聲明
本文章是基于 glide 3.6.1的
個(gè)各類的功能介紹
1.Glide:向外暴露單例靜態(tài)接口,構(gòu)建Request.配置資源類型,緩存策略,圖片處理等,可以直接通過該類完整簡單的圖片請(qǐng)求和填充,內(nèi)部持有一些變量BitmapPool,MemoryCache,ByteArrayPool,便于低內(nèi)存情況時(shí)自動(dòng)清理內(nèi)存
2.RequestManagerRetriever: (RequestManager的獲取類 單例類)提供靜態(tài)方法去創(chuàng)建新的RequestManager 或者從Activity或者fragment中檢索已經(jīng)存在的請(qǐng)求
3.RequestManager:(管理請(qǐng)求的類 實(shí)現(xiàn)了LiftcycleListener) 可以依賴Activity和Fragment的聲明周期進(jìn)行請(qǐng)求的start,stop,reStart等操作
4.RequestManagerFragment:(用于竊聽Activity,Fragment頁面的生命周期變化的)一個(gè)沒有視圖的Fragment,內(nèi)部有RequestManager這個(gè)成員變量.每一個(gè)context(Activity或者Fragment)都會(huì)擁有一個(gè)RequestManagerFragment,用于監(jiān)聽Activity或者Fragment生命周期的變化,從而調(diào)用ActivityFragmentLifecycle的方法,當(dāng)內(nèi)存不足時(shí)會(huì)調(diào)用RequestManager的相關(guān)方法
5.ActivityFragmentLifecycle:(實(shí)現(xiàn)了Liftcycle接口)用于監(jiān)聽Activity和Fragment生命周期活動(dòng)的實(shí)現(xiàn)類.
6.DrawableTypeRequest:(繼承了DrawableRequestBuilder)一個(gè)用來創(chuàng)建加載請(qǐng)求的類,可以直接加載GIF動(dòng)畫,也可以直接加載Bitmap或者是資源文件
7.DrawableRequestBuilder:(繼承了GenericRequestBuilder) 創(chuàng)建請(qǐng)求GlideDrawable請(qǐng)求的類
8.GenericRequestBuilder:就是一個(gè)通用類,實(shí)現(xiàn)了一些請(qǐng)求通用的方法
9.GenericRequest:(實(shí)現(xiàn)了Request接口)這是一個(gè)請(qǐng)求的封裝類,會(huì)將資源加載到指定的目標(biāo)身上
10.RequestTracker:用于跟蹤,取消,重啟 完成和失敗請(qǐng)求的類,也就是說這個(gè)類可以對(duì)請(qǐng)求進(jìn)行開啟和暫停等操作
11.DataLoadProvider:(是一個(gè)接口) 一個(gè)負(fù)載提供程序，它提供了必要的編碼器和解碼器提完，以便從特定類型的數(shù)據(jù)中解碼特定類型的資源形纺。也就是一個(gè)內(nèi)部集成了不同情況下的編解碼器
12.LoadProvider:(是一個(gè)接口,他繼承了DataLoadProvider)其實(shí)就是DataLoadProvide的擴(kuò)展,在DataLoadProvide的基礎(chǔ)上也支持了ModelLoader和ResourceTranscoder
13.ModelLoader:(是一個(gè)接口) 用具將復(fù)雜的數(shù)據(jù)類型轉(zhuǎn)換為具體的數(shù)據(jù)類型,并且可以使用DataFetcher來獲取資源數(shù)據(jù)--->ModelLoader 是一個(gè)工廠接口。將任意復(fù)雜的 model 轉(zhuǎn)換為準(zhǔn)確具體的可以被 DataFetcher 獲取的數(shù)據(jù)類型徒欣。 每一個(gè) model 內(nèi)部實(shí)現(xiàn)了一個(gè) ModelLoaderFactory逐样，內(nèi)部實(shí)現(xiàn)就是將 model 轉(zhuǎn)換為 Data
14.DataFetcher:(是一個(gè)接口) 就是加載器的頂級(jí)接口
15.Engine:負(fù)責(zé)啟動(dòng)下載,管理活動(dòng)和緩存資源的類-->任務(wù)創(chuàng)建，發(fā)起打肝，回調(diào)脂新，管理存活和緩存的資源
16.EngineJob:(負(fù)責(zé)加載每一個(gè)請(qǐng)求，它里面有線程池成員變量)下載的管理類,也就是Engine的管理類--->將線程回調(diào)到主線程的類
17.EngineRunnable:(實(shí)現(xiàn)了Runnable接口) 就是一個(gè)任務(wù),在下載完成后或者找到緩存圖片后進(jìn)行解碼
18.DecodeJob:調(diào)度任務(wù)的核心類闯睹，整個(gè)請(qǐng)求的繁重工作都在這里完成,處理來自緩存或者原始的資源戏羽，應(yīng)用轉(zhuǎn)換動(dòng)畫以及 transcode
19.HttpUrlFetcher:(實(shí)現(xiàn)了DataFetcher) 該類是專門從網(wǎng)絡(luò)中加載圖片的加載器.
20.EngineRunnableManager:(是一個(gè)接口,繼承了ResourceCallback)用于監(jiān)聽圖片獲取成功的監(jiān)聽器,
21.ResourceCallback:(是一個(gè)接口)用于監(jiān)聽資源是否加載成功或者失敗的回到
22.Target:(是一個(gè)接口)request 的載體担神，各種資源對(duì)應(yīng)的加載類楼吃，含有生命周期的回調(diào)方法，方便開發(fā)人員進(jìn)行相應(yīng)的準(zhǔn)備以及資源回收工作
23.Resource:(是一個(gè)接口)對(duì)資源進(jìn)行包裝的接口妄讯，提供 get孩锡，recycle，getSize亥贸，以及原始類的 getResourceClass 方法躬窜。 其實(shí)現(xiàn)類都在resource包下,resource 包下也就是各種資源：bitmap，bytes炕置，drawable荣挨，file，gif朴摊，以及相關(guān)解碼器默垄，轉(zhuǎn)換器
Glide.with(this).load("...imageurl..").into(iv);這段代碼內(nèi)部調(diào)用流程如下
首先上段代碼可以分解為
RequestManager requestManager = Glide.with(this);
DrawableTypeRequest<String> drawableTypeRequest = requestManager .load("...imageurl..");
drawableTypeRequest .into(iv);
首先我們先來看看 RequestManager requestManager = Glide.with(this); 這段代碼
1.Glide.with()方法中會(huì)調(diào)用RequestManagerRetriever的靜態(tài)get()方法獲取到RequestManagerRetriever的實(shí)例,然后調(diào)用RequestManagerRetriever的get()方法獲取到RequestManager的實(shí)例并返回
public static RequestManager with(FragmentActivity activity) {
RequestManagerRetriever retriever = RequestManagerRetriever.get();
return retriever.get(activity);
}
2.在RequestManagerRetriever的get()方法中有一個(gè)重要的操作就是給當(dāng)前的activity也就是Glide.with()方法中傳入的activity添加一個(gè)SupportRequestManagerFragment(繼承自Fragment TAG 為"com.bumptech.glide.manager")用于監(jiān)控傳入activity的聲明周期變化,從而讓Glide的操作達(dá)到和Activity的聲明周期一致的狀態(tài).還有一個(gè)重要的操作就是在RequestManager的構(gòu)造方法中將ActivityFragmentLifecycle和Lifecycle(RequestManager)進(jìn)行了綁定,也就是說將傳入Activity的生命周期傳入到了RequestManager中(這個(gè)過程下面有具體的分析) ** RequestManager requestManager = Glide.with(this); **
public RequestManager get(FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
//獲取到的當(dāng)前Activity的FragmentManager并傳入給下面方法
FragmentManager fm = activity.getSupportFragmentManager();
return supportFragmentGet(activity, fm);
}
}
RequestManager supportFragmentGet(Context context, FragmentManager fm) {
//獲取到SupportRequestManagerFragment實(shí)例并使用FragmentManager添加到當(dāng)前Activity中
SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
//創(chuàng)建RequestManager并設(shè)置到SupportRequestManagerFragment中保存起來
requestManager = new RequestManager(context, current.getLifecycle(), current.getRequestManagerTreeNode());
current.setRequestManager(requestManager);
}
return requestManager;
}
RequestManager(Context context, final Lifecycle lifecycle, RequestManagerTreeNode treeNode,
RequestTracker requestTracker, ConnectivityMonitorFactory factory) {
this.context = context.getApplicationContext();
this.lifecycle = lifecycle;
this.treeNode = treeNode;
this.requestTracker = requestTracker;
this.glide = Glide.get(context);
this.optionsApplier = new OptionsApplier();
ConnectivityMonitor connectivityMonitor = factory.build(context,
new RequestManagerConnectivityListener(requestTracker));
// 在這里將傳入的Activity的生命周期傳到了RequestManager身上
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
lifecycle.addListener(RequestManager.this);
}
});
} else {
lifecycle.addListener(this);
}
lifecycle.addListener(connectivityMonitor);
}
看完這些代碼以后我們來捋一捋到底R(shí)equestManager是如何獲取到傳入的Activity的生命周期的,
首先在執(zhí)行RequestManagerRetriever的get()方法的時(shí)候會(huì)給傳入的Activity設(shè)置一個(gè)沒有視圖的Fragment也就是SupportRequestManagerFragment,在SupportRequestManagerFragment中有一個(gè)成員變量是ActivityFragmenLifecycle它實(shí)現(xiàn)了Lifecycle接口是專門用來監(jiān)視SupportRequestmanagerFragment的生命周期的,其實(shí)這個(gè)聲明周期也就是傳入的Activity的生命周期.在ActivityFragmentLifecycle中有一個(gè)存儲(chǔ)著LifecycleListener的Set集合.當(dāng)Activity的生命周期方法被調(diào)用的時(shí)候在SupportRequestManagerFragment中也會(huì)調(diào)用ActivityFragmentLifecycle的方法,然后ActivityFragmentLifecycle在調(diào)用LifecycleListener的方法,而剛好RequestManager實(shí)現(xiàn)了LifecycleListener這個(gè)接口,所以從這里生命周期就傳到了RequestManager的身上.
