??上一次文章中分析了Glide的with()過(guò)程莱坎，接著來(lái)分析load()過(guò)程。
??在with()方法結(jié)束時(shí)我們得到了RequestManager對(duì)象糙箍，所以這個(gè)load()方法就是RequestManager類中的方法渤愁。
public DrawableTypeRequest<String> load(String string) {
return (DrawableTypeRequest<String>) fromString().load(string);
}
public DrawableTypeRequest<Uri> load(Uri uri) {
return (DrawableTypeRequest<Uri>) fromUri().load(uri);
}
public DrawableTypeRequest<File> load(File file) {
return (DrawableTypeRequest<File>) fromFile().load(file);
}
public DrawableTypeRequest<Integer> load(Integer resourceId) {
return (DrawableTypeRequest<Integer>) fromResource().load(resourceId);
}
??load()方法有很多重載的方法。這里只貼出來(lái)了一部分深夯《陡瘢可以從網(wǎng)絡(luò)Url，本地文件等加載資源咕晋，所以load()方法有很多的重載形式雹拄。
這次我們從加載String形式的Url字符串的get()方法開始分析。
load(string)方法中調(diào)用的方法
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));
}
??在fromString()方法中調(diào)用了loadGeneric()方法掌呜。這個(gè)方法的泛型的類型是String.class類型滓玖。在loadGeneric()方法中，
ModelLoader<T, InputStream> streamModelLoader = Glide.buildStreamModelLoader(modelClass, context);
首先是這行代碼质蕉，我們來(lái)分析一下這行代碼呢撞。分析一下得到這個(gè)ModelLoader對(duì)象的過(guò)程。
在這行代碼中饰剥，傳入的泛型的類型分別為String.class類型和InputStream類型殊霞，然后調(diào)用了Glide的buildStreamModelLoader()方法來(lái)生成了一個(gè)ModelLoader對(duì)象，因?yàn)閭魅氲姆盒偷念愋头謩e為String.class類型汰蓉，所以最后生成的是StreamStringLoader對(duì)象绷蹲，它是實(shí)現(xiàn)了ModelLoader接口的。
- ModelLoader對(duì)象是用于加載圖片的
Glide類里面的方法
public static <T> ModelLoader<T, InputStream> buildStreamModelLoader(Class<T> modelClass, Context context) {
return buildModelLoader(modelClass, InputStream.class, context);
}
public static <T, Y> ModelLoader<T, Y> buildModelLoader(Class<T> modelClass, Class<Y> resourceClass,
Context context) {
if (modelClass == null) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "Unable to load null model, setting placeholder only");
}
return null;
}
return Glide.get(context).getLoaderFactory().buildModelLoader(modelClass, resourceClass);
}
modelClass類型為String.class，resourceClass的類型為InputStream.class祝钢。然后在buildModelLoader()方法中調(diào)用了
Glide.get(context).getLoaderFactory().buildModelLoader(modelClass, resourceClass);
一步一步來(lái)分析比规，先看Glide的 get(Context context)方法
public static Glide get(Context context) {
if (glide == null) {
synchronized (Glide.class) {
if (glide == null) {
Context applicationContext = context.getApplicationContext();
List<GlideModule> modules = new ManifestParser(applicationContext).parse();
GlideBuilder builder = new GlideBuilder(applicationContext);
for (GlideModule module : modules) {
module.applyOptions(applicationContext, builder);
}
//通過(guò)GlideBuilder類的createGlide()方法來(lái)創(chuàng)建Glide對(duì)象
glide = builder.createGlide();
for (GlideModule module : modules) {
module.registerComponents(applicationContext, glide);
}
}
}
