android - DialogFragment使用接口(interface)回调到Target Fragment

我正试图从adialogfragment向目标fragment发送一些数据，但它不起作用。
我已经编写了以下代码，但它是通过exception编写的：

java.lang.NullPointerException: Attempt to invoke interface method 'void com.x.x.FragmentAlertDialog$Communicator.setI(java.lang.String)' on a null object reference

代码：

public class FragmentAlertDialog extends DialogFragment {

Communicator callback;

public interface Communicator {
    void setI(String name);
}

public static FragmentAlertDialog newInstance(String id, int title, int items) {
    FragmentAlertDialog frag = new FragmentAlertDialog();
    Bundle args = new Bundle();
    args.putString("id", id);
    args.putInt("title", title);
    args.putInt("items", items);
    frag.setArguments(args);
    return frag;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    callback = (Communicator) getTargetFragment();
}

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    String id = getArguments().getString("id");
    int title = getArguments().getInt("title");
    String[] items = getResources().getStringArray(getArguments().getInt("items"));
    switch (id) {
        case MainActivity.DIALOG_1:
            return new AlertDialog.Builder(getActivity())
                    .setTitle(title)
                    .setItems(items, new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            callback.setI("Important Data");
                        }
                    }).create();
    }
    return null;
}

碎片类

public class FragmentXYXY extends Fragment implements View.OnClickListener, FragmentAlertDialog.Communicator {

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.et_i:
            DialogFragment newFragment = FragmentAlertDialog.newInstance(MainActivity.DIALOG_I, R.string.i_select, R.array.i_array);
            newFragment.setTargetFragment(this, 0);
            newFragment.show(getFragmentManager(), "dialog");
    }
}

@Override
public void setI(String name) {
    textI.setText(name);
}

有人能帮忙吗？
谢谢你
代码修改-newfragment.setTargetFragment（this，0）；

最佳答案

你必须打电话setTargetFragment

setTargetFragment(this, 0);

为了获得FragmentXYXY中的参考。

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.et_i:
            DialogFragment newFragment = FragmentAlertDialog.newInstance(MainActivity.DIALOG_I, R.string.i_select, R.array.i_array);
            newFragment.setTargetFragment(this, 0);
            newFragment.show(getFragmentManager(), "dialog");
    }
}