Android 开发 Camera2开发_3_处理预览和拍照偏暗问题 通过调整曝光解决

//设置预览请求的方式
previewBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
 
...
 
//自动对焦
previewBuilder.set(CaptureRequest.CONTROL_AF_MODE,CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
//设置自动曝光帧率范围
previewBuilder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE,getRange());
 //对焦触发器设置为空闲状态
previewBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,CaptureRequest.CONTROL_AF_TRIGGER_IDLE);
captureSession.setRepeatingRequest(previewBuilder.build(),captureCallback, mainHandler);
 
 private Range<Integer> getRange() {
        CameraManager mCameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
        CameraCharacteristics chars = null;
        try {
            chars = mCameraManager.getCameraCharacteristics(cameraID);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
        Range<Integer>[] ranges = chars.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES);
 
        Range<Integer> result = null;
 
        for (Range<Integer> range : ranges) {
            //帧率不能太低，大于10
            if (range.getLower()<10)
                continue;
            if (result==null)
                result = range;
            //FPS下限小于15，弱光时能保证足够曝光时间，提高亮度。range范围跨度越大越好，光源足够时FPS较高，预览更流畅，光源不够时FPS较低，亮度更好。
            else if (range.getLower()<=15 && (range.getUpper()-range.getLower())>(result.getUpper()-result.getLower()))
                result = range;
        }
        return result;
    }