}
return glide;
}
可以看到在這個(gè)方法中，通過(guò)GlideBuilder類的createGlide()方法來(lái)創(chuàng)建Glide對(duì)象拦英，來(lái)看看創(chuàng)建Glide對(duì)象的過(guò)程蜒什。
GlideBuilder類createGlide()方法
private final Context context;
private Engine engine;
private BitmapPool bitmapPool;
private MemoryCache memoryCache;
private ExecutorService sourceService;
private ExecutorService diskCacheService;
private DecodeFormat decodeFormat;
private DiskCache.Factory diskCacheFactory;
public GlideBuilder(Context context) {
this.context = context.getApplicationContext();
}
Glide createGlide() {
if (sourceService == null) {
final int cores = Math.max(1, Runtime.getRuntime().availableProcessors());
sourceService = new FifoPriorityThreadPoolExecutor(cores);
}
if (diskCacheService == null) {
diskCacheService = new FifoPriorityThreadPoolExecutor(1);
}
MemorySizeCalculator calculator = new MemorySizeCalculator(context);
if (bitmapPool == null) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
int size = calculator.getBitmapPoolSize();
bitmapPool = new LruBitmapPool(size);
} else {
bitmapPool = new BitmapPoolAdapter();
}
}
if (memoryCache == null) {
//Glide實(shí)現(xiàn)內(nèi)存緩存所使用的
memoryCache = new LruResourceCache(calculator.getMemoryCacheSize());
}
if (diskCacheFactory == null) {
//Glide實(shí)現(xiàn)磁盤緩存所使用的
diskCacheFactory = new InternalCacheDiskCacheFactory(context);
}
if (engine == null) {
engine = new Engine(memoryCache, diskCacheFactory, diskCacheService, sourceService);
}
if (decodeFormat == null) {
decodeFormat = DecodeFormat.DEFAULT;
}
//創(chuàng)建Glide對(duì)象
return new Glide(engine, memoryCache, bitmapPool, context, decodeFormat);
}
里面初始化了很多對(duì)象，并把初始化的東西傳入了Glide的構(gòu)造器中疤估。
Glide的構(gòu)造器中
private final GenericLoaderFactory loaderFactory;
Glide(Engine engine, MemoryCache memoryCache, BitmapPool bitmapPool, Context context, DecodeFormat decodeFormat) {
......
loaderFactory = new GenericLoaderFactory(context);
......
register(String.class, InputStream.class, new StreamStringLoader.Factory());
}
在這個(gè)Glide的這個(gè)構(gòu)造器中就是進(jìn)行一些初始化的操作灾常，這里我只貼出了我們要分析的部分。在Glide的構(gòu)造器中初始化了GenericLoaderFactory類铃拇，并調(diào)用了Glide的register()方法
- GenericLoaderFactory類：相當(dāng)于一個(gè)工廠钞瀑。這個(gè)類里面保存了各種ModelLoader和各種ModelLoaderFactory，并且通過(guò)保存的各種ModelLoaderFactory來(lái)創(chuàng)建各種ModelLoader慷荔。這個(gè)類之后還要來(lái)分析雕什。
看一下Glide的register()方法的參數(shù)中傳入的new StreamStringLoader.Factory()。
StreamStringLoader.Factory()
public static class Factory implements ModelLoaderFactory<String, InputStream> {
@Override
public ModelLoader<String, InputStream> build(Context context, GenericLoaderFactory factories) {
return new StreamStringLoader(factories.buildModelLoader(Uri.class, InputStream.class));
}
@Override
public void teardown() {
// Do nothing.
