Glide知识简介

article/2025/10/12 10:49:27

首先Glide是Google为我们推荐的一个快速高效的图片加载库，使用简单。

第一步：添加依赖：

//glide的依赖 
implementation 'com.github.bumptech.glide:glide:4.9.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.9.0'

简单使用：一行代码即可搞定：

//一行代码搞定的方法
Glide.with(上下文).load(url地址).into(imageView);

复杂使用：需要设置placeholder图片显示类型：

1.老版本（glide版本4.6.0之前）：

//老版本写法：
Glide.with(this).load(url).placeholder(R.mipmap.myuser_nologin).dontAnimate().error(R.mipmap.myuser_nologin).centerCrop().into(imageView);

2.新版本（glide版本4.6.0之后）：

//新版Glide(4.6.0 之后)  需要设置optionsRequestOptions options = new RequestOptions().centerCrop().placeholder(R.drawable.booth_map).error(R.drawable.error).priority(Priority.HIGH).diskCacheStrategy(DiskCacheStrategy.NONE);Glide.with(mContext).load(listBean.getImage0()) .apply(options).into(viewHolder.ivPictureText);

Glide原理（源码解读）：

在Glide的with方法里返回了RequestManager对象：

而不管哪个调用哪个with方法，都会进入到get方法中，就是以下方法：

而get方法中返回有一个方法fragmentGet:

/** @deprecated */@Deprecated@NonNullprivate RequestManager fragmentGet(@NonNull Context context, @NonNull FragmentManager fm, @Nullable android.app.Fragment parentHint, boolean isParentVisible) {RequestManagerFragment current = this.getRequestManagerFragment(fm, parentHint, isParentVisible);RequestManager requestManager = current.getRequestManager();if (requestManager == null) {Glide glide = Glide.get(context);requestManager = this.factory.build(glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);current.setRequestManager(requestManager);}return requestManager;}

这里新建了一个视图的RequestManagerFragment:

RequestManagerFragment.class中持有一个lifecycle，在Fragment进入关键生命周期时会主动通知lifecycle执行相关方法

public class RequestManagerFragment extends Fragment {.......private final ActivityFragmentLifecycle lifecycle;......@Overridepublic void onStart() {super.onStart();lifecycle.onStart();}@Overridepublic void onStop() {super.onStop();lifecycle.onStop();}@Overridepublic void onDestroy() {super.onDestroy();lifecycle.onDestroy();unregisterFragmentWithRoot();}.........}

ActivityFragmentLifecycle.class中持有一个lifecycleListeners，在Fragment进入关键生命周期时Lifecycle会通知他的所有Listener:

class ActivityFragmentLifecycle implements Lifecycle {
.............private final Set<LifecycleListener> lifecycleListeners =Collections.newSetFromMap(new WeakHashMap<LifecycleListener, Boolean>());
.............
void onStart() {isStarted = true;for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) {lifecycleListener.onStart();}}void onStop() {isStarted = false;for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) {lifecycleListener.onStop();}}void onDestroy() {isDestroyed = true;for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) {lifecycleListener.onDestroy();}}
}

RequestManger.class关键生命周期中处理加载任务:

/*** Lifecycle callback that registers for connectivity events (if the* android.permission.ACCESS_NETWORK_STATE permission is present) and restarts failed or paused* requests.*/@Overridepublic synchronized void onStart() {resumeRequests();targetTracker.onStart();}/*** Lifecycle callback that unregisters for connectivity events (if the* android.permission.ACCESS_NETWORK_STATE permission is present) and pauses in progress loads.*/@Overridepublic synchronized void onStop() {pauseRequests();targetTracker.onStop();}/*** Lifecycle callback that cancels all in progress requests and clears and recycles resources for* all completed requests.*/@Overridepublic synchronized void onDestroy() {targetTracker.onDestroy();for (Target<?> target : targetTracker.getAll()) {clear(target);}targetTracker.clear();requestTracker.clearRequests();lifecycle.removeListener(this);lifecycle.removeListener(connectivityMonitor);mainHandler.removeCallbacks(addSelfToLifecycle);glide.unregisterRequestManager(this);}

总结：

首先在Glide加载绑定了Activity的生命周期，比如with(context)方法
然后在Activity内新建一个无UI的fragment，这个特殊的fragment持有一个Lifecycle。通过Lifecycle在Fragment关键生命周期通知RequestManager进行相关操作。
最后在生命周期onStart时继续加载，在onStop时暂停加载，在onDestory时停止加载任务和清除操作

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