I am trying to load a gridview with cards that hold product information.
I'm not sure if this is the best way of handling this sort of data loading.
First i'm setting my adapter:
cardView.setAdapter(new productCardAdapter(getActivity(),products));
Products is a object that holds a product object, inside the product object has values like image,name,price, etc..
in my public class productCardAdapter extends BaseAdapter
I set the products
this.products = products;
then in the
public View getView(int i, View view, ViewGroup viewGroup) {
I am setting the values based off the index i
if(view == null){
// CREATE NEW
view = inflater.inflate(R.layout.product_card,null);
// GET CURRENT PRODUCT
Products.Product product = products.products.get(i);
// CREATE WIDGETS
TextView cardTitle = (TextView)view.findViewById(R.id.txtProductName);
ImageView cardImage = (ImageView)view.findViewById(R.id.imgProductImage);
CardView card = (CardView)view.findViewById(R.id.tmpCard);
TextView cardSKU = (TextView)view.findViewById(R.id.txtProductSKU);
TextView cardPrice = (TextView)view.findViewById(R.id.txtProductPrice);
// GET IMAGE
if (product.picture.length() > 0) {
// PUT IMAGE
cardImage.setImageBitmap(BitmapFactory.decodeFile(functions.getLocalPicturePath(product.picture)));
}else{
// GENERATE GRADIENT
card.setBackground(colors.generateGradient());
}
// SET VALUES
cardTitle.setText(product.name);
cardSKU.setText(product.sku);
cardPrice.setText("$"+product.price);
// CHECK FOR SALE PRICE
if(product.salePrice > 0){
cardPrice.setText("$"+product.salePrice);
}
}
return view;
when loading it makes a choppy transition that lasts close to 1 second.
Is there ways I can improve on this?
First, enable StrictMode. It will then yell at you that you are doing disk I/O on the main application thread. It won't yell at you that you are doing an expensive bitmap-decoding operation on the main application thread, though that's a problem too.
Then, as njzk2 suggests, use one of the vast array of image-loading libraries for Android, such as Picasso, to load your image asynchronously.
Google's sample code https://developer.android.com/guide/topics/ui/layout/gridview.html is setting a bad example !
To fix that sample code, instead of :
imageView.setImageResource(mThumbIds[position]);
You'll want to use a library, I used Glide, to load the image in a thread. Like this:
public View getView(int position, View convertView, ViewGroup parent) {
CircleImageView imageView;
if (convertView == null) {
// not recycled
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_image, parent, false);
imageView = (CircleImageView) view;
} else {
// recycled
imageView = (CircleImageView) convertView;
}
Glide
.with(parent.getContext())
.load(mThumbIds[position])
.placeholder(R.mipmap.ic_launcher)//REQUIRED
.dontAnimate()//REQUIRED
.into(imageView);
//imageView.setImageResource(mThumbIds[position]);
return imageView;
}
Get CircleImageView here: https://github.com/hdodenhof/CircleImageView
Get Glide here: https://github.com/bumptech/glide
By the way, the XML for my R.layout.item_image is :
<?xml version="1.0" encoding="utf-8"?>
<de.hdodenhof.circleimageview.CircleImageView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/image_avatar"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
app:civ_border_width="1dp"
app:civ_border_color="#FF000000"/>
Related
I am working on a application where i need to show a user list. The user list is a custom list which have a imageview and textview. User image will be loaded in this imageview from server. I already worked with picasso library and which is really easy. I fetch the image url along with username from server using http request. Now the fact is as i need to use custom list i have implemented a custom adapter and in getView method i load the image using
Picasso.with(MainActivity.this).load("http://i.imgur.com/DvpvklR.png").into(container);
But my now question is when i need to show 30 user in list then i need to fetch 30 user image by above code. I don't know is this best practice or other way to handle such list. Again i don't know this list may occupied user memory. What can i do know?
Here is a link to Universal Image Loader:
https://github.com/nostra13/Android-Universal-Image-Loader
It is very customizable and comes with memory caching out the box.
You can use the Universal Image loader library to display images in your custom adapter.
