腾讯T10最喜欢的Glide巨图加载机制，入坑APP深度优化必学
2022-06-10 本文已影响0人
码农的地中海
一、Glide定义
Glide也是基于Flash的，并且它并没有模仿Windows或其它类似的桌面环境，取而代之的是它提供了独特的界面。它允许用户上传多达30GB的文件，用户能够阅读RSS feed，管理书签，约会，聊天，创建文档，浏览图片等。Glide的设计非常不错，然而某些方面跟Desktoptwo有些类似。首先，某些应用程序以弹出窗口方式打开，似乎并不是非要这么做不可。此外，其中有些应用程序没有像其它界面一样经过美化。有些应用程序，如日历就完全不能正常运行，一点击就会出错。
二、Glide特点
- 支持Memory和Disk图片缓存。
- 支持gif和webp格式图片。
- 根据Activity/Fragment生命周期自动管理请求。
- 使用Bitmap Pool可以使Bitmap复用。
- 对于回收的Bitmap会主动调用recycle，减小系统回收压力。
三、Glide和Picasso他们的对比的优缺点
1.Picasso和Glide的withi后面的参数不同
- Picasso.with(这里只能传入上下文) .
-
Glide.with,后面可以传入上下文,activity实例,FragmentActivity实例,Fragement.传入的对象要比前者多.
QQ图片20220610154946.jpg
2.加载后图片质量不同
Picasso采用的ARGB-8888,Glide采用的是RGB-565相对而言,Picasso加载的是全图,
图片质量和清晰对要比Glide的要高,但是,因为加载的采样率过高,导致,出现OOM异常的概率要比Glide要大很多.
3.加载Gif图片(备注:Gif图片消耗太对内存,尽量谨慎使用):
- Picasso不能加载git图片
- Glide可以加载缓存图片
4.缓存策略和加载速度.
- Picasso缓存的是全尺寸,而 Glide的缓存的更ImageView的尺寸相同.讲ImageView调整为不同的大小,不管大小如何设置,Picasso只缓存一个全尺寸的,Glide则不同,他会为每种大小不一致的ImageView都缓存一次.
-
Glide的这个特点,让加载显得特别的快,而Picasso则因为需要在显示之前重新调整大小而导致一些延迟,(即便是添加了noFade)
QQ图片20220610155013.jpg
四、Glide图片加载原理分析
4.1图片质量分类
安卓图片显示的质量配置主要分为四种:
ARGB_8888 :32位图,带透明度,每个像素占4个字节
ARGB_4444 :16位图,带透明度,每个像素占2个字节
RGB_565 :16位图,不带透明度,每个像素占2个字节
ALPHA_8 :32位图,只有透明度,不带颜色,每个像素占4个字节
(A代表透明度,RGB代表红绿蓝:即颜色)
4.2图片默认质量
Picasso的默认质量是 ARGB_8888
Glide的默认质量则为 RGB_565
Glide默认的图片质量比Picasso稍微差一些。
加载一张4000 * 2000(一般手机拍摄的都超过这个像素)的图片
4.3占用内存
Picasso需要占用的内存为: 32MB
4000 * 2000 * 4 / 1024 / 1024 = 30 (MB)
Glide需要占用的内存为: 16MB
4000 * 2000 * 2 / 1024 / 1024 = 15 (MB)
也就是说只要同时加载几张图片,你的应用就会OOM(内存溢出了),最恐怖的是就算你的ImageView的宽高只有10px,同样会占用那么多内存,这就是为什么需要做图片压缩的原因了
4.4加载图片分析
1、with
// Glide.java
public static RequestManager with(FragmentActivity activity) {
RequestManagerRetriever retriever = RequestManagerRetriever.get();
return retriever.get(activity);
}
// RequestManagerRetriever.java
public static RequestManagerRetriever get() { return INSTANCE; }
// Visible for testing. RequestManagerRetriever() { handler = new Handler(Looper.getMainLooper(), this /* Callback */); }
RequestManagerRetriever是一个单例模式，get方法返回RequestManager，get方法可以传递acitivity fragment context等
public RequestManager get(FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
FragmentManager fm = activity.getSupportFragmentManager();
return supportFragmentGet(activity, fm);
}
}
public RequestManager get(Context context) {
if (context == null) {
throw new IllegalArgumentException("You cannot start a load on a null Context");
} else if (Util.isOnMainThread() && !(context instanceof Application)) {
if (context instanceof FragmentActivity) {
return get((FragmentActivity) context);
} else if (context instanceof Activity) {
return get((Activity) context);
} else if (context instanceof ContextWrapper) {
return get(((ContextWrapper) context).getBaseContext());
}
}
return getApplicationManager(context);
}
如果传递的是Application，那么通过getApplicationManager()方法创建一个RequestManager对象并返回，这是因为application的生命周期比较长，只要应用程序没有被杀死，Glide就可以工作，加载图片
private RequestManager getApplicationManager(Context context) {
// Either an application context or we're on a background thread.
if (applicationManager == null) {
synchronized (this) {
if (applicationManager == null) {
// Normally pause/resume is taken care of by the fragment we add to the fragment or activity.
