android – Nullpointerexcepiton在光标上从对话框片段的画廊中选择照片

我正试图通过DialogFragment从图库中选择照片.但是我在初始化游标时遇到了nullpointerexception.任何想法为什么会出现此错误？

以下是我的代码：

if (resultCode == Activity.RESULT_OK) {
        Uri selectedImage = imageReturnedIntent.getData();
        String[] filePathColumn = {MediaStore.Images.Media.DATA};
        // Nullpointerexcepiton on this line
        Cursor cursor = getActivity().getContentResolver().query(selectedImage, filePathColumn, null, null, null);
        cursor.moveToFirst();
        int columnIndex = cursor.getColumnIndex(filePathColumn[0]);

        cursor.close();

    }

这是我的logcat错误：

03-24 12:34:37.645: E/AndroidRuntime(21479): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=65538, result=-1, data=Intent { dat=content://media/external/images/media/3890 flg=0x1 }} to activity {com.example/com.example.MainActivity}: java.lang.NullPointerException

    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread.deliverResults(ActivityThread.java:3462)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3505)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread.access$1100(ActivityThread.java:150)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1346)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.os.Handler.dispatchMessage(Handler.java:99)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.os.Looper.loop(Looper.java:213)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread.main(ActivityThread.java:5225)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at java.lang.reflect.Method.invokeNative(Native Method)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at java.lang.reflect.Method.invoke(Method.java:525)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at dalvik.system.NativeStart.main(Native Method)

    03-24 12:34:37.645: E/AndroidRuntime(21479): Caused by: java.lang.NullPointerException
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at com.example.MainDialogFragment.onActivityResult(MainDialogFragment.java:226)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at com.example.MainActivity.onActivityResult(DelictActivity.java:85)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.Activity.dispatchActivityResult(Activity.java:5322)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    at android.app.ActivityThread.deliverResults(ActivityThread.java:3458)
    03-24 12:34:37.645: E/AndroidRuntime(21479):    ... 11 more

你如何开始你的活动,从哪里开始？
如果您通过MainActivity传递结果,可以尝试在DialogFragment中创建一个新函数,如下所示：

public void onMyActivityResult(Context main, int resultCode... an so on){

     main.getContentResolver.......

}

编辑：
我这样做了：

获取onCreate中的活动：

@Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mActivity = (MainActivity) this.getActivity();
    }

然后：

@Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
       if (requestCode == REQUEST_GALLERY && resultCode == Activity.RESULT_OK) {
           ...

            Uri selectedImage = data.getData();
            String path = getRealPathFromURI(selectedImage);
           ...
            reloadImages();

        }
        super.onActivityResult(requestCode, resultCode, data);
        }

和：

private String getRealPathFromURI(Uri contentURI) {
    Cursor cursor = mActivity.getContentResolver().query(contentURI, null, null, null, null);
    if (cursor == null) { // Source is Dropbox or other similar local file
                  // path
        return contentURI.getPath();
    } else {
        cursor.moveToFirst();
        int idx = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
        String path = cursor.getString(idx);
        cursor.close();
        return path;
    }
    }