There you can use this code to display image.
imageLoader.displayImage(imageUrl, imageView, new ImageLoadingListener()
{
#Override
public void onLoadingStarted(String imageUri, View view)
{
}
#Override
public void onLoadingFailed(String imageUri, View view, FailReason failReason)
{
}
#Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage)
{
progress.setVisibility(View.GONE);
}
#Override
public void onLoadingCancelled(String imageUri, View view)
{
}
});
Here you can see Android Universal Image Loader
Picasso library is easy to use and implements a cache as well, so your resources are not wasted.
I use this library in a list view with many items and it works like a charm (the same way you are doing).
As getView is invoked when the item becomes visible (as user scrolls mainly) there won't be lots of images downloading at the same time.
My recomendation is to keep using Picasso and to implement the View holder pattern in your list view adapter (you'll improve performance and get smooth scrolls).
--- UPDATE -----------------------------------------------------------
ViewHolder pattern brief example based in this:
"findViewById" uses a loop to traverse items inside a view, so when you scroll a list view there are many invocations to it from "getView". It might causes bad performance problems in big lists.
Listview reuse view items, that's because getView receives a View parameter. This parameter is null the first time it's used, but later previously used views can be passed to this method.
The idea of View Holder is to store references to the subviews when the main view object is created, so there's no need to invoke findViewById in future uses.
Follow these steps:
Implement a class to hold view references:
static class ViewHolderItem {
TextView textViewItem;
// Add as many items as you need: check boxes, image views, ...
}
Implement getView in your adapter this way:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolderItem viewHolder;
// First time: the object is created
if(convertView==null){
// inflate the layout
LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
convertView = inflater.inflate(layoutResourceId, parent, false);
// Creates the ViewHolder and stores references to views
viewHolder = new ViewHolderItem();
viewHolder.textViewItem = (TextView) convertView.findViewById(R.id.textViewItem);
// Uses tag to store the holder with the main view.
convertView.setTag(viewHolder);
} else {
// View is beign resused.
// Avoids calling findViewById() just use the viewHolder.
viewHolder = (ViewHolderItem) convertView.getTag();
}
// Gets object item.
ObjectItem objectItem = getItem(position);
// assign values (if the object is not null)
if(objectItem != null) {
// Fill data in layout assigning values to views in the view holder.
viewHolder.textViewItem.setText(objectItem.itemName);
// Set images, check boxes state, or whatever you have in your layout.
}
// Finally returns the updated view.
return convertView;
}
I have the following situation.
I have a ListView, each item of the ListView is comprised of different widgets (TextViews, ImageViews, etc...) inflated form a Layout in the getView() method of the custom adapter.
Now, I would like to achieve the following:
when a certain event is triggered I want to change the background of a View which is inside the item.
Please how do I do it?
This is the the Item Layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/cardlayout"
android:layout_width="320dp"
android:layout_height="130dp"
android:background="#android:color/transparent"
android:orientation="vertical"
android:paddingBottom="5dp"
android:paddingRight="5dp"
android:paddingTop="5dp" >
<FrameLayout
android:layout_width="320dp"
android:layout_height="117dp" >
<View
android:id="#+id/card"
android:layout_width="320dp"
android:layout_height="117dp"
android:background="#drawable/card_selector" />
</FrameLayout>
</LinearLayout>
I need to change the background of card
I have tried doing this:
View v=lv.getAdapter().getView(index, null, lv);
View card =(View)v.findViewById(R.id.card);
card.setBackgroundResource(R.drawable.pressed_background_card);
But no success :-((
When your event is triggered you should just call a notifyDataSetChanged on your adapter so that it will call again getView for all your visible elements.
Your getView method should take into account that some elements may have different background colors (and not forget to set it to normal color if the element doesn't need the changed background, else with recycling you would have many elements with changed background when you scroll)
edit :
I would try something like this :
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null)
{
convertView = LayoutInflater.from(getContext()).inflate(R.layout.card, parent, false);
}
//This part should also be optimised with a ViewHolder
//because findViewById is a costly operation, but that's not the point of this example
CardView cardView =(CardView)convertView .findViewById(R.id.card);
//I suppose your card should be determined by your adapter, not a new one each time
Card card = getItem(position);
//here you should check sthg like the position presence in a map or a special state of your card object
if(mapCardWithSpecialBackground.contains(position))
{
card.setBackgroundResource(specialBackground);
}
else
{
card.setBackgroundResource(normalBackground);
}
cardView.setCard(card);
return convertView;
}
And on the special event i would add the position of the item into the map and call notifyDataSetChanged.
