回调：将imageView的实例传到into()中，当Glide将图片加载完后以后，图片就能显示到ImageView上去了
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.
}
}
// 构建target
return into(glide.buildImageViewTarget(view, transcodeClass));
}
public class ImageViewTargetFactory {
// 最终构建出来的target（一般情况下回事GlideDrawableIamgeViewTarget,当使用asBitmap的时候回构建出BitmapImageViewTarget对象）
@SuppressWarnings("unchecked")
public <Z> Target<Z> buildTarget(ImageView view, Class<Z> clazz) {
if (GlideDrawable.class.isAssignableFrom(clazz)) {
return (Target<Z>) new GlideDrawableImageViewTarget(view);
} else if (Bitmap.class.equals(clazz)) {
return (Target<Z>) new BitmapImageViewTarget(view);
} else if (Drawable.class.isAssignableFrom(clazz)) {
return (Target<Z>) new DrawableImageViewTarget(view);
} else {
throw new IllegalArgumentException("Unhandled class: " + clazz
+ ", try .as*(Class).transcode(ResourceTranscoder)");
}
}
}
回到into()方法中最终会通过buildRequest(target)把这个target传到GenericRqeust中，所以在GenericRequest中的target.onResourceReady，就是调用的GlideDrawableIamgeViewTarget的onResourceReady。
@Override
public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> animation) {
if (!resource.isAnimated()) {
//TODO: Try to generalize this to other sizes/shapes.
// This is a dirty hack that tries to make loading square thumbnails and then square full images less costly
// by forcing both the smaller thumb and the larger version to have exactly the same intrinsic dimensions.
// If a drawable is replaced in an ImageView by another drawable with different intrinsic dimensions,
// the ImageView requests a layout. Scrolling rapidly while replacing thumbs with larger images triggers
// lots of these calls and causes significant amounts of jank.
float viewRatio = view.getWidth() / (float) view.getHeight();
float drawableRatio = resource.getIntrinsicWidth() / (float) resource.getIntrinsicHeight();
if (Math.abs(viewRatio - 1f) <= SQUARE_RATIO_MARGIN
&& Math.abs(drawableRatio - 1f) <= SQUARE_RATIO_MARGIN) {
resource = new SquaringDrawable(resource, view.getWidth());
}
}
super.onResourceReady(resource, animation);
this.resource = resource;
resource.setLoopCount(maxLoopCount);
resource.start();
}
@Override
protected void setResource(GlideDrawable resource) {
view.setImageDrawable(resource);
}在这个方法中处理了图片的展示和GIF播放的逻辑，一张图片就显示出来了，这也就是Glide的一个回调
通过观察可以发现into()还可以直接传入一个target对象，所以我们可以自定义target来实现Glide的回调了观察target的继承图可以发现我们自诩在SimpleTarget和ViewTarget的基础上自定义就好了
SimpleTarget用法：
这里的泛型可以直接是Bitmap
SimpleTarget<GlideDrawable> simpleTarget = new SimpleTarget<GlideDrawable>() {
@Override
pulic void onResourceReady(GlideDrawable resource, GlideAnimation glideAnimation) {
// 在这里我们就可以拿到图片对象的实例resource
imageView.setImageDrawable(resource);
}
};
pulic void loadImage(View view) {
Glide.with(this)
.load(url)
.into(simpleTarget);
}ViewTarget用法：
创建一个自定义的布局：
public class MyLayout extends LinearLayout {
private final ViewTarget<MyLayout, GlideDrawable> viewTarget;
public MyLayout(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
viewTarget = new ViewTarget<MyLayout, GlideDrawable>(this) {
@Override
public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> glideAnimation) {
MyLayout myLayout = getView();
myLayout.setImageBackgroung(resource);
}
};
}
public ViewTarget<MyLayout, GlideDrawable> getTarget() {
return viewTarget;
}
public void setImageBackgroung(GlideDrawable resource) {
setBackground(resource);
}
}
在activity中调用
public class MainActivity extends AppCompatActivity {
public static final String url = "http://upload.sichuan.95504.net/mobile/special/s0/s0_05677934088858712.jpg?token=asdbjksdfjkasasjfb";
private MyLayout mLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLayout = findViewById(R.id.iv);
}
public void loadImg(View view) {
Glide.with(getApplicationContext())
.load(new MyGlideUrl(url))
.into(mLayout.getTarget());
}
}preload()预加载
用法：
在加载图片前先使用预加载将图片加入到缓存中，可以提高加载的速度
Glide.with(this).load(url).preload(); Glide.with(this).load(url).into(imageView);
public Target<TranscodeType> preload(int width, int height) {
final PreloadTarget<TranscodeType> target = PreloadTarget.obtain(width, height);
return into(target);
}
public Target<TranscodeType> preload() {
return preload(Target.SIZE_ORIGINAL, Target.SIZE_ORIGINAL);
}
public final class PreloadTarget<Z> extends SimpleTarget<Z> {
/**
* Returns a PreloadTarget.