}
}
這個(gè)靜態(tài)內(nèi)部類就是用來(lái)生成StreamStringLoader()對(duì)象的显晶。那就剛好也看一下ModelLoaderFactory接口贷岸。
ModelLoaderFactory接口
public interface ModelLoaderFactory<T, Y> {
ModelLoader<T, Y> build(Context context, GenericLoaderFactory factories);
void teardown();
}
可以看到這個(gè)接口的build()方法就是專門用來(lái)生成ModelLoader對(duì)象的。
Glide的register()方法
public <T, Y> void register(Class<T> modelClass, Class<Y> resourceClass, ModelLoaderFactory<T, Y> factory) {
ModelLoaderFactory<T, Y> removed = loaderFactory.register(modelClass, resourceClass, factory);
if (removed != null) {
removed.teardown();
}
}
在register()方法中GenericLoaderFactory的register()方法磷雇，看一下這個(gè)方法偿警。
GenericLoaderFactory里面的register()方法
//緩存各種ModelLoaderFactory
private final Map<Class/*T*/, Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/>> modelClassToResourceFactories =
new HashMap<Class, Map<Class, ModelLoaderFactory>>();
//緩存各種ModelLoader
private final Map<Class/*T*/, Map<Class/*Y*/, ModelLoader/*T, Y*/>> cachedModelLoaders =
new HashMap<Class, Map<Class, ModelLoader>>();
public synchronized <T, Y> ModelLoaderFactory<T, Y> register(Class<T> modelClass, Class<Y> resourceClass,
ModelLoaderFactory<T, Y> factory) {
cachedModelLoaders.clear();
//根據(jù)modelClass來(lái)判斷是否已經(jīng)存在與modelClass對(duì)應(yīng)的ModelLoaderFactory的Map
Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> resourceToFactories = modelClassToResourceFactories.get(modelClass);
if (resourceToFactories == null) {
resourceToFactories = new HashMap<Class/*Y*/, ModelLoaderFactory/*T, Y*/>();
//以modelClass為key，將新建的Map集合放入modelClassToResourceFactories中
modelClassToResourceFactories.put(modelClass, resourceToFactories);
}
//以resourceClass為key,將傳入的factory放入與modelClass對(duì)應(yīng)的Map中
ModelLoaderFactory/*T, Y*/ previous = resourceToFactories.put(resourceClass, factory);
if (previous != null) {
for (Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> factories : modelClassToResourceFactories.values()) {
if (factories.containsValue(previous)) {
previous = null;
break;
}
}
}
return previous;
}
GenericLoaderFactory里面的register()方法就是將Glide的register()方法中所傳來(lái)的factory存入了GenericLoaderFactory類里面的modelClassToResourceFactories中倦春。
創(chuàng)建Glide對(duì)象及Glide對(duì)象的創(chuàng)建過(guò)程中户敬，在Glide的構(gòu)造函數(shù)中都發(fā)生了什么，這個(gè)過(guò)程已經(jīng)結(jié)束了睁本∧蚵回到Glide.get(context).getLoaderFactory().buildModelLoader(modelClass, resourceClass);這行代碼。
Glide的getLoaderFactory()方法
private GenericLoaderFactory getLoaderFactory() {
return loaderFactory;
}
這個(gè)loaderFactory就是在Glide初始化時(shí)初始的GenericLoaderFactory對(duì)象呢堰。接著調(diào)用了GenericLoaderFactory類的buildModelLoader(modelClass, resourceClass)方法抄瑟。
GenericLoaderFactory類的buildModelLoader(modelClass, resourceClass)方法
public synchronized <T, Y> ModelLoader<T, Y> buildModelLoader(Class<T> modelClass, Class<Y> resourceClass) {
// 用getCachedLoader()這個(gè)方法得到之前緩存的ModelLoader
ModelLoader<T, Y> result = getCachedLoader(modelClass, resourceClass);
if (result != null) {
if (NULL_MODEL_LOADER.equals(result)) {
return null;
} else {
return result;
}
}
//如果得到的ModelLoader為null，用getFactory()方法來(lái)得到之前緩存的factory
