Android 官推 kotlin-first 的图片加载库——Coil的使用入门

目录

• 一、基本使用
• 二、常用的 API

• ImageLoader
• ImageRequest
• Disposable
• 图片变换

• Interceptors
• Mappers、Fetchers
• Decoders

implementation("io.coil-kt:coil:1.1.1") 

// URL
imageView.load("https://www.example.com/image.jpg")
// Resource
imageView.load(R.drawable.image)
// File
imageView.load(File("/path/to/image.jpg"))

imageView.load("https://www.example.com/image.jpg") {
  crossfade(true)
  placeholder(R.drawable.image)
  transformations(CircleCropTransformation())
}

val imageLoader = ImageLoader.Builder(context)
  .availableMemoryPercentage(0.25)
  .crossfade(true)
  .build()

val fakeImageLoader = object : ImageLoader {
  private val drawable = ColorDrawable(Color.BLACK)
  override fun enqueue(request: ImageRequest): Disposable {
    request.target?.onStart(drawable)
    request.target?.onSuccess(drawable)
    return disposable
  }
  override suspend fun execute(request: ImageRequest): ImageResult {
    return SuccessResult(
      drawable = drawable, request = request,
      metadata = ImageResult.Metadata(
        memoryCacheKey = MemoryCache.Key(""),
        isSampled = false,
        dataSource = DataSource.MEMORY_CACHE,
        isPlaceholderMemoryCacheKeyPresent = false
      )
    )
  }
}

val request = ImageRequest.Builder(context)
  .data("https://www.example.com/image.jpg")
  .target { drawable ->
    // Handle the result.
  }
  .build()
context.imageLoader.enqueue(request) 

interface Disposable {
  /**
   * 如果图片加载请求已经完成或者取消，则返回 true
   */
  val isDisposed: Boolean
  /**
   * 取消正在进行的图片加载请求以及释放相关的资源，而且该方法是幂等的
   */
  fun dispose()
  /**
   * 非阻塞式地等待任务结束
   */
  @ExperimentalCoilApi
  suspend fun await()
}

interface Transformation {
  fun key(): String
  suspend fun transform(pool: BitmapPool, input: Bitmap, size: Size): Bitmap
}
imageView.load("https://www.example.com/image.jpg") {
  transformations(CircleCropTransformation())
}

class CustomCacheInterceptor(
  private val context: Context,
  private val cache: LruCache<String, Drawable>
) : Interceptor {
  override suspend fun intercept(chain: Interceptor.Chain): ImageResult {
    val value = cache.get(chain.request.data.toString())
    if (value != null) {
      return SuccessResult(
        drawable = value.bitmap.toDrawable(context),
        request = chain.request,
        metadata = TODO()
      )
    }
    return chain.proceed(chain.request)
  }
}

imageView.load("android.resource://example.package.name/drawable/image")
imageView.load("https://www.example.com/image.jpg")

internal class StringMapper : Mapper<String, Uri> {
  override fun map(data: String) = data.toUri()
}

internal class HttpUriFetcher(callFactory: Call.Factory) : HttpFetcher<Uri>(callFactory) {
  override fun handles(data: Uri) = data.scheme == "http" || data.scheme == "https"
  override fun key(data: Uri) = data.toString()
  override fun Uri.toHttpUrl(): HttpUrl = HttpUrl.get(toString())
}

implementation("io.coil-kt:coil-gif:1.1.1")

val imageLoader = ImageLoader.Builder(context)
  .componentRegistry {
    if (SDK_INT >= 28) {
      add(ImageDecoderDecoder())
    } else {
      add(GifDecoder())
    }
  }
  .build()

implementation("io.coil-kt:coil-svg:1.1.1")

val imageLoader = ImageLoader.Builder(context)
  .componentRegistry {
    add(SvgDecoder(context))
  }
  .build()

implementation("io.coil-kt:coil-video:1.1.1")

val imageLoader = ImageLoader.Builder(context)
  .componentRegistry {
     add(VideoFrameFileFetcher())
     add(VideoFrameUriFetcher())
  }
  .build()