Develop Reference

List view showing images jumbled after downloading images using asynctask

I have used the async task to download the data and then showing those images in the list view I used the cache to store the images as they are repeating but not in an order. But the images gets jumbled up and sometimes they don't download. I tried searching this, but couldn't find that.
This was one of mine dream company question and i didn't clear because of this.
Please help me around.
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private static final String BASE_URL = "https://ajax.googleapis.com/ajax/services/search/images?v=1.0&q=android&start=";
private static final String IMAGE_JSON_KEY = "unescapedUrl";
private static final String RESULTS_JSON_KEY = "results";
private static final String RESPONSE_DATA_JSON_KEY = "responseData";
private int mCurrentPage;
private ListView mListView;
private Context mContext;
ArrayList<String> mImageUrls;
private LruCache<String, Bitmap> mCache;
private CustomListAdapter mAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get memory class of this device, exceeding this amount will throw an
// OutOfMemory exception.
final int memClass = ((ActivityManager) getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();
// Use 1/8th of the available memory for this memory cache.
final int cacheSize = 1024 * 1024 * memClass / 8;
// Initialize variables
mContext = this;
mCache = new LruCache<String, Bitmap>(cacheSize) {
#Override
protected int sizeOf(String key, Bitmap value) {
// The cache size will be measured in bytes rather than number of items.
return value.getByteCount();
}
};
mListView = (ListView) findViewById(R.id.list_view);
mAdapter = new CustomListAdapter();
mImageUrls = new ArrayList<>();
// If the urls are wrong then
if (mImageUrls.isEmpty() || checkDiff()) {
fetchNewImageUrls();
}
// Set the adapter to the list view
mListView.setAdapter(mAdapter);
}
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
private final WeakReference<ImageView> imageViewReference;
private String mUrl;
public BitmapWorkerTask(ImageView imageView) {
// Use a WeakReference to ensure the ImageView can be garbage collected
imageViewReference = new WeakReference<ImageView>(imageView);
}
#Override
protected Bitmap doInBackground(String... params) {
String imageUrl = params[0];
mUrl = imageUrl;
Bitmap bitmap = getBitmapFromMemCache(imageUrl);
if (bitmap == null) {
try {
URL url = new URL(imageUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.connect();
// Closing the stream after getting the sample size
InputStream inputStream = connection.getInputStream();
byte[] imageByteArray = convertToByteArray(inputStream);
bitmap = decodeSampledBitmap(imageByteArray, 200, 200);
inputStream.close();
if (bitmap != null) {
Log.d(TAG, "Image downloaded: " + imageUrl);
addBitmapToMemoryCache(imageUrl, bitmap);
} else {
Log.d(TAG, "Null Bitmap downloaded for: " + imageUrl);
}
connection.disconnect();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} else {
Log.d(TAG, "Already present in the Cache");
}
return bitmap;
}
#Override
protected void onPostExecute(Bitmap bitmap) {
if (imageViewReference != null && bitmap != null) {
final ImageView imageView = (ImageView) imageViewReference.get();
if (imageView != null && imageView.getTag().equals(mUrl)) {
imageView.setImageBitmap(bitmap);
}
}
}
}
public class CustomListAdapter extends BaseAdapter {
#Override
public int getCount() {
return mImageUrls.size();
}
#Override
public Object getItem(int position) {
return mImageUrls.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Log.d(TAG, "Get View is called for position: " + position);
View view = convertView;
Holder holder = null;
// Holder represents the elements of the view to use
// Here are initialized
if (view == null) {
view = LayoutInflater.from(mContext).inflate(R.layout.row_item, parent, false);
holder = new Holder();
holder.mRowImage = (ImageView) view.findViewById(R.id.image_view);
holder.mRowText = (TextView) view.findViewById(R.id.row_text);
view.setTag(holder);
} else {
holder = (Holder) view.getTag();
}
// Set default image background
holder.mRowImage.setImageResource(R.drawable.ic_launcher);
// here do operations in holder variable example
holder.mRowText.setText("Image Number: " + position);
// Set the tag for the imageview
holder.mRowImage.setTag(mImageUrls.get(position));
new BitmapWorkerTask(holder.mRowImage).execute(mImageUrls.get(position));
return view;
}
}
public static class Holder {
TextView mRowText;
ImageView mRowImage;
}
public void addBitmapToMemoryCache(String key, Bitmap bitmap) {
if (getBitmapFromMemCache(key) == null) {
mCache.put(key, bitmap);
}
}
public Bitmap getBitmapFromMemCache(String key) {
return (Bitmap) mCache.get(key);
}
public Bitmap decodeSampledBitmap(byte[] imageByteArray, int reqWidth, int reqHeight) {
Bitmap bm = null;
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeByteArray(imageByteArray, 0, imageByteArray.length, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
options.inJustDecodeBounds = false;
bm = BitmapFactory.decodeByteArray(imageByteArray, 0, imageByteArray.length, options);
return bm;
}
public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
if (width > height) {
inSampleSize = Math.round((float) height / (float) reqHeight);
} else {
inSampleSize = Math.round((float) width / (float) reqWidth);
}
}
Log.d(TAG, "Sample size is: " + inSampleSize);
return inSampleSize;
}
private void fetchNewImageUrls() {
new AsyncTask<String, Void, Boolean>() {
#Override
protected Boolean doInBackground(String... params) {
try {
StringBuilder response = new StringBuilder();
URL url = new URL(params[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
response.append(inputLine);
in.close();
connection.disconnect();
String resp = response.toString();
Log.d(TAG, "Response is: " + response);
// Parsing the response
JSONObject jsonObject = new JSONObject(resp);
JSONObject jsonObject1 = jsonObject.getJSONObject(RESPONSE_DATA_JSON_KEY);
JSONArray jsonArray = jsonObject1.getJSONArray(RESULTS_JSON_KEY);
for (int i = 0; i < 4; i++) {
JSONObject dataObject = jsonArray.getJSONObject(i);
mImageUrls.add(dataObject.getString(IMAGE_JSON_KEY));
}
mCurrentPage++;
Log.d(TAG, "Number of image urls are: " + mImageUrls.size());
return true;
} catch (JSONException e) {
e.printStackTrace();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
#Override
protected void onPostExecute(Boolean value) {
super.onPostExecute(value);
if (checkDiff() && value) {
Log.d(TAG, "Again fetching the Images");
fetchNewImageUrls();
}
if (!value) {
Log.d(TAG, "Error while getting the response");
}
mAdapter.notifyDataSetChanged();
}
}.execute(BASE_URL + mCurrentPage);
}
private boolean checkDiff() {
int diff = mImageUrls.size() - mCurrentPage * 4;
Log.d(TAG, "Diff is: " + diff);
return diff < 8;
}
public static byte[] convertToByteArray(InputStream input) {
byte[] buffer = new byte[8192];
int bytesRead;
ByteArrayOutputStream output = new ByteArrayOutputStream();
try {
while ((bytesRead = input.read(buffer)) != -1) {
output.write(buffer, 0, bytesRead);
}
} catch (IOException e) {
e.printStackTrace();
}
return output.toByteArray();
}
}

