本文转载自微信公众号「Android开发编程」，作者Android开发编程。转载本文请联系Android开发编程公众号。
glide缓存策略我们分析过了;
glide加载流程我们上一篇文章也分析过了;
那么这次我们再来分析下Glide生命周期管理详解
复制
![[[421375]]](https://s5.51cto.com/oss/202109/04/181ca4d11c16c93584565f5c7901891c.jpg){kind=link}
Glide.with(this) // .asBitmap()//只允许加载静态图片，若传入gif图会展示第一帧（要在load之前） // .asGif()//指定gif格式（要在load之前） // .asDrawable()//指定drawable格式（要在load之前） .load(imageUrl)//被加载图像的url地址 .placeholder(R.drawable.ic_placeholder)//占位图片 .error(R.drawable.ic_error)//错误图片 .transition(GenericTransitionOptions.with(R.anim.zoom_in))//图片动画 .override(800,800)//设置加载尺寸 .skipMemoryCache(true)//禁用内存缓存功能 .diskCacheStrategy(DiskCacheStrategy.NONE)//不缓存任何内容 // .diskCacheStrategy(DiskCacheStrategy.DATA)//只缓存原始图片 // .diskCacheStrategy(DiskCacheStrategy.RESOURCE)//只缓存转换后的图片 // .diskCacheStrategy(DiskCacheStrategy.ALL)//缓存所有 // .diskCacheStrategy(DiskCacheStrategy.AUTOMATIC)//Glide根据图片资源智能地选择使用哪一种缓存策略（默认） .listener(new RequestListener<Drawable>() {//监听图片加载状态 //图片加载完成 @Override public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Drawable> target, boolean isFirstResource) { return false; } //图片加载失败 @Override public boolean onResourceReady(Drawable resource, Object model, Target<Drawable> target, DataSource dataSource, boolean isFirstResource) { return false; } }) .into(imageView);//图片最终要展示的地方
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
with方法可以接受Context，Activity，FragmentActivity，Fragment和View不同的类型
复制
private static volatile Glide glide; public static Glide get(@NonNull Context context) { if (glide == null) { synchronized (Glide.class) { if (glide == null) { checkAndInitializeGlide(context); } } } return glide; }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
双重检测单例模式(DCL)保证Glide对象的唯一性，get方法里面初始化了Glide，通过建造者模式创建了一个GlideBuilder对象(资源请求线程池，本地缓存加载线程池，动画线程池，内存缓存器，磁盘缓存工具等等);
构造完RequestManagerRetriever通过get返回一个 RequestManager(以Activity为例);
复制
//通过Activity拿到RequestManager public RequestManager get(@NonNull Activity activity) { if (Util.isOnBackgroundThread()) { //如果是子线程就用Application级别的context，也就是不进行生命周期管理 return get(activity.getApplicationContext()); } else { //检查Activity是否销毁 assertNotDestroyed(activity) //拿到当前Activity的FragmentManager android.app.FragmentManager fm = activity.getFragmentManager(); //生成一个Fragment去绑定一个请求管理RequestManager return fragmentGet( activity, fm, /*parentHint=*/ null, isActivityVisible(activity)); } }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
如果当前线程是子线程，则不需要对Glide生命周期进行管理，否则通过fragmentGet函数创建一个fragment：
复制
private RequestManager fragmentGet(@NonNull Context context, @NonNull android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint, boolean isParentVisible) { //①在当前Activity添加一个Fragment用于管理请求的生命周期 RequestManagerFragment current = getRequestManagerFragment(fm, parentHint, isParentVisible); //获取RequestManager RequestManager requestManager = current.getRequestManager(); //如果不存在RequestManager，则创建 if (requestManager == null) { Glide glide = Glide.get(context); //②构建RequestManager //current.getGlideLifecycle()就是ActivityFragmentLifecycle，也就是构建RequestManager时会传入fragment中的ActivityFragmentLifecycle requestManager = factory.build( glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context); //将构建出来的RequestManager绑定到fragment中 current.setRequestManager(requestManager); } //返回当前请求的管理者 return requestManager; }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
复制
