Android-Universal-ImageLoader源代码分析1

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[TOC]

写在前面

AUIL 的特点

  • 多线程下载图片(同步异步)
  • 提供多种ImageLoader的用户配置(thread executors, downloaders,decoder, memory and disk cache, display image options, etc.)
  • 为每一个显示图片的调用提供了非常丰富的配置(stub image, caching switch, decoding options, Bitmap processing and displaying, etc)
  • 提供图片的内存和文件缓存
  • 图片加载的监听和下载进度的监听

使用

QuickSetup

  1. include library

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    implementation 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'

  2. config manifest permission

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    manifest>
    	<!-- Include following permission if you load images from Internet -->
    	<uses-permission android:name="android.permission.INTERNET" />
    	<!-- Include following permission if you want to cache images on SD card -->
    	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    	...
    </manifest>

  3. config imageloader and initial 

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    public class MyActivity extends Activity {
    	@Override
    	public void onCreate() {
    		super.onCreate();

    		// Create global configuration and initialize ImageLoader with this config
    		ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this)
    			...
    			.build();
    		ImageLoader.getInstance().init(config);
    		...
    	}
    }

  4. Display Options

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    // DON'T COPY THIS CODE TO YOUR PROJECT! This is just example of ALL options using.
    // See the sample project how to use ImageLoader correctly.
    DisplayImageOptions options = new DisplayImageOptions.Builder()
    		.showImageOnLoading(R.drawable.ic_stub) // resource or drawable
    		.showImageForEmptyUri(R.drawable.ic_empty) // resource or drawable
    		.showImageOnFail(R.drawable.ic_error) // resource or drawable
    		.resetViewBeforeLoading(false)  // default
    		.delayBeforeLoading(1000)
    		.cacheInMemory(false) // default
    		.cacheOnDisk(false) // default
    		.preProcessor(...)
    		.postProcessor(...)
    		.extraForDownloader(...)
    		.considerExifParams(false) // default
    		.imageScaleType(ImageScaleType.IN_SAMPLE_POWER_OF_2) // default
    		.bitmapConfig(Bitmap.Config.ARGB_8888) // default
    		.decodingOptions(...)
    		.displayer(new SimpleBitmapDisplayer()) // default
    		.handler(new Handler()) // default
    		.build();

Usage

可接受的的URI资源示例

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"http://site.com/image.png" // from Web
"file:///mnt/sdcard/image.png" // from SD card
"file:///mnt/sdcard/video.mp4" // from SD card (video thumbnail)
"content://media/external/images/media/13" // from content provider
"content://media/external/video/media/13" // from content provider (video thumbnail)
"assets://image.png" // from assets
"drawable://" + R.drawable.img // from drawables (non-9patch images)

NOTE: Use drawable:// only if you really need it! Always consider the native way to load drawables - ImageView.setImageResource(...) instead of using of ImageLoader.

简单使用

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// Load image, decode it to Bitmap and display Bitmap in ImageView (or any other view 
//	which implements ImageAware interface)
ImageLoader imageLoader = ImageLoader.getInstance();
imageLoader.loadImage(imageUri, imageview);
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// Load image, decode it to Bitmap and return Bitmap to callback
imageLoader.loadImage(imageUri, new SimpleImageLoadingListener() {
	@Override
	public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
		// Do whatever you want with Bitmap
	}
});
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// Load image, decode it to Bitmap and return Bitmap synchronously
Bitmap bmp = imageLoader.loadImageSync(imageUri);

完全使用

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// Load image, decode it to Bitmap and display Bitmap in ImageView (or any other view 
//	which implements ImageAware interface)
imageLoader.displayImage(imageUri, imageView, options, 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) {
		...
	}
	@Override
	public void onLoadingCancelled(String imageUri, View view) {
		...
	}
}, new ImageLoadingProgressListener() {
	@Override
	public void onProgressUpdate(String imageUri, View view, int current, int total) {
		...
	}
});
// Load image, decode it to Bitmap and return Bitmap to callback
ImageSize targetSize = new ImageSize(80, 50); // 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
	}
});
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// Load image, decode it to Bitmap and return Bitmap synchronously
ImageSize targetSize = new ImageSize(80, 50); // result Bitmap will be fit to this size
Bitmap bmp = imageLoader.loadImageSync(imageUri, targetSize, options);

Load & Display Task Flow

重要, 这个是AUIL的加载图片流程

AUIL

用户须知

  1. Caching is NOT enabled by default如果需要开启内存或者是磁盘缓存,需要配置DisplayImageOptions

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    // Create default options which will be used for every 
    //  displayImage(...) call if no options will be passed to this method
    DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
       		...
               .cacheInMemory(true)
               .cacheOnDisk(true)
               ...
               .build();
    ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getApplicationContext())
               ...
               .defaultDisplayImageOptions(defaultOptions)
               ...
               .build();
    ImageLoader.getInstance().init(config); // Do it on Application start
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    // Then later, when you want to display image
    ImageLoader.getInstance().displayImage(imageUrl, imageView); // Default options will be used

    或者这样:

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    DisplayImageOptions options = new DisplayImageOptions.Builder()
       		...
               .cacheInMemory(true)
               .cacheOnDisk(true)
               ...
               .build();
    ImageLoader.getInstance().displayImage(imageUrl, imageView, options); // Incoming options will be used

  2. 注意WRITE_EXTERNAL_STORAGE这个权限的申请.

  3. 如果发生OOM可以尝试关掉内存缓存, 或减少线程池的大小, 或使用RGB-565的图像配置替换ARGB-8888, 或者裁剪图片显示小图.

  4. MemoryChache的配置

    1. 强引用 LruMemoryCache
    2. 强弱引用混用 1,3除外的算法.
    3. 只是用弱引用 WeakMemoryCache

  5. DiscChache也是可配置的UnlimitedDiscCache 是最快的,但是占用存储空间

  6. 使用RoundedBigmaDisplayer或FadeInbitmapDisplayer 装饰图片加载

  7. 为了是ListView or GrideView的性能提升, 使用PauseOnScrollListener

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    boolean pauseOnScroll = false; // or true
    boolean pauseOnFling = true; // or false
    PauseOnScrollListener listener = new PauseOnScrollListener(imageLoader, pauseOnScroll, pauseOnFling);
    listView.setOnScrollListener(listener);

  8. If you see in logs some strange supplement at the end of image URL (e.g. http://anysite.com/images/image.png_230x460) then it doesn’t mean this URL is used in requests. This is just “URL + target size”, also this is key for Bitmap in memory cache. This postfix (_230x460) is NOT used in requests.