final ModelLoaderFactory<T, Y> factory = getFactory(modelClass, resourceClass);
if (factory != null) {
//factory.build()用來(lái)生成相對(duì)應(yīng)的ModleLoader
result = factory.build(context, this);
//緩存生成的ModleLoader
result = factory.build(context, this);
cacheModelLoader(modelClass, resourceClass, result);
} else {
cacheNullLoader(modelClass, resourceClass);
}
return result;
}
private <T, Y> ModelLoader<T, Y> getCachedLoader(Class<T> modelClass, Class<Y> resourceClass) {
//根據(jù)modelClass的到對(duì)應(yīng)的Map
Map<Class/*Y*/, ModelLoader/*T, Y*/> resourceToLoaders = cachedModelLoaders.get(modelClass);
ModelLoader/*T, Y*/ result = null;
if (resourceToLoaders != null) {
//根據(jù)resourceClass得到對(duì)應(yīng)的ModelLoader
result = resourceToLoaders.get(resourceClass);
}
return result;
}
private <T, Y> ModelLoaderFactory<T, Y> getFactory(Class<T> modelClass, Class<Y> resourceClass) {
//利用modelClass得到相對(duì)于的Map
Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> resourceToFactories = modelClassToResourceFactories.get(modelClass);
ModelLoaderFactory/*T, Y*/ result = null;
if (resourceToFactories != null) {
//利用resourceClass得到之前緩存的Factory
result = resourceToFactories.get(resourceClass);
}
if (result == null) {
for (Class<? super T> registeredModelClass : modelClassToResourceFactories.keySet()) {
if (registeredModelClass.isAssignableFrom(modelClass)) {
Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> currentResourceToFactories =
modelClassToResourceFactories.get(registeredModelClass);
if (currentResourceToFactories != null) {
result = currentResourceToFactories.get(resourceClass);
if (result != null) {
break;
}
}
}
}
}
return result;
}
這個(gè)過(guò)程分析結(jié)束了枉疼，實(shí)際上就是利用GenericLoaderFactory類得到相應(yīng)的ModelLoader的過(guò)程皮假，在這個(gè)過(guò)程中骂维，我們傳入的modelClass類型為String.Class褪测，傳入的resourceClass類型為InputStream類型侮措，最終得到了StreamStringLoader類型的對(duì)象澄成。
Glide.get(context).getLoaderFactory().buildModelLoader(modelClass, resourceClass);這行代碼分析結(jié)束了，所以最后Glide.buildStreamModelLoader(modelClass, context)這句代碼最后的到了StreamStringLoader類型的對(duì)象歉胶≈嗝回到loadGeneric()方法漏策，再貼一下掺喻。
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));
}
ModelLoader<T, ParcelFileDescriptor> fileDescriptorModelLoader =
Glide.buildFileDescriptorModelLoader(modelClass, context);
這個(gè)上面貼的過(guò)程和上面分析的得到StreamStringLoader類型的對(duì)象的過(guò)程類似感耙，所以這個(gè)過(guò)程最后得到的是FileDescriptorUriLoader類型的對(duì)象逃片。
回到loadGeneric()方法，在這個(gè)方法的最后生成了一個(gè)DrawableTypeRequest對(duì)象损离。并將剛剛生成的StreamStringLoader類型的對(duì)象和FileDescriptorUriLoader類型的對(duì)象還有requestTracker, lifecycle,等一起傳入其構(gòu)造器中。
進(jìn)入這個(gè)DrawableTypeRequest類看看哩俭。
DrawableTypeRequest類的構(gòu)造函數(shù)
public class DrawableTypeRequest<ModelType> extends DrawableRequestBuilder<ModelType> implements DownloadOptions {
private final ModelLoader<ModelType, InputStream> streamModelLoader;
private final ModelLoader<ModelType, ParcelFileDescriptor> fileDescriptorModelLoader;
private final RequestManager.OptionsApplier optionsApplier;
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;
}
//1.得到GifBitmapWrapperDrawableTranscoder類型對(duì)象
if (transcoder == null) {