private RequestManagerFragment getRequestManagerFragment( @NonNull final android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint, boolean isParentVisible) { //通过TAG拿到已经实例化过的fragment（也就是同一个Activity Glide.with多次，没必要创建多个fragment） RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG); if (current == null) { //如果当前Activity中没有拿到管理生命周期的fragment，那就从缓存取 current = pendingRequestManagerFragments.get(fm); if (current == null) { //如果缓存也没有，直接new一个 current = new RequestManagerFragment(); current.setParentFragmentHint(parentHint); if (isParentVisible) { //执行请求 current.getGlideLifecycle().onStart(); } //添加到Map缓存中（防止fragment重复创建） pendingRequestManagerFragments.put(fm, current); //将fragment绑定到activity fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss(); //添加后发送清理缓存 handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget(); } } return current; }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
复制
//此工厂就是为了构建出 RequestManager对象 private static final RequestManagerFactory DEFAULT_FACTORY = new RequestManagerFactory() { @NonNull @Override public RequestManager build(@NonNull Glide glide, @NonNull Lifecycle lifecycle, @NonNull RequestManagerTreeNode requestManagerTreeNode, @NonNull Context context) { //实例化一个RequestManager return new RequestManager(glide, lifecycle, requestManagerTreeNode, context); } }; public class RequestManager implements LifecycleListener, ModelTypes<RequestBuilder<Drawable>> { RequestManager( Glide glide, Lifecycle lifecycle, RequestManagerTreeNode treeNode, RequestTracker requestTracker, ConnectivityMonitorFactory factory, Context context) { this.glide = glide; this.lifecycle = lifecycle; this.treeNode = treeNode; this.requestTracker = requestTracker; this.context = context; connectivityMonitor = factory.build( context.getApplicationContext(), new RequestManagerConnectivityListener(requestTracker)); //添加生命周期监听 if (Util.isOnBackgroundThread()) { //子线程通过handler将当前对象注册到ActivityFragmentLifecycle mainHandler.post(addSelfToLifecycle); } else { //将当前对象注册到ActivityFragmentLifecycle lifecycle.addListener(this); } //添加网络变化的监听 lifecycle.addListener(connectivityMonitor); defaultRequestListeners = new CopyOnWriteArrayList<>(glide.getGlideContext().getDefaultRequestListeners()); setRequestOptions(glide.getGlideContext().getDefaultRequestOptions()); glide.registerRequestManager(this); } //... //RequestManager实现了fragment生命周期回调 @Override public synchronized void onStart() { resumeRequests(); targetTracker.onStart(); } @Override public synchronized void onStop() { pauseRequests(); targetTracker.onStop(); } @Override public 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); } }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
构建RequestManager的时候将RequestManager的生命周期与Fragment关联起来了;
复制
public class RequestManagerFragment extends Fragment { //生命周期的关键就在ActivityFragmentLifecycle private final ActivityFragmentLifecycle lifecycle; public RequestManagerFragment() { this(new ActivityFragmentLifecycle()); } RequestManagerFragment(@NonNull ActivityFragmentLifecycle lifecycle) { this.lifecycle = lifecycle; } @Override public void onStart() { super.onStart(); lifecycle.onStart(); } @Override public void onStop() { super.onStop(); lifecycle.onStop(); } @Override public void onDestroy() { super.onDestroy(); lifecycle.onDestroy(); unregisterFragmentWithRoot(); } //... }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
生命周期的关键就在lifecycle，Fragment生命周期变化时会主动通知lifecycle执行相应方法;
接着看下ActivityFragmentLifecycle：
复制
class ActivityFragmentLifecycle implements Lifecycle { //在Fragment生命周期变化时会通知所有的它的Listener private final Set<LifecycleListener> lifecycleListeners = Collections.newSetFromMap(new WeakHashMap<LifecycleListener, Boolean>()); private boolean isStarted; private boolean isDestroyed; @Override public void addListener(@NonNull LifecycleListener listener) { lifecycleListeners.add(listener); if (isDestroyed) { listener.onDestroy(); } else if (isStarted) { listener.onStart(); } else { listener.onStop(); } } @Override public void removeListener(@NonNull LifecycleListener listener) { lifecycleListeners.remove(listener); } 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(); } } }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
