android - 如果已经添加了 fragment ......如何重新加载它

Question

我在做什么::

• 我正在从 actionbar 启动一个项目的 fragment onClick

发生了什么::

• 我能够第一次启动 fragment 。

• 现在，当我第二次单击操作栏菜单项时。我是得到日志中显示的错误

• 应该发生的是我应该重新加载 fragment ，如果它已经在容器中

• 如果 fragment 已经添加了如何重新加载

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



        @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getSupportMenuInflater();
        menuInflater.inflate(R.menu.actionbar_sort_menu, menu);

        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) {
        selectItem(position);

    }

    private void drawerConfig(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        myfriendname = new String[] { "Home", "Login","List", "Photo", "Filter" };
        photo = new int[] { R.drawable.ic_action_map, R.drawable.ic_action_accounts, R.drawable.ic_action_view_as_list, R.drawable.ic_action_photo, R.drawable.ic_action_photo};

        drawlayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        listview = (ListView) findViewById(R.id.listview_drawer);

        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setDisplayShowTitleEnabled(true);

        drawlayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
        drawlayout.setBackgroundColor(Color.WHITE);

        DrawerMenuListAdapter menuadapter=new DrawerMenuListAdapter(getApplicationContext(), myfriendname, photo); 
        listview.setAdapter(menuadapter);

        actbardrawertoggle= new ActionBarDrawerToggle(this, drawlayout, R.drawable.ic_drawer, R.string.drawer_open, R.string.drawer_close)
        {
            public void onDrawerClosed(View view) {
                super.onDrawerClosed(view);
            }

            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);

            }

        };
        drawlayout.setDrawerListener(actbardrawertoggle);

        listview.setOnItemClickListener(this);

        if (savedInstanceState == null) {
            selectItem(0);
        }
    }

    private void selectItem(int position) {

        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();

        // Locate Position
        switch (position) {
        case 0:
            mFragSortingHome fragment1=new mFragSortingHome();
            ft.replace(R.id.content_frame, fragment1);/*
            Bundle b = new Bundle();
            b.putString("name",myfriendname[position]);
            b.putInt("photo",photo[position]);
            fragment1.setArguments(b);*/
            break;
        case 1:
            FilterBuffetFragment fragment2=new FilterBuffetFragment();
            ft.replace(R.id.content_frame, fragment2);/*
            Bundle b1 = new Bundle();
            b1.putString("name",myfriendname[position]);
            b1.putInt("photo",photo[position]);
            fragment2.setArguments(b1);*/
            break;
        case 2:
            mFragment3 fragment3=new mFragment3();
            ft.replace(R.id.content_frame, fragment3);/*
            Bundle b2 = new Bundle();
            b2.putString("name",myfriendname[position]);
            b2.putInt("photo",photo[position]);
            fragment3.setArguments(b2);*/
            break;
        case 3:
            mFragment4 fragment4=new mFragment4();
            ft.replace(R.id.content_frame, fragment4);/*
            Bundle b3 = new Bundle();
            b3.putString("name",myfriendname[position]);
            b3.putInt("photo",photo[position]);
            fragment4.setArguments(b3);*/
            break;
        case 4:
            FilterBuffetFragment fragment5=new FilterBuffetFragment();
            ft.replace(R.id.content_frame, fragment5);
            ft.addToBackStack(null);/*
            Bundle b4 = new Bundle();
            b4.putString("name",myfriendname[position]);
            b4.putInt("photo",photo[position]);
            fragment5.setArguments(b4);*/
            break;

        }
        ft.commit();
        listview.setItemChecked(position, true);
        /*setTitle(myfriendname[position]);*/
        drawlayout.closeDrawer(listview);
    }

}

我正在加载操作栏项目的 fragment oncick 的代码是

}else if(item.getItemId()==R.id.searchID){
            //SEARCH Button Handling
            ft1=getSupportFragmentManager().beginTransaction();
            ft1.hide(fragment1);
            ft1.add(R.id.content_frame, fragSearch);
            ft1.addToBackStack(null);
            ft1.commit();
            return true;

日志::

05-04 00:42:01.896: E/AndroidRuntime(2253): FATAL EXCEPTION: main
05-04 00:42:01.896: E/AndroidRuntime(2253): java.lang.IllegalStateException: Fragment already added: FragSearch{415a4748 #1 id=0x7f04003e}
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1159)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:616)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:429)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.os.Handler.handleCallback(Handler.java:605)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.os.Handler.dispatchMessage(Handler.java:92)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.os.Looper.loop(Looper.java:137)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at android.app.ActivityThread.main(ActivityThread.java:4340)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at java.lang.reflect.Method.invokeNative(Native Method)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at java.lang.reflect.Method.invoke(Method.java:511)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-04 00:42:01.896: E/AndroidRuntime(2253):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

使用 FragmentManager.findFragmentById 或 FragmentManager.findFragmentByTag 查找您已添加的 fragment 。如果这些方法返回 null，则 fragment 尚未添加，您可以像现在一样继续操作。当这些方法找到该 fragment 时，您就有了一个可以使用的引用:设计您的 fragment 类以具有 reload 方法或类似方法，您可以在这种情况下调用它。