transcoder = glide.buildTranscoder(resourceClass, transcodedClass);
}
//2.得到ImageVideoGifDrawableLoadProvider類型對(duì)象
DataLoadProvider<ImageVideoWrapper, Z> dataLoadProvider = glide.buildDataProvider(ImageVideoWrapper.class,
resourceClass);
//3.傳入StreamStringLoader類型的對(duì)象和FileDescriptorUriLoader類型的對(duì)象來(lái)生成ImageVideoModelLoader對(duì)象。
ImageVideoModelLoader<A> modelLoader = new ImageVideoModelLoader<A>(streamModelLoader,
fileDescriptorModelLoader);
//在這個(gè)buildProvider()方法中隙赁，將ImageVideoModelLoader類型的ModelLoader，GlideBitmapDrawableTranscoder類型的ResourceTranscoder厚掷，ImageVideoGifDrawableLoadProvider類型的DataLoadProvider傳入FixedLoadProvider的構(gòu)造器中
return new FixedLoadProvider<A, ImageVideoWrapper, Z, R>(modelLoader, transcoder, dataLoadProvider);
}
//在DrawableTypeRequest的構(gòu)造函數(shù)中级解，初始化從父類繼承來(lái)的實(shí)例
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;
}
}
先來(lái)分析一下代碼中標(biāo)記的1,2過(guò)程。
1過(guò)程transcoder = glide.buildTranscoder(resourceClass, transcodedClass);調(diào)用了Glide的buildTranscoder()方法勤哗。
Glide的buildTranscoder()方法
private final TranscoderRegistry transcoderRegistry = new TranscoderRegistry();
Glide(Engine engine, MemoryCache memoryCache, BitmapPool bitmapPool, Context context, DecodeFormat decodeFormat) {
......
//注冊(cè)GlideBitmapDrawableTranscoder到transcoderRegistry
transcoderRegistry.register(GifBitmapWrapper.class, GlideDrawable.class,
new GifBitmapWrapperDrawableTranscoder(
new GlideBitmapDrawableTranscoder(context.getResources(), bitmapPool)));
......
}
<Z, R> ResourceTranscoder<Z, R> buildTranscoder(Class<Z> decodedClass, Class<R> transcodedClass) {
return transcoderRegistry.get(decodedClass, transcodedClass);
}
Glide的buildTranscoder()方法所用到的方法如上，可以看到是通過(guò)transcoderRegistry.get(decodedClass, transcodedClass);來(lái)得到ResourceTranscoder對(duì)象的芒划。
- ResourceTranscoder接口:它是用于對(duì)圖片進(jìn)行轉(zhuǎn)碼的
TranscoderRegistry類中
public class TranscoderRegistry {
private static final MultiClassKey GET_KEY = new MultiClassKey();
//這個(gè)Map以MultiClassKey為key,ResourceTranscoder對(duì)象為value.
private final Map<MultiClassKey, ResourceTranscoder<?, ?>> factories =
new HashMap<MultiClassKey, ResourceTranscoder<?, ?>>();
//之前在Glide的構(gòu)造方法中已經(jīng)注冊(cè)過(guò)了冬竟。用這個(gè)方法得到之前注冊(cè)的
public <Z, R> ResourceTranscoder<Z, R> get(Class<Z> decodedClass, Class<R> transcodedClass) {
if (decodedClass.equals(transcodedClass)) {
return (ResourceTranscoder<Z, R>) UnitTranscoder.get();
}
final ResourceTranscoder<?, ?> result;
synchronized (GET_KEY) {
GET_KEY.set(decodedClass, transcodedClass);
//利用MultiClassKey從Map中得到注冊(cè)的GlideBitmapDrawableTranscoder
result = factories.get(GET_KEY);
}
if (result == null) {
throw new IllegalArgumentException("No transcoder registered for " + decodedClass + " and "
+ transcodedClass);
}
return (ResourceTranscoder<Z, R>) result;
}
}
所以總結(jié)1過(guò)程，傳入的resourceClass, transcodedClass分別為GifBitmapWrapper, GlideDrawable類型缴挖。最后得到的是GifBitmapWrapperDrawableTranscoder對(duì)象苟鸯。GlideBitmapDrawableTranscoder繼承自ResourceTranscoder接口，該接口用于圖片的轉(zhuǎn)碼瘫析。
