摘要：请求处理将要加载的资源放入到其中这段代码涉及属性暂且放到一边，而这段代码表明当同一个上要加载两个资源，不论资源是否一致，将前一个资源请求取消创建新的资源请求绑定有两个列表，用来存储所有的和暂停掉的加载图片的过程开启资源请求加载图片分几步
2.Request请求处理
DrawableRequestBuilder.into(ImageView)
RequestManager.load将要加载的资源放入到GenericRequestBuilder
GenericRequestBuilder.java:
public Target into(ImageView view) {
Util.assertMainThread();
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();
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
applyFitCenter();
break;
//$CASES-OMITTED$
default:
// Do nothing.
}
}
return into(glide.buildImageViewTarget(view, transcodeClass));
}
public > Y into(Y target) {
Util.assertMainThread();
... ...
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
Request request = buildRequest(target);
target.setRequest(request);
lifecycle.addListener(target);
requestTracker.runRequest(request);
return target;
}
其中这段代码涉及ImageView.scaleType属性
switch (view.getScaleType()) {
case CENTER_CROP:
applyCenterCrop();
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
applyFitCenter();
break;
//$CASES-OMITTED$
default:
// Do nothing.
}
暂且放到一边，
而
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
Request request = buildRequest(target);
target.setRequest(request);
lifecycle.addListener(target);
requestTracker.runRequest(request);
RequestTracker.java:
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}
这段代码表明：
当同一个target上要加载两个资源，不论资源是否一致，
1).将前一个资源请求取消;
2).创建新的资源请求,绑定target,
RequestTracker有两个request列表，用来存储所有的request和暂停掉的request
private final Set requests = Collections.newSetFromMap(new WeakHashMap());
private final List pendingRequests = new ArrayList();
3.加载图片的过程
开启资源请求：
GenericRequest.java:
@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);
ModelLoader modelLoader = loadProvider.getModelLoader();
final DataFetcher dataFetcher = modelLoader.getResourceFetcher(model, width, height);
if (dataFetcher == null) {
onException(new Exception("Failed to load model: "" + model + """));
return;
}
ResourceTranscoder transcoder = loadProvider.getTranscoder();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadedFromMemoryCache = true;
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));
}
}
Engine.java:
public LoadStatus load(Key signature, int width, int height, DataFetcher fetcher,
DataLoadProvider loadProvider, Transformation transformation, ResourceTranscoder transcoder,
Priority priority, boolean isMemoryCacheable, DiskCacheStrategy diskCacheStrategy, ResourceCallback cb) {
Util.assertMainThread();
long startTime = LogTime.getLogTime();
final String id = fetcher.getId();
EngineKey key = keyFactory.buildKey(id, signature, width, height, loadProvider.getCacheDecoder(),
loadProvider.getSourceDecoder(), transformation, loadProvider.getEncoder(),
transcoder, loadProvider.getSourceEncoder());
EngineResource cached = loadFromCache(key, isMemoryCacheable);
if (cached != null) {
cb.onResourceReady(cached);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from cache", startTime, key);
}
return null;
}
EngineResource active = loadFromActiveResources(key, isMemoryCacheable);
if (active != null) {
cb.onResourceReady(active);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from active resources", startTime, key);
}
return null;
}
EngineJob current = jobs.get(key);
if (current != null) {
current.addCallback(cb);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Added to existing load", startTime, key);
}
return new LoadStatus(cb, current);
}
EngineJob engineJob = engineJobFactory.build(key, isMemoryCacheable);
DecodeJob decodeJob = new DecodeJob(key, width, height, fetcher, loadProvider, transformation,
transcoder, diskCacheProvider, diskCacheStrategy, priority);
EngineRunnable runnable = new EngineRunnable(engineJob, decodeJob, priority);
jobs.put(key, engineJob);
engineJob.addCallback(cb);
engineJob.start(runnable);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
加载图片分几步：
1）.生成资源对应的Key，与width,height相关
相同的资源，不同的width,height，Key不相同
2）.从Cache中获取
private final MemoryCache cache;
private EngineResource loadFromCache(Key key, boolean isMemoryCacheable) {
if (!isMemoryCacheable) {
return null;
}
EngineResource cached = getEngineResourceFromCache(key);
if (cached != null) {
cached.acquire();
activeResources.put(key, new ResourceWeakReference(key, cached, getReferenceQueue()));
}
return cached;
}
@SuppressWarnings("unchecked")
private EngineResource getEngineResourceFromCache(Key key) {
Resource cached = cache.remove(key);
final EngineResource result;
if (cached == null) {
result = null;
} else if (cached instanceof EngineResource) {
// Save an object allocation if we"ve cached an EngineResource (the typical case).
result = (EngineResource) cached;
} else {
result = new EngineResource(cached, true /*isCacheable*/);
}
return result;
}
3）从常用的中获取：
private final Map>> activeResources;
private EngineResource loadFromActiveResources(Key key, boolean isMemoryCacheable) {
if (!isMemoryCacheable) {
return null;
}
EngineResource active = null;
WeakReference> activeRef = activeResources.get(key);
if (activeRef != null) {
active = activeRef.get();
if (active != null) {
active.acquire();
} else {
activeResources.remove(key);
}
}
return active;
}
private EngineResource loadFromCache(Key key, boolean isMemoryCacheable) {
if (!isMemoryCacheable) {
return null;
}
EngineResource cached = getEngineResourceFromCache(key);
if (cached != null) {
cached.acquire();
activeResources.put(key, new ResourceWeakReference(key, cached, getReferenceQueue()));
}
return cached;
}
在cache中获取，放入activeResources
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