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How to Update Custom Listview Images

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#1
afolery

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SDK Version:

M3

So this tutorial shows you how to refresh imageviews’ contents periodically (let say by Handlers if you download the picture from web).

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() { }.

Posted Image

Here is how it works:

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

* hashMapListForListView = new ArrayList<HashMap<String,String>>();
*we can fill it up by calling:
*entitiesHashMap.put("name", "Ball");
*entitiesHashMap.put("category", "Sport");
*entitiesHashMap.put("price", "2.99");
*entitiesHashMap.put("imageUri", ball.Uri);

and then, we add it to the List:

*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() {}

*adapterForList = new SimpleAdapter(Main.this,
*hashMapListForListView, R.layout.detailedview,
*new String[] {"name", "category", "price", "imageUri"},
*new int[] { R.id.EntityName, R.id.Category, R.id.Price, R.id.ThumbImage });
*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

*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, enjoy!

Edited by afolery, 09 August 2010 - 01:34 AM.

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#2
Uxian

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Might also want to add a call to BaseAdapter.notifyDataSetChanged() in step 3 otherwise the images already on the screen won't refresh until they get invalidated by scrolling off-screen and new entries won't get picked up.

Edited by Uxian, 09 August 2010 - 10:16 PM.

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#3
z12ent

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This is exactly what I've been looking for! Quick question for you? I am new to all of this but by tutorials such as yours I'm gaining the experiance I need to create wonderful apps like the one you have listed. My question is, can you implement something like this to read from a database? So anytime the user inputs their information it would automaticly get updated to the listvew? Also, is there anyway you can email me a working copy of this project so I can play around with it and better understand how you created it? I work better with working examples. =)
Thank you. :D

SDK Version:

M3

So this tutorial shows you how to refresh imageviews’ contents periodically (let say by Handlers if you download the picture from web).

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() { }.

Posted Image

Here is how it works:

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

* hashMapListForListView = new ArrayList<HashMap<String,String>>();
*we can fill it up by calling:
*entitiesHashMap.put("name", "Ball");
*entitiesHashMap.put("category", "Sport");
*entitiesHashMap.put("price", "2.99");
*entitiesHashMap.put("imageUri", ball.Uri);

and then, we add it to the List:

*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() {}

*adapterForList = new SimpleAdapter(Main.this,
*hashMapListForListView, R.layout.detailedview,
*new String[] {"name", "category", "price", "imageUri"},
*new int[] { R.id.EntityName, R.id.Category, R.id.Price, R.id.ThumbImage });
*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

*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, enjoy!


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