Android:空对象引用上的android.database.Cursor.moveToFirst()' [英] Android: android.database.Cursor.moveToFirst()' on a null object reference
本文介绍了Android:空对象引用上的android.database.Cursor.moveToFirst()'的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在研究照片应用程序，我想在我的项目中实现cirople裁剪器，但是我对片段和裁剪器类有疑问.当我选择图片并按裁剪按钮，然后旋转片段后，我出现此错误:
I'm working about photo application and i want to implement cirlcle cropper in my project, but i have a problem about my fragment and cropper class. When i'm selected picture and press crop button and after turning fragment i'm giving this error:
06-04 02:09:34.595 21914-21914/com.stamplessapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.stamplessapp, PID: 21914
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=131094, result=-1, data=Intent { dat=file:///storage/emulated/0/Pictures/Stampless/IMG_20160604_020934.jpg }} to activity {com.stamplessapp/com.stamplessapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean android.database.Cursor.moveToFirst()' on a null object reference
at android.app.ActivityThread.deliverResults(ActivityThread.java:4058)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4101)
at android.app.ActivityThread.access$1400(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1497)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean android.database.Cursor.moveToFirst()' on a null object reference
at com.stamplessapp.ProfileFragment.onActivityResult(ProfileFragment.java:582)
at android.support.v4.app.FragmentActivity.onActivityResult(FragmentActivity.java:176)
at android.app.Activity.dispatchActivityResult(Activity.java:6543)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4054)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4101)
at android.app.ActivityThread.access$1400(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1497)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
圆形割草机活动需要上下文，而我正在这样的片段上下文中:
Circle cropper activity want context and i'm getting in fragment context like this:
private static Context myContext;
...
OnCreate();
myContext = getActivity().getApplicationContext();
...
public static Context getAppContext() {
return ProfileFragment.myContext;
}
这是错误:
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean android.database.Cursor.moveToFirst()' on a null object reference
这是农作物活动
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_circle_crop);
Intent intent = getIntent();
final CropImageLayout mCropLayout = (CropImageLayout) findViewById(R.id.cil_crop);
mCropLayout.setImageUri(intent.getData());
context = ProfileFragment.getAppContext();
Uri imageUri = intent.getData();
try {
mBitmap = MediaStore.Images.Media.getBitmap(context.getContentResolver(),imageUri);
}catch(IOException ex) {
//Do something witht the exception
}
findViewById(R.id.btn_crop).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCropLayout.saveOutput(new CropImageLayout.CropListener() {
@Override
public void onSuccess(Uri saveUri) {
Intent intent = new Intent();
intent.setData(saveUri);
setResult(RESULT_OK, intent);
finish();
}
这是我的Fragment获取代码:
And here is my Fragment get code:
else if (requestCode == REQUEST_CROP && resultCode == Activity.RESULT_OK&& null != data) {
Uri selectedImage = data.getData();
String[] filePathColumn = { MediaStore.Images.Media.DATA };
Cursor cursor = context.getContentResolver().query(selectedImage,
filePathColumn, null, null, null);
cursor.moveToFirst();
// String selectedPhoto contains the path of selected Image
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
selectedPhoto = cursor.getString(columnIndex);
cursor.close();
UploadPhoto uploadProfilePhoto = new UploadPhoto();
uploadProfilePhoto.execute();
}
错误行指向此行:
cursor.moveToFirst();
我该如何解决此问题?
这是在库中保存的裁剪图像代码:
Here is the saving cropped image code in library :
public class FileUtils {
public static File getOutputMediaFileUri() {
File mediaStorageDir = new File(
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
"Stampless");
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d("crop", "failed to create directory");
return null;
}
}
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
File mediaFile = new File(mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp
+ ".jpg");
return mediaFile;
}
/**
* Get the file path from the given Uri.
*
* @param context The context of the calling activity.
* @param uri The Uri whose file path is returned.