// However, in this case since the manager attached to the application will not receive lifecycle
// events, we must force the manager to start resumed using ApplicationLifecycle.
applicationManager = new RequestManager(context.getApplicationContext(),
new ApplicationLifecycle(), new EmptyRequestManagerTreeNode());
}
}
}
return applicationManager;
},
如果传递的是非application，会在当前的activity创建一个隐藏的fragment，这是因为Glide无法知道activity fragment的生命周期，如正在网络加载图片时，activity被销毁，这个时候应该退出加载图片，因为fragment的生命周期同acitivity，activity退出后，fragment收到通知，停止加载图片
RequestManager supportFragmentGet(Context context, FragmentManager fm) {
SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
requestManager = new RequestManager(context, current.getLifecycle(), current.getRequestManagerTreeNode());
current.setRequestManager(requestManager);
}
return requestManager;
}
2、load
public class RequestManager implements LifecycleListener {
// RequestManager
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));
}
public DrawableRequestBuilder<ModelType> load(ModelType model) {
super.load(model);
return this;
}
public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> load(ModelType model) {
this.model = model;
isModelSet = true;
return this;
}
其中继承关系是GenericRequestBuilder<-DrawbleRequestBuilder<-DrawbleTypeRequest，load方法最终会返回一个DrawbleTypeRequest对象
// DrawbleTyperequest.java
public BitmapTypeRequest<ModelType> asBitmap() {
return optionsApplier.apply(new BitmapTypeRequest<ModelType>(this, streamModelLoader,
fileDescriptorModelLoader, optionsApplier));
}
// DrawbleTypeRequest.java
public GifTypeRequest<ModelType> asGif() {
return optionsApplier.apply(new GifTypeRequest<ModelType>(this, streamModelLoader, optionsApplier));
}
指定静态图片返回BitmapTypeRequest，动态图片返回GifTypeRequest，不指定默认返回DrawbleTypeRequest，总之，load方法返回一个DrawbleTypeRequest对象
3、into
调用父类GenericRequestBuilder的into方法，
public Target<TranscodeType> 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
public <Y extends Target<TranscodeType>> Y into(Y target) {
Util.assertMainThread();
if (target == null) {
throw new IllegalArgumentException("You must pass in a non null Target");
}
if (!isModelSet) {
throw new IllegalArgumentException("You must first set a model (try #load())");
}
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;
}
Request是用来发出网络加载图片请求的，是Glide非常重要的一个组件，看一下如何构建Requst
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
private Request buildRequestRecursive(Target<TranscodeType> target, ThumbnailRequestCoordinator parentCoordinator) {
if (thumbnailRequestBuilder != null) {
if (isThumbnailBuilt) {
throw new IllegalStateException("You cannot use a request as both the main request and a thumbnail, "
+ "consider using clone() on the request(s) passed to thumbnail()");
}
// Recursive case: contains a potentially recursive thumbnail request builder.
if (thumbnailRequestBuilder.animationFactory.equals(NoAnimation.getFactory())) {
thumbnailRequestBuilder.animationFactory = animationFactory;
}
if (thumbnailRequestBuilder.priority == null) {
thumbnailRequestBuilder.priority = getThumbnailPriority();
}
if (Util.isValidDimensions(overrideWidth, overrideHeight)
&& !Util.isValidDimensions(thumbnailRequestBuilder.overrideWidth,
thumbnailRequestBuilder.overrideHeight)) {
thumbnailRequestBuilder.override(overrideWidth, overrideHeight);
}
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
Request fullRequest = obtainRequest(target, sizeMultiplier, priority, coordinator);
// Guard against infinite recursion.
isThumbnailBuilt = true;
// Recursively generate thumbnail requests.
Request thumbRequest = thumbnailRequestBuilder.buildRequestRecursive(target, coordinator);
isThumbnailBuilt = false;
coordinator.setRequests(fullRequest, thumbRequest);
return coordinator;
} else if (thumbSizeMultiplier != null) {
// Base case: thumbnail multiplier generates a thumbnail request, but cannot recurse.
