使用回撥介面將事件傳送回活動

如果需要將事件從片段傳送到活動，可能的解決方案之一是定義回撥介面並要求主機活動實現它。

例

單擊片段按鈕時，將回撥傳送到活動

首先，定義回撥介面：

public interface SampleCallback {
    void onButtonClicked();
}

下一步是在片段中分配此回撥：

public final class SampleFragment extends Fragment {

    private SampleCallback callback;

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof SampleCallback) {
            callback = (SampleCallback) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement SampleCallback");
        }
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.sample, container, false);
        // Add button's click listener
        view.findViewById(R.id.actionButton).setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                callback.onButtonClicked(); // Invoke callback here
            }
        });
        return view;
    }
}

最後，在 activity 中實現回撥：

public final class SampleActivity extends Activity implements SampleCallback {

    // ... Skipped code with settings content view and presenting the fragment

    @Override
    public void onButtonClicked() {
        // Invoked when fragment's button has been clicked
    }
}