Develop Reference

images in my Grid View disappear as I scroll

I'm using Grid View in order to show images I have stored, but as I scroll down the images disappear in Image View and don't load again.I also use thread for loading images into Image View.
Here is my code(also these codes are in my grid view adapter class) :
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
Log.e("sara" , "this part takes time");
LayoutInflater inflater = getLayoutInflater();
convertView = getLayoutInflater().inflate(R.layout.gallery_gridsq, parent, false);
iv = (ImageView) convertView.findViewById(R.id.icon);
file = new File(Uri.parse(getItem(position).toString()).getPath());
new myTask(iv, file).execute();
return convertView;
}
private class myTask extends AsyncTask <Void , Void ,Bitmap> {
ImageView iv;
File file;
public myTask(ImageView iv, File file) {
this.iv=iv;
this.file= file;
}
#Override
protected Bitmap doInBackground(Void... params) {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
options.inJustDecodeBounds = false;
options.inSampleSize = 8;
try {
bmp = BitmapFactory.decodeStream(new FileInputStream(file), null, options);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return bmp;
}
#Override
protected void onPostExecute(Bitmap aVoid) {
iv.setImageBitmap(aVoid);
}
}

I can think of the memory issue that caused me the similar trouble.
Check if your getView is still called when you scroll down with your log: Log.e("sara" , "this part takes time");
If that line is called when you scroll down, check the memory from android monitor provided in the android studio.
click android monitor at the bottom > monitors> and observe if memory reaches the cap depending on the set up (probably 128 or 256MB).
If so you are having issues with memory. The very possible reason is that you are not recycling the list and the memory is stacking. At the peak of memory, the images will not be loaded.
It should be implemented in a way that the images that you already loaded be deleted as you scroll down and load new images.
Also, try using glide for it has a good solution with memory issues and generally better in many fields than bitmapfactory.

How to keep ViewHolder's width after view was recycled

I'm using RecyclerView as horizontal list to show my images.
If I scroll to the fifth picture, the first two or three are recycled and ViewHolder loses its width. If I scroll back to the first image, the images are loaded again and that leads to jumps while scrolling.
Here is R.layout.fragment_details_view_img_item
<ImageView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/details_view_img_item"
android:background="#color/red"
android:adjustViewBounds="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
</ImageView>
My ViewHolder and Adapter:
private class ViewHolder extends RecyclerView.ViewHolder {
ImageView img;
public ViewHolder(ImageView imgV){
super(imgV);
img = imgV;
}
}
private class ImageListAdapter extends RecyclerView.Adapter<ViewHolder> {
[...]
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int position) {
View v = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_details_view_img_item, parent, false);
v.setOnClickListener(listener);
logDebug("onCreateViewHolder");
return new ViewHolder((ImageView) v);
}
#Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {
logDebug("onBindViewHolder");
ImageItem item = data.get(i);
if (item != null) {
ImageView imgView = viewHolder.img;
imgView.setTag(item);
String imgurl = ImageUtil.imgUrlForAvailableHeightInPX(item, parentHeight);
ImageLoader.instance().loadASYNC(imgurl, imgView);
}
}
#Override
public void onViewRecycled(ViewHolder holder) {
super.onViewRecycled(holder);
logDebug("onViewRecycled: " + holder.img.getTag());
}
}
So how can I keep ViewHolder's width?