2過(guò)程類似1過(guò)程砌梆，最后得到的對(duì)象類型為ImageVideoGifDrawableLoadProvider默责，ImageVideoGifDrawableLoadProvider類繼承DataLoadProvider接口。
- DataLoadProvider接口：用于對(duì)圖片進(jìn)行編解碼的咸包。
再來(lái)看一下標(biāo)記3
ImageVideoModelLoader<A> modelLoader = new ImageVideoModelLoader<A>(streamModelLoader,
fileDescriptorModelLoader);
ImageVideoModelLoader類
public class ImageVideoModelLoader<A> implements ModelLoader<A, ImageVideoWrapper> {
private final ModelLoader<A, InputStream> streamLoader;
private final ModelLoader<A, ParcelFileDescriptor> fileDescriptorLoader;
public ImageVideoModelLoader(ModelLoader<A, InputStream> streamLoader,
ModelLoader<A, ParcelFileDescriptor> fileDescriptorLoader) {
if (streamLoader == null && fileDescriptorLoader == null) {
throw new NullPointerException("At least one of streamLoader and fileDescriptorLoader must be non null");
}
//傳進(jìn)來(lái)的StreamStringLoader類型的對(duì)象
this.streamLoader = streamLoader;
//傳入的FileDescriptorUriLoader類型的對(duì)象
this.fileDescriptorLoader = fileDescriptorLoader;
}
@Override
public DataFetcher<ImageVideoWrapper> getResourceFetcher(A model, int width, int height) {
DataFetcher<InputStream> streamFetcher = null;
if (streamLoader != null) {
//1.
streamFetcher = streamLoader.getResourceFetcher(model, width, height);
}
DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher = null;
if (fileDescriptorLoader != null) {
//2.
fileDescriptorFetcher = fileDescriptorLoader.getResourceFetcher(model, width, height);
}
if (streamFetcher != null || fileDescriptorFetcher != null) {
//返回的ImageVideoFetcher對(duì)象是ImageVideoModelLoader類的內(nèi)部類
return new ImageVideoFetcher(streamFetcher, fileDescriptorFetcher);
} else {
return null;
}
}
static class ImageVideoFetcher implements DataFetcher<ImageVideoWrapper> {
private final DataFetcher<InputStream> streamFetcher;
private final DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher;
public ImageVideoFetcher(DataFetcher<InputStream> streamFetcher,
DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher) {
this.streamFetcher = streamFetcher;
this.fileDescriptorFetcher = fileDescriptorFetcher;
}
@SuppressWarnings("resource")
// @see ModelLoader.loadData
@Override
public ImageVideoWrapper loadData(Priority priority) throws Exception {
InputStream is = null;
if (streamFetcher != null) {
try {
is = streamFetcher.loadData(priority);
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception fetching input stream, trying ParcelFileDescriptor", e);
}
if (fileDescriptorFetcher == null) {
throw e;
}
}
}
ParcelFileDescriptor fileDescriptor = null;
if (fileDescriptorFetcher != null) {
try {
fileDescriptor = fileDescriptorFetcher.loadData(priority);
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception fetching ParcelFileDescriptor", e);
}
if (is == null) {
throw e;
}
}
}
return new ImageVideoWrapper(is, fileDescriptor);
}
}
}
將傳入DrawableTypeRequest構(gòu)造器的StreamStringLoader類型的對(duì)象和FileDescriptorUriLoader類型的對(duì)象傳入ImageVideoModelLoader的構(gòu)造器中來(lái)生成ImageVideoModelLoader對(duì)象桃序。這個(gè)ImageVideoModelLoader類繼承自ModelLoader接口，在該類的getResourceFetcher()方法中烂瘫，來(lái)分析一下1和2過(guò)程媒熊。
1過(guò)程
