在 Android 中使用片段时处理后按 [英] Handling back press when using fragments in Android

问题描述

我在我的应用程序中使用带有导航抽屉的 Android 滑动菜单，并且在应用程序中使用片段而不是活动.当我打开抽屉时，单击一个出现片段的项目.我使用以下代码从一个片段移动到另一个片段:

I am using Android Sliding Menu using Navigation Drawer in my application and Fragments are used in the app instead of Activities. When I open the drawer, click on an item a Fragment appears. I move from one fragment to another fragment using the following code:

Fragment fragment = null;
fragment = new GalleryFragment(selectetdMainMenu.getCategoryID());
                    FragmentTransaction ft = getFragmentManager().beginTransaction();
                    ft.addToBackStack("menuFrag");
                    ft.add(R.id.frame_container, fragment, "menuFrag");
                    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
                    ft.commit();

通过这种方式，我可以从一个片段转到另一个片段，但在按下后退按钮时我无法到达前一个片段.我设法想出了这段代码来处理初始化抽屉的 MainActivity 中的后按:

In this way I can go from one fragment to another but I fail to come to the previous fragment on back button press. I managed to come up with this code to handle back press in MainActivity where Drawer is Initialized:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    super.onKeyDown(keyCode, event);
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        Fragment fragment_byTag = fragmentManager.findFragmentByTag("menuFrag");
        Fragment menuFragment_by_tag = fragmentManager.findFragmentByTag("galleryFrag");
        Fragment commentsFrag_by_tag = fragmentManager.findFragmentByTag("commentsFrag");
        Fragment dealDetail = fragmentManager.findFragmentByTag("promoFrag");
            if(commentsFrag_by_tag != null){
                if (commentsFrag_by_tag.isVisible()) {
                    Log.e("comments back  ", " clicked");
                    //menuDetailsFrag.onBackPressed();
                    FragmentManager fragmentManager = getSupportFragmentManager();
                    fragmentManager.beginTransaction().remove(commentsFrag_by_tag).commit();
                    fragmentManager.beginTransaction().show(menuFragment_by_tag).commit();
                }
            }else if(menuFragment_by_tag.isVisible()){
                Log.e("menu back  ", " clicked");
                menuDetailsFrag.onBackPressed();
                FragmentManager fragmentManager = getSupportFragmentManager();
                fragmentManager.beginTransaction().remove(menuFragment_by_tag).commit();
                fragmentManager.beginTransaction().show(fragment_byTag).commit();
            }
        }



    return false;
}

这有时有效，但大部分时间都失败了.如果可以显示更好的导航方式，我将不胜感激.

This works at times but fails most of the time. I would greatly appreciate if a better way to navigate back can be shown.

推荐答案

我通常在onResume中的View中设置一个onKeyListener.根据我了解到的情况，您必须注意在 View 上设置 setFocusableInTouchMode() 和 requestFocus.

I usually set an onKeyListener to the View in onResume. From what I learned you have to take care to set setFocusableInTouchMode() and requestFocus on the View.

这是我用于此目的的示例:

This is a sample of what I use for this purpose:

@Override
public void onResume() {

    super.onResume();

    getView().setFocusableInTouchMode(true);
    getView().requestFocus();
    getView().setOnKeyListener(new View.OnKeyListener() {
        @Override
        public boolean onKey(View v, int keyCode, KeyEvent event) {

            if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){

                // handle back button

                return true;

            }

            return false;
        }
    });
}

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