这个ActivityFragmentLifecycle持有一个lifecycleListeners，在Fragment生命周期变化时会通知所有的它的Listener
Glide.with(this)绑定了Activity的生命周期。在Activity内新建了一个无UI的Fragment，这个Fragment持有一个Lifecycle，通过Lifecycle在Fragment关键生命周期通知RequestManager进行相关从操作。在生命周期onStart时继续加载，onStop时暂停加载，onDestory时停止加载任务和清除操作
在构建RequestManager的时候通过lifecycle.addListener(connectivityMonitor);添加网络变化的监听 ，Fragment生命周期的变化会通知到默认实现类DefaultConnectivityMonitor中对应的方法。在onStart中registerReceiver(注册监听手机网络变化的广播)， 在onStop中unregisterReceiver。有网络重连后重启请求。
复制
final class DefaultConnectivityMonitor implements ConnectivityMonitor { private static final String TAG = "ConnectivityMonitor"; private final Context context; @SuppressWarnings("WeakerAccess") @Synthetic final ConnectivityListener listener; @SuppressWarnings("WeakerAccess") @Synthetic boolean isConnected; private boolean isRegistered; private final BroadcastReceiver connectivityReceiver = new BroadcastReceiver() { @Override public void onReceive(@NonNull Context context, Intent intent) { boolean wasConnected = isConnected; //判断网络状态 isConnected = isConnected(context); if (wasConnected != isConnected) { if (Log.isLoggable(TAG, Log.DEBUG)) { Log.d(TAG, "connectivity changed, isConnected: " + isConnected); } listener.onConnectivityChanged(isConnected); } } }; DefaultConnectivityMonitor(@NonNull Context context, @NonNull ConnectivityListener listener) { this.context = context.getApplicationContext(); this.listener = listener; } private void register() { if (isRegistered) { return; } // Initialize isConnected. isConnected = isConnected(context); try { // See #1405 context.registerReceiver(connectivityReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)); isRegistered = true; } catch (SecurityException e) { // See #1417, registering the receiver can throw SecurityException. if (Log.isLoggable(TAG, Log.WARN)) { Log.w(TAG, "Failed to register", e); } } } private void unregister() { if (!isRegistered) { return; } context.unregisterReceiver(connectivityReceiver); isRegistered = false; } @SuppressWarnings("WeakerAccess") @Synthetic // Permissions are checked in the factory instead. @SuppressLint("MissingPermission") boolean isConnected(@NonNull Context context) { ConnectivityManager connectivityManager = Preconditions.checkNotNull( (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE)); NetworkInfo networkInfo; try { networkInfo = connectivityManager.getActiveNetworkInfo(); } catch (RuntimeException e) { if (Log.isLoggable(TAG, Log.WARN)) { Log.w(TAG, "Failed to determine connectivity status when connectivity changed", e); } // Default to true; return true; } return networkInfo != null && networkInfo.isConnected(); } @Override public void onStart() { register(); } @Override public void onStop() { unregister(); } @Override public void onDestroy() { // Do nothing. } }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
回调ConnectivityListener的onConnectivityChanged来处理请求
复制
private class RequestManagerConnectivityListener implements ConnectivityMonitor.ConnectivityListener { @GuardedBy("RequestManager.this") private final RequestTracker requestTracker; RequestManagerConnectivityListener(@NonNull RequestTracker requestTracker) { this.requestTracker = requestTracker; } @Override public void onConnectivityChanged(boolean isConnected) { if (isConnected) { synchronized (RequestManager.this) { //网络重连后重启请求 requestTracker.restartRequests(); } } } }
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
使用简单
可配置度高，自适应程度高
支持常见图片格式(jpg、png、gif、webp)
支持多种数据源(网络、本地、资源、Assets等)
高效缓存策略(支持Memory和Disk图片缓存，默认Bitmap格式采用RGB_565内存小)
生命周期集成(根据Activity/Fragment生命周期自动管理请求)
高效处理Bitmap(使用BitmapPool复用Bitmap，主动调用recycle回收需要回收的Bitmap)
2、关于glide的知识点还是有很多的，我们还会继续总结分享给各位老铁们