Since you do not cancel the unfinished "out of view" downloads these may interfere with your gui.
Example
listview line1 shows item#1 with has an async task to download image "a" not completed yet
scroll down, line1 is now invisible;
listview line8 becomes visible recycling item#1 new async task to download image "x"
async task to download image "a" finishes displaying wrong image. Line8 shows image "a" instead of "x"
to solve this you have to cancel the pending unnecessary unfinished async task-s
public static class Holder {
ImageView mRowImage;
String mImageUrl;
// neccessary to cancel unfinished download
BitmapWorkerTask mDownloader;
}
static class BitmapWorkerTask extends AsyncTask<Holder, Void, Bitmap> {
Holder mHolder;
protected Bitmap doInBackground(Holder... holders) {
mHolder = holders[0];
...
}
protected void onPostExecute(...) {
mHolder.mDownloader = null;
if (!isCancelled()) {
this.mHolder.mRowImage.setImageBitmap(image);
}
this.mHolder = null;
}
}
public class CustomListAdapter extends BaseAdapter {
#Override
public View getView(int position, ...) {
...
if (view == null) {
holder = ...
...
} else {
holder = (Holder) view.getTag();
}
...
// cancel unfinished mDownloader
if (holder.mDownloader != null) {
holder.mDownloader.cancel(false);
holder.mDownloader = null;
}
holder.mImageUrl = mImageUrls.get(position);
holder.mDownloader = new BitmapWorkerTask()
holder.mDownloader.execute(holder);
}
}
Here is a working example for this combination of Adapter + Holder + AsyncTask
[Update]
Potential problems with this solution.
Most modern android versions execute only one async task at a time. If you are fetching the images via the web you cannot download multible images at the same time. See running-parallel-asynctask#stackoverflow for details.
There may be promlems with configuration change(like orientation). See #Selvin-s comment below. I have posted this question "what-happens-with-view-references-in-unfinished-asynctask-after-orientation-chan#stackoverflow" to find out more about it.

