Glide源码剖析-load

本篇将分析源码Glide.load()方法

Glide源码剖析-load

将分析源码Glide.load()

load()

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Glide.with(this).load("图片资源")

load()一共有9个重载方法，都返回RequestBuilder<Drawable>

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

这些重载方法内部都会调用asDrawable().load()，这里就拿最常用的load(String string)来作为例子

我们先来看一下asDrawable()

asDrawable()

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#RequestManager
@NonNull
@CheckResult
public RequestBuilder<Drawable> asDrawable() {
  return as(Drawable.class);
}

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

上述代码就是通过使用传递进来的参数来创建一个RequestBuilder()，所以asDrawable()方法最终创建了 RequestBuilder 的实例并返回，查看RequestBuilder的构造函数：

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#RequestBuilder
  protected RequestBuilder(
      @NonNull Glide glide,
      RequestManager requestManager,
      Class<TranscodeType> transcodeClass,
      Context context) {
    this.glide = glide;
    this.requestManager = requestManager;
    this.transcodeClass = transcodeClass;
    this.context = context;
    this.transitionOptions = requestManager.getDefaultTransitionOptions(transcodeClass);
    this.glideContext = glide.getGlideContext();

    initRequestListeners(requestManager.getDefaultRequestListeners());
    apply(requestManager.getDefaultRequestOptions());
  }

构造函数里也是将参数赋值给了一些常量，之后初始化了请求监听

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initRequestListeners(requestManager.getDefaultRequestListeners());

最后调用了apply()将默认选择应用于请求

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#RequestBuilder
  @NonNull
  @CheckResult
  @Override
  public RequestBuilder<TranscodeType> apply(@NonNull BaseRequestOptions<?> requestOptions) {
    Preconditions.checkNotNull(requestOptions);
    return super.apply(requestOptions);
  }

代码很少，就执行了两个操作。先判断传入及拿来的Options是否是为空，其次调用父类的apply，将Options传入

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#BaseRequestOptions
  public T apply(@NonNull BaseRequestOptions<?> o) {
    // 基本上就是设置一些默认配置项
    if (isAutoCloneEnabled) {
      return clone().apply(o);
    }
    BaseRequestOptions<?> other = o;

    if (isSet(other.fields, SIZE_MULTIPLIER)) {
      sizeMultiplier = other.sizeMultiplier;
    }
    if (isSet(other.fields, USE_UNLIMITED_SOURCE_GENERATORS_POOL)) {
      useUnlimitedSourceGeneratorsPool = other.useUnlimitedSourceGeneratorsPool;
    }
    if (isSet(other.fields, USE_ANIMATION_POOL)) {
      useAnimationPool = other.useAnimationPool;
    }
    if (isSet(other.fields, DISK_CACHE_STRATEGY)) {
      diskCacheStrategy = other.diskCacheStrategy;
    }
    if (isSet(other.fields, PRIORITY)) {
      priority = other.priority;
    }
    if (isSet(other.fields, ERROR_PLACEHOLDER)) {
      errorPlaceholder = other.errorPlaceholder;
      errorId = 0;
      fields &= ~ERROR_ID;
    }
    if (isSet(other.fields, ERROR_ID)) {
      errorId = other.errorId;
      errorPlaceholder = null;
      fields &= ~ERROR_PLACEHOLDER;
    }
    if (isSet(other.fields, PLACEHOLDER)) {
      placeholderDrawable = other.placeholderDrawable;
      placeholderId = 0;
      fields &= ~PLACEHOLDER_ID;
    }
    if (isSet(other.fields, PLACEHOLDER_ID)) {
      placeholderId = other.placeholderId;
      placeholderDrawable = null;
      fields &= ~PLACEHOLDER;
    }
    if (isSet(other.fields, IS_CACHEABLE)) {
      isCacheable = other.isCacheable;
    }
    if (isSet(other.fields, OVERRIDE)) {
      overrideWidth = other.overrideWidth;
      overrideHeight = other.overrideHeight;
    }
    if (isSet(other.fields, SIGNATURE)) {
      signature = other.signature;
    }
    if (isSet(other.fields, RESOURCE_CLASS)) {
      resourceClass = other.resourceClass;
    }
    if (isSet(other.fields, FALLBACK)) {
      fallbackDrawable = other.fallbackDrawable;
      fallbackId = 0;
      fields &= ~FALLBACK_ID;
    }
    if (isSet(other.fields, FALLBACK_ID)) {
      fallbackId = other.fallbackId;
      fallbackDrawable = null;
      fields &= ~FALLBACK;
    }
    if (isSet(other.fields, THEME)) {
      theme = other.theme;
    }
    if (isSet(other.fields, TRANSFORMATION_ALLOWED)) {
      isTransformationAllowed = other.isTransformationAllowed;
    }
    if (isSet(other.fields, TRANSFORMATION_REQUIRED)) {
      isTransformationRequired = other.isTransformationRequired;
    }
    if (isSet(other.fields, TRANSFORMATION)) {
      transformations.putAll(other.transformations);
      isScaleOnlyOrNoTransform = other.isScaleOnlyOrNoTransform;
    }
    if (isSet(other.fields, ONLY_RETRIEVE_FROM_CACHE)) {
      onlyRetrieveFromCache = other.onlyRetrieveFromCache;
    }

    // Applying options with dontTransform() is expected to clear our transformations.
    if (!isTransformationAllowed) {
      transformations.clear();
      fields &= ~TRANSFORMATION;
      isTransformationRequired = false;
      fields &= ~TRANSFORMATION_REQUIRED;
      isScaleOnlyOrNoTransform = true;
    }

    fields |= other.fields;
    options.putAll(other.options);

    return selfOrThrowIfLocked();
  }

isSet()：将两个Int类型参数进行与运算。（就是比较二进制数，是1为1，否则为0）

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private static boolean isSet(int fields, int flag) {
 return (fields & flag) != 0;
}

上面基本上都是在配置配置项，包括磁盘缓存策略，加载中的占位图，加载失败的占位图等。 到这里 asDrawable() 方法完成了。接下来查看load部分

asDrawable().load()

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#RequestBuilder
  @NonNull
  @Override
  @CheckResult
  public RequestBuilder<TranscodeType> load(@Nullable String string) {
    return loadGeneric(string);
  }

里面也就调用了loadGeneric()

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#RequestBuilder
  @NonNull
  private RequestBuilder<TranscodeType> loadGeneric(@Nullable Object model) {
    if (isAutoCloneEnabled()) {
      return clone().loadGeneric(model);
    }
    this.model = model;
    isModelSet = true;
    return selfOrThrowIfLocked();
  }

  1. 先判断需不需要进行克隆，需要的话则会将克隆一个RequestBuilder，包括目前为止的所有配置项

    返回此请求生成器的副本，其中包含到目前为止在此生成器上放置的所有选项。

    该方法返回一个“深度”副本，其中所有非不可变参数都被复制，这样对一个构建器的更改不会影响到另一个构建器。 然而，除了不可变参数外，当前模型不会被复制，因此对模型的更改将影响两个构建器。

    [^Ps]: 以上内容来自有道翻译

  2. 将传入进来的图片资源赋值给成员变量model，在设置isModelSet为true，代表着已经设置过了

总结

load()方法就比较简单了，主要就是通过之前创建的Glide和RequestManager来构建RequestBuilder，将参数赋值给成员变量model。还要就是设置一些默认配置项