相关疑难解决方法(0)

我的Android应用由三个片段:A,B和C.它们被加载到MainActivity布局中定义的两个容器中.

当应用程序启动时,它会显示在left_container中加载的fragmentA和在right_container中加载的fragmentC.

如果按在按钮fragmentA,一个FragmentTransaction改变FragmentC通过FragmentB.

一切都好.但是当我尝试使用加载的fragmentB的引用时出现问题 findFragmentByTag(),因为它返回null.我已经使用了方法替换,FragmentTransaction并且我已经完成了它commit(),但是没有办法调用FragmentB方法.我的代码:

MainActivity.java:

 public class MainActivity extends Activity{
 static String fragmentTag = "FRAGMENTB_TAG";

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    //Adds the left container's fragment
    getFragmentManager().beginTransaction().add(R.id.left_container, new FragmentA()).commit(); //Adds the fragment A to the left container

    //Adds the right container's fragment
    getFragmentManager().beginTransaction().add(R.id.right_container, new FragmentC()).commit(); //Adds the Fragment C …

我想从FragmentActivity中更改片段中的ImageView(在代码中创建).(XML中没有片段和标记).

从FragmentActivity扩展的MainActivity和从GooglePlayServicesClient.ConnectionCallbacks实现的:

...
FragmentAdapter mAdapter;
ViewPager mPager;
...

public void onCreate(Bundle savedInstanceState){
    ...
    FragmentManager fm = getSupportFragmentManager();
    mAdapter = new FragmentAdapter(fm);
    mPager.setAdapter(mAdapter);
    ...}

@Override
public void onConnected(Bundle connectionHint){
//*** I want to change a ImageView on Fragment1 here
}

从FragmentPagerAdapter扩展的FragmentAdapter:

...
private FragmentManager mFragmentManager;

public FragmentAdapter(FragmentManager fm){
    super(fm);
}

@Override
public Fragment getItem(int pos){
// String name = makeFragmentName(R.id.mainPager, pos);
// Fragment fragmentObject = mFragmentManager.findFragmentByTag(name);
Fragment fragmentObject = null;

switch(pos){
    case 0:
        fragmentObject = new Fragment1();
        break;
    ...
}

return …