android camera2实现自动对焦，点击屏幕后坐标转换后进行对焦

要实现Android Camera2的自动对焦功能，需要使用Camera2 API中的AutoFocus类。首先，在CameraCaptureSession.CaptureCallback的onCaptureCompleted()方法中，您需要检查CaptureResult的CONTROL_AF_STATE是否为FOCUSED_LOCKED或FOCUSING_LOCKED。如果是，则对焦已完成。

在点击屏幕后，您需要将屏幕上的坐标转换为相机预览视图上的坐标，然后使用CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE属性来计算相应的焦点区域。最后，您可以使用CaptureRequest.CONTROL_AF_REGIONS和CaptureRequest.CONTROL_AF_MODE属性来设置相应的焦点区域和对焦模式。

以下是一个示例代码，可以帮助您实现这个功能：

private void setAutoFocus(int x, int y) {
    try {
        // Convert touch position to focus area
        Rect rect = getCameraFocusRect(x, y);

        // Calculate focus metering area
        MeteringRectangle[] meteringRectangle = new MeteringRectangle[] {
            new MeteringRectangle(rect, MeteringRectangle.METERING_WEIGHT_MAX)
        };

        // Create capture request builder
        CaptureRequest.Builder builder =
            mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);

        // Set focus and metering areas
        builder.set(CaptureRequest.CONTROL_AF_REGIONS, meteringRectangle);
        builder.set(CaptureRequest.CONTROL_AE_REGIONS, meteringRectangle);
        builder.set(CaptureRequest.CONTROL_AF_MODE,
            CaptureRequest.CONTROL_AF_MODE_AUTO);
        builder.set(CaptureRequest.CONTROL_AE_MODE,
            CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

        // Send capture request
        mCaptureSession.setRepeatingRequest(builder.build(), mCaptureCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

private Rect getCameraFocusRect(int x, int y) {
    // Get active sensor size
    Size sensorSize = mCameraCharacteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);

    // Convert screen coordinates to view coordinates
    float viewX = x / (float) mPreviewView.getWidth();
    float viewY = y / (float) mPreviewView.getHeight();

    // Calculate focus rect coordinates
    int rectLeft = (int) ((viewX * sensorSize.width) - 100);
    int rectTop = (int) ((viewY * sensorSize.height) - 100);
    int rectRight = rectLeft + 200;
    int rectBottom = rectTop + 200;

    // Limit focus rect coordinates to sensor size
    rectLeft = Math.max(rectLeft, 0);
    rectTop = Math.max(rectTop, 0);
    rectRight = Math.min(rectRight, sensorSize.width);
    rectBottom = Math.min(rectBottom, sensorSize.height);

    // Create focus rect
    return new Rect(rectLeft, rectTop, rectRight, rectBottom);
}

private CameraCaptureSession.CaptureCallback mCaptureCallback =
    new CameraCaptureSession.CaptureCallback() {

    @Override
    public void onCaptureCompleted(@NonNull CameraCaptureSession session,
            @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
        super.onCaptureCompleted(session, request, result);

        // Check autofocus state
        Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
        if (afState == null) {
            return;
        }

        switch (afState) {
            case CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED:
            case CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED:
                // Auto-focus has completed
                break;
        }
    }
};

在上面的代码中，我们首先在setAutoFocus()方法中将屏幕上的坐标转换为相机预览视图上的焦点区域。然后，我们使用CaptureRequest.CONTROL_AF_REGIONS和CaptureRequest.CONTROL_AF_MODE属性来设置相应的焦点区域和对焦模式。最后，我们将该捕获请求发送到相机设备并设置回调以接收自动对焦完成事件。

请注意，如果您的相机设备不支持自动对焦，则可能需要手动对焦。