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Keeping state of a view constant in Recyclerview after calling notifydatasetchanged()

I have a recycler adapter which has 3 itemviewtypes. No.1 type of view has an initial animation to show the view which I've written under the holder instance check in the OnBindView . it works fine. but when there is any change in the other view types, notifydatasetchanged() is called and the adapter is set again which makes the animation start again.
i tried putting a flag for the animation where it would only animate the first time. is there a smarter way to do this?
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int
viewType) {
mSharedPreferencesManager.setVersionNewFeatureCheck(BuildConfig.VERSION_NAME);
Logger.i(TAG, "onCreateViewHolder, " + viewType);
if (viewType == TYPE_HEADER) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.converation_header_row, parent, false);
return new HeaderViewHolder(v);
} else if(viewType == TYPE_ANNOUNCEMENT) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_new_feature_notification, parent, false);
return new FeatureNotificationViewHolder(v);
}
else{
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.conversation_row, parent, false);
return new ConversationRowViewHolder(v);
}
}
f (holder instanceof FeatureNotificationViewHolder) {
final FeatureNotificationViewHolder featureNotificationViewHolder = (FeatureNotificationViewHolder) holder;
featureNotificationViewHolder.chatNewFeatureNotif.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
final int height = featureNotificationViewHolder.chatNewFeatureNotif.getMeasuredHeight();
featureNotificationViewHolder.chatNewFeatureNotif.setVisibility(View.GONE);
featureNotificationViewHolder.chatNewFeatureNotif.getViewTreeObserver().removeOnPreDrawListener(this);
mOverflowAnimations.showView(featureNotificationViewHolder.chatNewFeatureNotif, height, 6);
return false;
}
});

.notifyDataSetChanged() will notify all of your items inside the RecyclerView, if you don't want everything to reset consider using .notifyItemChanged(int position) method on your adapter instance. You'll need to know exactly the index/position of the item to be notified.

Instead of using notifyDataSetChanged, you should use notifyItemChanged to only change the item that needs to be changed, and not the whole adapter or data set.
This won't lead to the unnecessary animation because you're only changing a specific item. This is also much faster and takes up less processing and rendering power.
You can read more about it here.

Want to use same Adapter with different Activities and different row_layouts

I want my Adapter to choose either one row_layout or another row_layout, depending on which Activity is sending the data. There are two Activities sending data.
At the moment I only know how to make the Adapter use one row_layout. I can't work out how to write the extra code to make it choose a different row_layout, depending on which Activity is sending the data. (There wont be any checkbox in the second row_layout).
Here is my Adapter:
public class ShopItemAdapter extends ArrayAdapter<ShopItem> {
public ShopItemAdapter(Context context, ArrayList<ShopItem> shopItem){
super(context, 0, shopItem);
}
#NonNull
#Override
public View getView(int position, View convertView, #NonNull ViewGroup parent) {
if(convertView == null){
convertView = LayoutInflater.from(getContext()).inflate(R.layout.row_layout, parent, false);
}
TextView tvItem = (TextView)convertView.findViewById(R.id.tvItemName);
TextView tvQty = (TextView)convertView.findViewById(R.id.tvQuantity);
CheckBox cbIsPurchased = (CheckBox)convertView.findViewById(R.id.cbIsPurchased);
ShopItem _shopItem = getItem(position);
tvItem.setText(_shopItem.getItemName());
tvQty.setText(String.valueOf(_shopItem.getQuantity()));
if(_shopItem.getIsPurchased() == 1){
cbIsPurchased.setChecked(true);
}
else{
cbIsPurchased.setChecked(false);
}
return convertView;
}
}

You can add some parameter to the ShopItemAdapter constructor to distinguish from which Activity is called, but if that implies to use many if conditionals in getView code then i think it's better to write several adapters, you will have a much clear code.