streamFetcher = streamLoader.getResourceFetcher(model, width, height);
streamLoader的類型是StreamStringLoader類坟比，看一下StreamStringLoader類的getResourceFetcher()方法芦鳍。發(fā)現(xiàn)這個(gè)類里面沒(méi)有getResourceFetcher()方法，但是它繼承于StringLoader類葛账，發(fā)現(xiàn)getResourceFetcher()方法就在StringLoader類中柠衅。
StringLoader類中的getResourceFetcher()方法
private final ModelLoader<Uri, T> uriLoader;
public DataFetcher<T> getResourceFetcher(String model, int width, int height) {
Uri uri;
if (TextUtils.isEmpty(model)) {
return null;
} else if (model.startsWith("/")) {
uri = toFileUri(model);
} else {
uri = Uri.parse(model);
final String scheme = uri.getScheme();
if (scheme == null) {
uri = toFileUri(model);
}
}
return uriLoader.getResourceFetcher(uri, width, height);
}
在這個(gè)StringLoader類中的getResourceFetcher()方法的最后返回了uriLoader的getResourceFetcher()方法。這個(gè)uriLoader的類型是HttpUrlGlideUrlLoader籍琳。那進(jìn)入HttpUrlGlideUrlLoader的getResourceFetcher()方法菲宴。
HttpUrlGlideUrlLoader的getResourceFetcher()方法
public DataFetcher<InputStream> getResourceFetcher(GlideUrl model, int width, int height) {
// GlideUrls memoize parsed URLs so caching them saves a few object instantiations and time spent parsing urls.
GlideUrl url = model;
if (modelCache != null) {
url = modelCache.get(model, 0, 0);
if (url == null) {
modelCache.put(model, 0, 0, model);
url = model;
}
}
return new HttpUrlFetcher(url);
}
看到在這個(gè)HttpUrlGlideUrlLoader的getResourceFetcher()方法的最后返回了一個(gè)HttpUrlFetcher()對(duì)象。StringLoader類中的getResourceFetcher()方法中最后返回的是一個(gè)HttpUrlFetcher()對(duì)象巩割，即StreamStringLoader類的getResourceFetcher()方法最后得到了一個(gè)HttpUrlFetcher()對(duì)象裙顽。所以1過(guò)程最后得到了一個(gè)HttpUrlFetcher()對(duì)象付燥。
2過(guò)程類似于1過(guò)程宣谈。
回到ImageVideoModelLoader類的getResourceFetcher方法中，最后將得到的HttpUrlFetcher()對(duì)象傳入ImageVideoFetcher()的構(gòu)造器中键科，這個(gè)ImageVideoFetche類是ImageVideoModelLoader類的內(nèi)部類闻丑。
總結(jié)一下，從開始到現(xiàn)在的3個(gè)很重要的接口
- ModelLoader接口：是用于加載圖片的
- ResourceTranscoder接口：它是用于對(duì)圖片進(jìn)行轉(zhuǎn)碼的
- DataLoadProvider接口：用于對(duì)圖片進(jìn)行編解碼的勋颖。
這里還要補(bǔ)充一下嗦嗡，DrawableTypeRequest類里面的asBitmap()方法和asGif()方法。
DrawableTypeRequest類里面的asBitmap()方法
public BitmapTypeRequest<ModelType> asBitmap() {
return optionsApplier.apply(new BitmapTypeRequest<ModelType>(this, streamModelLoader,
fileDescriptorModelLoader, optionsApplier));
}
asBitmap()方法里面生成了BitmapTypeRequest對(duì)象饭玲，它類似于DrawableTypeRequest侥祭，這個(gè)BitmapTypeRequest的最終的父類也是GenericRequestBuilder。
asGif()方法與asBitmap()方法類似茄厘。
回到DrawableTypeRequest類的構(gòu)造函數(shù)中矮冬。
DrawableTypeRequest類的構(gòu)造函數(shù)中又初始化了從父類那里繼承得到的實(shí)例對(duì)象，我們看一下DrawableTypeRequest類的父類次哈。
DrawableRequestBuilder類
public class DrawableRequestBuilder<ModelType>
extends GenericRequestBuilder<ModelType, ImageVideoWrapper, GifBitmapWrapper, GlideDrawable>
implements BitmapOptions, DrawableOptions {
DrawableRequestBuilder(Context context, Class<ModelType> modelClass,
LoadProvider<ModelType, ImageVideoWrapper, GifBitmapWrapper, GlideDrawable> loadProvider, Glide glide,
RequestTracker requestTracker, Lifecycle lifecycle) {
super(context, modelClass, loadProvider, GlideDrawable.class, glide, requestTracker, lifecycle);
// Default to animating.
