旋转设备后从 DialogFragment 接收回调时片段未附加到 Activity

Question

我正在创建一个应用程序，允许用户从图库中上传图像或使用设备相机拍照。单击适当的按钮时，会出现一个对话框，用户可以选择“拍照”或“选择图像”。这一切都很好，问题是当我在屏幕上显示对话框时旋转设备然后选择一个选项应用程序崩溃，IllegalStateException 表示我的 Fragment 未附加到 Activity。我已经包含了我用来与目标片段进行通信的 Dialog：

创建 DialogFragment：

public void onClick() {
    // Display a Dialog for choice between pick/ take picture
    ListDialogFragment dialogFragment = ListDialogFragment.newInstance(R.string.take_photo, R.array.add_picture_options_array);
    dialogFragment.setTargetFragment(this, 0);
    dialogFragment.show(getFragmentManager(), "Moo");
}

DialogFragment 类：

public class ListDialogFragment extends DialogFragment {

private static final String TITLE_RESOURCE_ID = "title_resource_id";
private static final String ARRAY_RESOURCE_ID = "array_resource_id";

private DialogItemSelectedListener listener;

public interface DialogItemSelectedListener {
    void onTakePhotoSelected();

    void onSelectImageSelected();
}

public ListDialogFragment() {
    // Default empty constructor
}

public static ListDialogFragment newInstance(@StringRes final int titleResourceId, @ArrayRes final int arrayResourceId) {
    ListDialogFragment dialogFragment = new ListDialogFragment();
    Bundle bundle = new Bundle();
    bundle.putInt(TITLE_RESOURCE_ID, titleResourceId);
    bundle.putInt(ARRAY_RESOURCE_ID, arrayResourceId);
    dialogFragment.setArguments(bundle);
    return dialogFragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    try {
        listener = (DialogItemSelectedListener) getTargetFragment();
    } catch (ClassCastException e) {
        throw new ClassCastException("Calling Fragment must implement DialogItemSelectedListener");
    }
}

@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    final int title = getArguments().getInt(TITLE_RESOURCE_ID);
    final int listItems = getArguments().getInt(ARRAY_RESOURCE_ID);

    return new AlertDialog.Builder(getActivity()).setTitle(title).setItems(listItems, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            switch (which) {
                case 0:
                    listener.onTakePhotoSelected();
                    break;
                case 1:
                    listener.onSelectImageSelected();
                    break;
                default:
                    dismiss();
            }
        }
    }).create();
}

}

片段实现DialogItemSelectedListener，并在调用onTakePhotoSelected() 时尝试执行以下操作：

private void takePicture() {
    Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    // Here, we make sure that an Activity to handle the Camera Intent actually exists
    if (cameraIntent.resolveActivity(context.getApplicationContext().getPackageManager()) != null) {
        // This is where the photo itself will actually go
        imageFile = null;
        try {
            imageFile = createImageFile();
        } catch (IOException ex) {
            // Could not create the file
        }

        // At this point, we can safely assume that the file was created successfully
        if (imageFile != null) {
            cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(imageFile));
            startActivityForResult(cameraIntent, REQUEST_IMAGE_CAPTURE);
        }
    }
}

活动：

public class TestActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.test_activity);
    attachFragment();
}

private void attachFragment() {
    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, TestFragment.newInstance()).commit();
}

}

调用startActivityForResult();时应用崩溃

java.lang.IllegalStateException: Fragment MyTestFragment{22b2a6a0} not attached to Activity

我在这里做错了什么；这种行为是可以预期的吗？ 我已经尝试过setRetainInstance(true);，但这不起作用。

Answer 1

这里的问题是，每次方向更改时，您都会创建一个新的 Fragment 实例。并且其中只有一个实际上附加到了 Activity。试试这个

    public class TestActivity extends ActionBarActivity {

    TestFragment testFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.test_activity);
        attachFragment(savedInstanceState);
    }

    private void attachFragment(Bundle savedInstanceState) {
        if (savedInstanceState == null) {
           testFragment = TestFragment.newInstance();
           getSupportFragmentManager().beginTransaction()
           .replace(R.id.fragment_container, testFragment, "testFragment").commit();
        } else {
           testFragment = (TestFragment) getSupportFragmentManager().findFragmentByTag("testFragment");
        }
    }

Answer 2

1. 使用getChildFragmentManager() 代替getFragmentManager() ;
2. 不要使用setTargetFragment()和getTargetFragment()，而是在DialogFragment中使用getParentFragment()。

这在我的情况下有效，但我应该注意我只使用其onActivityResult() 方法将值传递给片段。