在這里ActivityFragmentLifecycle是一個(gè)被觀察者,RequestManager是一個(gè)觀察者他們的綁定是在RequestManager的構(gòu)造方法中.
.....
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
lifecycle.addListener(RequestManager.this);
}
});
.....
如下圖所示
下來我們?cè)倏纯? DrawableTypeRequest<String> drawableTypeRequest = requestManager .load("...imageurl.."); 這段代碼
1.這里首先調(diào)用了RequestManager的load()方法,然后在RequestManager中調(diào)用fromString()方法,然后在fromString()中調(diào)用loadGeneric()方法創(chuàng)建一個(gè)DrawableTypeRequest,然后右調(diào)用了DrawableTypeRequest方法并返回
public DrawableTypeRequest<String> load(String string) {
return (DrawableTypeRequest<String>) fromString().load(string);
}
public DrawableTypeRequest<String> fromString() {
return loadGeneric(String.class);
}
private <T> DrawableTypeRequest<T> loadGeneric(Class<T> modelClass) {
ModelLoader<T, InputStream> streamModelLoader = Glide.buildStreamModelLoader(modelClass, context);
ModelLoader<T, ParcelFileDescriptor> fileDescriptorModelLoader =
Glide.buildFileDescriptorModelLoader(modelClass, context);
if (modelClass != null && streamModelLoader == null && fileDescriptorModelLoader == null) {
throw new IllegalArgumentException("Unknown type " + modelClass + ". You must provide a Model of a type for"
+ " which there is a registered ModelLoader, if you are using a custom model, you must first call"
+ " Glide#register with a ModelLoaderFactory for your custom model class");
}
return optionsApplier.apply(
new DrawableTypeRequest<T>(modelClass, streamModelLoader, fileDescriptorModelLoader, context,
glide, requestTracker, lifecycle, optionsApplier));
}
@Override
public DrawableRequestBuilder<ModelType> load(ModelType model) {
super.load(model);
return this;
}
其實(shí)load()方法干的事兒很簡單,就是根據(jù)load()方法中傳入的不同類型的值,來生成不同的DrawableTypeRequest并進(jìn)行返回
最后我們來看看 drawableTypeRequest .into(iv); 這段代碼
1.首先會(huì)調(diào)用DrawableTypeRequest中的into方法,其實(shí)是DrawableRequestBuilder的into方法,因?yàn)镈rawableTypeRequest繼承了DrawableRequestBuilder而且沒有重寫into方法,然后在調(diào)用DrawableRequestBuilder的父類GenericRequestBuilder的into方法,然后在調(diào)用GenericRequestBuilder中的into的重載方法,在這個(gè)into方法中首先會(huì)判斷 傳入的ImageView是否已經(jīng)攜帶請(qǐng)求,如果攜帶請(qǐng)求就將這個(gè)請(qǐng)求清除掉,再加上新的請(qǐng)求,(這就解決了listView中圖片錯(cuò)位的現(xiàn)象).
2.下來就會(huì)調(diào)用buildRequest()方法去創(chuàng)建一個(gè)請(qǐng)求
3.buildRequest()方法中會(huì)調(diào)用buildRequestRecursive()方法去創(chuàng)建一個(gè)請(qǐng)求
4.buildRequestRecursive()方法中回到用obtainRequest()方法去真正的創(chuàng)建一個(gè)請(qǐng)求在該方法中回去判斷是否先加載隨略圖,如果是則會(huì)創(chuàng)建一個(gè)載縮略圖請(qǐng)求和一個(gè)原始尺寸的請(qǐng)求否則只創(chuàng)建原始尺寸的請(qǐng)求
5.obtainRequest()方法中調(diào)用 GenericRequest中obtain()方法
6.在obtain()方法中會(huì)調(diào)用init()方法對(duì)請(qǐng)求進(jìn)行初始化 這一上2-6步驟都是在創(chuàng)建一個(gè)請(qǐng)求.
7.在執(zhí)行完buildRequest()方法以后,下面就執(zhí)行了RequestTracker 的runRequest(Request request)方法
8.在runRequest(Request request)方法中 調(diào)用了Request的begin()方法,因?yàn)镚enericRequest就是實(shí)現(xiàn)了Request接口,所以也就是GenericRequest的begin()方法
9.在begin()方法中執(zhí)行了onSizeReady()方法
10.onSizeReady()方法中首先調(diào)用ModelLoader.getResourceFetcher發(fā)方法去獲取對(duì)應(yīng)資源的加載器,然后調(diào)用Engine.load()方法開始加載
11.Engine.load()方法也是先從內(nèi)存中找 ,然后在本地找最后在從網(wǎng)絡(luò)下載,執(zhí)行下載流程的話首先會(huì)獲取到EngineJob的實(shí)例
12.創(chuàng)建一個(gè)工作線程 EngineRunnable用于解碼下載得到的流或者是緩存中找的的圖片
13.將EngineRunnable添加到EngineJob中開始執(zhí)行
14.EngineRunnable既然已經(jīng)開始執(zhí)行那我們就來看看他的run方法,在run方法中首先會(huì)調(diào)用decode()方法,在decode方法中首先會(huì)判斷是否從緩存中找,我們這里直接看在網(wǎng)絡(luò)中下載的流程,所以這里走的是decodeFromSource()
15.decodeFromSource()中又調(diào)用了DecodeJob的decodeFromSource()方法
16.在DecodeFromSource方法中又調(diào)用了decodeSource()方法
17.decodeSource()方法中調(diào)用了一個(gè)重要的方法,fetcher.loadData()這個(gè)方法就是從不同的途徑中找到我們要的圖片,比如緩存或者網(wǎng)絡(luò),這里的fetcher就是HttpUrlFetcher
18.HttpUrlFetcher的loadData()方法會(huì)調(diào)用loadDataWithRedirects()方法,在這個(gè)方法中我們看到了久違的HttpUrlConnection,也就是說Glide這個(gè)框架是從這里進(jìn)行聯(lián)網(wǎng)請(qǐng)求圖片的,最后這個(gè)方法返回一個(gè)流對(duì)象,然后loadData()也返回了一個(gè)流對(duì)象到DecodeJob的decodeSource()方法中
19.然后在DecodeJob的decodeSource()中對(duì)返回的這個(gè)流對(duì)象使用decodeFromSourceData()方法進(jìn)行包裝,包裝成Resource對(duì)象進(jìn)行返回,返回到DecodeJob的decodeFromSource()方法中.
20DecodeJob的decodeFromSource()方法中再調(diào)用transformEncodeAndTranscode()方法.
21.在transformEncodeAndTranscode()方法中會(huì)調(diào)用writeTransformedToCache()方法將獲得的流對(duì)象緩存到硬盤中.
22.緩存完以后調(diào)用transcode()方法將獲得的流對(duì)象進(jìn)行轉(zhuǎn)化然后進(jìn)行返回,返回到EngineRunnabl的decodeFormSource()中.
24.然后在返回到EngineRunnable的Decode()方法中
25.然后再返回到EngineRunnable的run()方法中
26.然后在run()方法中執(zhí)行onLoadComplete()方法
27.然后執(zhí)行了EngineRunnableManager的onResourceReady()方法,因?yàn)閷?shí)現(xiàn)了EngineRunnableManager接口的只有EngineJob,所以這里執(zhí)行的是EngineJob的OnResourceReady()方法
28.在EngineJob的OnResourceReady()方法中做了一件重要的事情,就是使用主線程的Handler將線程切換到主線程中
29.然后進(jìn)入到了EngineJob的MainTreadCallback類的handleMessage()方法中,在加載成功的情況下回執(zhí)行EngineJob中的handleResultOnMainThread()方法
30.在EngineJob的handleResultOnMainThread()方法中會(huì)循環(huán)調(diào)用ResourceCallBack的OnResourceReady()方法,因?yàn)镚enericRequest實(shí)現(xiàn)了RequestCallback接口,所以就執(zhí)行了GenericRequest的onResourceReady()方法
31.在GenericRequest的onResourceReady()方法中調(diào)用了Target的onResourceReady()方法,因?yàn)檫@里我們傳入的是ImageView,所以這里的Target是ImageViewTarget,所以也就是ImageViewTarget的onResourceReady.
32.ImageViewTarget的onResourceReady中有調(diào)用了setResource()方法這是一個(gè)抽象方法,所以我們隨便看一個(gè)他的子類是怎么實(shí)現(xiàn)的,比如DrawableImageViewTarget中就是調(diào)用 view.setImageDrawable(resource); 方法將Bitmap設(shè)置到ImageView中.到此為止整個(gè)加載流程就完畢了.
//DrawableRequestBuilder中
@Override
public Target<GlideDrawable> into(ImageView view) {
return super.into(view);
}
//GenericRequestBuilder中
public Target<TranscodeType> into(ImageView view) {
............
return into(glide.buildImageViewTarget(view, transcodeClass));
}
//GenericRequestBuilder中
public <Y extends Target<TranscodeType>> Y into(Y target) {
..........
Request previous = target.getRequest();
//如果傳入的ImageView已經(jīng)攜帶請(qǐng)求就像這個(gè)請(qǐng)求給清除
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
//創(chuàng)建了一個(gè)請(qǐng)求
Request request = buildRequest(target);
target.setRequest(request);
lifecycle.addListener(target);
//開始執(zhí)行這個(gè)請(qǐng)求
requestTracker.runRequest(request);
return target;
}
//GenericRequestBuilder中
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
//GenericRequestBuilder中
private Request buildRequestRecursive(Target<TranscodeType> target, ThumbnailRequestCoordinator parentCoordinator) {
..........
else if (thumbSizeMultiplier != null) {
// Base case: thumbnail multiplier generates a thumbnail request, but cannot recurse.
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
//創(chuàng)建一個(gè)原始尺寸的請(qǐng)求
Request fullRequest = obtainRequest(target, sizeMultiplier, priority, coordinator);
//創(chuàng)建一個(gè)縮略圖請(qǐng)求
Request thumbnailRequest = obtainRequest(target, thumbSizeMultiplier, getThumbnailPriority(), coordinator);
coordinator.setRequests(fullRequest, thumbnailRequest);
return coordinator;
} else {
//去建造一個(gè)原始尺寸的請(qǐng)求
return obtainRequest(target, sizeMultiplier, priority, parentCoordinator);
..........
}
//GenericRequestBuilder中
private Request obtainRequest(Target<TranscodeType> target, float sizeMultiplier, Priority priority,
RequestCoordinator requestCoordinator) {
//創(chuàng)建一個(gè)請(qǐng)求并對(duì)其初始化
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);
}
//GenericRequest中
public static <A, T, Z, R> GenericRequest<A, T, Z, R> obtain(
LoadProvider<A, T, Z, R> loadProvider,
A model,
Key signature,
Context context,
Priority priority,
Target<R> target,
float sizeMultiplier,
Drawable placeholderDrawable,
int placeholderResourceId,
Drawable errorDrawable,
int errorResourceId,
Drawable fallbackDrawable,
int fallbackResourceId,
RequestListener<? super A, R> requestListener,
RequestCoordinator requestCoordinator,
Engine engine,
Transformation<Z> transformation,
Class<R> transcodeClass,
boolean isMemoryCacheable,
GlideAnimationFactory<R> animationFactory,
int overrideWidth,
int overrideHeight,
DiskCacheStrategy diskCacheStrategy) {
@SuppressWarnings("unchecked")
GenericRequest<A, T, Z, R> request = (GenericRequest<A, T, Z, R>) REQUEST_POOL.poll();
if (request == null) {
//創(chuàng)建請(qǐng)求
request = new GenericRequest<A, T, Z, R>();
}
//初始化請(qǐng)求
request.init(loadProvider,
model,
signature,
context,
priority,
target,
sizeMultiplier,
placeholderDrawable,
placeholderResourceId,
errorDrawable,
errorResourceId,
fallbackDrawable,
fallbackResourceId,
requestListener,
requestCoordinator,
engine,
transformation,
transcodeClass,
isMemoryCacheable,
animationFactory,
overrideWidth,
overrideHeight,
diskCacheStrategy);
//將請(qǐng)求返回 最終返回到到GenericRequestBuilder的into()方法中,然后執(zhí)行 requestTracker.runRequest(request);這句代碼,開始執(zhí)行請(qǐng)求
return request;
}
//RequestTracker中
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
//開始執(zhí)行請(qǐng)求
request.begin();
} else {
pendingRequests.add(request);
}
}
//GenericRequest中
@Override
public void begin() {
......
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
//當(dāng)ImageView的大小已經(jīng)確定
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}
......
}
//GenericRequest中
@Override
public void onSizeReady(int width, int height) {
......
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
......
ResourceTranscoder<Z, R> transcoder = loadProvider.getTranscoder();
......
loadedFromMemoryCache = true;
//開始加載圖片
loadStatus = engine.load(signature, width, height, dataFetcher, loadProvider, transformation, transcoder,
priority, isMemoryCacheable, diskCacheStrategy, this);
loadedFromMemoryCache = resource != null;
......
}
//Engine中
public <T, Z, R> LoadStatus load(Key signature, int width, int height, DataFetcher<T> fetcher,
DataLoadProvider<T, Z> loadProvider, Transformation<Z> transformation, ResourceTranscoder<Z, R> 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());
//從緩存中加載
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<T, Z, R> decodeJob = new DecodeJob<T, Z, R>(key, width, height, fetcher, loadProvider, transformation,
transcoder, diskCacheProvider, diskCacheStrategy, priority);
//創(chuàng)建從網(wǎng)絡(luò)加載圖片的線程
EngineRunnable runnable = new EngineRunnable(engineJob, decodeJob, priority);
jobs.put(key, engineJob);
engineJob.addCallback(cb);
//啟動(dòng)線程下載圖片,啟動(dòng)線程后就會(huì)進(jìn)入到EngineRunnable的run()方法
engineJob.start(runnable);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
//EngineRunnable中
@Override
public void run() {
if (isCancelled) {
return;
}
Exception exception = null;
Resource<?> resource = null;
try {
//進(jìn)行下載
resource = decode();
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception decoding", e);
}
exception = e;
}
........
if (resource == null) {
onLoadFailed(exception);
} else {
//當(dāng)下載成功
onLoadComplete(resource);
}
}
//EngineRunnable中
private Resource<?> decode() throws Exception {
if (isDecodingFromCache()) {
//從緩存中加載
return decodeFromCache();
} else {
//從網(wǎng)絡(luò)中加載
return decodeFromSource();
}
}
//EngineRunnable中
private Resource<?> decodeFromSource() throws Exception {
return decodeJob.decodeFromSource();
}
//DecodeJob中
public Resource<Z> decodeFromSource() throws Exception {
Resource<T> decoded = decodeSource();
return transformEncodeAndTranscode(decoded);
}
//DecodeJob中
private Resource<T> decodeSource() throws Exception {
Resource<T> decoded = null;
try {
long startTime = LogTime.getLogTime();
//使用加載器去網(wǎng)絡(luò)中加載圖片
final A data = fetcher.loadData(priority);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Fetched data", startTime);
}
if (isCancelled) {
return null;
}
//對(duì)結(jié)果進(jìn)行包裝
decoded = decodeFromSourceData(data);
} finally {
fetcher.cleanup();
}
return decoded;
}
//HttpUrlFetcher中
@Override
public InputStream loadData(Priority priority) throws Exception {
return loadDataWithRedirects(glideUrl.toURL(), 0 /*redirects*/, null /*lastUrl*/, glideUrl.getHeaders());
}
//HttpUrlFetcher中
//這里是真正使用HttpURLConnection下載圖片的地方,
//最后將結(jié)果返回,在經(jīng)過各種包裝最終返回到EngineRunnable中調(diào)用onLoadComplete(resource);執(zhí)行加載成功后的流程
private InputStream loadDataWithRedirects(URL url, int redirects, URL lastUrl, Map<String, String> headers)
throws IOException {
if (redirects >= MAXIMUM_REDIRECTS) {
throw new IOException("Too many (> " + MAXIMUM_REDIRECTS + ") redirects!");
} else {
// Comparing the URLs using .equals performs additional network I/O and is generally broken.
// See http://michaelscharf.blogspot.com/2006/11/javaneturlequals-and-hashcode-make.html.
try {
if (lastUrl != null && url.toURI().equals(lastUrl.toURI())) {
throw new IOException("In re-direct loop");
}
} catch (URISyntaxException e) {
// Do nothing, this is best effort.
}
}
urlConnection = connectionFactory.build(url);
for (Map.Entry<String, String> headerEntry : headers.entrySet()) {
urlConnection.addRequestProperty(headerEntry.getKey(), headerEntry.getValue());
}
urlConnection.setConnectTimeout(2500);
urlConnection.setReadTimeout(2500);
urlConnection.setUseCaches(false);
urlConnection.setDoInput(true);
// Connect explicitly to avoid errors in decoders if connection fails.
urlConnection.connect();
if (isCancelled) {
return null;
}
final int statusCode = urlConnection.getResponseCode();
if (statusCode / 100 == 2) {
return getStreamForSuccessfulRequest(urlConnection);
} else if (statusCode / 100 == 3) {
String redirectUrlString = urlConnection.getHeaderField("Location");
if (TextUtils.isEmpty(redirectUrlString)) {
throw new IOException("Received empty or null redirect url");
}
URL redirectUrl = new URL(url, redirectUrlString);
return loadDataWithRedirects(redirectUrl, redirects + 1, url, headers);
} else {
if (statusCode == -1) {
throw new IOException("Unable to retrieve response code from HttpUrlConnection.");
}
throw new IOException("Request failed " + statusCode + ": " + urlConnection.getResponseMessage());
}
}
//EngineRunnable中
private void onLoadComplete(Resource resource) {\
//這里的manager是EngineRunnableManager,實(shí)現(xiàn)了這個(gè)接口的只有EngineJob,也就是說調(diào)用的是EngineJob中國的onRequestReady()方法
manager.onResourceReady(resource);
}
//EngineJob中
@Override
public void onResourceReady(final Resource<?> resource) {
this.resource = resource;
//使用Handler將結(jié)果發(fā)送到主線程中 ,結(jié)果會(huì)在EngineJob中的內(nèi)部類MainThreadCallBack中收到 MAIN_THREAD_HANDLER.obtainMessage(MSG_COMPLETE, this).sendToTarget();
}
//EngineJob中
private static class MainThreadCallback implements Handler.Callback {
@Override
public boolean handleMessage(Message message) {
if (MSG_COMPLETE == message.what || MSG_EXCEPTION == message.what) {
EngineJob job = (EngineJob) message.obj;
if (MSG_COMPLETE == message.what) {
//接收到成功的消息
job.handleResultOnMainThread();
} else {
//接收到失敗的消息
job.handleExceptionOnMainThread();
}
return true;
}
return false;
}
}
//EngineJob中
private void handleResultOnMainThread() {
if (isCancelled) {
resource.recycle();
return;
} else if (cbs.isEmpty()) {
throw new IllegalStateException("Received a resource without any callbacks to notify");
}
engineResource = engineResourceFactory.build(resource, isCacheable);
hasResource = true;
// Hold on to resource for duration of request so we don't recycle it in the middle of notifying if it
// synchronously released by one of the callbacks.
engineResource.acquire();
listener.onEngineJobComplete(key, engineResource);
//循環(huán)接口集合,調(diào)用接口的onResourceReady()方法,通知資源已經(jīng)加載完畢,因?yàn)镚enericRequest實(shí)現(xiàn)了該接口,
//所以GenericRequest的onResourceReady()方法會(huì)被電泳
for (ResourceCallback cb : cbs) {
if (!isInIgnoredCallbacks(cb)) {
engineResource.acquire();
cb.onResourceReady(engineResource);
}
}
// Our request is complete, so we can release the resource.
engineResource.release();
}
//GenericRequest中
@Override
public void onResourceReady(Resource<?> resource) {
.......
if (!canSetResource()) {
releaseResource(resource);
// We can't set the status to complete before asking canSetResource().
