How to lazy load images in ListView in Android

Question

I am using a ListView to display some images and captions associated with those images. I am getting the images from the Internet. Is there a way to lazy load images so while the text displays, the UI is not blocked and images are displayed as they are downloaded?

The total number of images is not fixed.

Comments

I have used it. It is a wonderful implementation. Bad news that AsyncImageView is a part of a large GreenDroid project, which make your application larger even in the case all you need is AsyncImageView. Also, seems, GreenDroid project is not updated since 2011.

jezrael Nov 13, 2022 - 03:48:01

Answer 1

Here's what I created to hold the images that my app is currently displaying. Please note that the "Log" object in use here is my custom wrapper around the final Log class inside Android.

package com.wilson.android.library;

/*
 Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/
import java.io.IOException;

public class DrawableManager {
    private final Map<String, Drawable> drawableMap;

    public DrawableManager() {
        drawableMap = new HashMap<String, Drawable>();
    }

    public Drawable fetchDrawable(String urlString) {
        if (drawableMap.containsKey(urlString)) {
            return drawableMap.get(urlString);
        }

        Log.d(this.getClass().getSimpleName(), "image url:" + urlString);
        try {
            InputStream is = fetch(urlString);
            Drawable drawable = Drawable.createFromStream(is, "src");


            if (drawable != null) {
                drawableMap.put(urlString, drawable);
                Log.d(this.getClass().getSimpleName(), "got a thumbnail drawable: " + drawable.getBounds() + ", "
                        + drawable.getIntrinsicHeight() + "," + drawable.getIntrinsicWidth() + ", "
                        + drawable.getMinimumHeight() + "," + drawable.getMinimumWidth());
            } else {
              Log.w(this.getClass().getSimpleName(), "could not get thumbnail");
            }

            return drawable;
        } catch (MalformedURLException e) {
            Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e);
            return null;
        } catch (IOException e) {
            Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e);
            return null;
        }
    }

Comments

I think you should use SoftReferences so that your program will never cause OutOfMemoryException. As GC can clear softreferences when heap size is increasing... you can manage your own generation like after some seconds you can put your images to that list and before loading you should check that if image exists then don't download it again rather collect it from that list and also putting it back to your softref list and after sometime you can purge your hardlist :) 

Allan Cameron Nov 13, 2022 - 03:50:12