Android 中如何实现 Fragment 和 Adapter 之间的通信？

Interface Implementation between Fragment and Adapter

In the realm of Android development, interfacing between fragments and adapters is a common task. To facilitate this, a custom CursorAdapter can be employed with an adapter interface embedded within. This interface serves as a communication channel between the adapter and the fragment.

Consider a scenario where a fragment (MyListFragment) contains a ListView and a customized CursorAdapter. Each row in the list contains a button, and upon clicking it, an action needs to be performed in the fragment. To achieve this, an interface, AdapterInterface, is defined within the adapter.

public class MyListAdapter extends CursorAdapter {

    public interface AdapterInterface {
        public void buttonPressed();
    }

    private AdapterInterface buttonListener;

    // ...
}

Within the adapter's bindView method, an OnClickListener is set for the button in each row.

@Override
public void bindView(final View view, final Context context, final Cursor cursor) {
    // ...
    holder.button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            // some action
            // need to notify MyListFragment
            if (buttonListener != null) {
                buttonListener.buttonPressed();
            }
        }
    });
}

The AdapterInterface should be implemented in the fragment (MyListFragment) to handle the button click event.

public class MyListFragment extends Fragment implements AdapterInterface {

    @Override
    public void buttonPressed() {
        // some action
    }
}

To establish communication between the adapter and fragment, a new constructor is introduced in the adapter, along with an instance variable to hold the interface reference.

AdapterInterface buttonListener;

public MyListAdapter (Context context, Cursor c, int flags, AdapterInterface buttonListener)
{
  super(context,c,flags);
  this.buttonListener = buttonListener;
}

When creating the adapter, the fragment is passed as the argument to the constructor to provide the interface implementation.

MyListAdapter adapter = new MyListAdapter (getActivity(), myCursor, myFlags, this);

This approach ensures that when the button in the adapter is clicked, the buttonPressed method in the fragment is invoked, facilitating the desired communication between the adapter and the fragment.

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