Question

让我们考虑一下Fragment A和Fragment B的情况。

B声明：

public interface MyInterface {
    public void onTrigger(int position);
}

A实现了这个界面。

将Fragment B推入堆栈时，如何在Fragment A中为Bundle传递A的引用，以便onTrigger可以在需要时获得A回调。

我的用例场景是ListView有B个项目，ViewPager有B -> A个项目。两者都包含相同的项目，当用户在弹出B之前从A开始时，它应触发ListView的回调，以更新它的B位置以匹配{{ 1}}寻呼机位置。

感谢。

Answer 1

Passing interface to Fragment

我认为您正在两个Fragment

之间进行通信

为了做到这一点，您可以查看Communicating with Other Fragments

public class FragmentB extends Fragment{
    MyInterface mCallback;

    // Container Activity must implement this interface
    public interface MyInterface {
        public void onTrigger();
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (MyInterface ) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement MyInterface ");
        }
    }

    ...
}

Answer 2

对于Kotlin 1.0.0-beta-3595

interface SomeCallback {}

class SomeFragment() : Fragment(){

    var callback : SomeCallback? = null //some might want late init, but I think this way is safer

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        callback = activity as? SomeCallback //returns null if not type 'SomeCallback'

        return inflater!!.inflate(R.layout.frag_some_view, container, false);
    }
}

Answer 3

两个片段仅通过活动进行通信是最佳的。因此，您可以在活动中实现的Fragment B中定义接口。然后在活动中，在接口方法中定义要在片段A中发生的内容。

在片段B中，

MyInterface mCallback;
 public interface MyInterface {
        void onTrigger(int position);
    }

@Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (MyInterface) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement MyInterface");
        }
}

确定用户是否从B到A的方法

public void onChangeFragment(int position){
//other logic here
 mCallback.onTrigger(position);
}

在活动中，

public void onTrigger(int position) {
    //Find listview in fragment A
    listView.smoothScrollToPosition(position);
    }

古德勒克！

Answer 4

使用@Amit的回答，并适应OP问题，以下是所有相关代码：

public class FragmentA extends BaseFragment implements MyInterface {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        // THIS IS JUST AN EXAMPLE OF WHERE YOU MIGHT CREATE FragmentB
        FragmentB myFragmentB = new FragmentB();        
    }


    void onTrigger(int position){
        // My Callback Happens Here!
    }
}

...

public class FragmentB extends BaseFragment {

    private MyInterface callback;

    public interface MyInterface {
        void onTrigger(int position);
    }   

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            callback = (MyInterface ) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement MyInterface");
        }
    }
}

Answer 5

我认为您应该使用交流方式，如下所述。这段代码来自this Android Dev page of communication between Fragments：

标题片段

public class HeadlinesFragment extends ListFragment {
OnHeadlineSelectedListener mCallback;

public void setOnHeadlineSelectedListener(Activity activity) {
    mCallback = activity;
}

// Container Activity must implement this interface
public interface OnHeadlineSelectedListener {
    public void onArticleSelected(int position);
}

// ...
}

MainActivity

public static class MainActivity extends Activity
    implements HeadlinesFragment.OnHeadlineSelectedListener{
// ...

@Override
public void onAttachFragment(Fragment fragment) {
    if (fragment instanceof HeadlinesFragment) {
        HeadlinesFragment headlinesFragment = (HeadlinesFragment) fragment;
        headlinesFragment.setOnHeadlineSelectedListener(this);
    }
}

public static class MainActivity extends Activity
    implements HeadlinesFragment.OnHeadlineSelectedListener {
...

public void onArticleSelected(int position) {
    // The user selected the headline of an article from the HeadlinesFragment
    // Do something here to display that article
}

将接口传递给Fragment

5 个答案: