android - 显示在 android 中按下的隐藏 fragment onbackkey

Question

我在做什么::

• 我在按下 Actionbar 按钮时将 fragment 添加到容器中 同时我隐藏了之前的 fragment
• 现在按下后退键我只想显示隐藏的 fragment

发生了什么::

• 不再显示之前的 fragment ，而是删除了整个 Activity
• 如何克服这个问题
• 我也试过 onBackpressed ... 还是一样的结果

发生此操作的代码::

}else if(item.getItemId()==R.id.searchID){
            /*Intent intent=new Intent(MainActivity.this,SearchActivity.class);
            startActivity(intent);*/

            ft1=getSupportFragmentManager().beginTransaction();
            ft1.hide(fragment1);
            ft1.add(R.id.content_frame, fragSearch);
            ft1.commit();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }    


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        if (keyCode == KeyEvent.KEYCODE_BACK)
        {
            ft1=getSupportFragmentManager().beginTransaction();
            ft1.show(fragment1);
            ft1.commit();
        }
        return super.onKeyDown(keyCode, event);
    }

{完整代码}

MainActivity.java

 public class MainActivity extends SherlockFragmentActivity implements OnItemClickListener{

        private DrawerLayout drawlayout=null;
        private ListView listview=null;
        private ActionBarDrawerToggle actbardrawertoggle=null;

        FragmentTransaction ft1 ;
        FragSearch fragSearch=new FragSearch();
        mFragSortingHome fragment1=new mFragSortingHome();

        private String[] myfriendname=null;
        private int[] photo=null;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.drawer_activity_main);
            //Code moved to a seperate function from onCreate with a call in it for clarity
            drawerConfig(savedInstanceState);

        }

        @Override
        protected void onPostCreate(Bundle savedInstanceState) {
            super.onPostCreate(savedInstanceState);
            actbardrawertoggle.syncState();
        }

        @Override
        public void onConfigurationChanged(Configuration newConfig) {
            super.onConfigurationChanged(newConfig);
            actbardrawertoggle.onConfigurationChanged(newConfig);
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {

            if(item.getItemId()==android.R.id.home)
            {
                if(drawlayout.isDrawerOpen(listview))
                {
                    drawlayout.closeDrawer(listview);
                }
                else {
                    drawlayout.openDrawer(listview);
                }
            }else if(item.getItemId()==R.id.searchID){
                /*Intent intent=new Intent(MainActivity.this,SearchActivity.class);
                startActivity(intent);*/

                ft1=getSupportFragmentManager().beginTransaction();
                ft1.hide(fragment1);
                ft1.add(R.id.content_frame, fragSearch);
                ft1.commit();
                return true;
            }
            return super.onOptionsItemSelected(item);
        }    


        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event)
        {
            if (keyCode == KeyEvent.KEYCODE_BACK)
            {
                ft1=getSupportFragmentManager().beginTransaction();
                ft1.show(fragment1);
                ft1.commit();
            }
            return super.onKeyDown(keyCode, event);
        }
.             .            .      .
. . . . . other code . . .. . . . . .
.            .           .       .

{编辑}

else if(item.getItemId()==R.id.searchID){
            /*Intent intent=new Intent(MainActivity.this,SearchActivity.class);
            startActivity(intent);*/

            ft1=getSupportFragmentManager().beginTransaction();
            //ft1.hide(fragment1);
            ft1.add(R.id.content_frame, fragSearch);
            ft1.addToBackStack(null);
            ft1.commit();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }    

    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        if (keyCode == KeyEvent.KEYCODE_BACK)
        {
            getSupportFragmentManager().popBackStack();
        }
        return super.onKeyDown(keyCode, event);
    }

---

我可以回到之前的 fragment ，但 Activity 也立即被删除，我无法阻止 Activity 被删除

Answer 1

在返回时尝试弹出当前 fragment 以显示前一个 fragment

public boolean onKeyDown(int keyCode, KeyEvent event)
        {
            if (keyCode == KeyEvent.KEYCODE_BACK)
            {
                getActivity().getSupportFragmentManager().popBackStack();
            }
            return super.onKeyDown(keyCode, event);
        }

当添加一个 fragment 时，你也应该将它添加到backstack..所以放在ft1.commit()之前;

ft1.addToBackStack(null);