How to update custom listview images simply


SDK Version: 
M3
So in this tutorial I'm going to show you how to refresh imageviews' contents periodically (let say by Handlers if you download the picture from web).
I had painful 2 days figuring out what's a good solution here, I tried to give IDs to imageviews and that sort of sick things, but believe me, it wasn't worth it. The solution is so simply that I hardly can believe.
What we're lookign for here is instead of create new Adapters and HashMaps (which contains ListView data), we just update it's values, and Android will do the trick for us.
The most important thing is DO NOT AT ANY CIRCUMSTANCES CREATE A NEW ADAPTER (or a new data source that holds the Adapter's data).
There's an exception of course, you obviously have to create a new Adapter in OnCreate() { }.

Let me show you how it works:

1. Step
Create a new ArrayList of HashMaps that holds the data

  1. hashMapListForListView = new ArrayList<HashMap<String,String>>();

we can fill it up by calling:
  1. entitiesHashMap.put("name", "Ball");
  2. entitiesHashMap.put("category", "Sport");
  3. entitiesHashMap.put("price", "2.99");
  4. entitiesHashMap.put("imageUri", ball.Uri);

and then, we add it to the List:
  1. hashMapListForListView.add(entitiesHashMap);

We can do this over n over, as many times as we want.

2. Step
Create a new Adapter in your OnCreate() {}

  1. adapterForList = new SimpleAdapter(Main.this,
  2.                                 hashMapListForListView, R.layout.detailedview,
  3.                                 new String[] {"name", "category", "price", "imageUri"},
  4.                                 new int[] { R.id.EntityName, R.id.Category, R.id.Price, R.id.ThumbImage });
  5.                         listView.setAdapter(adapterForList);

What we're doing here is that we create a new SimpleAdapter, and tell it to use hashMapForListView as data source, and also tell the listView to use adapterForList as Adapter.
R.layout.detailedview is my own Layout file, that includes 3 textviews called "R.id.EntityName, R.id.Category, R.id.Price, " and an ImageView called "R.id.ThumbImage".
As you can see, we tell the Adapter to use these UI elements.

3. Step
The refreshing
Since we have data in the List of HashMaps, we can overwrite the values, simply by calling

  1. hashMapListForListView.set(index, entitiesHashMap);

Don't forget to create a new instance of entitiesHashMap, and set it's values just as we did in 1. Step. to get the result you'd expect.

That's all you have to do, really!

Feel free to leave comments and to share your ideas!

See you next week!