Question

我只是在学习Android开发。目前，我正在练习活动和片段之间的沟通，并处理他们的结果。我有一个关于以下情况的问题：ActivityA启动托管FragmentB的ActivityB，而ActivityA希望得到结果。我经常看到以下代码：

// ActivityA start ActivityB code
Intent i = new Intent(getActivity(), ActivityB.class);
i.putExtra(FragmentB.EDIT_TEXT, textView.getText());
startActivityForResult(i, REQUEST_CODE);

// FragmentB (hosted by ActivityB) set result code
Intent i = new Intent();
i.putExtra(EDIT_TEXT, value);
setResult(Activity.RESULT_OK, i);
finish();

// ActivityA handle result code
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  if (requestCode == REQUEST_CODE && resultCode == Activity.RESULT_OK) {
    CharSequence val = data.getCharSequenceExtra(FragmentB.EDIT_TEXT);
    textView.setText(val);
  }
}

这对我来说看起来不是一个干净的方法，因为ActivityA必须知道ActivityB的实现细节 - 即主机FragmentB。我提出了一个更简洁的方法是在FragmentB和ActivityB之间放置一个接口：ActivityB实现了FragmentB的接口。当ActivityB可以完成自己时，FragmentB会调用此接口的方法（我尝试使代码尽可能短： - ）：

public class ActivityA extends Activity {

  private static final int REQUEST_CODE = 1;

  private TextView textView;

  private void startEditActivity() {
    Intent i = new Intent(getActivity(), ActivityB.class);
    i.putExtra(ActivityB.EDIT_TEXT, textView.getText());
    startActivityForResult(i, REQUEST_CODE);
  }

  @Override
  public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_CODE && resultCode == Activity.RESULT_OK) {
      CharSequence val = data.getCharSequenceExtra(ActivityB.EDIT_TEXT);
      textView.setText(val);
    }
  }

}

public class ActivityB extends Activity
  implements FragmentB.OnEditSetListener
{
  public final static String EDIT_TEXT = "nl.michiel.testapp.editTextActivity";

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    CharSequence val = getIntent().getCharSequenceExtra(EDIT_TEXT);

    getFragmentManager().beginTransaction()
      .add(R.id.fragmentContainer, FragmentB.newInstance(val))
      .commit();
    }
  }

  @Override
  public void onEditSet(CharSequence value) {
    Intent i = new Intent();
    i.putExtra(EDIT_TEXT, value);
    setResult(Activity.RESULT_OK, i);
    finish();
  }

}

public class FragmentB extends Fragment {

  public final static String EDIT_TEXT = "nl.michiel.testapp.editTextFragment";

  private CharSequence value;
  private EditText editText;
  private OnEditSetListener editSetListener;

  public interface OnEditSetListener {
    public void onEditSet(CharSequence val);
  }

  public static FragmentB newInstance(CharSequence value) {
    FragmentB fragment = new FragmentB();
    Bundle args = new Bundle();
    args.putCharSequence(EDIT_TEXT, value);
    fragment.setArguments(args);
    return fragment;
  }

  @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    if (activity instanceof OnEditSetListener) {
      editSetListener = (OnEditSetListener)activity;
    } else {
      throw new ClassCastException(activity.toString()
        + " must implement OnEditSetListener");
    }
  }

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    value = getArguments().getCharSequence(EDIT_TEXT);
  }

  // Called when edit has finished, for example after a button click
  private void editFinished() {
    editSetListener.onEditSet(editText.getText());
  }

}

这是一个很好的解决方案，还是有一些常用的方法来处理这些情况？

从托管片段的Android活动中获取结果

0 个答案: