4. into()方法，最重要 最核心的方法。
实际的加载请求，
// 1.
Glide.with(getApplicationContext()).load(url).into(imageView);
↓
public Target<GlideDrawable> into(ImageView view) {
return super.into(view); //2.调用父类方法
}
↓
//3. GenericRequestBuilder.java
public Target<TranscodeType> into(ImageView view) {
Util.assertMainThread(); //判断是否主线程，非主线程抛异常
if (view == null) {
throw new IllegalArgumentException("You must pass in a non null View");
}
if (!isTransformationSet && view.getScaleType() != null) {
switch (view.getScaleType()) {
case CENTER_CROP:
applyCenterCrop(); //3.1 按比例扩大，居中显示
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
applyFitCenter();
break;
default: // Do nothing.
}
}
// 4.
return into(glide.buildImageViewTarget(view, transcodeClass));
}
↓
//3.1 DrawableRequestBuilder.java
void applyCenterCrop() {
centerCrop();
}
↓
// 3.2
public DrawableRequestBuilder<ModelType> centerCrop() {
return transform(glide.getDrawableCenterCrop());
}
// 3.3
public DrawableRequestBuilder<ModelType> transform(Transformation<GifBitmapWrapper>... transformation) {
super.transform(transformation);
return this;
}
// 3.4 GenericRequestBuilder.java
public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> transform(
Transformation<ResourceType>... transformations) {
isTransformationSet = true; //初始化操作 赋值
if (transformations.length == 1) {
transformation = transformations[0];
} else {
transformation = new MultiTransformation<ResourceType>(transformations);
}
return this;
}
接上面，第四步骤 创建好Target
// 4.0
return into(glide.buildImageViewTarget(view, transcodeClass));
// public interface Target<R> extends LifecycleListener
// 4.1 封装成Target，通过工厂构建。
<R> Target<R> buildImageViewTarget(ImageView imageView, Class<R> transcodedClass) {
return imageViewTargetFactory.buildTarget(imageView, transcodedClass);
}
// 4.2 通过clazz，判断到底加载那种图片，就创建对应的Target。
public class ImageViewTargetFactory {
@SuppressWarnings("unchecked")
public <Z> Target<Z> buildTarget(ImageView view, Class<Z> clazz) {
if (GlideDrawable.class.isAssignableFrom(clazz)) {//默认的返回 GlideDrawableImageViewTarget
return (Target<Z>) new GlideDrawableImageViewTarget(view);
} else if (Bitmap.class.equals(clazz)) { //已调用asBitmap，返回BitmapImageViewTarget
return (Target<Z>) new BitmapImageViewTarget(view);
} else if (Drawable.class.isAssignableFrom(clazz)) {
return (Target<Z>) new DrawableImageViewTarget(view);
} else {
throw new IllegalArgumentException("Unhandled class: " + clazz
+ ", try .as*(Class).transcode(ResourceTranscoder)");
}
}
}
//Target 实现类有 ImageViewTarget 用于显示图片。
// 内有抽象方法 protected abstract void setResource(Z resource);
// BitmapImageViewTarget:
@Override
protected void setResource(Bitmap resource) {
view.setImageBitmap(resource);
}
//当Activity销毁，控制图片不继续加载。
public interface LifecycleListener { //接口定义3个生命周期方法
void onStart();
void onStop();
void onDestroy();
}
//-------------------------------------------
上面构建好了Target，传入给into方法。
public <Y extends Target<TranscodeType>> Y into(Y target) {
Util.assertMainThread(); // 5.0 主线程判断
if (target == null) {
throw new IllegalArgumentException("You must pass in a non null Target");
}
if (!isModelSet) {
throw new IllegalArgumentException("You must first set a model (try #load())");
}
//5.1 获取当前target 绑定的request，先删除旧的，再绑定新的request到target中。
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);//暂停request，避免图片错位。
previous.recycle(); //成员变量清空
//REQUEST_POOL.offer(this); //放到请求池中，以供复用
}
//5.2 创建新的request，imageView与 request请求绑定。
Request request = buildRequest(target);
target.setRequest(request); //绑定setTag，target绑定request，防止列表中图片错位
lifecycle.addListener(target);//设置监听事件
requestTracker.runRequest(request);//【重要】6.
return target;
}
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
private Request buildRequestRecursive(Target<TranscodeType> target, ThumbnailRequestCoordinator parentCoordinator) {
if (thumbnailRequestBuilder != null) {
} else if (thumbSizeMultiplier != null) {
} else {
// Base case: no thumbnail.
