Android-Universal-Image-Loader图片加载框架使用



一、介绍

     Android-Universal-Image-Loader是一个非常强大的开源的图片异步加载库，提供一个可重复使用的仪器为异

步图像加载，缓存和显示，而且使用也非常简单。使用它我们可以少考虑加载图片遇到的多线程，缓存，内存溢出等

很多方面的问题。国内外很多有名的应用程序都有使用，在该类库的默认缓存文件夹中甚至发现了google,

instagram, qq, baidu都有在用。 Android-Universal-Image-Loader的代码托管在GitHub上：

https://github.com/nostra13/Android-Universal-Image-Loader

本文已同步到个人对立域名博客：http://www.fengchaokm.com/

加载显示任务流

二、特点

多线程的图像加载

尽可能多的配置选项（线程池，加载器，解析器，内存/磁盘缓存，显示参数等等）

图片可以缓存在内存中，或者设备文件目录下，或者SD卡中

可以添加图片加载监听器

可以自定义显示每一张图片时都带不同参数

支持Widget

Android 1.5以上支持

1.9.4+版本添加了一个新的API：DisplayImageOptions.targetSize(ImageSize)，提供可设置图片的大小。

三、使用方法

1、涉及权限：

通过网络加载图片涉及到网络请求权限

<code class="hljs xml has-numbering"><span style="font-size:18px;"><span style="font-family:SimSun;"><span class="hljs-tag"><<span class="hljs-title">uses-permission</span> <span class="hljs-attribute">android:name</span>=<span class="hljs-value">"android.permission.INTERNET"</span> /></span>  </span></span></code>

缓存设置需要设置权限

<code class="hljs xml has-numbering"><span style="font-size:18px;"><span style="font-family:SimSun;"><span class="hljs-tag"><<span class="hljs-title">uses-permission</span> <span class="hljs-attribute">android:name</span>=<span class="hljs-value">"android.permission.WRITE_EXTERNAL_STORAGE"</span> /></span>  </span></span></code>

2、URL类型：

<code class="hljs cs has-numbering"><span style="font-size:18px;"><span style="font-family:SimSun;"><span class="hljs-string">"http://site.com/image.png"</span> <span class="hljs-comment">// from Web 从网络获取</span>
<span class="hljs-string">"file:///mnt/sdcard/image.png"</span> <span class="hljs-comment">// from SD card 从SD卡获取</span>
<span class="hljs-string">"file:///mnt/sdcard/video.mp4"</span> <span class="hljs-comment">// from SD card (video thumbnail)</span>
<span class="hljs-string">"content://media/external/images/media/13"</span><span class="hljs-comment">//from content provider 从内容提供器获取</span>
<span class="hljs-string">"content://media/external/video/media/13"</span> <span class="hljs-comment">// from content provider (video thumbnail)</span>
<span class="hljs-string">"assets://image.png"</span> <span class="hljs-comment">// from assets 从assets目录获取</span>
<span class="hljs-string">"drawable://"</span> + R.drawable.img <span class="hljs-comment">// from drawables (non-9patch images)</span></span></span></code>

3、MyApplication class

<code class="hljs avrasm has-numbering"><span style="font-family:SimSun;font-size:18px;">public class MyApplication extends Application {
    @Override
    public void onCreate() {
    super<span class="hljs-preprocessor">.onCreate</span>()<span class="hljs-comment">;</span>
    File cacheDir = StorageUtils<span class="hljs-preprocessor">.getCacheDirectory</span>(getApplicationContext())<span class="hljs-comment">;</span>
Environment<span class="hljs-preprocessor">.getExternalStorageDirectory</span>()<span class="hljs-preprocessor">.getPath</span>())<span class="hljs-comment">;</span>
//ImageLoaderConfiguration 
所有的选项都是可选的，只选择你真正想制定的去配置
        ImageLoaderConfiguration config = new ImageLoaderConfiguration<span class="hljs-preprocessor">.Builder</span>(
                getApplicationContext())
    // 如果图片尺寸大于了这个参数，那么就会这按照这个参数对图片大小进行限制并缓存
                <span class="hljs-preprocessor">.memoryCacheExtraOptions</span>(<span class="hljs-number">480</span>, <span class="hljs-number">800</span>)
                <span class="hljs-preprocessor">.taskExecutor</span>(AsyncTask<span class="hljs-preprocessor">.sExecutor</span>)
                <span class="hljs-preprocessor">.taskExecutorForCachedImages</span>(AsyncTask<span class="hljs-preprocessor">.sExecutor</span>)
                <span class="hljs-preprocessor">.threadPoolSize</span>(<span class="hljs-number">5</span>)
                <span class="hljs-preprocessor">.threadPriority</span>(Thread<span class="hljs-preprocessor">.NORM</span>_PRIORITY-<span class="hljs-number">2</span>)
                <span class="hljs-preprocessor">.threadPriority</span>(Thread<span class="hljs-preprocessor">.NORM</span>_PRIORITY - <span class="hljs-number">1</span>)
                <span class="hljs-preprocessor">.tasksProcessingOrder</span>(QueueProcessingType<span class="hljs-preprocessor">.FIFO</span>)
                <span class="hljs-preprocessor">.denyCacheImageMultipleSizesInMemory</span>()
                <span class="hljs-preprocessor">.memoryCache</span>(new LruMemoryCache(<span class="hljs-number">2</span> * <span class="hljs-number">1024</span> * <span class="hljs-number">1024</span>))
                <span class="hljs-preprocessor">.memoryCacheSize</span>(<span class="hljs-number">2</span> * <span class="hljs-number">1024</span> * <span class="hljs-number">1024</span>)
                <span class="hljs-preprocessor">.diskCache</span>(new UnlimitedDiscCache(cacheDir))
                <span class="hljs-preprocessor">.diskCacheSize</span>(<span class="hljs-number">50</span> * <span class="hljs-number">1024</span> * <span class="hljs-number">1024</span>)
                <span class="hljs-preprocessor">.diskCacheFileCount</span>(<span class="hljs-number">100</span>)
                <span class="hljs-preprocessor">.writeDebugLogs</span>()
                <span class="hljs-preprocessor">.build</span>()<span class="hljs-comment">;</span>
        ImageLoader<span class="hljs-preprocessor">.getInstance</span>()<span class="hljs-preprocessor">.init</span>(config)<span class="hljs-comment">;</span>
    }
</span></code>