*
* @param width The width in pixels of the desired resource.
* @param height The height in pixels of the desired resource.
* @param <Z> The type of the desired resource.
*/
public static <Z> PreloadTarget<Z> obtain(int width, int height) {
return new PreloadTarget<Z>(width, height);
}
private PreloadTarget(int width, int height) {
super(width, height);
}
@Override
public void onResourceReady(Z resource, GlideAnimation<? super Z> glideAnimation) {
// 这里是告诉Glide图片已经缓存好了，可以释放资源了，而不是清除
Glide.clear(this);
}
}downloadonly()缓存图片到文件中
用法：
downloadOnly（int widht，int height）；设置宽高，用于在子线程中下载
downloadOnly（Y target）传入泛型，用于在主线程中下载
在子线程中下载图片：
private void downloadImage(View view) {
new Thread(new Runnable() {
@Override
public void run() {
try {
FutureTarget<File> target = Glide.with(getApplicationContext())
.load(url)
.downloadOnly(Target.SIZE_ORIGINAL, Target.SIZE_ORIGINAL);
final File imageFile = target.get();
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(getApplicationContext(), imageFile.getPath(), Toast.LENGTH_SHORT).show();
Glide.with(getApplicationContext())
.load(imageFile)
.into(mLayout.getTarget());
}
});
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}).start();
}downloadOnly源码：
public FutureTarget<File> downloadOnly(int width, int height) {
return getDownloadOnlyRequest().downloadOnly(width, height);
}获取一个GenericTranscodeRequest对象
private GenericTranscodeRequest<ModelType, InputStream, File> getDownloadOnlyRequest() {
return optionsApplier.apply(new GenericTranscodeRequest<ModelType, InputStream, File>(File.class, this,
streamModelLoader, InputStream.class, File.class, optionsApplier));
}
public FutureTarget<File> downloadOnly(int width, int height) {
return getDownloadOnlyRequest().into(width, height);
}构建一个图片下载的请求
private GenericRequestBuilder<ModelType, DataType, File, File> getDownloadOnlyRequest() {
ResourceTranscoder<File, File> transcoder = UnitTranscoder.get();
DataLoadProvider<DataType, File> dataLoadProvider = glide.buildDataProvider(dataClass, File.class);
FixedLoadProvider<ModelType, DataType, File, File> fixedLoadProvider =
new FixedLoadProvider<ModelType, DataType, File, File>(modelLoader, transcoder, dataLoadProvider);
return optionsApplier.apply(new GenericRequestBuilder<ModelType, DataType, File, File>(fixedLoadProvider,
File.class, this))
.priority(Priority.LOW)
.diskCacheStrategy(DiskCacheStrategy.SOURCE)
.skipMemoryCache(true);
}into()首先
public FutureTarget<TranscodeType> into(int width, int height) {
final RequestFutureTarget<ModelType, TranscodeType> target =
new RequestFutureTarget<ModelType, TranscodeType>(glide.getMainHandler(), width, height);
// TODO: Currently all loads must be started on the main thread...