Before I start to approach this problem, one thing needs to be clear. The ViewHolder doesn't have any width, the ImageView it "holds" does have width, and that's what you're trying to control.
Now, considering this, your issue is (after making certain assumptions from looking at your code) that you need to know the width of a certain image when it is at a certain given height and while maintaining aspect ratio - before it arrives from the server.
This is a tricky one.
One option would be to preload all your images. This, however, is very costly with memory and could lead to memory crashes.
A better option would be to load all the images' details, without actually downloading the images' pixels. Then, you'll need to remember the aspect ratio of all the images in some cache, and set the dimension of the image you're loading prior to actually downloading the image contents.
To download an image's dimensions without downloading the image itself, you should use something like this:
public float getImageAspectRatio(InputStream inputStreamFromServer)
{
BitmapFactory.Options decodeOptions = new BitmapFactory.Options();
decodeOptions.inJustDecodeBounds = true;
BitmapFactory.decodeStream(inputStreamFromServer, null, decodeOptions);
final float imageDesiredWidth = decodeOptions.outWidth;
final float imageDesiredHeight = decodeOptions.outHeight;
return imageDesiredWidth / imageDesiredHeight;
}
Once you have this method, you'll need to preload all your images using this function:
private float[] mAspectRatios;
public void decodeAllAspectRatios(List<String> imageUrls)
{
mAspectRatios = new float[imageUrls.size()];
InputStream inputStream;
int index = 0;
for (String url : imageUrls)
{
// Get the input stream from the image url using whatever method you use.
mAspectRatios[index] = getImageAspectRatio(inputStream);
index++;
}
}
Important: Your RecyclerView should not begin working until this method finished working.
Once you have preloaded all your aspect ratios, we go back to your ViewHolder:
#Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {
logDebug("onBindViewHolder");
ImageItem item = data.get(i);
if (item != null) {
ImageView imgView = viewHolder.img;
// set the layout params of the image, making it fit the correct size prior to loading the bitmap.
imgView.setLayoutParams(new LayoutParams(parentHeight * mAspectRatios[i], parentHeight));
imgView.setTag(item);
String imgurl = ImageUtil.imgUrlForAvailableHeightInPX(item, parentHeight);
ImageLoader.instance().loadASYNC(imgurl, imgView);
}
}
So long as you want your RecyclerView to display varying width images depending on their aspect ratio, I believe this is your best option.

how do you efficiently load bitmaps from drawable folder into a ListView?

How do you load images from drawable folder into a ListView in a way this happens fast and does not use large amounts of RAM?