Alternate color of ListView disappears on scrolling the screen in Android

I am using ListView with alternate rows colored. But when the ListView exceeds the length of the screen, on scrolling, the alternate color disappears.
Below is my code:
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = getActivity().getLayoutInflater()
.inflate(R.layout.problem_list_row, null);
if(position%2!=0) {
convertView.setBackgroundColor(Color.parseColor("#ebebeb"));
}
}
if(position%2!=0){
convertView.setBackgroundColor(Color.parseColor("#ebebeb"));
}
/* some code */
return convertView;
}
Attached below, the image of the ListView.

Try this code
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = getActivity().getLayoutInflater()
.inflate(R.layout.problem_list_row, null);
}
if(position%2==0)
{
// SET EVEN POSITION COLOR
convertView.setBackgroundColor(Color.parseColor("#ebebeb"));
}
else
{
//SET ODD POSITION COLOR
}
/* some code */
return convertView;
}
I hope this helps you.

convertView is null if the entire ListView fits on the screen. However once you start scrolling, Views that move off the screen get passed to the getView() method as convertView. Sometimes the convertView received will be grey even though you want the View to be white. Your code doesn't deal with this case because it only colours Views grey, it never clears the background colour when it is no longer wanted. To solve this problem you need to set the colour both for odd and even positions.
This should work.
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = getActivity().getLayoutInflater()
.inflate(R.layout.problem_list_row, null);
}
convertView.setBackgroundColor(Color.parseColor(position%2!=0 ? "#ebebeb" : "#ffffff"));
/* some code */
return convertView;
}

I would recommend you to use multiple views, so two .xml file in your case.
I did exactly the same thing you want in an article on my website: http://raverat.github.io/android-listview-multi-views/
Hope this will help!

How to correctly implement a custom listview with images using Picasso library?

I created a custom listview layout with images which are loaded from web like this:
http://i.stack.imgur.com/l8ZOc.png
It works fine when scrolling down. However, when you scroll down, the previous items go out of screen then destroyed. When you try to scroll up again, it gets loaded again (from cache, faster but not instant) which causes a delay and it is not fluent as it should be.
1.Is there an example of how to do this properly?
2.Is there a way to prevent listview items being destroyed when they are out of screen?
3.If so, will it cause problems to keep too many items?
Bellow is my code:
MenuAdapter:
public class MenuAdapter extends BaseAdapter{
Context context;
List<MyMenuItem> menuItems;
MenuAdapter(Context context, List<MyMenuItem> menuItems) {
this.context = context;
this.menuItems = menuItems;
}
#Override
public int getCount() {
return menuItems.size();
}
#Override
public Object getItem(int position) {
return menuItems.get(position);
}
#Override
public long getItemId(int position) {
return menuItems.indexOf(getItem(position));
}
private class ViewHolder {
ImageView ivMenu;
TextView tvMenuHeader;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
convertView = mInflater.inflate(R.layout.menu_item, null);
holder = new ViewHolder();
holder.tvMenuHeader = (TextView) convertView.findViewById(R.id.tvMenuHeader);
holder.ivMenu = (ImageView) convertView.findViewById(R.id.ivMenuItem);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
MyMenuItem row_pos = menuItems.get(position);
Picasso.with(context)
.load(row_pos.getItem_image_url())
.into(holder.ivMenu);
holder.tvMenuHeader.setText(row_pos.getItem_header());
Log.e("Test", "headers:" + row_pos.getItem_header());
return convertView;
}
}
MyMenuItem:
public class MyMenuItem {
private String item_header;
private String item_image_url;
public MyMenuItem(String item_header, String item_image_url){
this.item_header=item_header;
this.item_image_url=item_image_url;
}
public String getItem_header(){
return item_header;
}
public void setItem_header(String item_header){
this.item_header=item_header;
}
public String getItem_image_url(){
return item_image_url;
}
public void setItem_image_url(String item_image_url){
this.item_image_url=item_image_url;
}
}
MainActivity:
public class MyActivity extends Activity implements AdapterView.OnItemClickListener {
List<MyMenuItem> menuItems;
ListView myListView;
JSONArray jsonArray;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
Bundle extras = getIntent().getExtras();
if(extras!=null){
try{
jsonArray = new JSONArray(extras.getString("Data"));
}catch (Exception e){
e.printStackTrace();
}
}
menuItems = new ArrayList<MyMenuItem>();
for (int i = 0; i < jsonArray.length(); i++) {
try {
MyMenuItem item = new MyMenuItem(jsonArray.getJSONObject(i).getString("title"), jsonArray.getJSONObject(i).getString("imageURL"));
menuItems.add(item);
}catch (Exception e){
e.printStackTrace();
}
}
myListView = (ListView) findViewById(R.id.list);
MenuAdapter adapter = new MenuAdapter(this, menuItems);
myListView.setAdapter(adapter);
myListView.setOnItemClickListener(this);
}
}
MenuItem.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/ivMenuItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="center"
android:src="#drawable/em" />
<TextView
android:id="#+id/tvMenuHeader"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#55000000"
android:paddingBottom="15dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="15dp"
android:textColor="#android:color/white"
android:layout_gravity="left|top"
android:layout_alignBottom="#+id/ivMenuItem"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</RelativeLayout>