Get the LinearLayout inside a ListView from an Async Task onRetainNonConfigurationInstance()

I hope the title is not mis-leading. I am trying to implement onRetainNonConfigurationInstance() of an AsyncTask of loading images and am getting this error "Java.lang.RuntimeException:Unable to retain Activity". Here is my code for onRetainNonConfigurationInstance():
public Object onRetainNonConfigurationInstance(){
//final ListView listview = list;
final int count = list.getChildCount();
final LoadedImage[] mylist = new LoadedImage[count];
for(int i = 0; i < count; i++){
final ImageView v = (ImageView)list.getChildAt(i); // getting error here
mylist[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
}
return mylist;
}
Here is the Logcat:
05-18 08:43:15.385: E/AndroidRuntime(28130): java.lang.RuntimeException: Unable to retain activity {com.MyApps.ImageGen/com.MyApps.ImageGen.Wallpapers}: java.lang.ClassCastException: android.widget.LinearLayout
05-18 08:43:15.385: E/AndroidRuntime(28130): at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:2989)
05-18 08:43:15.385: E/AndroidRuntime(28130): at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3100)
05-18 08:43:15.385: E/AndroidRuntime(28130): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3216)
05-18 08:43:15.385: E/AndroidRuntime(28130): at android.app.ActivityThread.access$1600(ActivityThread.java:132)
Here is my layout with the ListView:
<?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">
<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:cacheColorHint="#00000000"
android:listSelector="#android:color/transparent" >
</ListView>
</LinearLayout>
Here is how I setup the ListView:
private void setupViews() {
list = (ListView)findViewById(android.R.id.list);
list.setDivider(null);
list.setDividerHeight(0);
imageAdapter = new ImageAdapter(getApplicationContext());
list.setAdapter(imageAdapter);
list.setOnItemClickListener(this);
}
my async task and Item Adapter:
class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> {
#Override
protected Object doInBackground(Object... params) {
Bitmap bitmap = null;
Bitmap newbitmap = null;
Uri uri = null;
String [] img = {MediaStore.Images.Media._ID};
String state = Environment.getExternalStorageState();
if(Environment.MEDIA_MOUNTED.equals(state)){
cursor = getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, img, null, null, null);
} else {
// cursor = getContentResolver().query(MediaStore.Images.Media.INTERNAL_CONTENT_URI, img, null, null, null);
inInternalStorage = true;
}
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);
int size = cursor.getCount();
if(size == 0){
//Toast.makeText(getApplicationContext(), "There are no Images on the sdcard", Toast.LENGTH_SHORT).show();
//System.out.println("size equals zero");
Wallpaper.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "There are no Images on the sdcard", Toast.LENGTH_SHORT).show();
}
});
return params;
}else {
}
for(int i = 0; i < size; i++){
cursor.moveToPosition(i);
int ImageId = cursor.getInt(column_index);
if(inInternalStorage == true){
uri = Uri.withAppendedPath(MediaStore.Images.Media.INTERNAL_CONTENT_URI, "" + ImageId);
}else {
uri = Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + ImageId);
}
try {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);
int imageHeight = options.outHeight;
int imageWidth = options.outWidth;
String imageType = options.outMimeType;
Log.i(TAG, "imageheight = " + imageHeight);
Log.i(TAG, "imagewidth = " + imageWidth);
Log.i(TAG, "imageType = " + imageType);
//options.inSampleSize=4;
options.inSampleSize = calculateInSampleSize(options, imageWidth, imageHeight);
options.inJustDecodeBounds = false;
//bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);
if(bitmap != null){
newbitmap = Bitmap.createScaledBitmap(bitmap, 180, 180, true);
