上一篇講了Glide源碼分析之Glide和RequestManager構建過程,有興趣能夠去看一下,這篇我從頭至尾又從新講解Glide從構建到請求網絡資源的整個過程,先看一下圖,這張圖是看源碼記錄的,不可能所有流程都記下來,這張圖只是把整個流程涉及到的比較重要的方法給畫出來。java
####Glide優點: 一、可配置度高,自適應度高; 二、支持多種數據源,本地、網絡、assets、gif; 三、高效緩存,支持memory和diskp圖片緩存,默認二級緩存; 四、使用BitmapPool高效處理Bitmap,避免頻繁GC; 五、圖片加載過程能夠監聽,咱們項目中使用了OkHttp做爲Glide的網絡層監聽下載圖片進度; 六、生命週期,Glide綁定Activity的生命週期;緩存
從圖中看可能要分幾個模塊講,按照圖中的步驟分類講解,分爲:一、二、三、四、五、六、七、八、9,儘可能詳細,固然因爲篇幅的緣由,僅僅講解Glide請求網絡的過程,像緩存、編解碼這些基本是不會講解,不事後面會分模塊功能講解。網絡
####一、Glide的初始化app
Glide.with:ide
public static RequestManager with(FragmentActivity activity) {
//第一步是構建RequestManagerRetriever和建立Glide,以後調用getRetriever方法
RequestManagerRetriever requestManagerRetriever = getRetriever(activity);
RequestManager requestManager = requestManagerRetriever.get(activity);
return requestManager;
}
@NonNull
private static RequestManagerRetriever getRetriever(@Nullable Context context) {
return Glide.get(context).getRequestManagerRetriever();
}
public static Glide get(@NonNull Context context) {
if (glide == null) {
synchronized (Glide.class) {
if (glide == null) {
checkAndInitializeGlide(context);
}
}
}
return glide;
}
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能夠看到在with方法中又調用getRetriever方法以後又調用get方法,其實真正作建立和初始化的操做在initializeGlide方法中源碼分析
private static void initializeGlide(@NonNull Context context, @NonNull GlideBuilder builder) {
//Application
Context applicationContext = context.getApplicationContext();
GeneratedAppGlideModule annotationGeneratedModule = getAnnotationGeneratedGlideModules();
List<com.bumptech.glide.module.GlideModule> manifestModules = Collections.emptyList();
//是否是在Manifest註冊了,在4.0以前就是使用了Manifest自定Module
if (annotationGeneratedModule == null || annotationGeneratedModule.isManifestParsingEnabled()) {
manifestModules = new ManifestParser(applicationContext).parse();
}
//4.0以後使用了註解的方式,可是Manifest尚未廢棄
if (annotationGeneratedModule != null && !annotationGeneratedModule.getExcludedModuleClasses().isEmpty()) {
Set<Class<?>> excludedModuleClasses = annotationGeneratedModule.getExcludedModuleClasses();
Iterator<com.bumptech.glide.module.GlideModule> iterator = manifestModules.iterator();
while (iterator.hasNext()) {
com.bumptech.glide.module.GlideModule current = iterator.next();
if (!excludedModuleClasses.contains(current.getClass())) {
continue;
}
}
iterator.remove();
}
}
//獲取RequestManager工程
RequestManagerRetriever.RequestManagerFactory factory = annotationGeneratedModule != null ? annotationGeneratedModule.getRequestManagerFactory() : null;
//將RequestManager工廠注入Builder
builder.setRequestManagerFactory(factory);
// 自定義Module,可更改Glide配置
for (com.bumptech.glide.module.GlideModule module : manifestModules) {
module.applyOptions(applicationContext, builder);
}
// 自定義Module,可更改Glide配置
if (annotationGeneratedModule != null) {
annotationGeneratedModule.applyOptions(applicationContext, builder);
}
//經過Builder建立Glide
Glide glide = builder.build(applicationContext);
//manifest註冊組件
for (com.bumptech.glide.module.GlideModule module : manifestModules) {
try {
module.registerComponents(applicationContext, glide, glide.registry);
} catch (AbstractMethodError e) {
}
}
// 註解生成並註冊組件
if (annotationGeneratedModule != null) {
annotationGeneratedModule.registerComponents(applicationContext, glide, glide.registry);
}
// 內存監控
applicationContext.registerComponentCallbacks(glide);
//最後賦值
Glide.glide = glide;
}
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在initializeGlide方法中主要有幾點:fetch
根據註解獲取各類組件和自定義模塊之類的東西動畫
annotationGeneratedModule.applyOptions(applicationContext, builder);