return obtainRequest(target, sizeMultiplier, priority, parentCoordinator);
}
}
private Request obtainRequest(Target<TranscodeType> target, float sizeMultiplier, Priority priority,
RequestCoordinator requestCoordinator) {
return GenericRequest.obtain(
loadProvider,
model,
signature,
context,
priority,
target,
sizeMultiplier,
placeholderDrawable,
placeholderId,
errorPlaceholder,
errorId,
fallbackDrawable,
fallbackResource,
requestListener,
requestCoordinator,
glide.getEngine(),
transformation,
transcodeClass,
isCacheable,
animationFactory,
overrideWidth,
overrideHeight,
diskCacheStrategy);
}
obtain() {
//从复用池中获取
GenericRequest<A, T, Z, R> request = (GenericRequest<A, T, Z, R>) REQUEST_POOL.poll();
request.init(); //初始化操作
return request;
}
6. requestTracker.runRequest(request);
// 6.0
public void runRequest(Request request) {
requests.add(request); //加入到set集合中
if (!isPaused) {
request.begin(); //6.1开始一个异步请求
} else {
pendingRequests.add(request); //一组尚未完成且已排队等待再次运行的请求。
}
}
// 6.1
@Override
public void begin() {
startTime = LogTime.getLogTime();
if (model == null) {
onException(null);
return;
}
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {//是否调用override方法。
onSizeReady(overrideWidth, overrideHeight); //****不要再计算****
} else { //未指定图片宽高， 6.2重新计算宽高，进行view的测量
target.getSize(this);
}
if (!isComplete() && !isFailed() && canNotifyStatusChanged()) {
//开始加载，设定占位符
target.onLoadStarted(getPlaceholderDrawable());
}
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
//6.2 ViewTarget
public void getSize(SizeReadyCallback cb) {
sizeDeterminer.getSize(cb);
}
//6.3 ViewTarget，计算应该展示的宽高值。
public void getSize(SizeReadyCallback cb) {
int currentWidth = getViewWidthOrParam(); //获取宽高
int currentHeight = getViewHeightOrParam();
if (isSizeValid(currentWidth) && isSizeValid(currentHeight)) {
cb.onSizeReady(currentWidth, currentHeight);//重点方法 6.4, 回调执行onSizeReady.
} else {
// We want to notify callbacks in the order they were added and we only expect one or two callbacks to
// be added a time, so a List is a reasonable choice.
if (!cbs.contains(cb)) {
cbs.add(cb);
}
if (layoutListener == null) {
final ViewTreeObserver observer = view.getViewTreeObserver();
layoutListener = new SizeDeterminerLayoutListener(this);
observer.addOnPreDrawListener(layoutListener);//测量完毕
}
}
}
// 6.4 GenericRequest.java 【重点方法】
@Override
public void onSizeReady(int width, int height) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("Got onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
if (status != Status.WAITING_FOR_SIZE) {
return;
}
status = Status.RUNNING;
width = Math.round(sizeMultiplier * width);
height = Math.round(sizeMultiplier * height);
// 7.获取modelLoader.dataFetcher，transcoder 。他们都与loadProvider 有关。
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
if (dataFetcher == null) {
onException(new Exception("Failed to load model: \'" + model + "\'"));
return;
}
//负责原始数据解码，原始数据解码成bitmap
ResourceTranscoder<Z, R> transcoder = loadProvider.getTranscoder();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadedFromMemoryCache = true;
// 7.1 传入参数，进行实际的图片加载
loadStatus = engine.load(signature, width, height, dataFetcher, loadProvider, transformation, transcoder,
priority, isMemoryCacheable, diskCacheStrategy, this);
loadedFromMemoryCache = resource != null;
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
}
ModelLoader 从数据源获取原始数据，inputStream-data
DataFetcher 从不同的文件、视频中获取 data。
loadProvider 是什么时候赋值的？
DrawableTypeRequest.java 的 buildProvider()
DrawableTypeRequest(Class<ModelType> modelClass, ModelLoader<ModelType, InputStream> streamModelLoader,
ModelLoader<ModelType, ParcelFileDescriptor> fileDescriptorModelLoader, Context context, Glide glide,
RequestTracker requestTracker, Lifecycle lifecycle, RequestManager.OptionsApplier optionsApplier) {
super(context, modelClass,
buildProvider(glide, streamModelLoader, fileDescriptorModelLoader, GifBitmapWrapper.class,
GlideDrawable.class, null),
glide, requestTracker, lifecycle);
this.streamModelLoader = streamModelLoader;
this.fileDescriptorModelLoader = fileDescriptorModelLoader;
this.optionsApplier = optionsApplier;
}
// buildProvider() 返回FixedLoadProvider
DrawableTypeRequest.java
private static <A, Z, R> FixedLoadProvider<A, ImageVideoWrapper, Z, R> buildProvider(Glide glide,
ModelLoader<A, InputStream> streamModelLoader,
ModelLoader<A, ParcelFileDescriptor> fileDescriptorModelLoader, Class<Z> resourceClass,
Class<R> transcodedClass,
ResourceTranscoder<Z, R> transcoder) {
if (streamModelLoader == null && fileDescriptorModelLoader == null) {
return null;
}
if (transcoder == null) {
transcoder = glide.buildTranscoder(resourceClass, transcodedClass);
}
//用于图片编解码
DataLoadProvider<ImageVideoWrapper, Z> dataLoadProvider = glide.buildDataProvider(ImageVideoWrapper.class,
resourceClass);
//【重要】：两个modelLoader包装类.
ImageVideoModelLoader<A> modelLoader = new ImageVideoModelLoader<A>(streamModelLoader,fileDescriptorModelLoader);
//创建FixedLoadProvider：获取原始图片，解码转码。
return new FixedLoadProvider<A, ImageVideoWrapper, Z, R>(modelLoader, transcoder, dataLoadProvider);
}