bitmap.recycle();
}
if(newbitmap != null){
publishProgress(new LoadedImage(newbitmap));
}
}catch(IOException e){
}
//cursor.close();
}
cursor.close();
return null;
}
#Override
public void onProgressUpdate(LoadedImage... value){
addImage(value);
}
#Override
protected void onPostExecute(Object result) {
setProgressBarIndeterminateVisibility(false);
}
}
private static class LoadedImage {
Bitmap mBitmap;
LoadedImage(Bitmap bitmap) {
mBitmap = bitmap;
}
public Bitmap getBitmap() {
return mBitmap;
}
}
/*Image Adapter to populate grid view of images*/
public class ImageAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>();
public ImageAdapter(Context context){
this.mContext = context;
}
public void addPhotos(LoadedImage photo){
photos.add(photo);
}
#Override
public int getCount() {
return photos.size();
}
#Override
public Object getItem(int position) {
return position;
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView image;
ViewHolder holder;
if(convertView == null){
LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
//convertView = inflater.inflate(R.layout.image_list,null);
convertView = inflater.inflate(R.layout.media_view, null);
holder = new ViewHolder();
holder.image = (ImageView)convertView.findViewById(R.id.media_image_id);
//holder.item_name = (TextView)convertView.findViewById(R.id.media_image_id);
convertView.setTag(holder);
} else{
holder = (ViewHolder)convertView.getTag();
}
//holder.image.setLayoutParams(new GridView.LayoutParams(100, 100));
//String item_name = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DISPLAY_NAME));
holder.image.setImageBitmap(photos.get(position).getBitmap());
//holder.item_name.setText(item_name);
return convertView;
}
}
static class ViewHolder {
ImageView image;
TextView item_name;
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Cursor cursor = null;
int image_column_index = 0;
String[] proj = {MediaStore.Images.Media.DATA};
String state = Environment.getExternalStorageState();
if(Environment.MEDIA_MOUNTED.equals(state)){
cursor = managedQuery(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,proj,null, null,null);
}else{
cursor = managedQuery(MediaStore.Images.Media.INTERNAL_CONTENT_URI,proj,null, null,null);
}
cursor.moveToPosition(position);
image_column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
String info = cursor.getString(image_column_index);
Intent imageviewer = new Intent(getApplicationContext(), ViewImage.class);
imageviewer.putExtra("pic_name", info);
startActivity(imageviewer);
cursor.close();
}
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 2;
if (height > reqHeight || width > reqWidth) {
if (width > height) {
inSampleSize = Math.round((float)height / (float)reqHeight);
} else {
inSampleSize = Math.round((float)width / (float)reqWidth);
}
}
/*final int REQUIRED_SIZE = 180;
int scale = 1;
if(reqWidth > REQUIRED_SIZE || reqHeight > REQUIRED_SIZE){
scale = (int)Math.pow(2, (int)Math.round(Math.log(REQUIRED_SIZE/(double)Math.max(reqHeight, reqWidth)) / Math.log(0.5)));
}*/
return inSampleSize;
}
other Methods within Async Task:
private void loadImages() {
final Object data = getLastNonConfigurationInstance();
if(data == null){
new LoadImagesFromSDCard().execute();
}else {
final LoadedImage[] photos = (LoadedImage[])data;
if(photos.length == 0){
new LoadImagesFromSDCard().execute();
}
for(LoadedImage photo:photos){
addImage(photo);
}
}
}
private void addImage(LoadedImage... value) {
for(LoadedImage photo: value){
imageAdapter.addPhotos(photo);
imageAdapter.notifyDataSetChanged();
}
}
I am assuming I should first get the root element before I get the ListView from the logcat error, but I don't know how, I can't seem to find a suitable method from the documentation.
P.S: I am using an Activity and not a ListActivity.