Use the onitemclicklistener which has method onclicksomething..that takes four or five parameters. (View parent, View view, int position, int id). Use the view parameter to customize your background.
Update
Here's some of my code, If you don't understand I recommend to read about recycling and ViewHolder pattern.
#Override
public View getView(int position, View convertView, ViewGroup parent) {
{
ViewHolder viewHolder;
// If convertView isn't a recycled view, create a new.
if(convertView == null){
LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.row_gallery_frame, parent, false);
viewHolder = new ViewHolder();
// Here you must be able to find your Widget inside convertView and set a listener to it I guess?
viewHolder.nameHolder = (TextView) convertView.findViewById(R.id.nameTv);
// Set a reference to newly inflated view
convertView.setTag(viewHolder);
}
// If it is, then get the ViewHolder by tag
else{
viewHolder = (ViewHolder)convertView.getTag();
}
// Set the data
GalleryFrame galleryFrame = galleryFrameArrayList.get(position);
viewHolder.nameHolder.setText(galleryFrame.getName());
return convertView;
}
}
// Viewholder pattern which holds all widgets used
public static class ViewHolder{
public TextView nameHolder;
}
I assume you have a model object that you use to "draw" the list item , and for example the background color is determined based on a boolean or something.
All you need to do, is change the value on which you base your decision which background color should that TextView have.
Your getView() method should have code like that
if (myModelObj.isBrown()) {
myTextView.setBackgroundResource(R.drawable.brown_bg);
else
myTextView.setBackgroundResource(R.drawable.not_brown_bg);
All you should do when ur event is triggered, is set the value of the brown boolean in your model
and call notifyDataSetChanged() on your adapter
EDIT
If for some reason you don't wanna call nofitfyDataSetChanged(), althought it won't move the scroll position of your list and with the right recyclying it won't cause bad performance
You can find the View object that represent the list item you want to edit-if it's visisble-, and simply change the background in it, without refreshing the list at all.
int wantedPosition = 10; // Whatever position you're looking for
int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount();
int wantedChild = wantedPosition - firstPosition
if (wantedChild < 0 || wantedChild >= listView.getChildCount()) {
// Wanted item isn't displayed
return;
}
View wantedView = listView.getChildAt(wantedChild);
then use wantedView to edit your background
This answer can be found here
try this one:
View v=lv.getAdapter().getView(index, null, lv);
View card =(View)v.findViewById(R.id.card);
card.setBackgroundResource(R.drawable.pressed_background_card);
card.invalidate();
v.invalidate();
those function force your views to redraw itself and they will render again.
look at invalidate()
What I normally do is this:
public static class EventDetailsRenderer {
private TextView title;
private TextView description;
private Event item;
public EventDetailsRenderer(View view) {
extractFromView(view);
}
private final void extractFromView(View view) {
title = (TextView) view.findViewById(R.id.EventTitle);
description = (TextView) view.findViewById(R.id.Description);
}
public final void render() {
render(item);
}
public final void render(Event item) {
this.item= item;
title.setText(item.getTitle());
description.setText(item.getDescription());
}
}
private class EventsAdapter
extends ArrayAdapter<Event> {
public EventsAdapter(Context context) {
super(context, R.layout.list_node__event_details, 0);
}
public void addAllItems(Event... services) {
for (int i = 0; i < services.length; i++) {
add(services[i]);
}
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Event event = getItem(position);
EventDetailsRenderer eventRenderer;
if (convertView != null && convertView.getTag() != null) {
eventRenderer = (EventDetailsRenderer) convertView.getTag();
} else {
convertView = getActivity().getLayoutInflater().inflate(R.layout.list_node__event_details, null);
eventRenderer = new EventDetailsRenderer(convertView);
convertView.setTag(eventRenderer);
}
eventRenderer.render(event);
return convertView;
}
}
NOTE: that this example might not compile I pasted it from some code I have and deleted some lines to show an example but the logic it the same.
And then when you want to render it, just get the children from the list, iterate over them, check if the renderer contains the card you want to flip and call its render method... then you render a specific item in the list without effecting the rest of the items.
Let me know if this works...
Adam.
User EasyListViewAdapters library https://github.com/birajpatel/EasyListViewAdapters
Features
Easier than implementing your own Adapter (ie handling
BaseAdaper#getView).Very Easier to provide multi-row support.
