【源码阅读】Glide源码阅读之with方法（一）

骑猪看日落 2022-10-01 05:50 184阅读 0赞

### 前言 ###

本篇基于4.8.0版本

*  【源码阅读】Glide源码阅读之with方法（一）
 *  [【源码阅读】Glide源码阅读之load方法（二）][Glide_load]
 *  [【源码阅读】Glide源码阅读之into方法（三）][Glide_into]

大多数情况下，我们使用glide 就一句代码

## `Glide.with(context).load(url).into(imageView);` ##

但是这一句代码里面蕴含着成吨的代码！

`with`方法有以下几个重载方法

public static RequestManager with(@NonNull Context context) {
        return getRetriever(context).get(context);
      }
      public static RequestManager with(@NonNull Activity activity) {
        return getRetriever(activity).get(activity);
      }
      public static RequestManager with(@NonNull FragmentActivity activity) {
        return getRetriever(activity).get(activity);
      }
     public static RequestManager with(@NonNull Fragment fragment) {
        return getRetriever(fragment.getActivity()).get(fragment);
      }
      public static RequestManager with(@NonNull android.app.Fragment fragment) {
        return getRetriever(fragment.getActivity()).get(fragment);
      }
      public static RequestManager with(@NonNull View view) {
        return getRetriever(view.getContext()).get(view);
      }
    复制代码

其中，`getRetriever`返回的是个`RequestManagerRetriever`对象

private static RequestManagerRetriever getRetriever(@Nullable Context context) {
        // Context could be null for other reasons (ie the user passes in null), but in practice it will
        // only occur due to errors with the Fragment lifecycle.
        Preconditions.checkNotNull(
            context,
            "You cannot start a load on a not yet attached View or a Fragment where getActivity() "
                + "returns null (which usually occurs when getActivity() is called before the Fragment "
                + "is attached or after the Fragment is destroyed).");
        return Glide.get(context).getRequestManagerRetriever();
      }
    复制代码

接着是`RequestManagerRetriever.get`方法，在传入`Context`、`Activity`、`FragmentActivity`、`Fragment`、 `android.app.Fragment`、`View`几种情况略有不同，大致可以分为`Application`和`非Application`

*  `Application` 它生命周期即应用程序的生命周期，如果应用程序关闭的话，`Glide`的加载也会同时终止。

@NonNull
      private RequestManager getApplicationManager(@NonNull 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.
    
              // TODO(b/27524013): Factor out this Glide.get() call.
              Glide glide = Glide.get(context.getApplicationContext());
              applicationManager =
                  factory.build(
                      glide,
                      new ApplicationLifecycle(),
                      new EmptyRequestManagerTreeNode(),
                      context.getApplicationContext());
            }
          }
        }
    
        return applicationManager;
      }
    复制代码

*  `非Application` 都是向当前`Activity`添加一个隐藏的`Fragment`，当`Activity`销毁时，该`Fragment`也会销毁，销毁时，`Glide` 就会取消本次加载。

public RequestManager get(@NonNull 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);
      }
    复制代码

唯一有区别的是，`FragmentActivity`和`Fragment`使用的是`SupportRequestManagerFragment`，`Activity`使用的是`RequestManagerFragment`；`SupportRequestManagerFragment`继承的是v4包的，而`RequestManagerFragment`是继承`android.app.Fragment`。

@NonNull
      private SupportRequestManagerFragment getSupportRequestManagerFragment( @NonNull final FragmentManager fm, @Nullable Fragment parentHint, boolean isParentVisible) {
        SupportRequestManagerFragment current =
            (SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
        if (current == null) {
          current = pendingSupportRequestManagerFragments.get(fm);
          if (current == null) {
            current = new SupportRequestManagerFragment();
            current.setParentFragmentHint(parentHint);
            if (isParentVisible) {
              current.getGlideLifecycle().onStart();
            }
            pendingSupportRequestManagerFragments.put(fm, current);
            fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
            handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
          }
        }
        return current;
      }
    
    复制代码

@NonNull
      private RequestManagerFragment getRequestManagerFragment( @NonNull final android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint, boolean isParentVisible) {
        RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
        if (current == null) {
          current = pendingRequestManagerFragments.get(fm);
          if (current == null) {
            current = new RequestManagerFragment();
            current.setParentFragmentHint(parentHint);
            if (isParentVisible) {
              current.getGlideLifecycle().onStart();
            }
            pendingRequestManagerFragments.put(fm, current);
            fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
            handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget();
          }
        }
        return current;
      }
    复制代码

`SupportRequestManagerFragment`中部分代码

@Override
      public void onAttach(Context context) {
        super.onAttach(context);
        try {
          registerFragmentWithRoot(getActivity());
        } catch (IllegalStateException e) {
          // OnAttach can be called after the activity is destroyed, see #497.
          if (Log.isLoggable(TAG, Log.WARN)) {
            Log.w(TAG, "Unable to register fragment with root", e);
          }
        }
      }
    
      @Override
      public void onDetach() {
        super.onDetach();
        parentFragmentHint = null;
        unregisterFragmentWithRoot();
      }
    
      @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();
      }
    
    复制代码

`ActivityFragmentLifecycle`相关代码

@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();
        }
      }
    复制代码

### 总结：通过阅读源码，我们可以发现，`Glide`的生命周期取决于我们`with`方法传入的是`Application` 还是`非Application` ，所以，应该尽量使用`非Application`，避免造成内存泄漏。 ###

## 你的认可，是我坚持更新博客的动力，如果觉得有用，就请点个赞，谢谢 ##

转载于:https://juejin.im/post/5cb6ebcee51d456e747c5329

[Glide_load]: https://juejin.im/post/5cb7d94b6fb9a0689f4c2710
[Glide_into]: https://juejin.im/post/5cb7da2ae51d456e3d3a2bd9