android - 在前置摄像头上拉伸(stretch)的摄像头预览

Question

你好，我正在开发一个 Android 自定义相机应用程序，但在以下设备的前置摄像头上遇到相机预览拉伸(stretch)的问题:

1. 华为荣耀4c(仅前置摄像头)
2. HTC One M7(仅限前置摄像头)
3. 一些其他设备也...因为我只有以下设备要测试，所以问题也可能存在于其他设备上。

问题是相机预览与后置相机配合得很好，但只有当我将我的应用程序与前置相机一起使用时它才会拉伸(stretch)!

---

代码

这是我用于相机预览类的代码:

 import android.content.Context;
 import android.graphics.Rect;
 import android.hardware.Camera;
 import android.util.Log;
 import android.view.Gravity;
 import android.view.MotionEvent;
 import android.view.SurfaceHolder;
 import android.view.SurfaceView;
 import android.widget.FrameLayout;
 import android.widget.Toast;
 import java.util.ArrayList;
 import java.util.List;

 public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

//Variables de' Preview
private SurfaceHolder mHolder;
private List<Camera.Size> mSupportedPreviewSizes;
private Camera.Size mPreviewSize;
private int FOCUS_AREA_SIZE=300;
public static Camera previewCamera;
////////////////////////

//protected LOGGER keys
protected final String EXCEPTION_KEY="xception";
//////////////////////////

public CameraPreview(Context context, Camera camera) {
    super(context);

    //get the camera
    previewCamera = camera;

    // supported preview sizes
    mSupportedPreviewSizes = previewCamera.getParameters().getSupportedPreviewSizes();

    // Install a SurfaceHolder.Callback so we get notified when the
    // underlying surface is created and destroyed.
    mHolder = getHolder();
    mHolder.addCallback(this);
    // deprecated setting, but required on Android versions prior to 3.0
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    mHolder.setKeepScreenOn(true);

}


@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
    try{
        //when the surface is created, we can set the camera to draw images in this surfaceholder
        previewCamera.setPreviewDisplay(surfaceHolder);
        previewCamera.startPreview();
    } catch(Exception exp){
        Log.i(EXCEPTION_KEY,"FROM surfaceCreated: "+exp.toString());
    }
}

@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i2, int i3) {
    //before changing the application orientation, you need to stop the preview, rotate and then start it again

    if(mHolder.getSurface() == null)//check if the surface is ready to receive camera data
        return;

    try{
        previewCamera.stopPreview();
    } catch (Exception e){
        //this will happen when you are trying the camera if it's not running
    }

    //now, recreate the camera preview
    try{
        //set the camera preview on every preview change
        setPreview();
        previewCamera.setPreviewDisplay(mHolder);
        previewCamera.startPreview();
    } catch(Exception exp){
        Log.i(EXCEPTION_KEY,"FROM surfaceChanged: "+exp.toString());
    }
}


public void setPreview(){
    try{
        //set the focusable true
        this.setFocusable(true);
        //set the touch able true
        this.setFocusableInTouchMode(true);
        //set the camera display orientation lock
        previewCamera.setDisplayOrientation(90);

        //get the camera parameters
        Camera.Parameters parameters = previewCamera.getParameters();
        //set the preview size
        parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
        //set the parameter
        previewCamera.setParameters(parameters);
    }catch(Exception exp){
        Log.i(EXCEPTION_KEY,"FROM setPreview: "+exp.toString());
    }
}


@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
    //our app has only one screen, so we'll destroy the camera in the surface
    //if you are using with more screens, please move this code your activity
    try{
        //handle in Activity onResume and onPause
    }catch(Exception exp){
        Log.i(EXCEPTION_KEY,"FROM surfaceDestroyed: "+exp.toString());
    }
}

//Override Methods here
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    try{
        final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
        setMeasuredDimension(width, height);

        if (mSupportedPreviewSizes != null) {
            mPreviewSize = PreviewSizeParameters.getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
        }
    }catch(Exception exp){
        Log.i(EXCEPTION_KEY,"FROM onMeasure: "+exp.toString());
    }
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////

private void stopPreviewAndFreeCamera() {

    if (previewCamera != null) {
        // Call stopPreview() to stop updating the preview surface.
        previewCamera.stopPreview();

        // Important: Call release() to release the camera for use by other
        // applications. Applications should release the camera immediately
        // during onPause() and re-open() it during onResume()).
        previewCamera.release();

        previewCamera = null;
    }
}

//end of class here

  }

---

谁能告诉我我的代码中遗漏了什么，因为它只影响某些使用前置摄像头的设备。

---

谢谢

Answer 1

以下代码在我的环境中有效。
在 surfaceChanged 中调用 getOptimalPreviewSize 与 SurfaceView 的高度。

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

    ...

    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int w, int h) {
        //before changing the application orientation, you need to stop the preview, rotate and then start it again

        if(mHolder.getSurface() == null)//check if the surface is ready to receive camera data
            return;

        try{
            previewCamera.stopPreview();
        } catch (Exception e){
            //this will happen when you are trying the camera if it's not running
        }

        //now, recreate the camera preview
        try{
            //set the focusable true
            this.setFocusable(true);
            //set the touch able true
            this.setFocusableInTouchMode(true);
            //set the camera display orientation lock
            previewCamera.setDisplayOrientation(90);

            Camera.Parameters params = previewCamera.getParameters();
            List<Camera.Size> sizes = params.getSupportedPreviewSizes();
            Camera.Size optimalSize = getOptimalPreviewSize(sizes,w,h);
            params.setPreviewSize(optimalSize.width,optimalSize.height);
            previewCamera.setParameters(params);

            previewCamera.setPreviewDisplay(mHolder);
            previewCamera.startPreview();
        } catch(Exception exp){
            Log.i(EXCEPTION_KEY,"FROM surfaceChanged: "+exp.toString());
        }
    }

    ...

    private Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {

        final double ASPECT_TOLERANCE = 0.1;
        double targetRatio=(double)h / w;

        if (sizes == null) return null;

        Camera.Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;

        int targetHeight = h;

        for (Camera.Size size : sizes) {
            double ratio = (double) size.width / size.height;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }

        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Camera.Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }
//end of class here

}