*/
@TargetApi(Build.VERSION_CODES.KITKAT)
public static String getFilePathFromUri(final Context context, final Uri uri) {
final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
// DocumentProvider
if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
// ExternalStorageProvider
if (isExternalStorageDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
if ("primary".equalsIgnoreCase(type)) {
return Environment.getExternalStorageDirectory() + "/" + split[1];
}
}
// DownloadsProvider
else if (isDownloadsDocument(uri)) {
final String id = DocumentsContract.getDocumentId(uri);
final Uri contentUri = ContentUris.withAppendedId(
Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));
return getDataColumn(context, contentUri, null, null);
}
// MediaProvider
else if (isMediaDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
Uri contentUri = null;
if ("image".equals(type)) {
contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
} else if ("video".equals(type)) {
contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
} else if ("audio".equals(type)) {
contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
}
final String selection = "_id=?";
final String[] selectionArgs = new String[]{split[1]};
return getDataColumn(context, contentUri, selection, selectionArgs);
}
}
// MediaStore (and general)
else if ("content".equalsIgnoreCase(uri.getScheme())) {
return getDataColumn(context, uri, null, null);
}
// File
else if ("file".equalsIgnoreCase(uri.getScheme())) {
return uri.getPath();
}
return null;
}
/**
* Get the value of the data column for this Uri. This is useful for
* MediaStore Uris, and other file-based ContentProviders.
*
* @param context The context.
* @param uri The Uri to query.
* @param selection (Optional) Filter used in the query.
* @param selectionArgs (Optional) Selection arguments used in the query.
* @return The value of the _data column, which is typically a file path.
*/
public static String getDataColumn(Context context, Uri uri, String selection,
String[] selectionArgs) {
Cursor cursor = null;
final String column = "_data";
final String[] projection = {column};
try {
cursor = context.getContentResolver()
.query(uri, projection, selection, selectionArgs, null);
if (cursor != null && cursor.moveToFirst()) {
final int column_index = cursor.getColumnIndexOrThrow(column);
return cursor.getString(column_index);
}
} finally {
if (cursor != null) {
cursor.close();
}
}
return null;
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is ExternalStorageProvider.
*/
public static boolean isExternalStorageDocument(Uri uri) {
return "com.android.externalstorage.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is DownloadsProvider.
*/
public static boolean isDownloadsDocument(Uri uri) {
return "com.android.providers.downloads.documents".equals(uri.getAuthority());
}
/**
* @param uri The Uri to check.
* @return Whether the Uri authority is MediaProvider.
*/
public static boolean isMediaDocument(Uri uri) {
return "com.android.providers.media.documents".equals(uri.getAuthority());
}
}
推荐答案
我已经解决了我的问题，首先是在调试我的应用程序时，它返回了file :，但是它希望内容:.因此，我首先将uri转换为文件:
I'm solved my problem, first of all when i debug my app , and it returned file:, however it want to content:. So i'm converting my uri to file first of all :
Uri uri =data.getData();
File myFile = new File(uri.getPath());
然后，我正在使用以下代码将文件转换为内容: 此处的示例
Then, i'm converting my file to content using this code : example here
Uri selectedImage=getImageContentUri(context,myFile);
然后我调用此函数:
public static Uri getImageContentUri(Context context, File imageFile) {
String filePath = imageFile.getAbsolutePath();
Cursor cursor = context.getContentResolver().query(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
new String[] { MediaStore.Images.Media._ID },
MediaStore.Images.Media.DATA + "=? ",
new String[] { filePath }, null);
if (cursor != null && cursor.moveToFirst()) {
int id = cursor.getInt(cursor
.getColumnIndex(MediaStore.MediaColumns._ID));
Uri baseUri = Uri.parse("content://media/external/images/media");
return Uri.withAppendedPath(baseUri, "" + id);
} else {
if (imageFile.exists()) {
ContentValues values = new ContentValues();
values.put(MediaStore.Images.Media.DATA, filePath);
return context.getContentResolver().insert(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
} else {
return null;
}
}}
仅此而已.
这篇关于Android:空对象引用上的android.database.Cursor.moveToFirst()'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