1. Is there an example of how to do this properly?
Your code looks pretty close to perfect. The Adapter's getView method is usually the critical path to optimize. Compare for example Picasso's own example SampleListDetailAdapter.java. The important points it (as well as your code) does
check for & re-use already inflated views, inflation is expensive.
use ViewHolder so you don't have to call findViewById every time. Not terribly expensive on simple views. Also cached afaik.
Picasso.with(context).load(url)... each time you need to display an image. This should finish instantly but still use caches and other magic.
There are some minor optimizations you can add, but I doubt that there are noticeable or even measurable changes:
pure style change: use BaseAdapter#getItem(position). This method
exists for you only. The framework doesn't use it.
#Override
public MyMenuItem getItem(int position) { // << subclasses can use subtypes in overridden methods!
return menuItems.get(position);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
...
MyMenuItem row_pos = getItem(position);
Use a sane id method
#Override
public long getItemId(int position) {
return menuItems.indexOf(getItem(position));
}
is equivalent to
#Override
public long getItemId(int position) {
return position;
}
but now infinitely faster. indexOf(Object) scales really badly with the number of objects.
Cache objects that don't change:
MenuAdapter(Context context, List<MyMenuItem> menuItems) {
this.mLayoutInflater = LayoutInflater.from(content);
this.mPicasso = Picasso.with(context);
}
..
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = mInflater.inflate(R.layout.menu_item, null);
...
mPicasso
.load(row_pos.getItem_image_url())
.into(holder.ivMenu);
2. Is there a way to prevent listview items being destroyed when they are out of screen?
No(*).
..(*) well you can essentially cache the result of getView e.g. in LruCache(position, View) or LruCache(MyMenuItem, View), then don't touch the convertView - they need to remain unconverted or you would kill those views in your cache. Also
#Override
public int getItemViewType(int position) {
return Adapter.IGNORE_ITEM_VIEW_TYPE;
}
seemed to be required because the standard adapter using code assumes that views it removes from visibility are gone. They are not and messing with them messes with your cache and caused weird display problems for me.
3. If so, will it cause problems to keep too many items?
Yes. This behavior is not intendend / expected. There is also more or less nothing you gain. You might be able to save you the call to holder.tvMenuHeader.setText(). Likewise the one to Picasso but both of them should complete instantly. Picasso should have your image cached already. By caching all Views you essentially add another cache that also contains all the images. I would rather check that the picasso cache works as intended and holds most items. The only reason you may want to do it with view caching is for cases that require complicated setup of the view, so it becomes worth caching the completely constructed view rather than just some content parts.
Profile
Profiling can actually tell you where you can / need / should improve. The first to look at IMO is traceview. You'll see if code blocks the main thread which results in choppy list scrolling. If you're doing complicated views and you see that the draw methods are executed most of the time, profile them as well.
http://www.curious-creature.org/docs/android-performance-case-study-1.html
http://blog.venmo.com/hf2t3h4x98p5e13z82pl8j66ngcmry/performance-tuning-on-android
http://www.vogella.com/tutorials/AndroidTools/article.html

