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。
前言
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
一、Glide生命周期原理详解
- 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、Glide.with(this)
with方法可以接受Context,Activity,FragmentActivity,Fragment和View不同的类型
- 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;
- }
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);
- //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));
- }
- }
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:
- 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;
- }
2、Fragment与Activity的绑定—>getRequestManagerFragment:
- 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;
- }
3、构建RequestManager并设置监听
- //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);
- }
- }
构建RequestManager的时候将RequestManager的生命周期与Fragment关联起来了;
4、Fragment是依附在Activity,所以Activity的生命周期在Fragment中都有,接着我们来看下RequestManagerFragment:
- 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();
- }
- //...
- }
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:
- 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();
- }
- }
- }
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
二、Glide如何监听网络变化
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。
- 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.
- }
- }
回调ConnectivityListener的onConnectivityChanged来处理请求
- 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();
- }
- }
- }
- }
总结
1、Glide使用特点:
- 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