The exception tells you that you try to do an invalid cast. My guess is that your row layout isn't a simple ImageView like you assume with the cast in the onRetainNonConfigurationInstance(), instead your row layout probably has a parent Linearlayout that wraps the ImageView(and other views?!). When you call the method getChildAt you get that parent Linearlayout which you try to cast to a ImageView. Instead you should do this:
//...
for(int i = 0; i < count; i++){
LinearLayout parent = (LinearLayout)list.getChildAt(i);
final ImageView v = (ImageView) parent.findViewById(R.id.the_id_of_the_imageview_from_theRow_layout);
mylist[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
}
Note: The getChildAt method returns the rows views for the visible rows only so if you try to access the View for a row that isn't currently visible you'll most likely end up with a NullPointerException(you should get the drawables directly from the adapter and not from parsing all the rows Views).
Edit based on the comments:
If I understood your problem, the behavior you see it's normal. You didn't say how you ended up getting the bitmaps in the onRetainNonConfigurationInstance but my guess is that you just save the images from the ListView rows that are currently visible to the user. When it's time to restore the adapter with the images from getLastNonConfigurationInstance() you end up getting only those images which were previously visible. This will get worse if you rotate the phone again as, most likely, there are fewer images visible in landscape orientation then in the portrait orientation.
I don't know if this will work but you could try to modify the LoadedImage class to store the id of the image from MediaStore.Images.Media. When it's time to save the configuration, stop the LoadImagesFromSDCard task and nullify all the images(remove the Bitmap to which LoadedImage points)from the LoadedImages ArrayList(in the adapter) except the ones that are currently visible to the user. Send the photos ArrayList from your adapter through
onRetainNonConfigurationInstance.
When it's time to restore the adapter set the photos ArrayList of your new adapter to the one you got back and put the ListView to the position of the visible images(so the user sees the sent images). In the getView method of your adapter you'll put a default image(like loading...) when you have a null value for the Bitmap in the associated LoadedImage class. Start a new LoadImagesFromSDCard task to get the images and parse them again. When you get the id from MediaStore.Images.Media you'll check if a LoadedImage with this id exists in the adapter and if it has a Bitmap set to it. If it doesn't exist(or it doesn't have a Bitmap associated) then load the image and put it in the adapter, if not the image already exists and move to the next one.
I don't know if the solution above will work or if it's efficient. I would recommend you to modify the code and load images on demand instead of loading all up in a big task.