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
Request fullRequest = obtainRequest(target, sizeMultiplier, priority, coordinator);
Request thumbnailRequest = obtainRequest(target, thumbSizeMultiplier, getThumbnailPriority(), coordinator);
coordinator.setRequests(fullRequest, thumbnailRequest);
return coordinator;
} else {
// Base case: no thumbnail.
return obtainRequest(target, sizeMultiplier, priority, parentCoordinator);
}
}
private Request obtainRequest(Target<TranscodeType> target, float sizeMultiplier, Priority priority,
RequestCoordinator requestCoordinator) {
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);
}
最后会调到 GenericRequest的obtain()方法，它的参数有一些是我们之前在load方法中设置进去的，如errorplaceholder，diskCacheStrategy，placeholderId等
public final class GenericRequest<A, T, Z, R> implements Request, SizeReadyCallback,
ResourceCallback {
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) {
request = new GenericRequest<A, T, Z, R>();
}
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);
return request;
}
obtain()方法实际上获得的就是一个GenericRequest对象，到这里我们获得了一个request对象，然后看一下这个request对象是怎么执行的，requestTracker.runRequest()方法来去执行这个Request
/**
* Starts tracking the given request.
*/
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}
request.begin()，request是一个接口，它的实现类是 GenericRequest中的begin()方法
@Override
public void begin() {
startTime = LogTime.getLogTime();
if (model == null) { // model是图片的url
onException(null);
return;
}
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}
if (!isComplete() && !isFailed() && canNotifyStatusChanged()) {
target.onLoadStarted(getPlaceholderDrawable()); // 加载图片之前显示加载占位图
}
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
@Override
public void onException(Exception e) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "load failed", e);
}
status = Status.FAILED;
//TODO: what if this is a thumbnail request?
if (requestListener == null || !requestListener.onException(e, model, target, isFirstReadyResource())) {
setErrorPlaceholder(e);
}
}
private void setErrorPlaceholder(Exception e) {
if (!canNotifyStatusChanged()) {
return;
}
Drawable error = model == null ? getFallbackDrawable() : null;
if (error == null) {
error = getErrorDrawable();
}
if (error == null) {
error = getPlaceholderDrawable();
}
target.onLoadFailed(e, error);
}
在onLoadFailed中将显示异常（错误）占位图，即url为空时显示异常或者placeholder占位图
public abstract class ImageViewTarget<Z> extends ViewTarget<ImageView, Z> implements GlideAnimation.ViewAdapter {
...
@Override
public void onLoadStarted(Drawable placeholder) {
view.setImageDrawable(placeholder);
}
@Override
public void onLoadFailed(Exception e, Drawable errorDrawable) {
view.setImageDrawable(errorDrawable);
}
...
}
在begin方法中还会调到onSizeReady方法，传入宽高，可能是用户override指定的，也可能是通过imageview计算的
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<A, T> modelLoader = loadProvider.getModelLoader();
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
if (dataFetcher == null) {
onException(new Exception("Failed to load model: \'" + model + "\'"));
return;
}
ResourceTranscoder<Z, R> 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));
}
}
此处省略几万行。。。。。。最后onSizeReady进入到真正的的网络请求代码
private InputStream loadDataWithRedirects(URL url, int redirects, URL lastUrl,
Map<String, String> headers) throws IOException {
if (redirects >= MAXIMUM_REDIRECTS) {
throw new HttpException("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 HttpException("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(timeout);
urlConnection.setReadTimeout(timeout);
urlConnection.setUseCaches(false);
urlConnection.setDoInput(true);
// Stop the urlConnection instance of HttpUrlConnection from following redirects so that
// redirects will be handled by recursive calls to this method, loadDataWithRedirects.
urlConnection.setInstanceFollowRedirects(false);
// Connect explicitly to avoid errors in decoders if connection fails.
urlConnection.connect();
// Set the stream so that it's closed in cleanup to avoid resource leaks. See #2352.
stream = urlConnection.getInputStream();
if (isCancelled) {
return null;
}
final int statusCode = urlConnection.getResponseCode();
if (isHttpOk(statusCode)) {
return getStreamForSuccessfulRequest(urlConnection);
} else if (isHttpRedirect(statusCode)) {
String redirectUrlString = urlConnection.getHeaderField("Location");
if (TextUtils.isEmpty(redirectUrlString)) {
throw new HttpException("Received empty or null redirect url");
}
URL redirectUrl = new URL(url, redirectUrlString);
// Closing the stream specifically is required to avoid leaking ResponseBodys in addition
// to disconnecting the url connection below. See #2352.
cleanup();
return loadDataWithRedirects(redirectUrl, redirects + 1, url, headers);
} else if (statusCode == INVALID_STATUS_CODE) {
throw new HttpException(statusCode);
} else {
throw new HttpException(urlConnection.getResponseMessage(), statusCode);
}
}
服务器返回InputStream，Glide进行解析，最终得到bitmap->drawable并显示。
五、总结
Glide的架构扩展性高，但是难以理解，各种接口、泛型，需要一定的学习才能熟练运用。
android开发大量进阶技术知识，尽在Android核心技术进阶手册、实战笔记
干我们这行，啥时候懈怠，就意味着长进的停止，长进的停止就意味着被淘汰，只能往前冲，直到凤凰涅槃的一天！