//經過Builder建立Glide,注意這裏爲何要把這段代碼寫在註冊組件和自定義模塊之間
Glide glide = builder.build(applicationContext);
annotationGeneratedModule.registerComponents(applicationContext, glide, glide.registry);
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最後將RequestManagerFactory注入GlideBiulder中:ui
//獲取RequestManager工程
RequestManagerRetriever.RequestManagerFactory factory = annotationGeneratedModule != null ? annotationGeneratedModule.getRequestManagerFactory() : null;
//將RequestManager工廠注入Builder
builder.setRequestManagerFactory(factory);
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加下來分析一下: Glide glide = builder.build(applicationContext);this
Glide build(@NonNull Context context) {
//通常都所有判斷是否爲null,因此咱們在自定義Module時,重寫applyOptions方法,可更改配置不使用默認的配置
if (sourceExecutor == null) {
sourceExecutor = GlideExecutor.newSourceExecutor();
}
//硬盤緩存線程池
if (diskCacheExecutor == null) {
diskCacheExecutor = GlideExecutor.newDiskCacheExecutor();
}
// 動畫線程池
if (animationExecutor == null) {
animationExecutor = GlideExecutor.newAnimationExecutor();
}
//內存緩存大小計算
if (memorySizeCalculator == null) {
memorySizeCalculator = new MemorySizeCalculator.Builder(context).build();
}
//網絡監視器工程
if (connectivityMonitorFactory == null) {
connectivityMonitorFactory = new DefaultConnectivityMonitorFactory();
}
//Bitmap複用池(享元)
if (bitmapPool == null) {
int size = memorySizeCalculator.getBitmapPoolSize();
if (size > 0) {
bitmapPool = new LruBitmapPool(size);
} else {
bitmapPool = new BitmapPoolAdapter();
}
}
if (arrayPool == null) {
arrayPool = new LruArrayPool(memorySizeCalculator.getArrayPoolSizeInBytes());
}
//內存緩存
if (memoryCache == null) {
memoryCache = new LruResourceCache(memorySizeCalculator.getMemoryCacheSize());
}
//磁盤緩存工廠
if (diskCacheFactory == null) {
diskCacheFactory = new InternalCacheDiskCacheFactory(context);
}
if (engine == null) {
engine = new Engine(
memoryCache,
diskCacheFactory,
diskCacheExecutor,
sourceExecutor,
GlideExecutor.newUnlimitedSourceExecutor(),
animationExecutor,
isActiveResourceRetentionAllowed);
}
//請求觀察者,成功或失敗
if (defaultRequestListeners == null) {
defaultRequestListeners = Collections.emptyList();
} else {
defaultRequestListeners = Collections.unmodifiableList(defaultRequestListeners);
}
// 在Glide.java文件中 builder.setRequestManagerFactory(factory)
// requestManagerRetriever主要是檢查RequestManager
RequestManagerRetriever requestManagerRetriever = new RequestManagerRetriever(requestManagerFactory);
return new Glide(
context,
engine,
memoryCache,
bitmapPool,
arrayPool,
requestManagerRetriever,
connectivityMonitorFactory,
logLevel,
defaultRequestOptions.lock(),
defaultTransitionOptions,
defaultRequestListeners,
isLoggingRequestOriginsEnabled);
}
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這段代碼不少,不過邏輯是通簡單的;無非就是各類線程池的構建和RequestManagerRetriever的建立還有Engine的建立這個比較重要,管理者整個Glide的資源的工做都是Engine作的。
####二、建立RequestManager和生命週期的關聯
RequestManager requestManager = requestManagerRetriever.get(activity);
在with方法中調用了requestManagerRetriever.get(activity)方法,進去瞄一眼:
public RequestManager get(@NonNull FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
FragmentManager fm = activity.getSupportFragmentManager();
return supportFragmentGet(activity, fm, /*parentHint=*/ null, isActivityVisible(activity));
}
}
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實際上get方法有不少重載的方法,其實邏輯是同樣的,暫時無論,先看看supportFragmentGet方法:
private RequestManager supportFragmentGet(@NonNull Context context, @NonNull FragmentManager fm, @Nullable Fragment parentHint, boolean isParentVisible) {
//1 獲取Fragment
SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm, parentHint, isParentVisible);
//嘗試在Fragment中獲取RequestManager
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {//不存在
Glide glide = Glide.get(context);
//建立RequestManager
requestManager = factory.build(glide,
current.getGlideLifecycle(),//生命週期的回調
current.getRequestManagerTreeNode(), context);
//並保存到Fragment中
current.setRequestManager(requestManager);
}
return requestManager;
}
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看到1了嗎:
private SupportRequestManagerFragment getSupportRequestManagerFragment(@NonNull final FragmentManager fm, @Nullable Fragment parentHint, boolean isParentVisible) {
//檢索是否存在SupportRequestManagerFragment,若是不存在則建立一個Fragmment並添加到緩存中
SupportRequestManagerFragment current = (SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
if (current == null) {//不存在
//嘗試從緩存中讀取
current = pendingSupportRequestManagerFragments.get(fm);
if (current == null) {//仍是不存在
//那麼就建立一個新的Fragment
current = new SupportRequestManagerFragment();
current.setParentFragmentHint(parentHint);
if (isParentVisible) {
current.getGlideLifecycle().onStart();
}
//添加到緩存中
pendingSupportRequestManagerFragments.put(fm, current);
fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
//綁定成功後則從pendingRequestManagerFragments移除fragment。這裏的pendingRequestManagerFragments主要是防止fragment重複建立,由於每一個activity必須對應一個惟一的fragment。
handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
}
}
return current;
}
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檢索是否存在SupportRequestManagerFragment,若是不存在則建立一個Fragmment並添加到緩存中, 由於Glide使用一個隱藏的Fargment做爲監聽聲明週期做用,至於爲何添加Fragment又移除,我在谷歌查了一下說是這裏的pendingRequestManagerFragments主要是防止fragment重複建立,由於每一個activity必須對應一個惟一的fragment。
通過上面的步驟基本上就是Glide建立和初始化,並建立了RequestManager,並將RequestManager保存至Fragment中,以及關聯生命週期。
####三、接下來就是使用load()和into()方法:
public RequestBuilder<Drawable> load(@Nullable String string) {
return asDrawable().load(string);
}
@NonNull
@CheckResult
public <ResourceType> RequestBuilder<ResourceType> as(
@NonNull Class<ResourceType> resourceClass) {
return new RequestBuilder<>(glide, this, resourceClass, context);
}
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實際上load方法主要是構建RequestBuilder,接着沒什麼好說的,看一下into
private <Y extends Target<TranscodeType>> Y into(@NonNull Y target, @Nullable RequestListener<TranscodeType> targetListener, BaseRequestOptions<?> options, Executor callbackExecutor) {
Preconditions.checkNotNull(target);
/**
* 若是不先調用load就拋這個異常
*/
if (!isModelSet) {
throw new IllegalArgumentException("You must call #load() before calling #into()");
}
//構建請求會返回一個SingleRequest
Request request = buildRequest(target, targetListener, options, callbackExecutor);
Request previous = target.getRequest();
//上一個請求的處理,就是上一個請求因爲某種緣由暫停請求
if (request.isEquivalentTo(previous) && !isSkipMemoryCacheWithCompletePreviousRequest(options, previous)) {
request.recycle();
if (!Preconditions.checkNotNull(previous).isRunning()) {
previous.begin();
}
return target;
}
requestManager.clear(target);
target.setRequest(request);//target綁定一個請求
// 真正開始請求的地方
requestManager.track(target, request);
return target;
}
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其實這段代碼看註釋應該就能明白大致是作什麼的,主要是若是請求暫停,就開始請求,比較重要的是requestManager.track(target, request)這段代碼是要開始新請求,Glide加載圖片的整個觸發點。
synchronized void track(@NonNull Target<?> target, @NonNull Request request) {
targetTracker.track(target);
requestTracker.runRequest(request);
}
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走了那麼久,終於看到runRequest(),運行請求?那就看一下。
/**
* 開始追蹤請求
* <p>
* Starts tracking the given request.