Android List view update

I am struggling to update a list view with data from a database, this works nicely by using a SimpleCursorAdapter. But the image view on the rows is not updated on the activity start, I have to scroll through the list a few times and only then the images are loaded in the image view.
This is the binder i am using for the SimpleCursorAdapter:
private class PromotionViewBinder implements SimpleCursorAdapter.ViewBinder {
private int done;
public boolean setViewValue(View view, Cursor cursor, int index) {
Log.e(""+cursor.getCount(),"");
View tmpview = view;
if (index == cursor.getColumnIndex(PromotionsTable.SEEN_COL)) {
boolean read = cursor.getInt(index) > 0 ? true : false;
TextView title = (TextView) tmpview;
if (!read) {
title.setTypeface(Typeface.DEFAULT_BOLD, 0);
} else {
title.setTypeface(Typeface.DEFAULT);
}
return true;
} else if (tmpview.getId() == R.id.promotions_list_row_image){
String imageURL = cursor.getString(index);
Log.e("",imageURL);
imageRetriever.displayImage(imageURL, (ImageView)tmpview);
return true;
} else {
return false;
}
}
}
The image retriever class is the LazyList example from here. As you will see this is using a runnable to retrieve the images and once the task is done is automatically updating the given imageView...Do you think that the reference to the imageView is lost somewhere on the way?
Thanx in advance,
Nick
package com.tipgain.promotions;
The image retriever class:
/**
* This class is used for retrieving images from a given web link. it uses local
* storage and memory to store the images. Once a image is downloaded
* successfully the UI gets updated automatically.
*
*
*/
public class ImageRetriever {
private final String TAG = ImageRetriever.class.getName();
private MemoryImageCache memoryImgCache = new MemoryImageCache();
private LocalStorageImageCache localFileCache;
private Map<ImageView, String> imageViewHolders = Collections
.synchronizedMap(new WeakHashMap<ImageView, String>());
private ExecutorService execService;
final int defaultImageID = R.drawable.photo_not_available;
public ImageRetriever(Context context) {
localFileCache = new LocalStorageImageCache(context);
execService = Executors.newFixedThreadPool(5);
}
public void displayImage(String url, ImageView imageView) {
imageViewHolders.put(imageView, url);
Bitmap bmp = memoryImgCache.retrieve(url);
if (bmp != null) {
Log.e("case 1", " " + (bmp != null));
imageView.setImageBitmap(bmp);
} else {
Log.e("case 2", " " + (bmp == null));
addImageToQueue(url, imageView);
imageView.setImageResource(defaultImageID);
}
}
private void addImageToQueue(String url, ImageView imageView) {
NextImageToLoad img = new NextImageToLoad(url, imageView);
execService.submit(new ImagesRetriever(img));
}
/**
* This method is used for retrieving the Bitmap Image.
*
* #param url
* String representing the url pointing to the image.
* #return Bitmap representing the image
*/
private Bitmap getBitmap(String url) {
File imageFile = localFileCache.getFile(url);
// trying to get the bitmap from the local storage first
Bitmap bmp = decodeImageFile(imageFile);
if (bmp != null)
return bmp;
// if the file was not found locally we retrieve it from the web
try {
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) imageUrl
.openConnection();
conn.setConnectTimeout(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is = conn.getInputStream();
OutputStream os = new FileOutputStream(imageFile);
Utils.CopyStream(is, os);
os.close();
bmp = decodeImageFile(imageFile);
return bmp;
} catch (MalformedURLException e) {
Log.e(TAG, e.getMessage());
} catch (FileNotFoundException e) {
Log.e(TAG, e.getMessage());
} catch (IOException e) {
Log.e(TAG, e.getMessage());
}
return null;
}
/**
* This method is used for decoding a given image file. Also, to reduce
* memory, the image is also scaled.
*
* #param imageFile
* #return
*/
private Bitmap decodeImageFile(File imageFile) {
try {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(imageFile), null,
options);
// Find the correct scale value. It should be the power of 2.
// Deciding the perfect scaling value. (^2).
final int REQUIRED_SIZE = 100;
int tmpWidth = options.outWidth, tmpHeight = options.outHeight;
int scale = 1;
while (true) {
if (tmpWidth / 2 < REQUIRED_SIZE
|| tmpHeight / 2 < REQUIRED_SIZE)
break;
tmpWidth /= 2;
tmpHeight /= 2;
scale *= 2;
}
// decoding using inSampleSize
BitmapFactory.Options option2 = new BitmapFactory.Options();
option2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(imageFile),
null, option2);
} catch (FileNotFoundException e) {
Log.e(TAG, e.getLocalizedMessage());
}
return null;
}
private boolean reusedImage(NextImageToLoad image) {
Context c = image.imageView.getContext();
c.getContentResolver().notifyChange(PromotionsProvider.CONTENT_URI, null);
String tag = imageViewHolders.get(image.imageView);
if ((tag == null) || (!tag.equals(image.url)))
return true;
return false;
}
/**
* Clears the Memory and Local cache
*/
public void clearCache() {
memoryImgCache.clear();
localFileCache.clear();
}
/**
* This class implements a runnable that is used for updating the promotions
* images on the UI
*
*
*/
class UIupdater implements Runnable {
Bitmap bmp;
NextImageToLoad image;
public UIupdater(Bitmap bmp, NextImageToLoad image) {
this.bmp = bmp;
this.image = image;
Log.e("", "ui updater");
}
public void run() {
Log.e("ui updater", "ui updater");
if (reusedImage(image))
return;
Log.e("nick", "" + (bmp == null) + " chberugv");
if (bmp != null){
image.imageView.setImageBitmap(bmp);
Context c = image.imageView.getContext();
c.getContentResolver().notifyChange(PromotionsProvider.CONTENT_URI, null);
}else
image.imageView.setImageResource(defaultImageID);
}
}
private class ImagesRetriever implements Runnable {
NextImageToLoad image;
ImagesRetriever(NextImageToLoad image) {
this.image = image;
}
public void run() {
Log.e("images retirever", " images retriever");
if (reusedImage(image))
return;
Bitmap bmp = getBitmap(image.url);
memoryImgCache.insert(image.url, bmp);
if (reusedImage(image))
return;
UIupdater uiUpdater = new UIupdater(bmp, image);
Activity activity = (Activity) image.imageView.getContext();
activity.runOnUiThread(uiUpdater);
//Context c = image.imageView.getContext();
//c.getContentResolver().notifyChange(PromotionsProvider.CONTENT_URI, null);
}
}
/**
* This class encapsulates the image being downloaded.
*
* #author Nicolae Anca
*
*/
private class NextImageToLoad {
public String url;
public ImageView imageView;
public NextImageToLoad(String u, ImageView i) {
url = u;
imageView = i;
}
}
}
Modified Runnable:
class UIupdater implements Runnable {
Bitmap bmp;
NextImageToLoad image;
public UIupdater(Bitmap bmp, NextImageToLoad image) {
this.bmp = bmp;
this.image = image;
}
public void run() {
if (reusedImage(image))
return;
if (bmp != null){
image.imageView.setImageBitmap(bmp);
Context c = image.imageView.getContext();
c.getContentResolver().notifyChange(PromotionsProvider.CONTENT_URI, null);
}else
image.imageView.setImageResource(defaultImageID);
}
}