Library takes care of recycling all views, that ensures performance
& helps your list view scroll smoothly.
Cleaner code. By keeping different RowViewSetter classes for
different row-types makes your code easy to manage & easy to reuse.
No data browsing, Library takes care of browsing data through
data-structure when View is being drawn or event occurs so that
Users does not have to look for their data to take actions.
Just by passing correct row-types library will Auto-map your
data-types to row-types to render views. Row views can be created by
using XML or Java (doesn't restrict to XML-Only Approach).
Load More callbacks can be registered to implement paginatation
support to your list.
Handling children viewclicks, you can also register for
Children(present inside your rows) view click events.
All these Views are registered with single OnClickListner so that
this mechanism is very memory efficient when click event occurs
users you gets clickedChildView, rowData,int eventId as callback
params.
I'm having trouble with a listview in android. When I start scrolling down my List, it is very slow and I see that the GC is called. When I'm at the bottom of my List, everything works fine and smooth. I think that at this point my ViewHolder does the work.
But I can't find the source that is calling the GC. I searched which lead to:
DDMS 436816 byte[] 1 android.graphics.Bitmap nativeCreate
I can't interpret that line. My ArrayAdapter and it's getView method looks like this:
public class DiagnoseAdapter extends ArrayAdapter<Visualizer> {
#Override
public View getView(int position, View convertView, ViewGroup parent) {
int type = TYPE_DEFAULT;
final Visualizer item = getItem(position);
switch(item.getType()){
case TYPE_DEFAULT:
convertView = DefaultTextView.getView(position, convertView, mlayoutInflater, item, parent);
break;
// more cases/types
}
return convertView;
}
}
which is calling the following getView Method of the class DefaultTextView
public class DefaultTextView{
public static View getView(int position, View convertView, LayoutInflater layoutInflater, Visualizer item, ViewGroup parent){
ViewHolder holder;
if (convertView == null || item.getReleatedObject() == null || convertView.getTag()!=TAG_DEFAULT) {
convertView = layoutInflater.inflate(R.layout.diagnose_item, null);
holder = new ViewHolder();
holder.value = (TextView) convertView.findViewById(R.id.diagnose_function_value);
holder.name = (TextView) convertView.findViewById(R.id.diagnose_function_setname);
holder.mLinLayout = (LinearLayout) convertView.findViewById(R.id.default_linlayout);
convertView.setTag(TAG_DEFAULT);
convertView.setTag(R.layout.diagnose_item,holder);
item.setReleatedObject(convertView);
} else {
holder = (ViewHolder) convertView.getTag(R.layout.diagnose_item);
}
holder.value.setText(item.toString());
holder.name.setText(item.getToolTip());
holder.mLinLayout.removeAllViews();
if (item.getUpdateFlag(4)) {
if (holder.back == null){
holder.back = new ImageView(convertView.getContext());
holder.back.setScaleType(ScaleType.FIT_CENTER);
holder.back.setAdjustViewBounds(true);
holder.back.setImageBitmap(bm1);
}
holder.mLinLayout.addView(holder.back);
}
if (item.getUpdateFlag(1)) {
if (holder.update == null){
holder.update = new ImageView(convertView.getContext());
holder.update.setScaleType(ScaleType.FIT_CENTER);
holder.update.setAdjustViewBounds(true);
holder.update.setImageBitmap(bm2);
}
holder.mLinLayout.addView(holder.update);
}
if (item.getUpdateFlag(2)) {
if (holder.timer == null){
holder.timer = new ImageView(convertView.getContext());
holder.timer.setScaleType(ScaleType.FIT_CENTER);
holder.timer.setAdjustViewBounds(true);
holder.timer.setImageBitmap(bm3)
}
holder.mLinLayout.addView(holder.timer);
}
if (item.getUpdateFlag(3)) {
if (holder.log == null){
holder.log = new ImageView(convertView.getContext());
holder.log.setScaleType(ScaleType.FIT_CENTER);
holder.log.setAdjustViewBounds(true);
holder.log.setImageBitmap(bm4);
}
holder.mLinLayout.addView(holder.log);
}
if (item.getUpdateFlag(0)) {
if (holder.forward == null){
holder.forward = new ImageView(convertView.getContext());
holder.forward.setScaleType(ScaleType.FIT_CENTER);
holder.forward.setAdjustViewBounds(true);
holder.forward.setImageBitmap(bm5);
}
holder.mLinLayout.addView(holder.forward);
}
return convertView;
}
static class ViewHolder {
TextView name, value;
ImageView back, update, timer, log, forward;
LinearLayout mLinLayout;
}
}
Even if I comment the LinearLayout out, so I just have a List with two TextViews.
