本文来自于[Fresco中文文档](http://www.fresco-cn.org/)，这仅仅是自己的学习笔记！！！大牛绕路，放我我。 关于Fresco的介绍，请查看[链接](http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2015/0402/2683.html) 关于android图片缓存，这是一个android程序员必须了解的。关于四大图片缓存框架的特性与对比，请移步MDCC[传送门](http://www.csdn.net/article/2015-10-21/2825984) 首先说明，本文的大多数内容来自于官方文档，请勿喷！！！ 那么今天我们就来了解下Fresco，作为FB出版的开源项目，据说是目前最好的缓存框架。 那么我们就先来了解下Fresco是个什么。 - Fresco是一个强大的图片加载组件 - Fresco中设计有一个叫做image pipeline 的模块。他负责从网络，从本地文件系统，本地资源加载图片。为了最大限度上节省空间和CPU时间，它含有3级缓存的设计(额，没三级能拿出手？) - Fresco中设计有一个叫做Drawees模块，方便地显示loading图，当图片不再显示在屏幕上时，及时地释放内存和空间占用。 - Fresco支持Android2.3及以上系统 简单的看下使用SimpleDraweeView显示一张占位图。在XML文件中加入 ~~~ <com.facebook.drawee.view.SimpleDraweeView android:id="@+id/my_image_view" android:layout_width="200dp" android:layout_height="200dp" android:layout_centerInParent="true" > </com.facebook.drawee.view.SimpleDraweeView> ~~~ 在代码中设置Uri， ~~~ draweeView = (SimpleDraweeView) findViewById(R.id.my_image_view); Uri uri = Uri.parse("https://raw.githubusercontent.com/facebook/fresco/gh-pages/static/fresco-logo.png"); // draweeView.setController(draweeController); draweeView.setImageURI(uri); ~~~ 最后添加网络权限，就可以了。我们在来看下这里的Uri支持什么格式： - 远程图片 http:// 或者 https：// - 本地文件 file：// - Content Provider content：// - asset目录下的资源 asset：// - res目录下的资源 res：//包名/+R…… 接下来便详细的介绍Drawee 举个栗子： ~~~ <com.facebook.drawee.view.SimpleDraweeView android:id="@+id/my_image_view" android:layout_width="20dp" android:layout_height="20dp" fresco:fadeDuration="300" fresco:actualImageScaleType="focusCrop" fresco:placeholderImage="@color/wait_color" fresco:placeholderImageScaleType="fitCenter" fresco:failureImage="@drawable/error" fresco:failureImageScaleType="centerInside" fresco:retryImage="@drawable/retrying" fresco:retryImageScaleType="centerCrop" fresco:progressBarImage="@drawable/progress_bar" fresco:progressBarImageScaleType="centerInside" fresco:progressBarAutoRotateInterval="1000" fresco:backgroundImage="@color/blue" fresco:overlayImage="@drawable/watermark" fresco:pressedStateOverlayImage="@color/red" fresco:roundAsCircle="false" fresco:roundedCornerRadius="1dp" fresco:roundTopLeft="true" fresco:roundTopRight="false" fresco:roundBottomLeft="false" fresco:roundBottomRight="true" fresco:roundWithOverlayColor="@color/corner_color" fresco:roundingBorderWidth="2dp" fresco:roundingBorderColor="@color/border_color" /> ~~~ 上面这个是官方的栗子，上面有所有的属性，我们就来看看，这些属性代表什么意思， - layout_width和layout_height 不支持warp_content，但是可以通过setAspectRetio()；来设置宽高比 - fadeDuration() 淡..时间 - actualImageScaleType 设置图片缩放，通常使用foucsCrop,该属性值会通过算法把人头像放在中间，关于缩放，请移步[黑洞](http://www.fresco-cn.org/docs/scaling.html#_) - placeholderImage 下载成功之前显示的图片 - placeholderImageScaleType - failureImage 加载失败时显示的图片 - failureImageScaleType - retryImage 加载失败，提示用户点击重新加载的图片 - retryImageScaleType - progressBarImage 提示 用户正在加载，和进度无关 - progressBarImageScaleType - progressBarAutoRotateInterval 图片自动旋转的时间间隔 - backgroundImage 背景 - overlayImage 叠加图 - pressedStateOverlayImage 按下时候的叠加图 - roundAsCircle 是否涉及圆圈 - roundedCornerRadius 圆角 - roundTopLeft、roundTopRight….. 分别设置4个角不同半径，设置为true以后可以再代码中设置角度。通过RoundingParams的setConnersRadii()方法 ~~~ public RoundingParams setCornersRadii(float topLeft, float topRight, float bottomRight, float bottomLeft) { float[] radii = this.getOrCreateRoundedCornersRadii(); radii[0] = radii[1] = topLeft; radii[2] = radii[3] = topRight; radii[4] = radii[5] = bottomRight; radii[6] = radii[7] = bottomLeft; return this; } ~~~ - roundWithOverlayColor，边框的叠加颜色 - roundingBorderWidth 边框宽度 - roundingBorderColor 边框颜色 我们看到，仅仅靠xml文件的属性，功能就已经很强大了。我们通过什么来在代码中设置各种效果呢？看代码 ~~~ GenericDraweeHierarchyBuilder builder = new GenericDraweeHierarchyBuilder(getResources()); GenericDraweeHierarchy hierarchy = builder .setFadeDuration(300) .setPlaceholderImage(new MyCustomDrawable()) .setBackgrounds(backgroundList) .setOverlays(overlaysList) .build(); mSimpleDraweeView.setHierarchy(hierarchy); ~~~ DraweeHierarchy的一些属性可以在运行时改变。 ~~~ GenericDraweeHierarchy hierarchy =mSimpleDraweeView.getHierarchy(); hierarchy.setPlaceholderImage(R.drawable.placeholderId); ~~~ 注意：对于同一个View，不要多次调用setHierarchy。 我们看看GenericDraweeHierarchy提供了哪些set方法  看到这里有相当多的drawable啊。我们在来看看，Fresco源码中有哪些Drawable，  我们在set…(new ..Drawable),就可以轻松使用了。我们以ProgressBarDrawable为例，看看他提供了哪些方法。  ，看起来还是很强大的。当然，我们可以自定义Drawable，关于自定义Drawable，我这里就不再说了，网上还是很多的。 我们在来看看ControllerBuilder，从字面上就可以看出，这个可以对图片做出一些控制。 ~~~ ControllerListener listener = new BaseControllerListener() {...} DraweeController controller = Fresco.newDraweeControllerBuilder() .setUri(uri) .setTapToRetryEnabled(true) .setOldController(mSimpleDraweeView.getController()) .setControllerListener(listener) .build(); mSimpleDraweeView.setController(controller); ~~~ 在指定一个新的controller的时候，使用setOldController，可以节省不必要的内存分配。 我们来看看Fresco.newDraweeControllerBuilder()有哪些set方法。  自定义图片加载请求 ~~~ Uri uri; Postprocessor myPostprocessor = new Postprocessor() { ... } ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) .setPostprocessor(myPostprocessor) .build(); DraweeController controller = Fresco.newDraweeControllerBuilder() .setImageRequest(request) .setOldController(mSimpleDraweeView.getController()) // 其他设置 .build(); ~~~ 渐进式JPEG图 ~~~ ProgressiveJpegConfig pjpegConfig = new ProgressiveJpegConfig() { @Override public int getNextScanNumberToDecode(int scanNumber) { return scanNumber + 2; } public QualityInfo getQualityInfo(int scanNumber) { boolean isGoodEnough = (scanNumber >= 5); return ImmutableQualityInfo.of(scanNumber, isGoodEnough, false); } } ImagePipelineConfig config = ImagePipelineConfig.newBuilder() .setProgressiveJpegConfig(pjpeg) .build(); ~~~ ~~~ Uri uri; ImageRequest request = ImageRequestBuilder .newBuilderWithSource(uri) .setProgressiveRenderingEnabled(true) .build(); PipelineDraweeController controller = Fresco.newControllerBuilder() .setImageRequest(requests) .setOldController(mSimpleDraweeView.getController()) .build(); mSimpleDraweeView.setController(controller); ~~~ Gif动态图 ~~~ Uri uri; ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) . // other setters .build(); DraweeController controller = Fresco.newDraweeControllerBuilder() .setImageRequest(request) .setAutoPlayAnimations(true) . // other setters .build(); mSimpleDraweeView.setController(controller); ~~~ 手动控制动态图播放 ~~~ ControllerListener controllerListener = new BaseControllerListener<ImageInfo>() { @Override public void onFinalImageSet( String id, @Nullable ImageInfo imageInfo, @Nullable Animatable anim) { if (anim != null) { // app-specific logic to enable animation starting anim.start(); } }; Uri uri; DraweeController controller = Fresco.newDraweeControllerBuilder() .setUri(uri) .setControllerListener(controllerListener) // other setters .build(); mSimpleDraweeView.setController(controller); ~~~ 使用动画 ~~~ Animatable animation = mSimpleDraweeView.getController().getAnimatable(); if (animation != null) { // 开始播放 animation.start(); // 一段时间之后，根据业务逻辑，停止播放 animation.stop(); } ~~~ 多图请求以及图片复用 ~~~ Uri lowResUri, highResUri; DraweeController controller = Fresco.newDraweeControllerBuilder() .setLowResImageRequest(ImageRequest.fromUri(lowResUri)) .setImageRequest(ImageRequest.fromUri(highResUri)) .setOldController(mSimpleDraweeView.getController()) .build(); mSimpleDraweeView.setController(controller); ~~~ 缩略图预览 ~~~ Uri uri; ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) .setLocalThumbnailPreviewsEnabled(true) .build(); DraweeController controller = Fresco.newDraweeControllerBuilder() .setImageRequest(request) .setOldController(mSimpleDraweeView.getController()) .build(); mSimpleDraweeView.setController(controller); ~~~ 本地图片复用 ~~~ Uri uri1, uri2; ImageRequest request = ImageRequest.fromUri(uri1); ImageRequest request2 = ImageRequest.fromUri(uri2); ImageRequest[] requests = { request1, request2 }; DraweeController controller = Fresco.newDraweeControllerBuilder() .setFirstAvailableImageRequests(requests) .setOldController(mSimpleDraweeView.getController()) .build(); mSimpleDraweeView.setController(controller); ~~~ 监听下载事件 ~~~ ControllerListener controllerListener = new BaseControllerListener<ImageInfo>() { @Override public void onFinalImageSet( String id, @Nullable ImageInfo imageInfo, @Nullable Animatable anim) { if (imageInfo == null) { return; } QualityInfo qualityInfo = imageInfo.getQualityInfo(); FLog.d("Final image received! " + "Size %d x %d", "Quality level %d, good enough: %s, full quality: %s", imageInfo.getWidth(), imageInfo.getHeight(), qualityInfo.getQuality(), qualityInfo.isOfGoodEnoughQuality(), qualityInfo.isOfFullQuality()); } @Override public void onIntermediateImageSet(String id, @Nullable ImageInfo imageInfo) { FLog.d("Intermediate image received"); } @Override public void onFailure(String id, Throwable throwable) { FLog.e(getClass(), throwable, "Error loading %s", id) } }; Uri uri; DraweeController controller = Fresco.newControllerBuilder() .setControllerListener(controllerListener) .setUri(uri); // other setters .build(); mSimpleDraweeView.setController(controller); ~~~ 修改图片尺寸 ~~~ Uri uri = "file:///mnt/sdcard/MyApp/myfile.jpg"; int width = 50, height = 50; ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) .setResizeOptions(new ResizeOptions(width, height)) .build(); PipelineDraweeController controller = Fresco.newDraweeControllerBuilder() .setOldController(mDraweeView.getController()) .setImageRequest(request) .build(); mSimpleDraweeView.setController(controller); ~~~ 自动旋转 ~~~ ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) .setAutoRotateEnabled(true) .build(); ~~~ 图片的修改。后处理器 ~~~ Uri uri; Postprocessor redMeshPostprocessor = new BasePostprocessor() { @Override public String getName() { return "redMeshPostprocessor"; } @Override public void process(Bitmap bitmap) { for (int x = 0; x < bitmap.getWidth(); x+=2) { for (int y = 0; y < bitmap.getHeight(); y+=2) { bitmap.setPixel(x, y, Color.RED); } } } } ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri) .setPostprocessor(redMeshPostprocessor) .build(); PipelineDraweeController controller = (PipelineDraweeController) Fresco.newDraweeControllerBuilder() .setImageRequest(request) .setOldController(mSimpleDraweeView.getController()) // other setters as you need .build(); mSimpleDraweeView.setController(controller); ~~~ 图片请求 Image Requests ~~~ Uri uri; ImageDecodeOptions decodeOptions = ImageDecodeOptions.newBuilder() .setBackgroundColor(Color.GREEN) .build(); ImageRequest request = ImageRequestBuilder .newBuilderWithSource(uri) .setAutoRotateEnabled(true) .setLocalThumbnailPreviewsEnabled(true) .setLowestPermittedRequestLevel(RequestLevel.FULL_FETCH) .setProgressiveRenderingEnabled(false) .setResizeOptions(new ResizeOptions(width, height)) .build(); ~~~ 上面我们说了Deawee，下面我们说下Image Pipeline 配置代码 ~~~ ImagePipelineConfig config = ImagePipelineConfig.newBuilder() .setBitmapMemoryCacheParamsSupplier(bitmapCacheParamsSupplier) .setCacheKeyFactory(cacheKeyFactory) .setEncodedMemoryCacheParamsSupplier(encodedCacheParamsSupplier) .setExecutorSupplier(executorSupplier) .setImageCacheStatsTracker(imageCacheStatsTracker) .setMainDiskCacheConfig(mainDiskCacheConfig) .setMemoryTrimmableRegistry(memoryTrimmableRegistry) .setNetworkFetchProducer(networkFetchProducer) .setPoolFactory(poolFactory) .setProgressiveJpegConfig(progressiveJpegConfig) .setRequestListeners(requestListeners) .setSmallImageDiskCacheConfig(smallImageDiskCacheConfig) .build(); Fresco.initialize(context, config); ~~~ 是在是太多了，我也懒的写了。 参考资料：[中文文档](http://www.fresco-cn.org/)