*/
public void runRequest(@NonNull Request request) {
requests.add(request);
if (!isPaused) {
//若是暫停就開始請求
request.begin();
} else {
request.clear();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Paused, delaying request");
}
//待處理的請求
pendingRequests.add(request);
}
}
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仍是沒看到什麼東西, 那就看一下request.begin(),實際上應該看SingleRequest的begin方法。
@Override
public synchronized void begin() {
if (model == null) {
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
width = overrideWidth;
height = overrideHeight;
}
onLoadFailed(new GlideException("Received null model"), logLevel);
return;
}
if (status == Status.RUNNING) {
throw new IllegalArgumentException("Cannot restart a running request");
}
//回調target,資源請求已經完成,好比內存緩存,這些不須要再請求網絡的
if (status == Status.COMPLETE) {
onResourceReady(resource, DataSource.MEMORY_CACHE);
return;
}
/**
*
*從新啓動既沒有完成也還沒不運行的請求,這些能夠被視爲新的請求,而且能夠從頭開始從新運行。
*/
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
//這裏面真的是要請求網絡了
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}
/**
* 回調給target通知請求已經開始
*
*/
if ((status == Status.RUNNING || status == Status.WAITING_FOR_SIZE) && canNotifyStatusChanged()) {
target.onLoadStarted(getPlaceholderDrawable());
}
}
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直接看我代碼的註釋吧,其實reSizeReady根據計算大小,而後開始加載圖片。
@Override
public synchronized void onSizeReady(int width, int height) {
if (status != Status.WAITING_FOR_SIZE) {
return;
}
// 狀態表示爲運行狀態
status = Status.RUNNING;
float sizeMultiplier = requestOptions.getSizeMultiplier();
this.width = maybeApplySizeMultiplier(width, sizeMultiplier);
this.height = maybeApplySizeMultiplier(height, sizeMultiplier);
loadStatus =
engine.load(
glideContext,
model,
requestOptions.getSignature(),
this.width,
this.height,
requestOptions.getResourceClass(),
transcodeClass,
priority,
requestOptions.getDiskCacheStrategy(),
requestOptions.getTransformations(),
requestOptions.isTransformationRequired(),
requestOptions.isScaleOnlyOrNoTransform(),
requestOptions.getOptions(),
requestOptions.isMemoryCacheable(),
requestOptions.getUseUnlimitedSourceGeneratorsPool(),
requestOptions.getUseAnimationPool(),
requestOptions.getOnlyRetrieveFromCache(),
this,
callbackExecutor);
if (status != Status.RUNNING) {
loadStatus = null;
}
}
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就是計算大小,而後開始加載圖片,看一下engine.load()方法吧。
public synchronized <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,
boolean isScaleOnlyOrNoTransform,
Options options,
boolean isMemoryCacheable,
boolean useUnlimitedSourceExecutorPool,
boolean useAnimationPool,
boolean onlyRetrieveFromCache,
ResourceCallback cb,
Executor callbackExecutor) {
long startTime = VERBOSE_IS_LOGGABLE ? LogTime.getLogTime() : 0;
// -------------開始檢測緩存----------------
EngineKey key = keyFactory.buildKey(model, signature, width, height, transformations, resourceClass, transcodeClass, options);
// 第一級內存緩存
EngineResource<?> active = loadFromActiveResources(key, isMemoryCacheable);