So my Question. Do I miss anything. Some stupid thing? How do I get my ListView smoother?
BTW: I read in a different thread, that it is happening if the ListView has the attribute android:cacheColorHint="#00000000. I don't have this attribute.
I hope anyone has a solution. Thanks!
About the source of GC calls. If I'm understanding your code correctly, everytime your ListView items are recycled and you call removeAllViews(), a previously dynamically created ImageView is removed and its Bitmap is garbage collected. So, Maybe those GC calls would be avoided if you use the same ImageView declaring it in your xml layout and just replace the Bitmap according to your getUpdateFlag().
And two more things about ListViews and Images. First thing is that if the image is too big, your ListView is going to be laggy no matter what. You would need to scale the image down if that is the case( Loading Large Bitmaps Efficiently). And second, maybe you would also need to implement a Lazy List, which loads images on demand, there is a famous question about that --> How do I do a lazy load of images in ListView?
I've finally solved my Problem. Like above, I thought the problem was based on the images of my list items. But that wasn't the problem. I just didn't use my ViewHolders and the getItemViewType(int position) method correctly. I have a list with many different item layouts and I saw, that my code above created a new convertView and a new ViewHolder for every single item, which wasn't supposed to be. I found a great tutorial about how to use multiple item layouts (see link below):
Multiple List Item Layouts
I have a ListView with custom ArrayAdapter. Each of the row in this ListView has an icon and some text. These icons are downloaded in background,cached and then using a callback, substituted in their respective ImageViews. The logic to get a thumbnail from cache or download is triggered every time getView() runs.
Now, according to Romain Guy:
"there is absolutely no guarantee on
the order in which getView() will be
called nor how many times."
I have seen this happen, for a row of size two getView() was being called six times!
How do I change my code to avoid duplicate thumbnail-fetch-requests and also handle view recycling?
Thanks.
Exactly, that could happen for example when you have
android:layout_height="wrap_content"
in your ListView definition. Changing it to fill_parent/match_parent would avoid it.
From api.
public abstract View getView (int position, View convertView,
ViewGroup parent)
convertView - The old view to reuse, if possible. Note: You should check that this view is non-null and of an appropriate type before using. If it is not possible to convert this view to display the correct data, this method can create a new view.
So if getView has already been called for this specific index then convertView will be the View object that was returned from that first call.
You can do something like.
if(!(convertView instanceof ImageView)){
convertView = new ImageView();
//get image from whereever
} else {} // ImageView already created
I m experiancing the same issue i change the layout_height of listView to match_parent resolve my issue.
My understanding is that you need to use the ViewHolder design pattern here. Just using a returned convertView can lead to reuse of a previous view (with some other image assigned in this case).
public class ImageAdapter extends ArrayAdapter<String> {
// Image adapter code goes here.
private ViewHolder {
public ImageView imageView;
public String url;
}
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
View view = null;
ViewHolder viewHolder;
String url = getUrl(position);
if (convertView == null) {
// There was no view to recycle. Create a new view.
view = inflator.inflate(R.layout.image_layout, parent, false);
viewHolder = new ViewHolder();
viewHolder.imageView = (ImageView) view.findViewById(R.id.image_view);
viewHolder.url = url;
view.setTag(viewHolder);
} else {
// We got a view that can be recycled.
view = convertView;
viewHolder = ((ViewHolder) view.getTag());
if (viewHolder.url.equals(url)) {
// Nothing to do, we have the view with the correct info already.
return view;
}
}
// Do work to set your imageView which can be accessed by viewHolder.imageView
return view;
}
}
The better would be to create a object with Thumbnail(bitmap) and the text. And read the thumbnail if its not available in the object.
Create an array of ImageView objects in your adapter and cache them as you retrive them (whether from cache or web). For example, in getView, before you fetch the ImageView, check if it's already in your local array, if so, use it, if not fetch, once received store in your local ImageView array for future use.