Mismatched images in table cells with Picasso Library

I'm trying to fix an issues that I've seen previously and fixed on iOS, but am unable to fix on android. In iOS, I used the SDWebImage library to download and cache images. However, when scrolling through a long list of cells, the images would come up in the wrong cells. I was able ot fix this by doing the following:
#property (weak) id <SDWebImageOperation> imageOperation;
...
- (void)setFriend:(TAGUser *)friend {
...
self.imageOperation = [[SDWebImageManager sharedManager] downloadWithURL:[NSURL URLWithString:friend.profileImageUrl] options:SDWebImageRetryFailed
progress:^(NSInteger receivedSize, NSInteger expectedSize) {
} completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) {
if(!error) {
self.profileImageView.image = image;
}
}];
...
}
- (void)prepareForReuse {
[super prepareForReuse];
if (self.imageOperation) {
[self.imageOperation cancel];
}
self.imageOperation = nil;
}
On Android, I am using the Picaso Libray and trying to achieve the same result like so:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
if (vi == null) {
vi = inflater.inflate(R.layout.friend_row, parent, false);
ViewHolder holder = new ViewHolder();
holder.friendImage = (ImageView) vi.findViewById(R.id.friend_image);
}
final ViewHolder holder = (ViewHolder) vi.getTag(); //Bad naming convention in my project I know, but it's a built-in method
//THIS SHOULD IN THEORY CANCEL THE REQUEST OF THE OLD FRIEND URL
Picasso.with(mActivity.getBaseContext()).cancelRequest(holder.friendImage);
holder.friendImage.setImageDrawable(mActivity.getResources().getDrawable(R.drawable.background_circle));
final TagUser user = (TagUser) getItem(position);
Picasso.with(mActivity.getBaseContext()).load(user.getProfileUrl()).transform(new RoundedTransformation(ViewUtility.convertPxToDp(mActivity, 23), 0)).fit().into(holder.friendImage,
new Callback() {
#Override
public void onSuccess() {
holder.friendInitials.setVisibility(View.INVISIBLE);
}
#Override
public void onError() {
holder.friendInitials.setVisibility(View.VISIBLE);
}
});
}
Even with cancelRequeset getting called, the profile images are still getting mismatched. Any help would be greatly appreciated!

You don't need to call cancel. Picasso automatically sees when views are being re-used and will cancel old downloads for that image view.
I would also recommend using Picasso's .placeholder API for the background circle.
You seem to be missing a call to setTag when the layout is inflated. Hopefully that's just an error in copying to the post.
Lastly, create the RoundedTransformation once and re-use the same instance for all calls to Picasso.
In the end your code should look like this:
private final Transformation roundTransform;
// Set the following in constructor:
// roundTransform = new RoundedTransformation(ViewUtility.convertPxToDp(mActivity, 23), 0)
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
if (vi == null) {
vi = inflater.inflate(R.layout.friend_row, parent, false);
ViewHolder holder = new ViewHolder();
vi.setTag(holder)
holder.friendImage = (ImageView) vi.findViewById(R.id.friend_image);
}
final ViewHolder holder = (ViewHolder) vi.getTag(); //Bad naming convention in my project I know, but it's a built-in method
final TagUser user = (TagUser) getItem(position);
Picasso.with(mActivity)
.load(user.getProfileUrl())
.placeholder(R.drawable.background_circle)
.transform(roundTransform)
.fit()
.into(holder.friendImage,
new Callback() {
#Override
public void onSuccess() {
holder.friendInitials.setVisibility(View.INVISIBLE);
}
#Override
public void onError() {
holder.friendInitials.setVisibility(View.VISIBLE);
}
});
}

I would advice to use Volley by Google. I have used it in many projects and it never gave mismatched results even in case I had nearly 1000 images in 3 column gridView. Volley