......
}
}
看到這個(gè)類同樣初始化了從父類那里繼承得到的實(shí)例對(duì)象胎署，我們看一下DrawableRequestBuilder類的父類。
GenericRequestBuilder類
public class GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> implements Cloneable {
private ChildLoadProvider<ModelType, DataType, ResourceType, TranscodeType> loadProvider;
GenericRequestBuilder(LoadProvider<ModelType, DataType, ResourceType, TranscodeType> loadProvider,
Class<TranscodeType> transcodeClass, GenericRequestBuilder<ModelType, ?, ?, ?> other) {
this(other.context, other.modelClass, loadProvider, transcodeClass, other.glide, other.requestTracker,
other.lifecycle);
......
}
GenericRequestBuilder(Context context, Class<ModelType> modelClass,
LoadProvider<ModelType, DataType, ResourceType, TranscodeType> loadProvider,
Class<TranscodeType> transcodeClass, Glide glide, RequestTracker requestTracker, Lifecycle lifecycle) {
this.loadProvider = loadProvider != null
? new ChildLoadProvider<ModelType, DataType, ResourceType, TranscodeType>(loadProvider) : null;
}
}
}
在這個(gè)類中窑滞，將DrawableTypeRequest類中生成的FixedLoadProvider類的對(duì)象在構(gòu)造函數(shù)中傳入ChildLoadProvider()的構(gòu)造器中琼牧，所以最后在該類中的loadProvider實(shí)例變量所指向的類型為ChildLoadProvider類型恢筝，ChildLoadProvider也是DataLoadProvider接口的實(shí)現(xiàn)類。
- GenericRequestBuilder類：這個(gè)類提供了加載各種資源的方法巨坊，是各種資源請(qǐng)求構(gòu)造類的父類撬槽。
好了，從在RequestManager類的loadGeneric()方法中趾撵，創(chuàng)建DrawableTypeRequest對(duì)象恢氯，又分析了很多。
現(xiàn)在回到RequestManager類的load(string)方法中鼓寺。
load(string)方法中
public DrawableTypeRequest<String> load(String string) {
return (DrawableTypeRequest<String>) fromString().load(string);
}
在load(string)方法中噪馏，fromString()方法的過(guò)程已經(jīng)分析過(guò)了卵佛，發(fā)現(xiàn)這個(gè)方法最終返回的是DrawableTypeRequest類型的對(duì)象，所以fromString()方法后面調(diào)用的.load()方法，就是DrawableTypeRequest類里面的方法彩扔，但是發(fā)現(xiàn)DrawableTypeRequest類里面根本沒(méi)有l(wèi)oad()方法，所以這個(gè)方法是其父類的方法莹妒。
DrawableRequestBuilder類中
public DrawableRequestBuilder<ModelType> load(ModelType model) {
super.load(model);
return this;
}
調(diào)用了其父類的load()方法铛绰。那就到GenericRequestBuilder類中看看。
GenericRequestBuilder類中
public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> load(ModelType model) {
this.model = model;
isModelSet = true;
return this;
}
這個(gè)model就是load()方法中傳入的String類型的字符串幔虏。
Glide的load()過(guò)程結(jié)束了纺念。這個(gè)分析過(guò)程中分析了很多其他的東西，但是分析的東西都是后面我們into()過(guò)程中要使用的想括，所以寫了很多陷谱。好滴，load()過(guò)程最終調(diào)用了GenericRequestBuilder類的load()方法瑟蜈。
