【源码阅读】Glide源码阅读之load方法（二）

前言

上一篇中，我们阅读了glide的with方法的相关代码，这一篇，我们来看看load方法。

• 【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）
• 【源码阅读】Glide源码阅读之into方法（三）

首先，load方法有以下几个重载方法：

  public RequestBuilder<Drawable> load(@Nullable Bitmap bitmap) {
    return asDrawable().load(bitmap);
  }
  public RequestBuilder<Drawable> load(@Nullable Drawable drawable) {
    return asDrawable().load(drawable);
  }
  public RequestBuilder<Drawable> load(@Nullable String string) {
    return asDrawable().load(string);
  }
  public RequestBuilder<Drawable> load(@Nullable Uri uri) {
    return asDrawable().load(uri);
  }
  public RequestBuilder<Drawable> load(@Nullable File file) {
    return asDrawable().load(file);
  }
  public RequestBuilder<Drawable> load(@RawRes @DrawableRes @Nullable Integer resourceId) {
    return asDrawable().load(resourceId);
  }
 public RequestBuilder<Drawable> load(@Nullable byte[] model) {
    return asDrawable().load(model);
  }
public RequestBuilder<Drawable> load(@Nullable URL url) {
    return asDrawable().load(url);
  }
 public RequestBuilder<Drawable> load(@Nullable Object model) {
    return asDrawable().load(model);
  }

我们发现，调用的都是 asDrawable().load(model)方法，再来看看asDrawable方法

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

我们可以看到，这里创建了一个RequestBuilder，并且指定了ResourceType为Drawable，同理的还有asFile、asGif、asBitmap方法

  public RequestBuilder<File> asFile() {
    return as(File.class).apply(skipMemoryCacheOf(true));
  }
  public RequestBuilder<GifDrawable> asGif() {
    return as(GifDrawable.class).apply(DECODE_TYPE_GIF);
  }
  public RequestBuilder<Bitmap> asBitmap() {
    return as(Bitmap.class).apply(DECODE_TYPE_BITMAP);
  }

接着，我们再看RequestBuilder的load方法

  public RequestBuilder<TranscodeType> load(@Nullable String string) {
    return loadGeneric(string);
  }
 public RequestBuilder<TranscodeType> load(@Nullable Drawable drawable) {
    return loadGeneric(drawable)
        .apply(diskCacheStrategyOf(DiskCacheStrategy.NONE));
  }
 public RequestBuilder<TranscodeType> load(@Nullable Bitmap bitmap) {
    return loadGeneric(bitmap)
        .apply(diskCacheStrategyOf(DiskCacheStrategy.NONE));
  }
  public RequestBuilder<TranscodeType> load(@Nullable Uri uri) {
    return loadGeneric(uri);
  }
public RequestBuilder<TranscodeType> load(@Nullable File file) {
    return loadGeneric(file);
  }
public RequestBuilder<TranscodeType> load(@RawRes @DrawableRes @Nullable Integer resourceId) {
    return loadGeneric(resourceId).apply(signatureOf(ApplicationVersionSignature.obtain(context)));
  }
public RequestBuilder<TranscodeType> load(@Nullable URL url) {
    return loadGeneric(url);
  }
 public RequestBuilder<TranscodeType> load(@Nullable byte[] model) {
    RequestBuilder<TranscodeType> result = loadGeneric(model);
    if (!result.requestOptions.isDiskCacheStrategySet()) {
        result = result.apply(diskCacheStrategyOf(DiskCacheStrategy.NONE));
    }
    if (!result.requestOptions.isSkipMemoryCacheSet()) {
      result = result.apply(skipMemoryCacheOf(true /*skipMemoryCache*/));
    }
    return result;
  }

可以看到，最后调用的都是loadGeneric方法，来看看loadGeneric的源码

private RequestBuilder<TranscodeType> loadGeneric(@Nullable Object model) {
    this.model = model;
    isModelSet = true;
    return this;
  }

。。。。。。就只是做了个变量的赋值，同样的还有其他一些常用的方法：apply、transition、listener、addListener、error等方法

 public RequestBuilder<TranscodeType> apply(@NonNull RequestOptions requestOptions) {
    Preconditions.checkNotNull(requestOptions);
    this.requestOptions = getMutableOptions().apply(requestOptions);
    return this;
  }
 public RequestBuilder<TranscodeType> transition(
      @NonNull TransitionOptions<?, ? super TranscodeType> transitionOptions) {
    this.transitionOptions = Preconditions.checkNotNull(transitionOptions);
    isDefaultTransitionOptionsSet = false;
    return this;
  }
  public RequestBuilder<TranscodeType> listener(
      @Nullable RequestListener<TranscodeType> requestListener) {
    this.requestListeners = null;
    return addListener(requestListener);
  }
public RequestBuilder<TranscodeType> addListener(
      @Nullable RequestListener<TranscodeType> requestListener) {
    if (requestListener != null) {
      if (this.requestListeners == null) {
        this.requestListeners = new ArrayList<>();
      }
      this.requestListeners.add(requestListener);
    }
    return this;
  }
public RequestBuilder<TranscodeType> error(@Nullable RequestBuilder<TranscodeType> errorBuilder) {
    this.errorBuilder = errorBuilder;
    return this;
  }

总结：通过with和load方法，Glide创建了一个RequestBuilder，它里面保存了请求需要的相关信息。

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