picasso 之Action及其子类ImageViewAction
Action代表的是一个具体的加载类。
里有一个静态内部类
static class RequestWeakReference<M> extends WeakReference<M> {
final Action action;
public RequestWeakReference(Action action, M referent, ReferenceQueue<? super M> q) {
super(referent, q);
this.action = action;
}
}
这里的referent，在ImageViewAction中传进来就是ImageView
Action主要定义了两个方法
abstract void complete(Bitmap result, Picasso.LoadedFrom from); abstract void error();
构造方法：
Action(Picasso picasso, T target, Request request, int memoryPolicy, int networkPolicy,
int errorResId, Drawable errorDrawable, String key, Object tag, boolean noFade) {
this.picasso = picasso;
this.request = request;
this.target =
target == null ? null : new RequestWeakReference<T>(this, target, picasso.referenceQueue);
this.memoryPolicy = memoryPolicy;
this.networkPolicy = networkPolicy;
this.noFade = noFade;
this.errorResId = errorResId;
this.errorDrawable = errorDrawable;
this.key = key;
this.tag = (tag != null ? tag : this);
}
现在看子类ImageViewAction：
构造方法
ImageViewAction(Picasso picasso, ImageView imageView, Request data, int memoryPolicy,
int networkPolicy, int errorResId, Drawable errorDrawable, String key, Object tag,
Callback callback, boolean noFade) {
super(picasso, imageView, data, memoryPolicy, networkPolicy, errorResId, errorDrawable, key,
tag, noFade);
this.callback = callback;
}
@Override public void complete(Bitmap result, Picasso.LoadedFrom from) {
if (result == null) {
throw new AssertionError(
String.format("Attempted to complete action with no result!\n%s", this));
}
ImageView target = this.target.get(); //这是一个虚引用
if (target == null) { //如果imageview已经被回收了，直接返回
return;
}
Context context = picasso.context;
boolean indicatorsEnabled = picasso.indicatorsEnabled;
PicassoDrawable.setBitmap(target, context, result, from, noFade, indicatorsEnabled);
if (callback != null) {
callback.onSuccess();
}
}