glide.getMainHandler().post(new Runnable() {
@Override
public void run() {
if (!target.isCancelled()) {
// 将RequestFutureTarget对象传入到GenericRqeustBUilder中的into
into(target);
}
}
});
return target;
}通过前面对downloadOnly的基础用法可以知道：
调用downloadOnly()之后再调用get()就可以得到图片的下载文件
这里的get()又是谁的？？？？
因为downloadOnly()返回的是一个FutureTarget的对象，也就是RequestFutureTarget的对象
@Override
public R get() throws InterruptedException, ExecutionException {
try {
// 实际上调用的是这里
return doGet(null);
} catch (TimeoutException e) {
throw new AssertionError(e);
}
}
private synchronized R doGet(Long timeoutMillis) throws ExecutionException, InterruptedException, TimeoutException {
if (assertBackgroundThread) {
Util.assertBackgroundThread();
}
if (isCancelled) {
throw new CancellationException();
} else if (exceptionReceived) {
throw new ExecutionException(exception);
} else if (resultReceived) {
// 判断是否下载完成，完成就直接返回
return resource;
}
if (timeoutMillis == null) {
// 这边有个waiter线程等待
waiter.waitForTimeout(this, 0);
} else if (timeoutMillis > 0) {
waiter.waitForTimeout(this, timeoutMillis);
}
if (Thread.interrupted()) {
throw new InterruptedException();
} else if (exceptionReceived) {
throw new ExecutionException(exception);
} else if (isCancelled) {
throw new CancellationException();
} else if (!resultReceived) {
throw new TimeoutException();
}
return resource;
}
static class Waiter {
public void waitForTimeout(Object toWaitOn, long timeoutMillis) throws InterruptedException {
toWaitOn.wait(timeoutMillis);
}
public void notifyAll(Object toNotify) {
toNotify.notifyAll();
}
}这也说明了为什么downloadOnly（int widht，int height）会在子线程中，如果放在主线程就会造成线程卡死
现在线程卡死又什么时候恢复呢？
@Override
public synchronized void onResourceReady(R resource, GlideAnimation<? super R> glideAnimation) {
// We might get a null result.
// 图片文件已经下载好，下次咋低调用get()时就不会阻塞线程了
resultReceived = true;
// 图片文件赋值给全局变量，在doGet()就能访问到resource了
this.resource = resource;
// 通知所有的waiter取消线程阻塞
waiter.notifyAll(this);
}这就是downloadOnly（int widht，int height）的基本用法和实现原理
downloadOnly（Y target）则是要求我们传入一个target，就不受RequestFutureTarget限制了
用法：自定义自己的Target实现Target接口（泛型必须是File类型的）
public class DownloadImageTarget implements Target<File> {
@Override
public void onLoadStarted(Drawable placeholder) {
}
@Override
public void onLoadFailed(Exception e, Drawable errorDrawable) {
}
@Override
public void onResourceReady(File resource, GlideAnimation<? super File> glideAnimation) {
//下载完成以后会回调到此处
Log.d("downloadPath::::", resource.getPath());
}
@Override
public void onLoadCleared(Drawable placeholder) {
}
@Override
public void getSize(SizeReadyCallback cb) {
//Glide在开始加载图片的时候会计算图片的大小，回调到onSizeReady()中（ Target.SIZE_ORIGINAL表示原始图片）
cb.onSizeReady(Target.SIZE_ORIGINAL, Target.SIZE_ORIGINAL);
}
@Override
public void setRequest(Request request) {
}
@Override
public Request getRequest() {
return null;
}
@Override
public void onStart() {
}
@Override
public void onStop() {
}
@Override
public void onDestroy() {
}
}在activity中调用：
private void downloadImage(View view) {
Glide.with(this)
.load(url)
.downloadOnly(new DownloadImageTarget());
}
listener()监听
基本用法：
Glide.with(this)
.load(url)
.listener(new RequestListener<File, GlideDrawable>() {
@Override
// 加载失败
public boolean onException(Exception e, File model, Target<GlideDrawable> target, boolean isFirstResource) {
// 返回true表示事件处理掉，就不向下执行
return false;
}
@Override
// 加载成功
public boolean onResourceReady(GlideDrawable resource, File model, Target<GlideDrawable> target, boolean isFromMemoryCache, boolean isFirstResource) {
// 返回true表示事件处理掉，就不向下执行
return false;
}
})
.into(imageView);listener()源码：
public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> listener(
RequestListener<? super ModelType, TranscodeType> requestListener) {
// 在构建GenericRequest的时候会把listener传进去
this.requestListener = requestListener;
return this;
}所以在图片加载完成的时候：
private void onResourceReady(Resource<?> resource, R result) {
// We must call isFirstReadyResource before setting status.
boolean isFirstResource = isFirstReadyResource();
status = Status.COMPLETE;
this.resource = resource;
// 在这会通过requestListener.onResourceReady(result, model, target, loadedFromMemoryCache,isFirstResource)这个就是我们在使用的时候所传入的boolean值
// 判断是否调用target的onResourceReady()
if (requestListener == null || !requestListener.onResourceReady(result, model, target, loadedFromMemoryCache,
isFirstResource)) {
GlideAnimation<R> animation = animationFactory.build(loadedFromMemoryCache, isFirstResource);
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);
}
}同理onException()也是一样的
@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?
// 在此处判断传入的Boolean值
if (requestListener == null || !requestListener.onException(e, model, target, isFirstReadyResource())) {
setErrorPlaceholder(e);
}
}