Android相机API详解-优快云博客

和你一起终身学习，这里是程序员Android

本篇文章主要介绍 Android 开发中的部分知识点，通过阅读本篇文章，您将收获以下内容:

一、openCamera 简单调用流程
二、CameraManager.getCameraCharacteristics 获取方法
三、supportsCamera2ApiLocked
四、CameraService.connectDevice
五、CameraManager.setRemoteDevice

一、openCamera 简单调用流程

打开相机是通过调用CameraManager.java (frameworks\base\core\java\android\hardware\camera2)的 openCamera 方法，根据指定的CameraId 打开。

1.1 CameraManager.openCamera 方法

cameraId 是一个标识，标识当前要打开的camera
callback 是一个状态回调，当前camera被打开的时候，这个状态回调会被触发的。
handler 是传入的一个执行耗时操作的handler
executor 操作线程池

    public void openCamera(@NonNull String cameraId...)
            throws CameraAccessException {
        // 通过Camera Id 打开Camera，调用1.2 openCameraForUid
        openCameraForUid(cameraId, callback, CameraDeviceImpl.checkAndWrapHandler(handler),
                USE_CALLING_UID);
    }
    public void openCamera(@NonNull String cameraId,
            @NonNull @CallbackExecutor Executor executor,
            @NonNull final CameraDevice.StateCallback callback)

1.2 CameraManager.openCameraForUid 方法

    public void openCameraForUid(@NonNull String cameraId,
          .... ... )
            throws CameraAccessException {
        ... ...
        //调用异步 Camera 助手 打开Camera ，调用 1.3 openCameraDeviceUserAsync
        openCameraDeviceUserAsync(cameraId, callback, executor, clientUid);
    }

1.3 CameraManager.openCameraDeviceUserAsync 方法

获取当前cameraId指定相机的设备信息
利用获取相机的设备信息创建CameraDeviceImpl实例
调用远程CameraService获取当前相机的远程服务
将获取的远程服务设置到CameraDeviceImpl实例中
返回CameraDeviceImpl实例

private CameraDevice openCameraDeviceUserAsync(String cameraId,... ...)
            throws CameraAccessException {
       //通过CamerService 获取CameraDevices的   Camera的设备信息 ，参考 二、getCameraCharacteristics 获取方法
        CameraCharacteristics characteristics = getCameraCharacteristics(cameraId);
        CameraDevice device = null;
            ... ...
            //  New 一个CameraDeviceImpl对象实例
            android.hardware.camera2.impl.CameraDeviceImpl deviceImpl =
                    new android.hardware.camera2.impl.CameraDeviceImpl(
                        cameraId,
                        callback,
                        executor,
                        characteristics,
                        mContext.getApplicationInfo().targetSdkVersion);

            ICameraDeviceCallbacks callbacks = deviceImpl.getCallbacks();

            try {
               //判断是否支持 Camera2API
                // 参考 三、supportsCamera2ApiLocked
                if (supportsCamera2ApiLocked(cameraId)) {
                    // Use cameraservice's cameradeviceclient implementation for HAL3.2+ devices
                    ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
                    if (cameraService == null) {
                        throw new ServiceSpecificException(
                            ICameraService.ERROR_DISCONNECTED,
                            "Camera service is currently unavailable");
                    }
                     //调用远程CameraService获取当前相机的远程服务
                     // 参考四、CameraService.connectDevice
                    cameraUser = cameraService.connectDevice(callbacks, cameraId,
                            mContext.getOpPackageName(), uid);
                } else {
                   ... ...
                }
            } catch (ServiceSpecificException e) {
              ... ...
            } catch (RemoteException e) {
              ... ...
            }

            // TODO: factor out callback to be non-nested, then move setter to constructor
            // For now, calling setRemoteDevice will fire initial
            // onOpened/onUnconfigured callbacks.
            // This function call may post onDisconnected and throw CAMERA_DISCONNECTED if
            // cameraUser dies during setup.
           //将获取的远程服务设置到CameraDeviceImpl实例中
            // 参考 五、setRemoteDevice 方法
            deviceImpl.setRemoteDevice(cameraUser);
            device = deviceImpl;
        }
        //返回CameraDeviceImpl实例
        return device;
    }