Thats an interesting way to do what you are doing. Have you tried extending the Simple Cursor Adapter?
What you do is implement a ViewHolder and put your imageview in it.
Then in your ImageRetriever, write a Listener which will be called once the image is ready and retrieved.
Implement this listener in the Viewholder.
You create the view in getView() and request for the image in BindView().
Once the image gets loaded, the list will be refreshed automatically.

one way to do it is by calling notifyDataSetChenged on listview, and another was is to have adapter as member variable and when something changes on listview you call a function that assigns new listadapter to member adapter. That way your list will be redraw on change.

I guess, you have to use some handler, calling after image load, which will call notifyDataSetChanged for list adapter

managedQuery(Media.EXTERNAL_CONTENT_URI, projection,null,null, null); returns null when running on device

String projection[] = new String[]{MediaStore.Images.Media.DATA};
cursor =managedQuery(Media.EXTERNAL_CONTENT_URI, projection,null,null, null);
this cursor is returning null when i am trying to run it on device. it works fine on emulator.
Can someone please point out if there is something that i am missing or doing wrong.

same for this code working
public class LoadImagesFromSDCardActivity extends Activity implements
OnItemClickListener {
/**
* Grid view holding the images.
**/
private GridView sdcardImages;
/**
* Image adapter for the grid view.
**/
private ImageAdapter imageAdapter;
/**
* Display used for getting the width of the screen.
**/
private Display display;
ImageView imgView;
/**
* Creates the content view, sets up the grid, the adapter, and the click listener.
*
* #see android.app.Activity#onCreate(android.os.Bundle)
**/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Request progress bar
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.main);
display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
imgView=(ImageView)findViewById(R.id.imgView);
setupViews();
setProgressBarIndeterminateVisibility(true);
loadImages();
}
/**
* Free up bitmap related resources.
**/
protected void onDestroy() {
super.onDestroy();
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
ImageView v = null;
for (int i = 0; i < count; i++) {
v = (ImageView) grid.getChildAt(i);
((BitmapDrawable) v.getDrawable()).setCallback(null);
}
}
/**
* Setup the grid view.
**/
private void setupViews() {
sdcardImages = (GridView) findViewById(R.id.sdcard);
sdcardImages.setNumColumns(display.getWidth()/95);
sdcardImages.setClipToPadding(false);
sdcardImages.setOnItemClickListener(LoadImagesFromSDCardActivity.this);
imageAdapter = new ImageAdapter(getApplicationContext());
sdcardImages.setAdapter(imageAdapter);
}
/**
* Load images.
*/
private void loadImages() {
final Object data = getLastNonConfigurationInstance();
if (data == null) {
new LoadImagesFromSDCard().execute();
} else {
final LoadedImage[] photos = (LoadedImage[]) data;
if (photos.length == 0) {
new LoadImagesFromSDCard().execute();
}
for (LoadedImage photo : photos) {
addImage(photo);
}
}
}
/**
* Add image(s) to the grid view adapter.
*
* #param value Array of LoadedImages references
*/
private void addImage(LoadedImage... value) {
for (LoadedImage image : value) {
imageAdapter.addPhoto(image);
imageAdapter.notifyDataSetChanged();
}
}
/**
* Save bitmap images into a list and return that list.
*
* #see android.app.Activity#onRetainNonConfigurationInstance()
*/
#Override
public Object onRetainNonConfigurationInstance() {
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
final LoadedImage[] list = new LoadedImage[count];
for (int i = 0; i < count; i++) {
final ImageView v = (ImageView) grid.getChildAt(i);
list[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
}
return list;
}
/**
* Async task for loading the images from the SD card.
*
* #author Mihai Fonoage
*
*/
class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> {
/**
* Load images from SD Card in the background, and display each image on the screen.
*
* #see android.os.AsyncTask#doInBackground(Params[])
*/
#Override
protected Object doInBackground(Object... params) {
//setProgressBarIndeterminateVisibility(true);
Bitmap bitmap = null;
Bitmap newBitmap = null;
Uri uri = null;
// Set up an array of the Thumbnail Image ID column we want
String[] projection = {MediaStore.Images.Thumbnails._ID};
// Create the cursor pointing to the SDCard
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null, // Return all rows
null,
null);
int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
int size = cursor.getCount();
// If size is 0, there are no images on the SD Card.
if (size == 0) {
//No Images available, post some message to the user
}
int imageID = 0;
for (int i = 0; i < size; i++) {
cursor.moveToPosition(i);
imageID = cursor.getInt(columnIndex);
uri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID);
try {
bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
if (bitmap != null) {
newBitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
bitmap.recycle();
if (newBitmap != null) {
publishProgress(new LoadedImage(newBitmap));
}
}
} catch (IOException e) {
//Error fetching image, try to recover
}
}
cursor.close();
return null;
}
/**
* Add a new LoadedImage in the images grid.
*
* #param value The image.
*/
#Override
public void onProgressUpdate(LoadedImage... value) {
addImage(value);
}
/**
* Set the visibility of the progress bar to false.
*
* #see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
#Override
protected void onPostExecute(Object result) {
setProgressBarIndeterminateVisibility(false);
}
}
/**
* Adapter for our image files.
*
* #author Mihai Fonoage
*
*/
class ImageAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>();
public ImageAdapter(Context context) {
mContext = context;
}
public void addPhoto(LoadedImage photo) {
photos.add(photo);
}
public int getCount() {
return photos.size();
}
public Object getItem(int position) {
return photos.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
final ImageView imageView;
if (convertView == null) {
imageView = new ImageView(mContext);
} else {
imageView = (ImageView) convertView;
}
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setPadding(8, 8, 8, 8);
imageView.setImageBitmap(photos.get(position).getBitmap());
return imageView;
}
}
/**
* A LoadedImage contains the Bitmap loaded for the image.
*/
private static class LoadedImage {
Bitmap mBitmap;
LoadedImage(Bitmap bitmap) {
mBitmap = bitmap;
}
public Bitmap getBitmap() {
return mBitmap;
}
}
/**
* When an image is clicked, load that image as a puzzle.
*/
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
int columnIndex = 0;
String[] projection = {MediaStore.Images.Media.DATA};
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection,
null,
null,
null);
if (cursor != null) {
columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToPosition(position);
String imagePath = cursor.getString(columnIndex);
FileInputStream is = null;
BufferedInputStream bis = null;
try {
is = new FileInputStream(new File(imagePath));
bis = new BufferedInputStream(is);
Bitmap bitmap = BitmapFactory.decodeStream(bis);
Bitmap useThisBitmap = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
Log.i("called","called");
imgView.setImageBitmap(useThisBitmap);
bitmap.recycle();
//Display bitmap (useThisBitmap)
}
catch (Exception e) {
//Try to recover
}
finally {
try {
if (bis != null) {
bis.close();
}
if (is != null) {
is.close();
}
cursor.close();
projection = null;
} catch (Exception e) {
}
}
}
}
}
And
main.xml
<GridView
android:id="#+id/sdcard"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:stretchMode="columnWidth"
android:gravity="center" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/imgView"
></ImageView>
</LinearLayout>

http://www.androidsnippets.com/list-all-music-files

How to get specified images from sdcard in android?

i am able to show all images from sdcard into grid but how to show only specified image from sdcard into grid in android.Can anybody help please?

