Android相机预览被拉伸

对于你来说可能有点晚了，但希望对其他人有所帮助。

你可以使用属性来确保特定比例：

layout_constraintDimensionRatio="ration_a:ratio_b"

它解决了我的问题。

我的要求是相机预览需要全屏并保持纵横比。

Hesam和Yoosuf的解决方案很棒，但出现了高变焦问题，原因不明。

思路是一样的，将预览容器居中在父容器中，并根据纵横比增加宽度或高度，直到覆盖整个屏幕。

需要注意的一点是，预览大小是横向的，因为我们设置了显示方向。

camera.setDisplayOrientation(90);

我们将把SurfaceView视图添加到的容器：

<RelativeLayout
    android:id="@+id/camera_preview_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_centerInParent="true"/>

在您的活动中，将预览与父级居中并添加到其容器中。

this.cameraPreview = new CameraPreview(this, camera);
cameraPreviewContainer.removeAllViews();
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(
    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
params.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
cameraPreviewContainer.addView(cameraPreview, 0, params);

在CameraPreview类内部：

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    // If your preview can change or rotate, take care of those events here.
    // Make sure to stop the preview before resizing or reformatting it.

    if (holder.getSurface() == null) {
        // preview surface does not exist
        return;
    }

    stopPreview();

    // set preview size and make any resize, rotate or
    // reformatting changes here
    try {
        Camera.Size nativePictureSize = CameraUtils.getNativeCameraPictureSize(camera);
        Camera.Parameters parameters = camera.getParameters();
        parameters.setPreviewSize(optimalSize.width, optimalSize.height);
        parameters.setPictureSize(nativePictureSize.width, nativePictureSize.height);
        camera.setParameters(parameters);
        camera.setDisplayOrientation(90);
        camera.setPreviewDisplay(holder);
        camera.startPreview();

    } catch (Exception e){
        Log.d(TAG, "Error starting camera preview: " + e.getMessage());
    }
}

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

    if (supportedPreviewSizes != null && optimalSize == null) {
        optimalSize = CameraUtils.getOptimalSize(supportedPreviewSizes, width, height);
        Log.i(TAG, "optimal size: " + optimalSize.width + "w, " + optimalSize.height + "h");
    }

    float previewRatio =  (float) optimalSize.height / (float) optimalSize.width;
    // previewRatio is height/width because camera preview size are in landscape.
    float measuredSizeRatio = (float) width / (float) height;

    if (previewRatio >= measuredSizeRatio) {
        measuredHeight = height;
        measuredWidth = (int) ((float)height * previewRatio);
    } else {
        measuredWidth = width;
        measuredHeight = (int) ((float)width / previewRatio);
    }
    Log.i(TAG, "Preview size: " + width + "w, " + height + "h");
    Log.i(TAG, "Preview size calculated: " + measuredWidth + "w, " + measuredHeight + "h");

    setMeasuredDimension(measuredWidth, measuredHeight);
}

以下解决方案是对 @Hesam 的 答案 进行的更新，解决了以下问题：

1. 在某些屏幕上，最终视图会变形。

2. 预览位于屏幕顶部，不居中，看起来非常奇怪。

---

你只需要像这样更新onMeasure，其他所有内容保持不变。

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {


    final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
    final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);

    //centralize preview
    FrameLayout.LayoutParams surfaceParams = new FrameLayout.LayoutParams(width, (int) height);
    surfaceParams.gravity = Gravity.CENTER;
    this.setLayoutParams(surfaceParams);

    if (mSupportedPreviewSizes != null) {
        mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
    }

    if (mPreviewSize != null) {
        float ratio;
        if (mPreviewSize.height >= mPreviewSize.width)
            ratio = (float) mPreviewSize.height / (float) mPreviewSize.width;
        else
            ratio = (float) mPreviewSize.width / (float) mPreviewSize.height;

        setMeasuredDimension(width, (int) (width * ratio));


        //fix distortion, based on this answer https://dev59.com/DGIk5IYBdhLWcg3wG63b#30634009
        float camHeight = (int) (width * ratio);
        float newCamHeight;
        float newHeightRatio;

        if (camHeight < height) {
            newHeightRatio = (float) height / (float) mPreviewSize.height;
            newCamHeight = (newHeightRatio * camHeight);
            Log.e(TAG, camHeight + " " + height + " " + mPreviewSize.height + " " + newHeightRatio + " " + newCamHeight);
            setMeasuredDimension((int) (width * newHeightRatio), (int) newCamHeight);
            Log.e(TAG, mPreviewSize.width + " | " + mPreviewSize.height + " | ratio - " + ratio + " | H_ratio - " + newHeightRatio + " | A_width - " + (width * newHeightRatio) + " | A_height - " + newCamHeight);
        } else {
            newCamHeight = camHeight;
            setMeasuredDimension(width, (int) newCamHeight);
            Log.e(TAG, mPreviewSize.width + " | " + mPreviewSize.height + " | ratio - " + ratio + " | A_width - " + (width) + " | A_height - " + newCamHeight);
        }
    }
}

您必须根据所需的长宽比设置cameraView.getLayoutParams().height和cameraView.getLayoutParams().width。

我放弃了计算，只是获取我想要相机预览显示的视图的大小，并在我的自定义SurfaceView实现中设置相机的预览大小相同（由于旋转而翻转宽度/高度）：

@Override // CameraPreview extends SurfaceView implements SurfaceHolder.Callback { 
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    Display display = ((WindowManager) getContext().getSystemService(
            Context.WINDOW_SERVICE)).getDefaultDisplay();

    if (display.getRotation() == Surface.ROTATION_0) {
        final Camera.Parameters params = camera.getParameters();
        // viewParams is from the view where the preview is displayed
        params.setPreviewSize(viewParams.height, viewParams.width);
        camera.setDisplayOrientation(90);
        requestLayout();
        camera.setParameters(params);
    }
    // I do not enable rotation, so this can otherwise stay as is
}