Develop Reference

How to avoid image flickering in a listview

I have a listivew that display a bunch of images. am using Universal Image Loader to load this images from files to imageviews.
This images have different dimensions and i want all of them to have same width but different height in respect to each image aspect ratio.
To achieve this, i have tried setting the following to my imageview
<ImageView
android:layout_width = "400dp"
android:layout_height="wrap_content"
android:scaleType="centerCrop"
android:adjustViewBounds="true"/>
The issue with this method is that there is a lot of flickering when one scrolls the listview since imageview height is not known in advance and images have to be scaled first using my width to calculate each image height in respect to it's aspect ratio.
How can i calculate each image height in advance instead of letting imageview handle it?
if i have an image which is 400 X 700, and i want the imageview to be 300px wide, how can i calculate imageview's height using my image dimension and maintain image aspect ratio? this can help avoid flickering wnen one scroll the listview.

The reason for this flicker is that, in listview list items are reused. When re-used, the imageviews in the list item retains the old image reference which is displayed first. Later on once new image is downloaded, it starts to show. this causes the flickering behavior.
To avoid this flickering issue, always clear the old image reference from the imageview when it is getting reused.
In your case, add holder.image.setImageBitmap(null); after holder = (ViewHolder) convertView.getTag();
So, your getView() method will look like:
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
...
if (convertView == null) {
LayoutInflater inflater = getLayoutInflater();
convertView = inflater.inflate(viewResourceId, null);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
holder.image.setImageBitmap(null)
}
...
return convertView;
}

After hours of research, i was able to know the method that i can use to calculate new imageview height while maintaining image aspect ratio.
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
//Returns null, sizes are in the options variable
BitmapFactory.decodeFile("/sdcard/image.png", options);
int width = options.outWidth;
int height = options.outHeight;
//calculating image aspect ratio
float ratio =(float) height/(float) width;
//calculating my image height since i want it to be 360px wide
int newHeight = Math.round(ratio*360);
//setting the new dimentions
imageview.getLayoutParams().width = 360;
imageview.getLayoutParams().height = newHeight;
//i'm using universal image loader to display image
imaheview.post(new Runnable(){
ImageLoader.getInstance().displayImage(imageuri,imageview,displayoptions);
});

You can do something like this :
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
//Returns null, sizes are in the options variable
BitmapFactory.decodeFile("/sdcard/image.png", options);
int width = options.outWidth;
int height = options.outHeight;
//If you want, the MIME type will also be decoded (if possible)
String type = options.outMimeType;

How I solved it was by creating a Bitmap[] array variable to store images, then in adapter's getView(), I used position to check if image in Bitmap[] array is null or has value. If it is has value, then I use the value instead of calling the new DownloadImageTask() construct again.
For example:
YourCustomArrayAdapter.java
public class MyCustomArrayAdapter extends ArrayAdapter {
private static Bitmap[] myListViewImageViewsArray = new Bitmap[listViewItemsArray.length];
private String[] myListViewImageURLsArray = new String[listViewItemsArray.length]{
"image_url_1",
"image_url_2",
...
...
};
#Override
public View getView(int position, View view, ViewGroup parent){
CustomViewHolder vHolder;
if(view == null){
view = inflater.inflate(R.layout.movies_coming_soon_content_template, null, true);
vHolder = new CustomViewHolder();
vHolder.imageView = (AppCompatImageView) view.findViewById(R.id.my_cutom_image);
vHolder.imageUrl = "";
view.setTag(vHolder);
}
else{
vHolder = (CustomViewHolder)view.getTag();
// -- Set imageview src to null or some predefined placeholder (this is not really necessary but it might help just to flush any conflicting data hanging around)
vHolder.imageView.setImageResource(null);
}
// ...
// -- THIS IS THE MAIN PART THAT STOPPED THE FLICKERING FOR ME
if(myListViewImageViewsArray[position] != null){
vHolder.imageView.setImageBitmap(myListViewImageViewsArray[position]);
}else{
new DownloadImageTask(position, vHolder.imageView).execute(vHolder.imageUrl);
}
// -- END OF THE FLICKERING CONTROL
}
}
Then, in your image downloader construct, after downloading the image, make an insertion into the Bitmap[] image array for that position. For example:
YourImageDownloaderClass.java
public class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
AppCompatImageView imageView;
int position;
public DownloadImageTask(int position, AppCompatImageView imageView){
this.imageView = imageView;
this.position = position;
}
#Override
protected Bitmap doInBackground(String...urls) {
String urlOfImage = urls[0];
Bitmap logo = null;
try{
logo = BitmapFactory.decodeStream((InputStream) new URL(urlOfImage).getContent());
}catch(Exception e){
e.printStackTrace();
}
return logo;
}
#Override
protected void onPostExecute(Bitmap result){
if(result != null) {
YourCustomArrayAdapter.myListViewImageViewsArray [position] = result;
imageView.setImageBitmap(result);
}else{
YourCustomArrayAdapter.myListViewImageViewsArray [position] = null;
imageView.setImageResource(null);
}
}
}

my suggestion is to use grid view to avoid flickering of images it will load at first time if it is same url , it will load from cache
Glide.with(mContext)
.load(item.getImageUrl())
.into(holder.mIVGridPic);