My Fragment.xml has a ListView, the layout setting of this ListView was android:layout_height="wrap_content", and this ListView will bind to SimpleCursorAdapter later. Then I have the same issue in ViewBinder be called 3 times. The issue resolved after I change the layout_height="wrap_content" to "95p". I do consider that the "wrap_content" height cause this issue.
Trying to modify your Fragment.xml and I guess the 3 times called issue will no longer exist.
I load data from Cursor to listview, but my Listview not really display "smooth". The data change when I drag up and down on the scollbar in my ListView. And some items look like duplicate display in my list.
I hava a "complex ListView" (two textview, one imageview) So I used newView(), bindView() to display data. Can someone help me?
I will describe you how to get such issue that you have. Possibly this will help you.
So, in list adapter you have such code:
public View getView(int position, View contentView, ViewGroup arg2)
{
ViewHolder holder;
if (contentView == null) {
holder = new ViewHolder();
contentView = inflater.inflate(R.layout.my_magic_list,null);
holder.label = (TextView) contentView.findViewById(R.id.label);
contentView.setTag(holder);
} else {
holder = (ViewHolder) contentView.getTag();
}
holder.label.setText(getLabel());
return contentView;
}
As you can see, we set list item value only after we have retrieved holder.
But if you move code into above if statement:
holder.label.setText(getLabel());
so it will look after like below:
if (contentView == null) {
holder = new ViewHolder();
contentView = inflater.inflate(R.layout.my_magic_list,null);
holder.label = (TextView) contentView.findViewById(R.id.label);
holder.label.setText(getLabel());
contentView.setTag(holder);
}
you will have your current application behavior with list item duplication.
Possibly it will help.
ListView is a tricky beast.
Your second question first: you're seeing duplicates because ListView re-uses Views via convertView, but you're not making sure to reset all aspects of the converted view. Make sure that the code path for convertView!=null properly sets all of the data for the view, and everything should work properly.
You'll want your getView() method to look roughly like the following if you're using custom views:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
final MyCustomView v = convertView!=null ? (MyCustomView)convertView : new MyCustomView();
v.setMyData( listAdapter.get(position) );
return v;
}
If you're not using your own custom view, just replace the call to new MyCustomView() with a call to inflater.inflate(R.layout.my_layout,null)
As to your first question, you'll want to watch Romain's techtalk on ListView performance here: http://code.google.com/events/io/sessions/TurboChargeUiAndroidFast.html
From his talk and in order of importance from my own experience,
Use convertView
If you have images, don't scale your images on the fly. Use Bitmap.createScaledBitmap to create a scaled bitmap and put that into your views
Use a ViewHolder so you don't have to call a bunch of findViewByIds() every time
Decrease the complexity of the views in your listview. The fewer subviews, the better. RelativeLayout is much better at this than, say, LinearLayout. And make sure to use if you're implementing custom views.
I'm facing this problem as well, but in my case I used threads to fetch the external images. It is important that the current executing thread do not change the imageView if it is reused!
public View getView(int position, View vi, ViewGroup parent) {
ViewHolder holder;
String imageUrl = ...;
if (vi == null) {
vi = inflater.inflate(R.layout.tweet, null);
holder = new ViewHolder();
holder.image = (ImageView) vi.findViewById(R.id.row_img);
...
vi.setTag(holder);
} else {
holder = (ViewHolder) vi.getTag();
}
holder.image.setTag(imageUrl);
...
DRAW_MANAGER.fetchDrawableOnThread(imageUrl, holder.image);
}
And then on the fetching thread I'm doing the important check:
final Handler handler = new Handler() {
#Override
public void handleMessage(Message message) {
// VERY IMPORTANT CHECK
if (urlString.equals(url))
imageView.setImageDrawable((Drawable) message.obj);
};
Thread thread = new Thread() {
#Override
public void run() {
Drawable drawable = fetchDrawable(urlString);
if (drawable != null) {
Message message = handler.obtainMessage(1, drawable);
handler.sendMessage(message);
}
}};
thread.start();
One could also cancel the current thread if their view is reused (like it is described here), but I decided against this because I want to fill my cache for later reuse.
Just one tip: NEVER use transparent background of item layout - it slows performance greatly
You can see the reocurring text in multiple rows if you handle it in the wrong way. I've blogged a bit about it recently - see here. Other than that you might want to take a look at ListView performance optimization. Generally it's because of the view reuse and I've seen it few times already.