/**
* Loads images from SD card.
* #author padma kumar
*/
public class LoadImagesFromSDCardActivity extends Activity implements
OnItemClickListener {
/**
* Grid view holding the images.
*/
private GridView sdcardImages;
/**
* Image adapter for the grid view.
*/
private ImageAdapter imageAdapter;
/**
* Display used for getting the width of the screen.
*/
private Display display;
/**
* Creates the content view, sets up the grid, the adapter, and the click listener.
*
* #see android.app.Activity#onCreate(android.os.Bundle)
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Request progress bar
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.sdcard);
display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
setupViews();
setProgressBarIndeterminateVisibility(true);
loadImages();
}
/**
* Free up bitmap related resources.
*/
protected void onDestroy() {
super.onDestroy();
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
ImageView v = null;
for (int i = 0; i < count; i++) {
v = (ImageView) grid.getChildAt(i);
((BitmapDrawable) v.getDrawable()).setCallback(null);
}
}
/**
* Setup the grid view.
*/
private void setupViews() {
sdcardImages = (GridView) findViewById(R.id.sdcard);
sdcardImages.setNumColumns(display.getWidth()/95);
sdcardImages.setClipToPadding(false);
sdcardImages.setOnItemClickListener(LoadImagesFromSDCardActivity.this);
imageAdapter = new ImageAdapter(getApplicationContext());
sdcardImages.setAdapter(imageAdapter);
}
/**
* Load images.
*/
private void loadImages() {
final Object data = getLastNonConfigurationInstance();
if (data == null) {
new LoadImagesFromSDCard().execute();
} else {
final LoadedImage[] photos = (LoadedImage[]) data;
if (photos.length == 0) {
new LoadImagesFromSDCard().execute();
}
for (LoadedImage photo : photos) {
addImage(photo);
}
}
}
/**
* Add image(s) to the grid view adapter.
*
* #param value Array of LoadedImages references
*/
private void addImage(LoadedImage... value) {
for (LoadedImage image : value) {
imageAdapter.addPhoto(image);
imageAdapter.notifyDataSetChanged();
}
}
/**
* Save bitmap images into a list and return that list.
*
* #see android.app.Activity#onRetainNonConfigurationInstance()
*/
#Override
public Object onRetainNonConfigurationInstance() {
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
final LoadedImage[] list = new LoadedImage[count];
for (int i = 0; i < count; i++) {
final ImageView v = (ImageView) grid.getChildAt(i);
list[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
}
return list;
}
/**
* Async task for loading the images from the SD card.
*/
class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> {
/**
* Load images from SD Card in the background, and display each image on the screen.
*
* #see android.os.AsyncTask#doInBackground(Params[])
*/
#Override
protected Object doInBackground(Object... params) {
//setProgressBarIndeterminateVisibility(true);
Bitmap bitmap = null;
Bitmap newBitmap = null;
Uri uri = null;
// Set up an array of the Thumbnail Image ID column we want
String[] projection = {MediaStore.Images.Thumbnails._ID};
// Create the cursor pointing to the SDCard
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null, // Return all rows
null,
null);
int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
int size = cursor.getCount();
// If size is 0, there are no images on the SD Card.
if (size == 0) {
//No Images available, post some message to the user
}
int imageID = 0;
for (int i = 0; i < size; i++) {
cursor.moveToPosition(i);
imageID = cursor.getInt(columnIndex);
uri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID);
try {
bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
if (bitmap != null) {
newBitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
bitmap.recycle();
if (newBitmap != null) {
publishProgress(new LoadedImage(newBitmap));
}
}
} catch (IOException e) {
//Error fetching image, try to recover
}
}
cursor.close();
return null;
}
/**
* Add a new LoadedImage in the images grid.
*
* #param value The image.
*/
#Override
public void onProgressUpdate(LoadedImage... value) {
addImage(value);
}
/**
* Set the visibility of the progress bar to false.
*
* #see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
#Override
protected void onPostExecute(Object result) {
setProgressBarIndeterminateVisibility(false);
}
}
/**
* Adapter for our image files.
*/
class ImageAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>();
public ImageAdapter(Context context) {
mContext = context;
}
public void addPhoto(LoadedImage photo) {
photos.add(photo);
}
public int getCount() {
return photos.size();
}
public Object getItem(int position) {
return photos.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
final ImageView imageView;
if (convertView == null) {
imageView = new ImageView(mContext);
} else {
imageView = (ImageView) convertView;
}
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setPadding(8, 8, 8, 8);
imageView.setImageBitmap(photos.get(position).getBitmap());
return imageView;
}
}
/**
* A LoadedImage contains the Bitmap loaded for the image.
*/
private static class LoadedImage {
Bitmap mBitmap;
LoadedImage(Bitmap bitmap) {
mBitmap = bitmap;
}
public Bitmap getBitmap() {
return mBitmap;
}
}
/**
* When an image is clicked, load that image as a puzzle.
*/
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
int columnIndex = 0;
String[] projection = {MediaStore.Images.Media.DATA};
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection,
null,
null,
null);
if (cursor != null) {
columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToPosition(position);
String imagePath = cursor.getString(columnIndex);
FileInputStream is = null;
BufferedInputStream bis = null;
try {
is = new FileInputStream(new File(imagePath));
bis = new BufferedInputStream(is);
Bitmap bitmap = BitmapFactory.decodeStream(bis);
Bitmap useThisBitmap = Bitmap.createScaledBitmap(bitmap, parent.getWidth(), parent.getHeight(), true);
bitmap.recycle();
//Display bitmap (useThisBitmap)
}
catch (Exception e) {
//Try to recover
}
finally {
try {
if (bis != null) {
bis.close();
}
if (is != null) {
is.close();
}
cursor.close();
projection = null;
} catch (Exception e) {
}
}
}
}
}