问题
I am naive in android.I am facing a nuNullPointerException when i picking an image from the gallery.my code is following like that and getting error in cursor and filePathColumn[0]. What to do..
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == PICK_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]);
String picturePath = cursor.getString(columnIndex);
cursor.close();
decodeFile(picturePath);
}
}
回答1:
Complete Code for selecting image from gallery or taking picture from camera..100% working.
protected static ImageView imPhoto;
private static int RESULT_LOAD_IMG = 1;
int REQUEST_CAMERA = 0, SELECT_FILE = 1;
String selectedImagePath;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.registration);
imPhoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
selectImage();
}
});
}
private void selectImage() {
final CharSequence[] items = {"Take Photo", "Choose from Library",
"Cancel"};
AlertDialog.Builder builder = new AlertDialog.Builder(Registration.this);
builder.setTitle("Add Photo!");
builder.setItems(items, new DialogInterface.OnClickListener() {
private DialogInterface dialog;
private int item;
@Override
public void onClick(DialogInterface dialog, int item) {
this.dialog = dialog;
this.item = item;
if (items[item].equals("Take Photo")) {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, REQUEST_CAMERA);
} else if (items[item].equals("Choose from Library")) {
Intent intent = new Intent(
Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
intent.setType("image/*");
startActivityForResult(
Intent.createChooser(intent, "Select File"),
SELECT_FILE);
} else if (items[item].equals("Cancel")) {
dialog.dismiss();
}
}
});
builder.show();
}
ublic void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == Activity.RESULT_OK) {
if (requestCode == SELECT_FILE)
onSelectFromGalleryResult(data);
else if (requestCode == REQUEST_CAMERA)
onCaptureImageResult(data);
}
}
private void onCaptureImageResult(Intent data) {
Bitmap thumbnail = (Bitmap) data.getExtras().get("data");
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
thumbnail.compress(Bitmap.CompressFormat.JPEG, 90, bytes);
byte[] byteArray = bytes.toByteArray();
File destination = new File(Environment.getExternalStorageDirectory(),
System.currentTimeMillis() + ".jpg");
FileOutputStream fo;
try {
destination.createNewFile();
fo = new FileOutputStream(destination);
fo.write(bytes.toByteArray());
fo.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
imPhoto.setImageBitmap(thumbnail);
}
@SuppressWarnings("deprecation")
private void onSelectFromGalleryResult(Intent data) {
Uri selectedImageUri = data.getData();
String[] projection = {MediaStore.MediaColumns.DATA};
Cursor cursor = managedQuery(selectedImageUri, projection, null, null,
null);
int column_index = cursor.getColumnIndexOrThrow(MediaStore.MediaColumns.DATA);
cursor.moveToFirst();
selectedImagePath = cursor.getString(column_index);
Bitmap bm;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(selectedImagePath, options);
final int REQUIRED_SIZE = 200;
int scale = 1;
while (options.outWidth / scale / 2 >= REQUIRED_SIZE
&& options.outHeight / scale / 2 >= REQUIRED_SIZE)
scale *= 2;
options.inSampleSize = scale;
options.inJustDecodeBounds = false;
bm = BitmapFactory.decodeFile(selectedImagePath, options);
imPhoto.setImageBitmap(bm);
}
回答2:
Use the below code for opening in the image gallery.
Intent browseIntent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(browseIntent, RESULT_LOAD_IMAGE);
and below code for pick the image from gallery.
@Override
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]);
imagePath = cursor.getString(columnIndex);
cursor.close();
try {
byte[] b;
Log.d("picture", imagePath);
bm = BitmapFactory.decodeFile(imagePath);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG, 100, baos); //bm is the bitmap object
b = baos.toByteArray();
encodedImageToBase64 = Base64.encodeToString(b, Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
}
index = imagePath.lastIndexOf("/");
attachmentImageName = imagePath.substring(index + 1);
}
}
may this will help you.
回答3:
you can use the below code. it works for me.
mainactivity.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:gravity="center" >
<ImageView
android:id="@+id/imgView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:layout_gravity="center" >
</ImageView>
<Button
android:id="@+id/buttonLoadPicture"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_weight="0"
android:onClick="loadImagefromGallery"
android:text="Load Picture" >
</Button>
</LinearLayout>
Mainactivity.java
public class MainActivity extends ActionBarActivity {
private static int RESULT_LOAD_IMG = 1;
String image_str,res,imgDecodableString,the_string_response;
Bitmap img;
Exception e;
int contentLength;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void loadImagefromGallery(View view) {
//Create intent to Open Image applications like Gallery, Google Photos
Intent galleryIntent = new Intent(Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
// Start the Intent
startActivityForResult(galleryIntent, RESULT_LOAD_IMG);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
try {
// When an Image is picked
if (requestCode == RESULT_LOAD_IMG && resultCode == RESULT_OK
&& null != data) {
// Get the Image from data
Uri selectedImage = data.getData();
String[] filePathColumn = { MediaStore.Images.Media.DATA };
// Get the cursor
Cursor cursor = getContentResolver().query(selectedImage,
filePathColumn, null, null, null);
// Move to first row
cursor.moveToFirst();
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
imgDecodableString = cursor.getString(columnIndex);
cursor.close();
ImageView imgView = (ImageView) findViewById(R.id.imgView);
// Set the Image in ImageView after decoding the String
img = Bitmap.createScaledBitmap(BitmapFactory
.decodeFile(imgDecodableString), 500, 500, false);
imgView.setImageBitmap(img);
} else {
Toast.makeText(this, "You haven't picked Image",
Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
Toast.makeText(this, "Something went wrong", Toast.LENGTH_LONG)
.show();
}
}
}
回答4:
Instead of trying it by yourself, take a look at recent-images library. It can help you. here is the link.
回答5:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// find the views
image = (ImageView) findViewById(R.id.uploadImage);
uploadButton = (Button) findViewById(R.id.uploadButton);
// on click select an image
selectImageButton = (Button) findViewById(R.id.selectImageButton);
selectImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
selectImageFromGallery();
}
});
}
public void selectImageFromGallery() {
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent, "Select Picture"),
PICK_IMAGE);
}
/**
* Retrives the result returned from selecting image, by invoking the method
* <code>selectImageFromGallery()</code>
*/
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == PICK_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]);
cursor.moveToFirst();
String picturePath = cursor.getString(columnIndex);
cursor.close();
decodeFile(picturePath);
}
}
/**
* The method decodes the image file to avoid out of memory issues. Sets the
* selected image in to the ImageView.
*
* @param filePath
*/
public void decodeFile(String filePath) {
// Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, o);
// The new size we want to scale to
final int REQUIRED_SIZE = 1024;
// Find the correct scale value. It should be the power of 2.
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true) {
if (width_tmp < REQUIRED_SIZE && height_tmp < REQUIRED_SIZE)
break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// Decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
bitmap = BitmapFactory.decodeFile(filePath, o2);
image.setImageBitmap(bitmap);
}
Here is the complete code. But still getting error on cursor. In besides, here used contentResolver query stuff.What I think I should add some extra code for that.Can someone tell me about contentResolver and my problem
回答6:
Try this...
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent, "Select Picture"), PICK_IMAGE);
来源：https://stackoverflow.com/questions/33607014/pick-an-image-from-the-image-gallery-in-android