Glide Request

Glide在加载图片的第一步既是初始化Glide实例

接着就会获取RequestManager，然后初始化一个RequestBuilder构建一个Request，

本文会对于Glide的RequestBuilder实例化过程做解析

begin

Glide的创建是在Glide.with内部进行的，通过with以后就能得到一个RequestManager的实例化对象

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Glide.with(this)

RequestManager

关于RequestManager公开的api如下

  • request hook

addDefaultRequestListener

为所有由该RequestManager构建的Request添加监听。

applyDefaultRequestOptions

对Request进行默认配置

  • 加载任务

as

进行RequestBuilder的实例化

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public <ResourceType> RequestBuilder<ResourceType> as(
    @NonNull Class<ResourceType> resourceClass) {
  return new RequestBuilder<>(glide, this, resourceClass, context);
}

asXX

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public RequestBuilder<Bitmap> asBitmap() {
    return as(Bitmap.class).apply(DECODE_TYPE_BITMAP);
}

public RequestBuilder<GifDrawable> asGif() {
    return as(GifDrawable.class).apply(DECODE_TYPE_GIF);
}

public RequestBuilder<Drawable> asDrawable() {
  return as(Drawable.class);
}

public RequestBuilder<File> asFile() {
    return as(File.class).apply(skipMemoryCacheOf(true));
}

public RequestBuilder<File> downloadOnly() {
    return as(File.class).apply(DOWNLOAD_ONLY_OPTIONS);
}
  • 其他

setPauseAllRequestsOnTrimMemoryModerate

在内存不足时暂停所有的请求

clear

取消Glide任务加载

RequestBuilder

Request的配置是通过RequestBuilder进行的，他会承载一些Request的参数信息

  • addListener
  • listener
  • load
  • error
  • thumbnail
  • transition
  • fallback
  • override
  • placeholder
  • transform
  • centerCrop

……

Request是如何被创建的

Request的创建是由RequestManager开启

asXXX方法几乎是RequestBuilder创建的唯一途径

而asXXX底层又调用了as方法

Glide默认只支持Bitmap，Gif，File，Drawable类型的配置。

image-20230516220234895

其中RequestBuilder的创建也很干脆

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public <ResourceType> RequestBuilder<ResourceType> as(
    @NonNull Class<ResourceType> resourceClass) {
  return new RequestBuilder<>(glide, this, resourceClass, context);
}
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protected RequestBuilder(
    @NonNull Glide glide,
    RequestManager requestManager,
    Class<TranscodeType> transcodeClass,
    Context context) {
    // 成员初始化
  this.glide = glide;
  this.requestManager = requestManager;
  this.transcodeClass = transcodeClass;
  this.context = context;
  this.transitionOptions = requestManager.getDefaultTransitionOptions(transcodeClass);
  this.glideContext = glide.getGlideContext();
	// 加入监听
  initRequestListeners(requestManager.getDefaultRequestListeners());
    // 应用默认配置
  apply(requestManager.getDefaultRequestOptions());
}

Request是如何进行配置的

RequestBuilder使用了建筑者模式，无非就是进行大量参数的配置。

也就是成员变量的设置

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public RequestBuilder<TranscodeType> transition(
    @NonNull TransitionOptions<?, ? super TranscodeType> transitionOptions) {
  if (isAutoCloneEnabled()) {
    return clone().transition(transitionOptions);
  }
  this.transitionOptions = Preconditions.checkNotNull(transitionOptions);
  isDefaultTransitionOptionsSet = false;
  return selfOrThrowIfLocked();
}
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public T error(@DrawableRes int resourceId) {
  if (isAutoCloneEnabled) {
    return clone().error(resourceId);
  }
  this.errorId = resourceId;
  fields |= ERROR_ID;

  this.errorPlaceholder = null;
  fields &= ~ERROR_PLACEHOLDER;

  return selfOrThrowIfLocked();
}
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public RequestBuilder<TranscodeType> addListener(
    @Nullable RequestListener<TranscodeType> requestListener) {
  if (isAutoCloneEnabled()) {
    return clone().addListener(requestListener);
  }
  if (requestListener != null) {
    if (this.requestListeners == null) {
      this.requestListeners = new ArrayList<>();
    }
    this.requestListeners.add(requestListener);
  }
  return selfOrThrowIfLocked();
}

之后不再一一例举