Nullpointerexcepiton在光标上，同时从对话框片段上的图库中选择照片 [英] Nullpointerexcepiton on cursor while selecting photo from gallery on dialog fragment

问题描述

我正在尝试通过 DialogFragment 从图库中选择照片。但是在初始化 cursor 时，我得到 nullpointerexception 。有什么想法为什么会得到这个错误？

I'm trying to select photo from gallery through DialogFragment. But I'm getting nullpointerexception while initializing cursor. Any ideas why getting this error?

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：

Here is my logcat error :

    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

推荐答案

如何开始你的活动，从哪里开始？
如果你通过MainActivity传递你的结果，你可以尝试在你的DialogFragment中创建一个新的函数，如下所示：

How do you start your Activity and from where? If you pass your result trough your MainActivity, you can try to make a new function in your DialogFragment like this:

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

     main.getContentResolver.......

}

编辑：
i这样做：

i have done it in this way:

在onCreate中获取活动：

Get the Activity in onCreate:

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

那么：

     @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;
    }
    }

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