if (active != null) {
// 若是內存中有,就當即返回
cb.onResourceReady(active, DataSource.MEMORY_CACHE);
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Loaded resource from active resources", startTime, key);
}
return null;
}
// 第二級內存緩存
EngineResource<?> cached = loadFromCache(key, isMemoryCacheable);
if (cached != null) {
cb.onResourceReady(cached, DataSource.MEMORY_CACHE);
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Loaded resource from cache", startTime, key);
}
return null;
}
EngineJob<?> current = jobs.get(key, onlyRetrieveFromCache);
if (current != null) {
current.addCallback(cb, callbackExecutor);
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Added to existing load", startTime, key);
}
return new LoadStatus(cb, current);
}
EngineJob<R> engineJob = engineJobFactory.build(key,
isMemoryCacheable,
useUnlimitedSourceExecutorPool,
useAnimationPool,
onlyRetrieveFromCache);
DecodeJob<R> decodeJob = decodeJobFactory.build(glideContext,
model,
key,
signature,
width,
height,
resourceClass,
transcodeClass,
priority,
diskCacheStrategy,
transformations,
isTransformationRequired,
isScaleOnlyOrNoTransform,
onlyRetrieveFromCache,
options,
engineJob);
jobs.put(key, engineJob);
engineJob.addCallback(cb, callbackExecutor);
// 開始執行任務
engineJob.start(decodeJob);
return new LoadStatus(cb, engineJob);
}
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看代碼代碼註釋,應該差很少,主要是 engineJob.start(decodeJob)啓動線程執行任務。
public synchronized void start(DecodeJob<R> decodeJob) {
this.decodeJob = decodeJob;
GlideExecutor executor = decodeJob.willDecodeFromCache()
? diskCacheExecutor
: getActiveSourceExecutor();
executor.execute(decodeJob);
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}
既然是線程,那必然decodeJob必定是Runnable,直奔DecodeJob的run方法,看看究竟幹啥。
@Override
public void run() {
//執行網絡
DataFetcher<?> localFetcher = currentFetcher;
try {
if (isCancelled) {
notifyFailed();
return;
}
runWrapped();
} catch (CallbackException e) {
throw e;
} catch (Throwable t) {
if (stage != Stage.ENCODE) {
throwables.add(t);
notifyFailed();
}
if (!isCancelled) {
throw t;
}
throw t;
} finally {
/**
* 咱們自定組件時回調cleanup(),如OkHttpStreamFetcher中
*
*/
if (localFetcher != null) {
localFetcher.cleanup();
}
}
}
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沒看到執行什麼操做?看一下runWrapped()方法。
private void runWrapped() {
switch (runReason) {
case INITIALIZE://由於剛初始化,
stage = getNextStage(Stage.INITIALIZE);
currentGenerator = getNextGenerator();
runGenerators();
break;
case SWITCH_TO_SOURCE_SERVICE:
runGenerators();
break;
case DECODE_DATA:
decodeFromRetrievedData();//直接解碼,而後返回解碼後的數據
break;
default:
throw new IllegalStateException("Unrecognized run reason: " + runReason);
}
}
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這個方法就至關重要了,其實就是根據當前的狀態,生成加載圖片資源的代Generator,不信?那就看一下getNextGenerator方法。
private DataFetcherGenerator getNextGenerator() {
switch (stage) {
case RESOURCE_CACHE:
return new ResourceCacheGenerator(decodeHelper, this);//須要解碼被轉換以後的緩存
case DATA_CACHE:
return new DataCacheGenerator(decodeHelper, this);//須要解碼原圖緩存
case SOURCE:
return new SourceGenerator(decodeHelper, this);//原始數據代,須要加載網絡數據
case FINISHED:
return null;
default:
throw new IllegalStateException("Unrecognized stage: " + stage);
}
}
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無論你信不信,反正我是信了,那建立這些加載圖片資源幹啥?回到剛纔的runWrapper方法,盡然還有runGenerators方法,看一波。
private void runGenerators() {
boolean isStarted = false;
/**
*
* 若是getNextGenerator()返回SourceGenerator類,那麼須要請求網絡了
* 開始網絡請求圖片
*/
while (!isCancelled && currentGenerator != null && !(isStarted = currentGenerator.startNext())) {
stage = getNextStage(stage);
currentGenerator = getNextGenerator();
if (stage == Stage.SOURCE) {
//從新調度startNext()
reschedule();
return;
}
}
if ((stage == Stage.FINISHED || isCancelled) && !isStarted) {
notifyFailed();
}
}
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代碼很少,看一下currentGenerator.startNext(),這個方法是啓動圖片加載代Generator的,是個接口,那咱們選SourceGenerator這個吧。
/**
* 準備開始拉取網絡數據
*
* @return
*/
@Override
public boolean startNext() {
// 判斷是否有數據須要取緩存
if (dataToCache != null) {
Object data = dataToCache;
dataToCache = null;
cacheData(data);
}
// 若是上一步建立了資源緩存代,就開始資源緩存代
if (sourceCacheGenerator != null && sourceCacheGenerator.startNext()) {
return true;
}
sourceCacheGenerator = null;
loadData = null;
boolean started = false;
while (!started && hasNextModelLoader()) {
loadData = helper.getLoadData().get(loadDataListIndex++);
if (loadData != null &&
(helper.getDiskCacheStrategy().isDataCacheable(loadData.fetcher.getDataSource())
|| helper.hasLoadPath(loadData.fetcher.getDataClass()))) {
started = true;
/**
* DataFetcher的loadData()方法的回調時機,請看實現類{@link HttpUrlFetcher}
*
* 還把回調傳進去
*/
loadData.fetcher.loadData(helper.getPriority(), this);
}
}
return started;
}
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DataFetcherGenerator有三個子類分別作不一樣的事情,
SourceGenerator: 使用已註冊的ModelLoaders和爲加載提供的model,從原始源數據生成DataFetcher DataFetchers。 根據磁盤緩存策略,源數據可能首先寫入磁盤,而後從緩存文件加載而不是直接返回。
ResourceCacheGenerator 從已轉換的資源數據的緩存文件中採樣數據生成DataFetchers。
DataCacheGenerator 從原始未修改源數據的緩存文件採樣數據生成DataFetchers。
選SourceGenetator分析:
loadData.fetcher.loadData(helper.getPriority(), this);
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使用已註冊的ModelLoaders和load提供的model,從原始源數據生成DataFetchers。 根據磁盤緩存策略,源數據可能首先寫入磁盤,而後從緩存文件加載而不是直接返回。
private volatile ModelLoader.LoadData<?> loadData;
class LoadData<Data> {
public final Key sourceKey;
public final List<Key> alternateKeys;
public final DataFetcher<Data> fetcher;
public LoadData(@NonNull Key sourceKey, @NonNull DataFetcher<Data> fetcher) {
this(sourceKey, Collections.<Key>emptyList(), fetcher);
}
public LoadData(@NonNull Key sourceKey, @NonNull List<Key> alternateKeys,
@NonNull DataFetcher<Data> fetcher) {
this.sourceKey = Preconditions.checkNotNull(sourceKey);
this.alternateKeys = Preconditions.checkNotNull(alternateKeys);
this.fetcher = Preconditions.checkNotNull(fetcher);
}
}
複製代碼
其實是若是咱們自定義模塊,那麼會從DataFetcher和ModelLoader中去作網絡請求。自此文章結束。