Universal Image Loader - Use same image in multiple views

I'm using Universal Image Loader to load images from a backend to display user images in a list; however, if the icon shows up multiple times, the Universal Image Loader doesn't fill out all the views.
[User Image 1] - No image
[User Image 1] - No Image
[User Image 2] - Fine
[User Image 2] - No Image
[User Image 3] - Fine
[User Image 1] - Fine
And then on another screen:
[User Image 1] - Fine
[User Image 1] - No image
I'm using cacheInMemory and cacheOnDisk, which seemed to improve it. As before it was only displaying it in one of the views, instead of most, but I need all of them to work.
DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
.cacheInMemory( true )
.cacheOnDisk( true )
.build();
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder( this )
.threadPoolSize( 3 )
.defaultDisplayImageOptions( defaultOptions )
.build();
ImageLoader.getInstance().init( config );
I'm not using a ListView for this task, I'm using a ScrollView and inflating it with a custom layout.
private View createSmallActivity( LayoutInflater inflater, final Event activity ) {
final View view;
view = inflater.inflate( R.layout.activity_posted_small, null );
...
// The owner's image.
if( activity.ownerImageUrl != null ) {
Loader.loadImage( getActivity(),
activity.ownerImageUrl,
R.drawable.postedactivitysmall_imageprofileempty,
( ImageView ) view.findViewById( R.id.profileImage ) );
}
return view;
}
// Loader.loadImage
// Setting the targetSize, and masking the image with a resource.
public static void loadImage( Context context, String url, int resource, ImageView view ) {
Drawable d = context.getResources().getDrawable( resource );
int h = d.getIntrinsicHeight();
int w = d.getIntrinsicWidth();
ImageSize targetSize = new ImageSize( w, h );
ImageLoader.getInstance().loadImage( url, targetSize, new MaskImageLoader( context, view, resource ) );
}
Any idea on how I can improve the Universal Image Loader to ensure all the views are correctly filled out?
Thanks for your help!

It's because Universal Image Loader cancel previous requests with same url (used as id). To prevent this behaviour, replace
ImageLoader.getInstance().loadImage( url, targetSize, new MaskImageLoader( context, view, resource ) );
by
ImageLoader.getInstance().displayImage(url,
new NonViewAware(new ImageSize(w, h), ViewScaleType.CROP),
new MaskImageLoader(context, view, resource));

I recommend you use ListView. Maybe you should declare ImageLoader globally. then use it.
ImageLoader imageLoader = ImageLoader.getInstance();
...
imageLoader.displayImage(imageUri, imageView);

OutOfMemoryError for Bitmap(List View)

I have read much about out of memory in android due to Bitmap and took various steps to prevent it but it keeps knocking endlessly. Here is my code :
CODE :
in = httpConn.getInputStream();
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPurgeable=true;
options.inJustDecodeBounds = true;
options.inSampleSize = 1;
options.inJustDecodeBounds = false;
image = BitmapFactory.decodeStream(in, null, options);
I am able to load around 15 images that are with a dimension 640*640. After that it throws me a OutOfMemoryError in the log cat. I have also implemented a external library(from GitHub) for "PullToRefresh" functionality. So obviously that involves a custom list view. Is there any way to avoid this Memory issue.
NOTE : I have already read this. I have also implemented those methods but it still fails to stand up.
Can I use Fragments with List View to avoid this memory issue ? Or, is am I missing something ? Any help would be much appreciated. Thanks in advance.

Just change the options.inSampleSize = 1; to options.inSampleSize = 4;
And also do
bitmap.reCycle();

Well, Now image loading time from internet has many solution. You may also use this library "Android-Query" https://code.google.com/p/android-query/wiki/ImageLoading .It will give you all the required activity.Make sure what you want to do ? and read library wiki page. and solve image loading restriction.
This is my code:-
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.row, null);
}
ImageView imageview = (ImageView) v.findViewById(R.id.icon);
AQuery aq = new AQuery(convertView);
String imageUrl = "http://www.vikispot.com/z/images/vikispot/android-w.png";
aq.id(imageview).progress(this).image(imageUrl, true, true, 0, 0, new BitmapAjaxCallback(){
#Override
public void callback(String url, ImageView iv, Bitmap bm, AjaxStatus status){
iv.setImageBitmap(bm);
}
});
}
return v;
}

