GridMain gridMain = (GridMain) fragment;
        if (!gridMain.onBackPressed()) {
            super.onBackPressed();
        }
    }
    else {
        super.onBackPressed();
    }
}

并在 GridMain.java 中跟随

   protected boolean onBackPressed() {
        FragmentManager frgManager;
        frgManager = getFragmentManager();
        frgManager.popBackStack();
        return true;
    }

使用日志我检查了 LandingActivity.java 的 onBackPressed() 是否被调用，但输出仍然相同..

Answer 1

这就是我解决它的方法..当您在片段中按下后退按钮时，如果您已声明，您的活动的 onBackPressed() 方法将被调用..因此，在导航抽屉中处理片段的后退按钮可以是其中之一方式..

主要活动

     public static boolean isMainActivityShown ;
     public static boolean isFragment1Shown=false ;
     public static boolean isFragment2Shown=false ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        isMainActivityShown=true  //inside onCreate method put isMainActivityShown true
        . 
        . 
        .
        {
        Fragment currentFragment = new Fragment1();
        isMainActivityShown=false;   //when moving to fragment1 
        isFragment1Shown=true;
        frgManager = getFragmentManager();
        frgManager.beginTransaction().replace(R.id.content_frame, currentFragment)
                                        .commit();
        }
        .
        .
        }
     @Override
        public void onBackPressed() {

            if(isMainActivityShown)
            {
                finish();
            }
            else if(isFragment1Shown)
            {
               //write the code to handle back button when you are in Fragment1
            }
           else if(isFragment2Shown)
            {  //When you are in Fragment 2 pressing back button will move to fragment1
                Fragment currentFragment = new Fragment1();
                isFragment2Shown=false;
                isFragment1Shown=true;

                FragmentManager frgManager;
                frgManager = getFragmentManager();
                frgManager.beginTransaction().replace(R.id.content_frame, currentFragment)
                        .commit();
            }

            }

片段1

Fragment currentFragment = new Fragment2();
MainActivity.isFragment1Shown=false;
MainActivity.isFragment2Shown=true;
frgManager = getFragmentManager();
frgManager.beginTransaction().replace(R.id.content_frame, currentFragment)
                                    .commit();

Answer 2

我尝试了这里建议的所有解决方案，但没有一个对我有用。 这就是我最终通过修改投票最高的答案来解决它的方法：

在托管片段的活动中，声明 FragmentManager

private FragmentManager fragmentManager;

在你的 onCreateMethod 中初始化它：

public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  fragmentManager = getFragmentManager();
  ...

最后，在你的 onBackPressed 方法中这样做：

 public void onBackPressed() {
    if(fragmentManager.getBackStackEntryCount() != 0) {
        fragmentManager.popBackStack();
        if (IS_MAIN_SHOWN) {
            finish();
        } else  {
            displayView(0);  //this is the method that changes the fragments, takes an int argument for the position of the fragment.
        }

    } else {
        super.onBackPressed();
    }
}

Answer 3

我建议使用 TAG 的片段替换来产生相同的结果。

简单例子如下图

使用 TAG 将片段 B 添加到活动中

fragmentTransaction.replace(R.id.main_fragment_container, new FragmentB(),"TAG_B");

Fragment A -> Fragment B [onBackPressed] -->Fragment A 覆盖 Activity 文件中的 onBackPressed() ，

// 检查片段 B 并且您正在查看片段 B

如果 (getSupportFragmentManager().findFragmentByTag("TAG_B")!=null) { fragmentTransaction.replace(R.id.main_fragment_container, new FragmentA(),"TAG_A");

}

Answer 4

这就是我通常处理后退按钮的方式：

// "State Machine" variables: to indicate which is the active Fragment.
private static boolean isHelpShown = false;
protected static boolean isInfoShown = false;
protected static boolean isMainShown = false;
private static boolean isViewShown = false;

// Used to switch between Fragments.
private static enum Fragments
{
    MAIN,
    VIEW,
    HELP,
    INFO
}

@Override
public final void onBackPressed()
{
    if (isMainShown)
    {
        // We're in the MAIN Fragment.
        finish();
    }
    else
    {
        // We're somewhere else, reload the MAIN Fragment.
        showFragment(Fragments.MAIN);
    }
}

private final void showFragment(final Fragments FragmentType)
{
    isViewShown = false;
    isHelpShown = false;
    isInfoShown = false;
    isMainShown = false;

    final FragmentTransaction ft =
        getSupportFragmentManager().beginTransaction();

    /*
    Replace whatever is in the fragment_container view with this
    fragment, and add the transaction to the back stack so the user can
    navigate back.
    */
    switch(FragmentType)
    {
        case HELP:
        {
            ft.replace(R.id.frgMaster, new FRG_Help());
            isHelpShown = true;
            break;
        }
        case INFO:
        {
            ft.replace(R.id.frgMaster, new FRG_Info());
            isInfoShown = true;
            break;
        }
        case VIEW:
        {
            ft.replace(R.id.frgMaster, new FRG_View());
            isViewShown = true;
            break;
        }
        case MAIN:
        {
            ft.replace(R.id.frgMaster, new FRG_Main());
            isMainShown = true;
            break;
        }
    }

    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);

    // Finalize the transaction...
    ft.commit();

    getSupportFragmentManager().executePendingTransactions();
}

如您所见，出于我的需要，我只在我们处于主片段（我退出）或不在时（我回到主片段：再次按下后退出）处理。

您可以在 onBackPressed 方法中添加更多检查，以检查您是否在另一个 Fragment 中并相应地加载另一个。