NOTE: this post is deprecated, please use the RecyclerView for creating lists
I've been playing around with loading some (quite large) images stored in the drawable folder into a ListView and in this post I'd like to share the result I came to. Maybe (I hope so) this will save someone plenty of time. I've tested the code I'm posting on several Android 4+ devices and I can say that it runs pretty smoothly and the amount of RAM used stays relatively low. Some explanations go as following:
we are extending the BaseAdapter
images will be loaded in background using an AsyncTask
as common for this kind of adapters, we'll be using an ArrayList<> parametrized with Objects of some custom class. In my app, this class is called Weapon
we will scale the images depending on the screen size
we will apply a font to the TextView in each List Row
Feel free to use this code for any purposes and modify it in any way. The only thing I'm asking for is to test the code properly before claiming that something doesn't work. It works, believe me.
If you have noticed any copy-paste-edit mistakes (since I removed some code that is irrelevant for this little tutorial), your feedback is welcome.
Before I post the code, here's a small state diagram demonstrating the logic of the getView() method:
The code for the Adapter class goes below, I've tried to explain everything you need in comments:
public class WeaponAdapter extends BaseAdapter implements View.OnClickListener {
private ArrayList<Weapon> items;
private LayoutInflater inflater = null;
private WeaponHolder weaponHolder;
private Weapon wp;
private Context c;
private Bitmap bmp;
/*--- a simple View Holder class ---*/
static class WeaponHolder {
public TextView text;
public ImageView image, addFav;
public AsyncImageSetter mImageLoader;
}
/*--- Context and all weapons of specified class are passed here ---*/
public WeaponAdapter(ArrayList<Weapon> items, Context c) {
this.items = (ArrayList<Weapon>) items;
inflater = LayoutInflater.from(c);
this.c = c;
}
#Override
public int getCount() {
return items.size();
}
#Override
public Weapon getItem(int position) {
return items.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
/*--- initialize our Weapon Object ---*/
wp = items.get(position);
if (convertView == null) {
/*--- no View is available. Inflate our list item layout and init the Views we need ---*/
convertView = inflater.inflate(R.layout.category_row, null);
weaponHolder = new WeaponHolder();
weaponHolder.text = (TextView) convertView
.findViewById(R.id.tvCatText);
weaponHolder.image = (ImageView) convertView
.findViewById(R.id.imgCatImage);
weaponHolder.addFav = (ImageView) convertView
.findViewById(R.id.imgAddFav);
convertView.setTag(weaponHolder);
} else {
weaponHolder = (WeaponHolder) convertView.getTag();
/*--- if convertView is not null, cancel the current loading operation to
* improve performance and decrease RAM usage ---*/
weaponHolder.mImageLoader.cancel();
}
/*--- load the image in background ---*/
weaponHolder.mImageLoader = new AsyncImageSetter(c, weaponHolder.image,
wp.getImage(), bmp, weaponHolder.text);
weaponHolder.mImageLoader.execute();
weaponHolder.text.setText(wp.getName());
weaponHolder.addFav.setOnClickListener(this);
return convertView;
}
#Override
public void onClick(View v) {
// do any stuff here
}
}
Here's our AsyncTask that will load and set the images in background.
NOTE: my Weapon class has a getImage() method which returns the resId of the drawable corresponding to a Weapon Object. You can modify this part in a way it works for you.
public class AsyncImageSetter extends AsyncTask<Void, Void, Bitmap> {
private ImageView img;
private int image_resId;
private Bitmap bmp;
private Context c;
private boolean cancel = false;
private int sampleSize;
private TextView txtGunName;
private Typeface font;
public AsyncImageSetter(Context c, ImageView img, int image_ResId,
Bitmap bmp, TextView txtGunName) {
this.img = img;
this.image_resId = image_ResId;
this.bmp = bmp;
this.c = c;
this.txtGunName = txtGunName;
}
public void cancel() {
cancel = true;
}
#Override
protected void onPreExecute() {
/*--- we hide the Views from the user until the content is ready. This will prevent
* the user from seeing an image being "transformed" into the next one (as a result of
* View recycling) on slow devices.
*/
img.setVisibility(View.GONE);
txtGunName.setVisibility(View.GONE);
font = Typeface.createFromAsset(c.getAssets(), "b_reg.otf");
super.onPreExecute();
}
#Override
protected Bitmap doInBackground(Void... params) {
if (!cancel) {
try {
return decodeAndScale(bmp);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(Bitmap result) {
img.setVisibility(View.VISIBLE);
try {
img.setImageBitmap(result);
} catch (Exception e) {
/*--- show an error icon in case something went wrong ---*/
img.setImageResource(R.drawable.ic_warn);
}
txtGunName.setVisibility(View.VISIBLE);
txtGunName.setTypeface(font);
super.onPostExecute(result);
}
private Bitmap decodeAndScale(Bitmap bmp) {
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = setSampleSize();
return BitmapFactory.decodeResource(c.getResources(), image_resId,
options);
}
private int setSampleSize() {
// TODO add multiple screens check
/*--- modify this method to match your needs ---*/
if (GetSettings.getScreenWidth((Activity) c) >= 320) {
/*--- physical width >= 480px ---*/
sampleSize = 2;
}
return sampleSize;
}}
You may have noticed that I use the getScreenWidth() method from the GetSettings class. Its code is quite simple and returns a dp value representing the device's screen width:
public static int getScreenWidth(Activity a) {
Display display = a.getWindowManager().getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics();
display.getMetrics(outMetrics);
float density = a.getResources().getDisplayMetrics().density;
float dpWidth = outMetrics.widthPixels / density;
return (int) dpWidth;
}
Well, that's all and I hope this post did help someone. Cheers.
P.S. if you are definitely sure something doesn't work, most likely it was caused by your internal app structure that is different from the one I use. In this case, I recommend you to do following steps:
Ask a new question so you'll be able to add properly formatted code and LogCat output
Notify me by adding a comment to my post. I will be glad to help you figure out what's wrong

Use the listview scroll state to set the images accordingly.
When listview is flinged, don't set images right at the same time, once the state is idle, use your code to set the images.
In this way it will avoid memory allocation for thos views which are not visible.If you try to set images when list view is scrolled, it can cause out of memory error.
Also, make sure that your drawable is having good size to fit in view. Getting images from drawable have always been fast, main concern here will be of memory usage.
Also create an array of drawables to set as your list item, so while setting the adapter you already have a hand full of drawables to be used for list item and do not populate list view with drawables based on condition

Is it necessary to store images in memory to show on list view in android

I'm showing list with one ImageView on every row of list.
For that, I download images from net in another AsyncTask using Drawable.createFromStream
And store them as Drawable in ArrayList which I pass to my Adapter class extending BaseAdapter class.
But the images are taken with high-resolution camera, so may be of very large size.
And I'm getting OutOfMemory error.
So my questions :
What is more efficient, storing images as drawable or as bitmap or any other format?
Am I doing right, by storing all images in memory(in array list). i.e. I'm thinking, once I get a image, I will show it on ImageView and will not store in ArrayList.
is there any way, I can compress the images after download, so they will take less space in memory.
My total code is present here

Android documentation provides a very good example showing how to handle bitmaps in your android app. The example uses an on-disk and in-memory cache and loads the images in the background. By doing so, the main UI thread is not slowed down by loading the images.
Loading Bitmaps effectively
In the example the images are loaded from picasa. It's easy, however, to adapt the example, so that pictures stored locally are used. You simply have to write your own ImageLoader extending from the 'ImageResizer':
public class ImageLoader extends ImageResizer {
public ImageLoader(Context context, int imageWidth, int imageHeight) {
super(context, imageWidth, imageHeight);
}
public ImageLoader(Context context, int imageSize) {
super(context, imageSize);
}
#Override
protected Bitmap processBitmap(Object data) {
return decodeSampledBitmapFromFile((String)data, imageWidth, imageHeight);
}
}
But to answer your question directly: it's ok to load images as Bitmaps. But you have to use a cache and weak references, so that the images can be garbage collected in case they are not visible on the screen. Caching them and using a background task for loading allows for a slick UI.

I don't see any efficiency in storing high-density images into memory - it's totally not recommended to store large ammount of images as bitmaps in memory (good for you that you have a good device ;))
See p.1
Try downscaling the images to fit the device's needs - that's not a simple job though. Also, see View.setTag(Object tag)
The adapter
public class MyImageListAdapter extends BaseAdapter implements ImageLoadingNotifier {
private LayoutInflater inflater = null;
public MyImageListAdapter() {
inflater = LayoutInflater)HomeActivity.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
return listImageInfo.size();
}
public Object getItem(int position) {
return listImageInfo.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
if (convertView == null) {
vi = inflater.inflate(R.layout.list_row, null);
}
TextView tvName = (TextView) vi.findViewById(R.id.tv_name);
TextView tvTime = (TextView) vi.findViewById(R.id.tv_time);
ImageView image = (ImageView) vi.findViewById(R.id.iv_image);
final Button btnDelete = (Button) vi.findViewById(R.id.btn_delete);
image.setImageDrawable(R.drawable.default_placeholder);//set default place-holder
new GetDrawableFromUrl(listImageInfo.get(position), vi).execute();
tvName.setText("Name: " + listImageInfo.get(position).getImage_name());
tvTime.setText("Date: " + listImageInfo.get(position).getDate_created());
btnDelete.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
final int position = listView.getPositionForView((View) v.getParent());
positionOgBtnToDelete = position;
Log.v("delete btn clicked", "delete btn no: " + position);
Toast.makeText(HomeActivity.this, "Btn delete position: " + position, Toast.LENGTH_LONG).show();
showAlertToConfirmDelete();
}
});
return vi;
}
}
The AsyncTask GetDrawableFromUrl
public class GetDrawableFromUrl extends AsyncTask<Void, Void, Drawable> {
public ImageInfo imageInfoObj;
private ImageView view;
GetDrawableFromUrl(ImageInfo imageInfo, ImageView view) {
imageInfoObj = imageInfo;
this.view = view;
}
#Override
protected Drawable doInBackground(Void... params) {
try {
return Drawable.createFromStream(((java.io.InputStream) new java.net.URL(imageInfoObj.getImageUrl()).getContent()), "src_name");
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(Drawable drawable) {
if (drawable != null) {
//imageInfoObj.setImage(drawable);
this.view.setImageDrawable(drawable);
//listImageInfo.add(imageInfoObj); //this one is called when the json is parsed
showImagesInList(); //don't know what it does (??)
}
}
}
The JSON parsing
JSONArray jsonArray = jsonObj.getJSONArray("result");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObjInner = jsonArray.getJSONObject(i);
ImageInfo imageInfo = new ImageInfo();
imageInfo.setImageUrl("http://www.dvimaytech.com/markphoto/" + jsonObjInner.getString("image"));
//new GetDrawableFromUrl(imageInfo).execute(); //don't needed here
imageInfo.setEmail(jsonObjInner.getString("emailid"));
imageInfo.setImage_id(jsonObjInner.getString("image_id"));
imageInfo.setImage_name(jsonObjInner.getString("image_name"));
imageInfo.setAmount(jsonObjInner.getString("amount"));
imageInfo.setImage_description(jsonObjInner.getString("image_description"));
imageInfo.setDate_created(jsonObjInner.getString("date_created"));
listImageInfo.add(imageInfo);
}
And, the use of any kind of List of images becomes unnecesary :)
Instead of starting the async task (GetDrawableFromUrl) when parsing the json objects, you can start the task in getView(...) method. This way you will not be constrained to store the drawables into that ArrayList, since you'll be modifying the ImageView after the image was downloaded. And, by default, you can put a placeholder, until the image is downloaded (or in case there are some network errors).
This way the images will start downloading only when the getView method will be called for that specific item.
The bottom line is that each view from the ListView will keep a reference to it's specific drawable (that was set using vi.setTag(image).
If this helps somehow, you know what to do ;)

There is pretty good library calling AQuery. YOu can use it and simple get all stuff like memory and file caching by writting only 2 line of code. So you even wouldn't need to prepare a drawable, you can call it directly from Adapter.getView() callback.
AQuery aq = new AQuery(rowView);
aq.id(R.id.image).image(url, false, true);
Hope it help you!
From AQuery docs:
Down Sampling (handling huge images)
We are loading a huge image from the network, but we only need the image to be bigger than 200 pixels wide. Passing in the target width of 200 will down sample the image to conserve memory.Aquery will only down sample with power of 2 (2,4,8...) for good image quality and
efficiency.The resulting image width will be between 200 and 399 pixels
String imageUrl = "http://farm6.static.flickr.com/5035/5802797131_a729dac808_b.jpg";
aq.id(R.id.image1).image(imageUrl, true, true, 200, 0);

Android Gallery control - need infinite loop of images

Without starting from the middle of the stack of images how do I rotate them in the infinite loop left to right and right to left? I tried setSelection(position) but for some reason I get that method called few times and inconsistently. My images increment has to be saved int he app state so it makes it a bit more complicated.
#Override
public void setSelection(int position){
int sectionPos = getCurrentPositionFromState();
if (sectionPos == (this._images - 1)){
setCurrentPositionFromState(0);
sectionPos = 0;
}
else {
setCurrentPositionInState(sectionPos +1);
}
if (sectionPos <= (this._images - 1) ){
super.setSelection(sectionPos);
}
}
gallery.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView parent, View view, int position, long id) {
gallery.setSelection(position);
#Override
public void onNothingSelected(AdapterView parent) {
}
});
I should also mention that I have an onFling() overriden like so:
#Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
return super.onFling(e1, e2, 0, velocityY);
}

There are a few ways to go about it, but in all cases, it's never technically "infinite." I got the basis of mine from snooping around for a while.
First we need to put a gallery into the xml file in the layout. So after creating the file put in a little snippet like this:
<!-- Gallery To show images Gallery -->
< Gallery
android:id="#+id/galleryView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingBottom="15dip"/>
Now lets set up a Vector of different images so we can loop through. We will be getting these images from our resources, but if you want to get them from somewhere else then just insert that instead. We are going to insert this into onCreate(). This will allow us to have a vector of id's that we can reference when getting images to put into the gallery later:
public Vector<Integer> mPhotoVector = new Vector<Integer>();
public void setPhotos() {
for(as many photos as you want){
int imageResource = getResources().getIdentifier("imageNAme", "drawable", getPackageName());
mPhotoVector.add(imageResource);
}
Where galView is my gallery view from the layout. And as we finish up this project we need to call the gallery view from the xml and initialize it to a gallery variable we will have in the code.
LoopingGalleryAdapter adapter;
Gallery galView;
adapter = new LoopingGalleryAdapter(this, mPhotoVector);
galView = (LoopingGallery)mLayoutView.findViewById(R.id.galleryView);
galView.setAdapter(adapter);
galView.setSelection((galView.getCount() / 2));
The setSelection() will have us looking at the middle of the gallery, this makes it appear to be "infinite" since there are now 1073741823 elements to each side.
Next we need to create the adapter. The basis is to make the largest gallery you can, so next we just add in our own little getCount method. This will create a gallery that is too large for the user to (plausibly) scroll to the end of.
Lastly on the adapter we have the meat of the project which requires us to set where our position is. This is the key. Once the position is set to the middle-ish of the gallery, it seems as though you have an infinite loop of images on either side.
I started mine off a little like this:
public class LoopingGalleryAdapter extends BaseAdapter {
private ImageView iv;
private Context mContext;
public PhotoVector mPhotoVector = null;
int mGalleryItemBackground;
public LoopingGalleryAdapter(Context c, PhotoVector aVector) {
this.mContext = c;
mPhotoVector = aVector;
}
public int getCount() {
return Integer.MAX_VALUE;
}
#Override
public Object getItem(int position) {
return position;
}
public ImageView getImage(){
return iv;
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
iv = new ImageView(mContext);
private final int middle = 1073741823; //this is the middle index of the gallery in galView
/************************************************************************
*if you have a vector/array/arrayList of photos you would like to display
************************************************************************/
if((position - middle) >= 0) { relativePosition = (position-middle) % mPhotoVector.size(); }
else { relativePosition = mPhotoVector.size() - (Math.abs(position - middle) % mPhotoVector.size()); }
Drawable draw = mContext.getResources().getDrawable(mPhotoVector.get(relativePosistion));
/*********************************************
*otherwise you can just insert a photo like so
*********************************************/
Drawable draw = mContext.getResources().getDrawable(R.drawable.what_you_want);
iv.setImageDrawable(draw);
return iv;
}
}
And we are now done!
Additionally, one of the tricks I have found quite useful, if not necessary when getting images from the internet is to keep a count of how many times you have gone through getView() and after 10-20 times clear your cache so you don't throw a OutOfMemoryError by doing:
if(counter >= 20){
galView.destroyDrawingCache();
counter = 0;
}
Or have getView() throw a OutOfMemoryError, catch it and return an empty ImageView (iv) and then clear then call galView.destroyDrawingCache();

A shameless self plug, just wrote an Infinite Scrolling Gallery tutorial:
http://blog.blundellapps.com/infinite-scrolling-gallery/
Source code can be downloaded also, you choose the image size.
You can use images on your SD card or images in your /resources/drawable directory.