Gallery is loading all the images but gallery should be load one image at a time

i have created a gallery for display images haveing pinchzoom with goto next and previous by touch . i were use to visit https://github.com/kilaka/ImageViewZoom library . i saw Gallery first upload all the images and then it is displaying images which is good activity. but gallery can upload max 4MB images , if images size go to greater than 4MB then it gives us Bitmap outofmemory error. i have used to bitmap.recycle() but it is recycle all the images.
do here any way, so my gallery upload images one by one from sdcard and when i will go to next or previous images by touch , my currently images memory should be delete . and next images should be uploaded in gallery memory . so my gallery can upload a number of images .
this is my code , this code is link from visit https://github.com/kilaka/ImageViewZoom :-
gallery = new GalleryTouch(this);
gallery = (GalleryTouch) findViewById(R.id.image);
gallery.setSpacing(20);
arrayAdapter = new ArrayAdapter<ImageView>(this, -1) {
#Override
public View getView(int position, View convertView, ViewGroup parent) {
bookM= position; return getItem(position);
}
};
if(!(it.isEmpty() )) {
Collections.sort(it);
for(int i=0; i<it.size();i++) {
ImageViewTouch imageView = new ImageViewTouch(imageTouch.this);
imageView.setLayoutParams(new Gallery.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
final Options options = new Options();
options.outHeight = (int) scaleHeight;
options.outWidth = (int) scaleWidth;
options.inScaled = true;
options.inPurgeable = true;
options.inSampleSize = 2;
String photoURL = it.get(i);
bitmap = BitmapFactory.decodeFile(photoURL,options);
imageView.setImageBitmap(bitmap);
arrayAdapter.add(imageView);
}
gallery.setAdapter(arrayAdapter);
}
Note:- in this code, "it" is a variable of List it; and list having a list of path of image from sd card like as sdcard/images/one.jpg , sdcard/images/two.jpg ........ etc.
please expert help me ,
thank you for your important time.

Android, How to add a bitmap layer over another bitmap layer, dynamically from list?

In my application, I have a list adapter. each row includes an imageView in left and two textViews in right. For getting images I'm using Universal-Image-Loader library.
my getView() method is this:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = myInflater.inflate(R.layout.list_news_adapter, null);
holder = new ViewHolder();
holder.ivIcon = (ImageView) convertView.findViewById(R.id.list_news_icon);
holder.tvTitle = (TextView) convertView.findViewById(R.id.list_news_title);
holder.tvDate = (TextView) convertView.findViewById(R.id.list_news_date);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.tvTitle.setText(video.getTitle().get(position));
holder.tvDate.setText(localTime.get(position));
// Load and display image
String imageUrl = (video.getDefaultImage128x96().get(position));
imageUrl = imageUrl.trim().replaceAll(" ", "%20");
imageLoader.displayImage(imageUrl, holder.ivIcon, options);
holder.ivIcon.buildDrawingCache();
Bitmap image = holder.ivIcon.getDrawingCache();
if(image != null) {
image = putOverlay(image, holder.ivIcon.getWidth(), holder.ivIcon.getHeight());
holder.ivIcon.setImageBitmap(image);
holder.ivIcon.destroyDrawingCache();
}
return convertView;
}
in following code, I'm giving list of URLs to that libray to be downloaded in different threads.
// Load and display image
String imageUrl = (video.getDefaultImage128x96().get(position));
imageUrl = imageUrl.trim().replaceAll(" ", "%20");
imageLoader.displayImage(imageUrl, holder.ivIcon, options);
after that in following code, i'm getting current image of imageView (which is downloaded) and ask other method to add a layer on top of this image.
holder.ivIcon.buildDrawingCache();
Bitmap image = holder.ivIcon.getDrawingCache();
if(image != null) {
image = putOverlay(image, holder.ivIcon.getWidth(), holder.ivIcon.getHeight());
holder.ivIcon.setImageBitmap(image);
holder.ivIcon.destroyDrawingCache();
}
putOverlay() method is like this:
public Bitmap putOverlay(Bitmap bmp, int width, int height) {
Bitmap overLay = BitmapFactory.decodeResource(context.getResources(), R.drawable.video_overlay);
Bitmap bmBackground = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
Canvas canvas = new Canvas(bmBackground);
Paint paint = new Paint(Paint.FILTER_BITMAP_FLAG);
canvas.drawBitmap(bmp, 0, 0, paint);
canvas.drawBitmap(overLay, width*3/8, height*3/8, paint);
return bmBackground;
}
It was functional part. What about result!
Universal Image Loader library uses predefined image as long as main image is under downloading. my code can merge this two layers.
However, when main image is downloaded it overrides previous image while i expect my overlay image sits on top of this image.
But, after scroll of screen, i can see my added image (most of images has and some of them doesn't have my added image).
any suggestion/comments would be appreciated.

Solution was easier than the thing that i was thinking.
First I removed those
holder.ivIcon.buildDrawingCache();
Bitmap image = holder.ivIcon.getDrawingCache();
if(image != null) {
image = putOverlay(image, holder.ivIcon.getWidth(), holder.ivIcon.getHeight());
holder.ivIcon.setImageBitmap(image);
holder.ivIcon.destroyDrawingCache();
}
and putOverlay() method from my list adapter and then in XML file of row (list_news_adapter), I added another imageView and set its source attribute with my image.
Wow, it works fine.