Android 从库中选择第二个图像时传递结果时出错

我正在尝试用项目列表完成我的第一个示例应用程序。为了使我在stackoverflow上找到的列表中的每个项目都有自己的图像，我使用了以下代码：

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
        Uri selectedImage = data.getData();
        String[] filePathColumn = {MediaStore.Images.Media.DATA};

        Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
        cursor.moveToFirst();

        int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
        picturePath = cursor.getString(columnIndex);
        cursor.close();

        main_datasource.pic.setPicturePath(picturePath);
    }
}

它的作品伟大，我可以选择图像，但只有一次。 当我尝试第二次选择时，会弹出以下错误：

11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime  FATAL EXCEPTION: main
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime  java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://media/external/images/media/2 }} to activity {example.CustomAdapter/example.CustomAdapter.MainActivity}: java.lang.NullPointerException
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread.deliverResults(ActivityThread.java:2532)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread.handleSendResult(ActivityThread.java:2574)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread.access$2000(ActivityThread.java:117)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:961)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.os.Handler.dispatchMessage(Handler.java:99)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.os.Looper.loop(Looper.java:123)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread.main(ActivityThread.java:3683)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at java.lang.reflect.Method.invokeNative(Native Method)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at java.lang.reflect.Method.invoke(Method.java:507)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at dalvik.system.NativeStart.main(Native Method)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime  Caused by: java.lang.NullPointerException
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at example.CustomAdapter.MainActivity.onActivityResult(MainActivity.java:303)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.Activity.dispatchActivityResult(Activity.java:3908)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      at android.app.ActivityThread.deliverResults(ActivityThread.java:2528)
11:14:41.472    1212    example.CustomAdapter   ERROR   AndroidRuntime      ... 11 more

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由于我是一个新的家伙在安卓你能帮我更新这个代码的方式时，我将能够选择图像。如果有人能向我解释一下这段代码是如何工作的，这也会非常有用。

你明白了吗？我也有同样的问题。