Display Options

显示参数可以分别被每一个显示任务调用(ImageLoader.displayImage(…))

<code class="hljs r has-numbering"><span style="font-family:SimSun;font-size:18px;">DisplayImageOptions options = new DisplayImageOptions.Builder()
    .showStubImage(R.drawable.ic_stub)  // 在显示真正的图片前，会加载这个资源
    .showImageForEmptyUri(R.drawable.ic_empty) //空的Url时
    .showImageOnFail(R.drawable.ic_error) 
    .resetViewBeforeLoading() // 
    .delayBeforeLoading(<span class="hljs-number">1000</span>)     // 延长1000ms 加载图片  （想不出来用在什么场景下）
    .cacheInMemory()              
    .cacheOnDisc()               
    .preProcessor(<span class="hljs-keyword">...</span>)            
    .postProcessor(<span class="hljs-keyword">...</span>)           
    .extraForDownloader(<span class="hljs-keyword">...</span>)      //可以向加载器携带一些参数 
    .imageScaleType(ImageScaleType.IN_SAMPLE_POWER_OF_2) // default  
    .bitmapConfig(Bitmap.Config.ARGB_8888) // default
    .decodingOptions(<span class="hljs-keyword">...</span>)
    .displayer(new SimpleBitmapDisplayer()) // default
    .handler(new Handler()) // default
    .build();</span></code>

简单实例

<code class="hljs java has-numbering"><span style="font-size:18px;"><span style="font-family:SimSun;"><span class="hljs-comment">//无回调方法</span>
imageLoader.displayImage(imageUri, imageView);
<span class="hljs-comment">// 有回调方法</span>
imageLoader.loadImage(imageUri, <span class="hljs-keyword">new</span> SimpleImageLoadingListener() {
    <span class="hljs-annotation">@Override</span>
    <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onLoadingComplete</span>(String imageUri, View view, Bitmap loadedImage) {
        <span class="hljs-comment">// Do whatever you want with Bitmap</span>
    }
});
<span class="hljs-comment">// 返回Bitmap对象</span>
Bitmap bmp = imageLoader.loadImageSync(imageUri);</span></span></code>

完整版

<code class="hljs r has-numbering"><span style="font-family:SimSun;font-size:18px;">// Load image, decode it to Bitmap and display Bitmap <span class="hljs-keyword">in</span> ImageView (or any other view 
//  which implements ImageAware interface)
imageLoader.displayImage(imageUri, imageView, options, new ImageLoadingListener() {
    @Override
    public void onLoadingStarted(String imageUri, View view) {
        <span class="hljs-keyword">...</span>
    }
    @Override
    public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
        <span class="hljs-keyword">...</span>
    }
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        <span class="hljs-keyword">...</span>
    }
    @Override
    public void onLoadingCancelled(String imageUri, View view) {
        <span class="hljs-keyword">...</span>
    }
}, new ImageLoadingProgressListener() {
    @Override
    public void onProgressUpdate(String imageUri, View view, int current, int total) {
        <span class="hljs-keyword">...</span>
    }
});


// Load image, decode it to Bitmap and <span class="hljs-keyword">return</span> Bitmap to callback
ImageSize targetSize = new ImageSize(<span class="hljs-number">80</span>, <span class="hljs-number">50</span>); // result Bitmap will be fit to this size
imageLoader.loadImage(imageUri, targetSize, options, new SimpleImageLoadingListener() {
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        // Do whatever you want with Bitmap
    }
});

// Load image, decode it to Bitmap and <span class="hljs-keyword">return</span> Bitmap synchronously
ImageSize targetSize = new ImageSize(<span class="hljs-number">80</span>, <span class="hljs-number">50</span>); // result Bitmap will be fit to this size
Bitmap bmp = imageLoader.loadImageSync(imageUri, targetSize, options);</span></code>