Question

我有一个我已经设置的Main Fragment类。在那个Main Fragment中，我有一个带有onClick监听器的ImageView。一旦调用onClick，它就会打开一个Dialog Fragment。

在我的Dialog Fragment中，我在其中设置了一个简单的“Ok”或“Cancel”选项。一旦“好” 单击按钮，将其设置为将父活动强制转换为主片段，并执行在主片段内设置的名为“onDialogOKPressed”的方法，以便它仅响应该方法内部的代码。

我的代码中没有错误，一旦点击“确定”，我就无法看到“NullpointerException”的位置

非常感谢任何帮助，谢谢。

点击主要片段：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    final View v = inflater.inflate(R.layout.image_detail_fragment,
            container, false);

    mImageView = (RecyclingImageView) v.findViewById(R.id.imageView);
    mImageView.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            MyDialogFragment dialog = new MyDialogFragment();
            dialog.show(getActivity().getSupportFragmentManager(),
                    "MyDialogFragment");
        }

    });

    return v;
}

对话片段：

class MyDialogFragment extends DialogFragment {
private Button ButtonOk;
private Button ButtonCancel;

public MyDialogFragment() {
    // Empty constructor required for DialogFragment
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.prompt, container);
    ButtonOk = (Button) view.findViewById(R.id.button1);
    ButtonCancel = (Button) view.findViewById(R.id.button2);
    getDialog().setTitle("Set Wallpaper?");

    ButtonOk.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            ((ImageDetailFragment) (MyDialogFragment.this
                    .getParentFragment())).onDialogOKPressed();

        }

    });

    ButtonCancel.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            MyDialogFragment.this.dismiss();

        }
    });

    return view;

}
}

OnDialogOKPressed：

    public void onDialogOKPressed() {


    BitmapDrawable drawable = (BitmapDrawable) mImageView
            .getDrawable();
    Bitmap bitmap = drawable.getBitmap();


    bitmap = Bitmap.createScaledBitmap(bitmap, 950, 1000, true);



    WallpaperManager myWallpaperManager = WallpaperManager
            .getInstance(getActivity());

    try {

        myWallpaperManager.setBitmap(bitmap);
        ;
        Toast.makeText(getActivity(),
                "Wallpaper Successfully Set!", Toast.LENGTH_LONG)
                .show();
    } catch (IOException e) {
        Toast.makeText(getActivity(), "Error Setting Wallpaper",
                Toast.LENGTH_LONG).show();
    }

}

logcat的：

10-12 09:25:06.099: E/AndroidRuntime(9362):     FATAL EXCEPTION: main
10-12 09:25:06.099: E/AndroidRuntime(9362):     java.lang.NullPointerException
10-12 09:25:06.099: E/AndroidRuntime(9362):     at com.Question.ui.MyDialogFragment$1.onClick(MyDialogFragment.java:35)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.view.View.performClick(View.java:4128)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.view.View$PerformClick.run(View.java:17142)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.os.Handler.handleCallback(Handler.java:615)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.os.Handler.dispatchMessage(Handler.java:92)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.os.Looper.loop(Looper.java:213)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at android.app.ActivityThread.main(ActivityThread.java:4787)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at java.lang.reflect.Method.invokeNative(Native Method)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at  java.lang.reflect.Method.invoke(Method.java:511)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
10-12 09:25:06.099: E/AndroidRuntime(9362):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

getParentFragment()可能会返回null。

根据ParentFragment文档，如果DialogFragment附加到Activity而不是Fragment，就会发生这种情况。

Answer 2

看起来你要在弹出窗口上执行onClick事件后进行回调，我明白了吗？如果是这样，你可以在主片段中添加一个处理程序，并在Dialog Fragment的onClick（）方法中向处理程序发送一条消息。

Answer 3

public static MyHandler myHandler = new MyHandler();

public class MyHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        onDialogOKPressed()
    }
}


MyDialogFragment.myHandler.sendEmptyMessage();

如果静态处理程序无法为非静态引用调用onDialogOkPressed（）。你可以删除静态并尝试

new MyDialog().sendEmptyMessage();

将父片段强制转换为主片段时出现空指针异常

3 个答案: