保存选项卡内的片段状态 [英] Save fragment state inside a Tab

问题描述

我做了个动作条有两个选项卡 - 一个用于afragment和bfragment。 afragment包含一个按钮。点击afragment按钮，将导致其改为cfragment。但是，单击选项卡再次结果afragment被再次加载。我可以做prevent这算什么，基本上到标签，说：当有人点击你，加载最后一个片段的状态（在这种情况下，cfragment）？

I made an ActionBar with two tabs - one for afragment and bfragment. afragment contains a button. Clicking the button on afragment will result it to change to cfragment. However, clicking the tab again results to afragment being loaded again. What can I do to prevent this, to essentially say to the tab, "When somebody clicks on you, load the last fragment state (in this case, cfragment)?"

这是我的MainActivity.java：

This is my MainActivity.java:

public class MainActivity extends Activity {

public static Context appContext;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    appContext = getApplicationContext();

    //ActionBar
     ActionBar actionbar = getActionBar();
     actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

     ActionBar.Tab PlayerTab = actionbar.newTab().setText("Fragment A");
     ActionBar.Tab StationsTab = actionbar.newTab().setText("Fragment B");

     Fragment PlayerFragment = new AFragment();
     Fragment StationsFragment = new BFragment();

     PlayerTab.setTabListener(new MyTabsListener(PlayerFragment));
     StationsTab.setTabListener(new MyTabsListener(StationsFragment));

     actionbar.addTab(PlayerTab);
     actionbar.addTab(StationsTab);
}

我TabListener：

My TabListener:

class MyTabsListener implements ActionBar.TabListener {
public Fragment fragment;

public MyTabsListener(Fragment fragment) {
    this.fragment = fragment;
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    Toast.makeText(MainActivity.appContext, "Reselected!", Toast.LENGTH_LONG).show();
}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    ft.replace(R.id.fragment_container, fragment);
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    ft.remove(fragment);
}
}

最后，我AFragment.java：

And finally, my AFragment.java:

public class AFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.afragment, container, false);
    Button mButton = (Button) view.findViewById(R.id.button1);
    mButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            CFragment fragment = new CFragment();
            fragmentTransaction.replace(R.id.fragment_container, fragment);
            fragmentTransaction.commit();
        }
    });
    return view;
}
}

我如何保存cfragment到标签以这样一种方式，点击第一个选项卡将不会导致再次afragment加载？谢谢你。

How do I save cfragment into the tab in such a way that clicking the first tab would not result to afragment loading again? Thank you.

推荐答案

的状态不会被保存，因为你每次更换标签时添加一个新的片段。

The state is not being saved because you are adding a new fragment every time you change tabs.

在'onTabUnselected`，不要删除，但分离/隐藏

In 'onTabUnselected`, don't remove, but detach/hide

public void onTabUnselected(Tab tab, FragmentTransaction ft) {
  if (fragment != null) {
    ft.detach(fragment); 
  }
}

而在 onTabSelected ，请检查是否片段，而不是已经存在的替换

And in onTabSelected, check to see if the fragment exists already instead of replacing

public void onTabSelected(Tab tab, FragmentTransaction ft) {
  fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
  if( fragment == null ) {
    fragment = Fragment.instantiate(mActivity, mClass.getName());
    ft.add(R.id.fragment_container, fragment, tag);
  } else {
    ft.attach(fragment);
  }
}

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