status = Status.COMPLETE;
return;
}
//調(diào)用重載方法onResourceReady()
onResourceReady(resource, (R) received);
}
//GenericRequest中
private void onResourceReady(Resource<?> resource, R result) {
// We must call isFirstReadyResource before setting status.
boolean isFirstResource = isFirstReadyResource();
status = Status.COMPLETE;
this.resource = resource;
if (requestListener == null || !requestListener.onResourceReady(result, model, target, loadedFromMemoryCache,
isFirstResource)) {
GlideAnimation<R> animation = animationFactory.build(loadedFromMemoryCache, isFirstResource);
//調(diào)用Target子類的OnResourceReady()方法將圖片加載到ImageView上
target.onResourceReady(result, animation);
}
notifyLoadSuccess();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("Resource ready in " + LogTime.getElapsedMillis(startTime) + " size: "
+ (resource.getSize() * TO_MEGABYTE) + " fromCache: " + loadedFromMemoryCache);
}
}
//BitmapImageViewTarget中
@Override
public void onResourceReady(Z resource, GlideAnimation<? super Z> glideAnimation) {
if (glideAnimation == null || !glideAnimation.animate(resource, this)) {
setResource(resource);
}
}
//BitmapImageViewTarget中
@Override
protected void setResource(Bitmap resource) {
//調(diào)用Android API將資源加載到ImageView上
view.setImageBitmap(resource);
}
Glide Engine中into()方法的流程圖
Glide加載圖片的總流程圖
幾個(gè)問題
1.glide中的線程池的核心線程數(shù)有幾個(gè)
glide中線程池的初始化是在GlideBuilder中的createGlide中的,glide中的線程池有兩種,一個(gè)是sourceService他的核心線程數(shù)是CPU核心數(shù),最大線程數(shù)也是CPU核心數(shù),另一個(gè)是diskCacheService他的核心線程數(shù)是1,最大線程數(shù)也是1.為什么會(huì)核心線程數(shù)和最大線程數(shù)是一樣的?我們可以去看看FifoPriorityThreadPoolExecutor的構(gòu)造方法,這兩個(gè)線程池都是FifoPriorityThreadPoolExecutor,該線程池使用的是PriorityBlockingQueue這種阻塞隊(duì)列,該隊(duì)列是具有優(yōu)先級(jí)而且空間無限的隊(duì)列.所以也就是說這種線程池只有核心線程,是一種依賴優(yōu)先級(jí)的線程池,又來執(zhí)行g(shù)lide的加載,解碼和轉(zhuǎn)換任務(wù).sourceService和diskCacheService兩個(gè)線程池的區(qū)別是,sourceService是當(dāng)緩存中沒有展示的對(duì)象時(shí)使用,而diskCacheService是緩存中存在展示對(duì)象時(shí)使用
Glide createGlide() {
if (sourceService == null) {
final int cores = Math.max(1, Runtime.getRuntime().availableProcessors());
//依賴于優(yōu)先級(jí)的線程池，用來執(zhí)行Glide的加載甚纲，解碼和轉(zhuǎn)換任務(wù)（當(dāng)從緩存中沒有找到對(duì)應(yīng)的對(duì)象時(shí)）
//線程數(shù)是CPU核心數(shù)
sourceService = new FifoPriorityThreadPoolExecutor(cores);
}
if (diskCacheService == null) {
//依賴于優(yōu)先級(jí)的線程池口锭，用來執(zhí)行Glide的加載，解碼和轉(zhuǎn)換任務(wù)（當(dāng)從緩存中有對(duì)應(yīng)的對(duì)象時(shí)）
//線程數(shù)量為1
diskCacheService = new FifoPriorityThreadPoolExecutor(1);
}
.....
public FifoPriorityThreadPoolExecutor(int poolSize) {
this(poolSize, UncaughtThrowableStrategy.LOG);
}
/**
* Constructor to build a fixed thread pool with the given pool size using
* {@link com.bumptech.glide.load.engine.executor.FifoPriorityThreadPoolExecutor.DefaultThreadFactory}.
*
* @param poolSize The number of threads.
* @param uncaughtThrowableStrategy Dictates how the pool should handle uncaught and unexpected throwables
* thrown by Futures run by the pool.
*/
public FifoPriorityThreadPoolExecutor(int poolSize, UncaughtThrowableStrategy uncaughtThrowableStrategy) {
this(poolSize, poolSize, 0, TimeUnit.MILLISECONDS, new DefaultThreadFactory(),
uncaughtThrowableStrategy);
}
public FifoPriorityThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAlive, TimeUnit timeUnit,
ThreadFactory threadFactory, UncaughtThrowableStrategy uncaughtThrowableStrategy) {
super(corePoolSize, maximumPoolSize, keepAlive, timeUnit, new PriorityBlockingQueue<Runnable>(), threadFactory);
this.uncaughtThrowableStrategy = uncaughtThrowableStrategy;
}
2.glide中圖片的默認(rèn)格式
圖片的默認(rèn)格式是RGB-565
//DecodeFormat中
/** The default value for DecodeFormat. */
public static final DecodeFormat DEFAULT = PREFER_RGB_565;
3.glide的加載策略,glide的加載策略也是按照 內(nèi)存->硬盤->網(wǎng)絡(luò)的順序來的,但是他比其他的框架做的更細(xì)化一些,首先他會(huì)去內(nèi)存中找,如果沒有他會(huì)從最近活躍的資源中找,然后還會(huì)去下載隊(duì)列中去找,最后才是去下載
/**
* 1. 檢查內(nèi)存緩存
* 2. 檢查最近的活躍資源
* 3. 檢查最近的加載任務(wù)
* 4.去網(wǎng)絡(luò)中下載
* 活躍資源指的是那些不止一次被加載并沒有進(jìn)行過資源釋放的圖片介杆，一旦被釋放鹃操，
* 那么該資源則會(huì)從近期活躍資源中刪除并進(jìn)入到內(nèi)存緩存中韭寸，
* 但是如果該資源再次從內(nèi)存緩存中讀取，則會(huì)重新添加到活躍資源中
*/
public <R> LoadStatus load(
GlideContext glideContext,
Object model,
Key signature,
int width,
int height,
Class<?> resourceClass,
Class<R> transcodeClass,
Priority priority,
DiskCacheStrategy diskCacheStrategy,
Map<Class<?>, Transformation<?>> transformations,
boolean isTransformationRequired,
Options options,
boolean isMemoryCacheable,
ResourceCallback cb) {
Util.assertMainThread();
long startTime = LogTime.getLogTime();
//內(nèi)存緩存的唯一鍵值
EngineKey key = keyFactory.buildKey(model, signature, width, height, transformations, resourceClass, transcodeClass, options);
//首先從緩存中查找
EngineResource<?> cached = loadFromCache(key, isMemoryCacheable);
if (cached != null) {
cb.onResourceReady(cached, DataSource.MEMORY_CACHE);
...
return null;
}
//如果緩存中沒有找到荆隘，則去活躍資源中加載
//memCache中該bitmap則會(huì)被remove掉bitmap并進(jìn)入activeResource中
EngineResource<?> active = loadFromActiveResources(key, isMemoryCacheable);
if (active != null) {
cb.onResourceReady(active, DataSource.MEMORY_CACHE);
...
}
return null;
}
//如果該任務(wù)之前已經(jīng)在隊(duì)列中恩伺，則添加新的callback，然后返回
EngineJob current = jobs.get(key);
if (current != null) {
current.addCallback(cb);
...
return new LoadStatus(cb, current);
}
//如果是新的加載任務(wù)椰拒，先創(chuàng)建EngineJob和DecodeJob莫其，然后開始任務(wù)
EngineJob<R> engineJob = engineJobFactory.build(key, isMemoryCacheable);
DecodeJob<R> decodeJob = decodeJobFactory.build(glideContext,model,key,signature,width,height,resourceClass,transcodeClass, priority,diskCacheStrategy,transformations, isTransformationRequired,options,engineJob);
jobs.put(key, engineJob);
engineJob.addCallback(cb);
//開始任務(wù)
engineJob.start(decodeJob);
...
return new LoadStatus(cb, engineJob);
}
4.glide的diskLruCache的默認(rèn)緩存路徑在哪里,默認(rèn)緩存容量是多少?
在項(xiàng)目的cache目錄image_manager_disk_cache文件夾下,容量是250M
//DiskCache中
/** 250 MB of cache. */
int DEFAULT_DISK_CACHE_SIZE = 250 * 1024 * 1024;
String DEFAULT_DISK_CACHE_DIR = "image_manager_disk_cache";
5.diskLruCache的四種緩存策略
DiskCacheStrategy.NONE :不緩存圖片
DiskCacheStrategy.SOURCE :緩存圖片源文件
DiskCacheStrategy.RESULT:緩存修改過的圖片
DiskCacheStrategy.ALL:緩存所有的圖片，默認(rèn)
- 使用thumbnail(0.1f)//設(shè)置縮略圖, 以后Glide 會(huì)先去請(qǐng)求縮略圖,然后在請(qǐng)求 原圖,因?yàn)榭s略圖一般比較小所以請(qǐng)求的比較快.
7.如果一個(gè)應(yīng)用中有多個(gè)地方要使用同一張照片,但是可能尺寸有可能不一樣,那么我們只需要設(shè)置所有地方的Glide的磁盤緩存策略為 Source就可以使用一張照片了(因?yàn)槟憔彺娴氖莝ource,那么去查找緩存的時(shí)候肯定找的也是source了)
總結(jié)
Glide加載圖片,首先會(huì)在內(nèi)存中找,如果內(nèi)存中沒有就去最近本地磁盤中找,然后磁盤中沒有的話會(huì)去,任務(wù)隊(duì)列中找有沒有正在加載下載此圖片的任務(wù),如果也沒有那就會(huì)使用HttpURLConnaction進(jìn)行下載,現(xiàn)在完成后就會(huì)用new Handler(Loop.getMainLooper)獲取到主線程的Handler然后將獲取到的圖片發(fā)送到主線程中.
參考文章
http://www.cnblogs.com/guanmanman/p/7008259.html
這篇文章講的更細(xì)一點(diǎn)http://www.reibang.com/p/7125feef0ddf
