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现有的3函数回调Kotlin协同程序

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我有一个具体例子的一般性问题：在拍照时，我想在Android中使用Kotlin协程魔法而不是回调地狱 .

manager.openCamera(cameraId, object : CameraDevice.StateCallback() {
    override fun onOpened(openedCameraDevice: CameraDevice) {
        println("Camera onOpened")
        // even more callbacks with openedCameraDevice.createCaptureRequest()....
    }

    override fun onDisconnected(cameraDevice: CameraDevice) {
        println("Camera onDisconnected")
        cameraDevice.close()
    }
    ...

我怎么把它转换成......错误...不那么难看的东西？ Is it possible to take an average callback with three or so functions, and turn it into a promise-chain by designating the primary flow as the promise-result path? 如果是这样，我应该/我是否应该使用协程来使其异步？

我喜欢async和.await会产生的东西

manager.open(cameraId).await().createCaptureRequest()

我试图通过以下类似的方式来做，但是......我认为我没有使用CompletableDeferred！

suspend fun CameraManager.open(cameraId:String): CameraDevice {
    val response = CompletableDeferred<CameraDevice>()
    this.openCamera(cameraId, object : CameraDevice.StateCallback() {
        override fun onOpened(cameraDevice: CameraDevice) {
            println("camera onOpened $cameraDevice")
            response.complete(cameraDevice)
        }

        override fun onDisconnected(cameraDevice: CameraDevice) {
            response.completeExceptionally(Exception("Camera onDisconnected $cameraDevice"))
            cameraDevice.close()
        }

        override fun onError(cameraDevice: CameraDevice, error: Int) {
            response.completeExceptionally(Exception("Camera onError $cameraDevice $error"))
            cameraDevice.close()
        }
    }, Handler())
    return response.await()
}
android kotlin coroutine

2 回答

  • 20

    在这种特殊情况下，您可以使用一般方法通过 suspendCoroutine 函数将基于回调的API转换为挂起函数：

    suspend fun CameraManager.openCamera(cameraId: String): CameraDevice? =
    suspendCoroutine { cont ->
        val callback = object : CameraDevice.StateCallback() {
            override fun onOpened(camera: CameraDevice) {
                cont.resume(camera)
            }

            override fun onDisconnected(camera: CameraDevice) {
                cont.resume(null)
            }

            override fun onError(camera: CameraDevice, error: Int) {
                // assuming that we don't care about the error in this example
                cont.resume(null) 
            }
        }
        openCamera(cameraId, callback, null)
    }

    现在，在您的应用程序代码中，您可以执行 manager.openCamera(cameraId) 并获取对 CameraDevice 的引用（如果已成功打开）或 null （如果不是） .

    回复于
  • 2

    我已经为这类事情使用了2种解决方案 .

    1：将接口包装在扩展中

    CameraDevice.openCamera(cameraId: Integer, 
                onOpenedCallback: (CameraDevice) -> (), 
          onDisconnectedCallback: (CameraDevice) ->()) {

    manager.openCamera(cameraId, object : CameraDevice.StateCallback() {
        override fun onOpened(openedCameraDevice: CameraDevice) {
            onOpenedCallback(openedCameraDevice)
        }

        override fun onDisconnected(cameraDevice: CameraDevice) {
            onDisconnectedCallback(cameraDevice)
        }
   })
}

    2：创建一个具有更多功能接口的简单容器类：

    class StateCallbackWrapper(val onOpened: (CameraDevice) -> (), val onClosed: (CameraDevice) ->()): CameraDevice.StateCallback() {
    override fun onOpened(openedCameraDevice: CameraDevice) {
        onOpened(openedCameraDevice)
    }

    override fun onDisconnected(cameraDevice: CameraDevice) {
        onClosed(cameraDevice)
    }
}

    就个人而言，我会从这些事情开始，然后在此基础上构建任何线程差异 .

    回复于

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