Question

我有一个有接口的片段，所以我可以将其他事件转发给其他片段。

public class MyFragment extends Fragment {
    private MyListener mListener;

    public interface MyListener {
        public void doSomething(View o);
    }
}

然后我在按钮

上使用它

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
       mListener.doSomething(v);       
    }
});

但由于未分配，因此返回null。那么如何在当前片段上分配我的界面呢？

如果我想在另一个片段上实现这个怎么办？这可能吗？

public class AnotherFragment extends Fragment implements MyFragment.MyListener {
    @Override
    public void doSomething(View o){}      
}

Answer 1

试试这个

    @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 {
        mListener= (MyListener ) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement MyListener ");
    }
}

Answer 2

使用onAttach（）方法。来自谷歌的片段指南：

public static class MyFragment extends Fragment {
MyListener mListener;
...
@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    mListener = (MyListener) activity;    // <-- For this to work, you need to implement your interface in the activity
}
...
}

也不要忘记在onDetach（）中将引用归零

@Override
public void onDetach() {
  super.onDetach();
  mListener = null;
}

Answer 3

因为您的mListener为空 - >必须创造。要使用界面：

AnotherFragment abc = new AnotherFragment ();
mListener = abc;

然后你可以致电：mListener.doSomething(v)

在片段内分配接口

3 个答案: