Loading static images in list slows down scrolling - java

My static list consists of images and data.I am loading images in background asynchronously.Still loading of images slows down scrolling performance.If i comment out the image loading code list scrolls very fast.How can i imporove scrolling performance while loading images in list?Below is the code i am using for loading images-
public View getView(final int i, View v, ViewGroup viewGroup) {
thumbnailImageView = (ImageView) view.findViewById(R.id.video_thumbnail);
final String id = video.getId();
String thumbnailPath = FileUtils.getCachedFileName(0,video.getId());
BitmapWorkerTask task = new BitmapWorkerTask(thumbnailImageView);
task2.execute(thumbnailPath);
.
.
}
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap>
{
private final ImageView imageViewReference;
public BitmapWorkerTask(ImageView imageView)
{
imageViewReference = imageView;
}
#Override
protected Bitmap doInBackground(String... urls) {
return BitmapFactory.decodeFile(urls[0]);
}
#Override
protected void onPostExecute(Bitmap bitmap)
{
imageViewReference.setImageBitmap(bitmap);
}
}


You could use Universal Image Library for loading the images in the background. It has a feature to stop loading the image onScroll or Fling.


Try Picasso as it has support for local files as well:
Picasso.with(context).load(R.drawable.landing_screen).into(imageView1);
Picasso.with(context).load("file:///android_asset/DvpvklR.png").into(imageView2);
Picasso.with(context).load(new File(...)).into(imageView3);


Check the below code..It may help to you...You are not providing full code..So I assumed that you are extending your adapter from BaseAdapter and your list item is having one ImageView
final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
final int cacheSize = maxMemory / 8;
LruCache<Integer, Bitmap> mMemoryCache = new LruCache<Integer, Bitmap>(
cacheSize) {
#TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1)
#Override
protected int sizeOf(Integer key, Bitmap bitmap) {
return bitmap.getByteCount() / 1024;
}
};
/**
* This will return a bitmap from the cache
*
* #param key
* #return
*/
public Bitmap getBitmapFromMemCache(Integer key) {
return mMemoryCache.get(key);
}
/**
* This method will add the bitmap to the memory cache
*
* #param key
* #param bitmap
*/
public void addBitmapToMemoryCache(Integer key, Bitmap bitmap) {
if (getBitmapFromMemCache(key) == null) {
mMemoryCache.put(key, bitmap);
}
}
private View video;
#Override
public View getView(int position, View view, ViewGroup parent) {
ViewHolder holder = null;
if (view == null) {
view = LayoutInflater.from(context).inflate(R.layout.list_item,
null);
holder = new ViewHolder();
holder.thumbnailImageView = (ImageView) view
.findViewById(R.id.video_thumbnail);
view.setTag(holder);
}
else {
holder = (ViewHolder) view.getTag();
}
if (holder.bitmapWorkerTask!= null && holder.bitmapWorkerTask.getStatus() == Status.RUNNING) {
holder.bitmapWorkerTask.cancel(true);
}
Bitmap bitmapFromMemCache = getBitmapFromMemCache(position);
if (bitmapFromMemCache == null) {
holder.thumbnailImageView.setImageResource(R.drawable.default_image);
holder.bitmapWorkerTask = new BitmapWorkerTask(holder.thumbnailImageView,position);
String thumbnailPath = FileUtils.getCachedFileName(0, video.getId());
holder.bitmapWorkerTask.execute(thumbnailPath);
} else {
holder.thumbnailImageView.setImageBitmap(bitmapFromMemCache);
}
........
}
private class ViewHolder {
private ImageView thumbnailImageView;
private BitmapWorkerTask bitmapWorkerTask;
}
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
private final ImageView imageViewReference;
private int position;
public BitmapWorkerTask(ImageView imageView,int position) {
imageViewReference = imageView;
this.position=position;
}
#Override
protected Bitmap doInBackground(String... urls) {
Bitmap bitmap= BitmapFactory.decodeFile(urls[0]);
addBitmapToMemoryCache(position, bitmap);
return bitmap
}
#Override
protected void onPostExecute(Bitmap bitmap) {
imageViewReference.setImageBitmap(bitmap);
}
}

Related

Error, cannot access an invalid/free'd bitmap here! while using a Model Class containing Bitmap

In my app I'm using model class containing a Bitmap for displaying an image on recyclerView
public class ImageModelClass {
Bitmap image;
public void setImage(Bitmap image) {
this.image = image;
}
public Bitmap getImage() {
return image;
}
Problem is when i am using Bitmap directly from my model class then this error is throwing Error, cannot access an invalid/free'd bitmap here!
and when i replace the Bitmap Class to a String in my model class and using encoded bitmap i converted bitmap Image into a String then this error isn't coming .
But encoding a Bitmap is taking lot of time load images.
public class ImageCollection extends AppCompatActivity {
public static final String IMAGE_SHARED_PREFS = "com.example.animproject_IMAGE_SHARED_PREFS";
public static final String IMAGE_DATA_KEY = "com.example.animproject_IMAGE_DATA_KEY";
private static final int REQUEST_CODE = 1;
RecyclerView recyclerView;
ImageCollectionAdapter adapter;
List<ImageModelClass> imageList;
FloatingActionButton fab;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_collection);
loadAlbumData();
recyclerView = findViewById(R.id.imageCollectionRecyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH);
adapter = new ImageCollectionAdapter(this,imageList);
StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(2, GridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(staggeredGridLayoutManager);
recyclerView.setAdapter(adapter);
fab = findViewById(R.id.fabButton);
fab.setOnClickListener(new View.OnClickListener() {
#RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR2)
#Override
public void onClick(View view) {
Intent gallery = new Intent(Intent.ACTION_PICK);
gallery.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
gallery.setType("image/*");
startActivityForResult(gallery, REQUEST_CODE);
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, #Nullable Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
assert data != null;
ClipData clipData = data.getClipData();
if (clipData != null) {
for (int i = 0; i < clipData.getItemCount(); i++) {
Uri imageUri = clipData.getItemAt(i).getUri();
InputStream inputStream;
try {
inputStream = getContentResolver().openInputStream(imageUri);
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
ImageModelClass imageModelClass = new ImageModelClass();
imageModelClass.setImage(bitmap);
imageList.add(imageModelClass);
adapter.notifyDataSetChanged();
saveGalleryData();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
} else {
Uri imageUri = data.getData();
InputStream inputStream = null;
try {
assert imageUri != null;
inputStream = getContentResolver().openInputStream(imageUri);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
ImageModelClass imageModelClass = new ImageModelClass();
imageModelClass.setImage(bitmap);
imageList.add(imageModelClass);
adapter.notifyDataSetChanged();
saveGalleryData();
}
}
}
private void saveGalleryData() {
SharedPreferences preferences = getSharedPreferences(IMAGE_SHARED_PREFS, MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
Gson gson = new Gson();
String json = gson.toJson(imageList);
editor.putString(IMAGE_DATA_KEY, json);
editor.apply();
}
private void loadAlbumData() {
SharedPreferences preferences = getSharedPreferences(IMAGE_SHARED_PREFS, MODE_PRIVATE);
Gson gson = new Gson();
Type type = new TypeToken<ArrayList<ImageModelClass>>() {
}.getType();
String data = preferences.getString(IMAGE_DATA_KEY, null);
imageList = gson.fromJson(data, type);
if (imageList == null) {
imageList = new ArrayList<>();
}
}
}
Adapter
public class ImageCollectionAdapter extends RecyclerView.Adapter<ImageCollectionAdapter.MyViewHolder> {
List<ImageModelClass> list;
Context context;
public ImageCollectionAdapter(Context context,List<ImageModelClass> list) {
this.list = list;
this.context = context ;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(parent.getContext())
.inflate(R.layout.image_collection_lists, parent, false));
}
#Override
public void onBindViewHolder(#NonNull
MyViewHolder holder, int position) {
ImageModelClass currentImage =
list.get(position);
Glide
.With(context.getApplicationContext)
.load(currentImages.getImages)
/* getting bitmap images from model
* class
*/
.into(holder.imageView);
}
#Override
public int getItemCount() {
return list.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
RoundedImageView imageView;
public MyViewHolder(#NonNull View itemView) {
super(itemView);
imageView = itemView.findViewById(R.id.galleryPicture);
}
}
}
please help it will be appreciatable :)

I was facing the same issue when I was trying to get the bitmap from the textView. The textView was in the RecyclerView inside a bottom sheet. When I clicked on textView I was getting the bitmap and dismissing the bottom sheet.
I got the bitmap from the drawing cache of the textView. I checked it using the debugger the bitmap was retrieved correctly. But when I passed it to callback (from recyclerView's adapter to activity), the bitmap in the callback is not shown in the debugger and I got the error 'cannot access an invalid/free'd bitmap here!'.
As of my understanding, When textView is not shown/rendered on the screen (In my case when I dismissed the bottom sheet) the cached bitmap becomes unavailable. Gotta read the relevant docs to know the exact cause of the problem.
What I did to solve this issue is to create a copy of the bitmap and pass it to the callback and It worked!
You can copy the bitmap like this:
Bitmap copyBitmap = bitmap.copy(bitmap.getConfig(), false);
The full code of retrieving the bitmap and creating new one:
holder.textView.setDrawingCacheEnabled(true);
holder.textView.buildDrawingCache();
Bitmap bitmap = holder.textView.getDrawingCache();
Bitmap copyBitmap = bitmap.copy(bitmap.getConfig(), false);
holder.textView.setDrawingCacheEnabled(false);
callback.onWidgetSelected(copyBitmap);
I hope you'll find it helpful. I'll make sure to study the docs as well and will update the answer when I find the cause of this problem.

How to get data from AsyncTask in android?

Iv tried some on the solutions in stack overflow, but was not able to work it out for my case.
I want to get the Bitmap data from onPostExecute or bmp from doInBackground and set it to ImageView imageurl using imageurl.setImageBitmap() in the getView() method
public class BooksAdapter extends ArrayAdapter<Books> {
public BooksAdapter(Activity context, ArrayList<Books> word) {
super(context, 0, word);
}
#NonNull
#Override
public View getView(int position, #Nullable View convertView, #NonNull ViewGroup parent) {
// Check if the existing view is being reused, otherwise inflate the view
View listItemView = convertView;
if (listItemView == null) {
listItemView = LayoutInflater.from(getContext()).inflate(
R.layout.list_item, parent, false);
}
// Get the {#link AndroidFlavor} object located at this position in the list
Books currentbook = getItem(position);
TextView bookView = (TextView) listItemView.findViewById(R.id.bookTittle);
String booktitle = currentbook.getBookName();
bookView.setText(booktitle);
TextView authorView = (TextView) listItemView.findViewById(R.id.authorname);
String authorname = currentbook.getAuthorName();
authorView.setText(authorname);
ImageView imageurl = (ImageView) listItemView.findViewById(R.id.imageView);
String imagelink = currentbook.getImageLink();
ImageAsyncTask task = new ImageAsyncTask();
task.execute(imagelink);
// imageurl.setImageBitmap();
return listItemView;
}
private class ImageAsyncTask extends AsyncTask<String, Void, Bitmap> {
#Override
protected Bitmap doInBackground(String... urls) {
URL url = null;
Bitmap bmp = null;
try {
url = new URL(urls[0]);
} catch (MalformedURLException e) {
Log.e(LOG_TAG, "Error with creating URL ", e);
}
try {
bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
} catch (IOException e) {
Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
}
return bmp;
}
#Override
protected void onPostExecute(Bitmap data) {
}
}
}

Just pass your ImageView to AsyncTask via constructor and then set image in onPostExecute like this:
ImageAsyncTask task = new ImageAsyncTask(myImageView);
private class ImageAsyncTask extends AsyncTask<String, Void, Bitmap> {
private ImageView img;
ImageAsyncTask(Imageview img){
this.img = img;
}
...
protected void onPostExecute(Bitmap data) {
this.img.setImageBitmap(data);
}

add image from url to viewpager in second and third position

Here i have two url but when i run this app this images are been loaded to second page means first image will load in second page after few second the second image also adds to same loaction by overlapping. i need to add this to second and third pages these url
viewPager = (ViewPager) findViewById(R.id.splash);
ImageAdapter adapter = new ImageAdapter(this);
viewPager.setAdapter(adapter);
public class ImageAdapter extends PagerAdapter {
Context context;
private int[] GalImages = new int[] {
R.drawable.slider,
R.drawable.slider,
R.drawable.slider,
};
ImageAdapter(Context context){
this.context=context;
}
#Override
public int getCount() {
return GalImages.length;
// return 10;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == ((ImageView) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(context);
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
imageView.setImageResource(GalImages[position]);
new LoadImage(imageView).execute("http://www.gadgetbaazar.com/wp-content/uploads/2016/12/Top-Mobile-Phones.jpg");
new LoadImage(imageView).execute("https://pisces.bbystatic.com/BestBuy_US/store/ee/2015/com/pm/nav_desktops_1115.jpg");
container.addView(imageView, 0);
return imageView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((ImageView) object);
}
private class LoadImage extends AsyncTask<String, String, Bitmap> {
ImageView img=null;
public LoadImage(ImageView img){
this.img=img;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
protected Bitmap doInBackground(String... args) {
Bitmap bitmap=null;
try {
bitmap = BitmapFactory.decodeStream((InputStream)new URL(args[0]).getContent());
} catch (Exception e) {
e.printStackTrace();
}
return bitmap;
}
protected void onPostExecute(Bitmap image) {
if(image != null){
img.setImageBitmap(image);
}
}
}
}

Try this
#Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(context);
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
if(position == 0){
imageView.setImageResource(GalImages[position]);
}else if(position == 1){
new LoadImage(imageView).execute("http://www.gadgetbaazar.com/wp-content/uploads/2016/12/Top-Mobile-Phones.jpg");
}else if(position ==2){
new LoadImage(imageView).execute("https://pisces.bbystatic.com/BestBuy_US/store/ee/2015/com/pm/nav_desktops_1115.jpg");
}
container.addView(imageView, 0);
return imageView;
}

Download and set bitmap into list view

I use this code to download and set images from link to an image view
but when i scroll the list view and scroll back to top the images starts to download and clear the first downloaded picture.
I tried to download and save them into a array bitmap then show them but i cant update array bitmap like an array list and show it one by one in list view what can i do ?
class aa extends ArrayAdapter<String> {
public aa() {
super(MainActivity.this, R.layout.home_row, IDS);
}
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
LayoutInflater li = getLayoutInflater();
View row = li.inflate(R.layout.home_row, parent, false);
TextView name=(TextView)row.findViewById(R.id.home_row_name);
ImageView pic=(ImageView)row.findViewById(R.id.home_row_pic);
name.setText(arrayNAME.get(position).toString());
new Download_image(bitmap_PIC,position,pic).execute(PIC[position]);
return (row);
}
}
And here is the download method :
class Download_image extends AsyncTask<String, Void, Bitmap> {
Bitmap[] bitMap;
int position;
ImageView bmImage;
public Download_image(Bitmap[] bitMap,int position,ImageView bmImage) {
this.bitMap = bitMap;
this.position = position;
this.bmImage = bmImage;
}
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap mIcon11 = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
mIcon11 = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return mIcon11;
}
protected void onPostExecute(Bitmap result) {
bitMap[position]=result;
bmImage.setImageBitmap(bitmap_PIC[position]);
}
}

Popup gridview cell onTOuch

I have a grid View In which I am adding Button dynamically.
I am setting OnTouch listener to grid view.
I want when my finger move on the particular cell then that cell element should get popup
similar way our android keyboard do.
public class MainActivity extends Activity {
private ArrayList<Integer> data;
private GridView gv;
private TextView biggerView = null;
#SuppressLint("NewApi")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
createData();
gv = (GridView) findViewById(R.id.grid);
gv.setNumColumns(10);
gv.setAdapter(new FilterButtonAdapter(data, this));
gv.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View arg0, MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_MOVE) {
try {
int position = gv.pointToPosition((int) event.getX(),
(int) event.getY());
View v = (View) gv.getChildAt(position);
if (v != null) {
gv.requestFocus();
gv.setSelection(gv.pointToPosition( (int)
event.getX(), (int) event.getY()));
}
return true;
} catch (Exception e) {
return true;
}
}
if (event.getAction() == MotionEvent.ACTION_UP) {
int position = gv.pointToPosition((int) event.getX(),
(int) event.getY());
View v = (View) gv.getChildAt(position);
if (v != null) {
gv.clearFocus();
TextView tv = (TextView) v.findViewById(R.id.texttoadd);
Toast.makeText(MainActivity.this, tv.getText(),
Toast.LENGTH_SHORT).show();
}
return true;
}
return false;
}
});
}
private void createData() {
data = new ArrayList<Integer>();
for (int i = 0; i < 200; i++) {
data.add(i);
}
}
enter code here
i have write this code which is giving me the selected item but when item are more then grid is scrolled and after that the am not getting the item which i am selecting
i have figured out that the x and y position is getting change when grid is scrolled
i may be wrong
please help

I think that suggested in the question way of touch position detection might be not effective, because there's more high-level way to obtain scrolling position.
The main ideas of the implementation are the following:
Use onScrollChanged() to track scroll position at every moment;
Display selection as separate view above GridView;
Track if selected item is visible (using this question);
So, to obtain proper scroll callback, slightly customized GridView is needed:
public class ScrollAwareGridView extends GridView {
/** Callback interface to report immediate scroll changes */
public interface ImmediateScrollListener {
void onImmediateScrollChanged();
}
/** External listener for */
private ImmediateScrollListener mScrollListener = null;
public ScrollAwareGridView(final Context context) {
super(context);
}
public ScrollAwareGridView(final Context context, final AttributeSet attrs) {
super(context, attrs);
}
public ScrollAwareGridView(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onScrollChanged(final int l, final int t, final int oldl, final int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if (null != mScrollListener) {
mScrollListener.onImmediateScrollChanged();
}
}
/**
* #param listener {#link ImmediateScrollListener}
*/
public void setImmediateScrollListener(final ImmediateScrollListener listener) {
mScrollListener = listener;
}
}
It will be placed in the xml the following way (main.xml):
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.example.TestApp.ScrollAwareGridView
android:id="#+id/grid"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="3" />
<!-- Selection view -->
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/selectedImage"
android:visibility="gone" />
</RelativeLayout>
In above xml there's also selection view presented.
Activity will handle selection of items (however, it might be better to keep selection and scroll tracking logic in separate object (grid adapter or specific grid fragment) in order not to keep grid-specific logic in Activity code):
public class MyActivity extends Activity implements ScrollAwareGridView.ImmediateScrollListener, AdapterView.OnItemClickListener {
private static final String TAG = "MyActivity";
/** To start / pause music */
private ImageView mSelectedImage = null;
/** position of selected item in the adapter */
private int mSelectedPosition;
/** Main grid view */
private ScrollAwareGridView mGrid;
/** Adapter for grid view */
private ImageAdapter mAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Show the layout with the test view
setContentView(R.layout.main);
mSelectedImage = (ImageView) findViewById(R.id.selectedImage);
mGrid = (ScrollAwareGridView) findViewById(R.id.grid);
if (null != mGrid) {
mAdapter = new ImageAdapter(this);
mGrid.setAdapter(mAdapter);
mGrid.setImmediateScrollListener(this);
mGrid.setOnItemClickListener(this);
}
}
#Override
protected void onPause() {
super.onPause();
}
#Override
protected void onResume() {
super.onResume();
mSelectedImage.setImageBitmap(null);
mSelectedImage.setVisibility(View.GONE);
mSelectedPosition = -1;
}
#Override
public void onImmediateScrollChanged() {
if (mSelectedPosition >= 0) {
int firstPosition = mGrid.getFirstVisiblePosition(); // This is the same as child #0
int wantedChild = mSelectedPosition - firstPosition;
// Say, first visible position is 8, you want position 10, wantedChild will now be 2
// So that means your view is child #2 in the ViewGroup:
if (wantedChild < 0 || wantedChild >= mGrid.getChildCount()) {
Log.w(TAG, "Unable to get view for desired position, because it's not being displayed on screen.");
mSelectedImage.setVisibility(View.INVISIBLE);
return;
} else {
mSelectedImage.setVisibility(View.VISIBLE);
}
// Could also check if wantedPosition is between listView.getFirstVisiblePosition() and listView.getLastVisiblePosition() instead.
final View selectedView = mGrid.getChildAt(wantedChild);
if (null != selectedView && mSelectedImage.getVisibility() == View.VISIBLE) {
// Put selected view on new position
final ViewGroup.MarginLayoutParams zoomedImageLayoutParams = (ViewGroup.MarginLayoutParams) mSelectedImage.getLayoutParams();
// 200 is difference between zoomed and not zoomed images dimensions
// TODO: Avoid hardcoded values and use resources
final Integer thumbnailX = mGrid.getLeft() + selectedView.getLeft() - (ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION - ImageAdapter.GRID_ITEM_DIMENSION) / 2;
final Integer thumbnailY = mGrid.getTop() + selectedView.getTop() - (ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION - ImageAdapter.GRID_ITEM_DIMENSION) / 2;
zoomedImageLayoutParams.setMargins(thumbnailX,
thumbnailY,
0,
0);
mSelectedImage.setLayoutParams(zoomedImageLayoutParams);
}
}
}
#Override
public void onItemClick(final AdapterView<?> parent, final View view, final int position, final long id) {
mSelectedPosition = position;
final Bitmap bm = mAdapter.getImage(position);
// Obtain image from adapter, with check if image presented
if (bm != null) {
final ViewGroup.MarginLayoutParams zoomedImageLayoutParams = (ViewGroup.MarginLayoutParams) mSelectedImage.getLayoutParams();
// 200 is difference between zoomed and not zoomed images dimensions
// TODO: Avoid hardcoded values and use resources
final Integer thumbnailX = mGrid.getLeft() + view.getLeft() - (ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION - ImageAdapter.GRID_ITEM_DIMENSION) / 2;
final Integer thumbnailY = mGrid.getTop() + view.getTop() - (ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION - ImageAdapter.GRID_ITEM_DIMENSION) / 2;
zoomedImageLayoutParams.setMargins(thumbnailX,
thumbnailY,
0,
0);
zoomedImageLayoutParams.height = ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION;
zoomedImageLayoutParams.width = ImageAdapter.HIGHLIGHTED_GRID_ITEM_DIMENSION;
mSelectedImage.setImageBitmap(bm);
mSelectedImage.setScaleType(ImageView.ScaleType.CENTER);
mSelectedImage.setLayoutParams(zoomedImageLayoutParams);
mSelectedImage.setVisibility(View.VISIBLE);
}
}
}
Below is GridViews adapter. However there's nothing specific in it which related to scrolling tracking (most of code I've reused from this answer):
public class ImageAdapter extends BaseAdapter {
private static final String TAG = "ImageAdapter";
/** For creation of child ImageViews */
private Context mContext;
public static final Integer[] IMAGES_RESOURCES = {
R.drawable.image001, R.drawable.image002, R.drawable.image003, R.drawable.image004,
R.drawable.image005, R.drawable.image006, R.drawable.image007, R.drawable.image008,
R.drawable.image009, R.drawable.image010, R.drawable.image011, R.drawable.image012,
R.drawable.image013, R.drawable.image014, R.drawable.image015, R.drawable.image016,
R.drawable.image017, R.drawable.image018, R.drawable.image019, R.drawable.image020,
R.drawable.image021, R.drawable.image022, R.drawable.image023, R.drawable.image024,
R.drawable.image025, R.drawable.image026, R.drawable.image027, R.drawable.image028,
R.drawable.image029, R.drawable.image030, R.drawable.image031, R.drawable.image032,
R.drawable.image033, R.drawable.image034, R.drawable.image035, R.drawable.image036,
R.drawable.image037, R.drawable.image038, R.drawable.image039, R.drawable.image040,
R.drawable.image041, R.drawable.image042, R.drawable.image043, R.drawable.image044,
R.drawable.image045, R.drawable.image046, R.drawable.image047, R.drawable.image048,
R.drawable.image049, R.drawable.image050
};
// TODO: use resources for that sizes, otherwise You'll GET PROBLEMS on other displays!
public final static int GRID_ITEM_DIMENSION = 300;
public final static int HIGHLIGHTED_GRID_ITEM_DIMENSION = 500;
private Bitmap mHolder = null;
private static final int CACHE_SIZE = 50 * 1024 * 1024; // 8 MiB cache
/** Cache to store all decoded images */
private LruCache<Integer, Bitmap> mBitmapsCache = new LruCache<Integer, Bitmap>(CACHE_SIZE) {
#Override
protected int sizeOf(final Integer key, final Bitmap value) {
return value.getByteCount();
}
#Override
protected void entryRemoved(final boolean evicted, final Integer key, final Bitmap oldValue, final Bitmap newValue) {
if (!oldValue.equals(mHolder)) {
oldValue.recycle();
}
}
};
// Constructor
public ImageAdapter(Context c){
mContext = c;
mHolder = BitmapFactory.decodeResource(c.getResources(), R.drawable.ic_launcher, null);
}
#Override
public int getCount() {
return IMAGES_RESOURCES.length;
}
#Override
public Object getItem(int position) {
return IMAGES_RESOURCES[position];
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) {
imageView = new ImageView(mContext);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setLayoutParams(new GridView.LayoutParams(GRID_ITEM_DIMENSION, GRID_ITEM_DIMENSION));
} else {
imageView = (ImageView) convertView;
}
final Bitmap itemBitmap = mBitmapsCache.get(IMAGES_RESOURCES[position]);
if (itemBitmap == null || itemBitmap.isRecycled()) {
Log.e(TAG, position + " is missed, launch decode for " + IMAGES_RESOURCES[position]);
imageView.setImageBitmap(mHolder);
mBitmapsCache.put(IMAGES_RESOURCES[position], mHolder);
new BitmapWorkerTask(mBitmapsCache, mContext.getResources(), this).execute(IMAGES_RESOURCES[position]);
} else {
Log.e(TAG, position + " is here for " + IMAGES_RESOURCES[position]);
imageView.setImageBitmap(itemBitmap);
}
return imageView;
}
/**
* Obtains image at position (if there's only holder, then null to be returned)
*
* #param position int position in the adapter
*
* #return {#link Bitmap} image at position or null if image is not loaded yet
*/
public Bitmap getImage(final int position) {
final Bitmap bm = mBitmapsCache.get(IMAGES_RESOURCES[position]);
return ((mHolder.equals(bm) || bm == null) ? null : bm.copy(Bitmap.Config.ARGB_8888, false));
}
/** AsyncTask for decoding images from resources */
static class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
private int data = 0;
private final LruCache<Integer, Bitmap> mCache;
private final Resources mRes;
private final BaseAdapter mAdapter;
public BitmapWorkerTask(LruCache<Integer, Bitmap> cache, Resources res, BaseAdapter adapter) {
// nothing to do here
mCache = cache;
mRes = res;
mAdapter = adapter;
}
// Decode image in background.
#Override
protected Bitmap doInBackground(Integer... params) {
data = params[0];
// Use sizes for selected bitmaps for good up-scaling
return decodeSampledBitmapFromResource(mRes, data, GRID_ITEM_DIMENSION, GRID_ITEM_DIMENSION);
}
// Once complete, see if ImageView is still around and set bitmap.
#Override
protected void onPostExecute(Bitmap bitmap) {
mCache.put(data, bitmap);
mAdapter.notifyDataSetChanged();
}
}
public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res, resId, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
options.outHeight = GRID_ITEM_DIMENSION;
options.outWidth = GRID_ITEM_DIMENSION;
return BitmapFactory.decodeResource(res, resId, options);
}
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 = 1;
if (height > reqHeight || width > reqWidth) {
// Calculate ratios of height and width to requested height and width
final int heightRatio = Math.round((float) height / (float) reqHeight);
final int widthRatio = Math.round((float) width / (float) reqWidth);
// Choose the smallest ratio as inSampleSize value, this will guarantee
// a final image with both dimensions larger than or equal to the
// requested height and width.
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}
return inSampleSize;
}
}

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