Camera2 API竖屏预览拉伸问题求助（三星Android9已试多方案无效）

Hey there, let's tackle this stubborn Samsung Android 9 Camera2 preview stretching issue in portrait mode. I’ve dealt with similar device-specific quirks before, so here are targeted fixes that should work:

Samsung's Android 9 ROM has a unique quirk in how it calculates TextureView transformation matrices for portrait mode. Skip the default AutoFitTextureView logic and manually adjust the matrix with these steps:

• In the onSurfaceTextureAvailable callback, fetch camera sensor orientation and your selected preview size first:

  CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraId);
  int sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
  Size previewSize = // Your chosen optimal preview size
  

• Calculate the correct scale and apply the matrix with Samsung-specific adjustments:

  float ratio;
  int viewWidth = textureView.getWidth();
  int viewHeight = textureView.getHeight();
  Configuration config = getResources().getConfiguration();
  
  if (config.orientation == Configuration.ORIENTATION_PORTRAIT) {
      // Swap width/height ratio for Samsung's portrait handling
      ratio = (float) previewSize.getHeight() / previewSize.getWidth();
      float scaleX, scaleY;
      
      if (sensorOrientation == 90 || sensorOrientation == 270) {
          scaleX = ratio;
          scaleY = 1.0f;
          // Adjust scale to fit view without stretching
          if (scaleX * viewWidth < viewHeight) {
              scaleX = (float) viewHeight / viewWidth / ratio;
          } else {
              scaleY = (float) viewWidth / viewHeight * ratio;
          }
      } else {
          scaleX = 1.0f;
          scaleY = ratio;
          if (scaleY * viewHeight < viewWidth) {
              scaleY = (float) viewWidth / viewHeight / ratio;
          } else {
              scaleX = (float) viewHeight / viewWidth * ratio;
          }
      }
      
      // Apply transformation matrix with rotation and center alignment
      Matrix matrix = new Matrix();
      matrix.setScale(scaleX, scaleY);
      matrix.postRotate(90); // Match portrait orientation
      float centerX = viewWidth / 2f;
      float centerY = viewHeight / 2f;
      matrix.postTranslate(
          (viewWidth - previewSize.getHeight() * scaleX) / 2,
          (viewHeight - previewSize.getWidth() * scaleY) / 2
      );
      textureView.setTransform(matrix);
  }
  

Some Samsung devices force stretching instead of cropping when preview size aspect ratio doesn't match the screen. Filter supported sizes to find an exact match:

• Use this method to pick the optimal size:

  private Size chooseOptimalSize(Size[] choices, int viewWidth, int viewHeight) {
      List<Size> exactMatches = new ArrayList<>();
      float targetRatio;
      Configuration config = getResources().getConfiguration();
      
      // Adjust target ratio for portrait mode
      if (config.orientation == Configuration.ORIENTATION_PORTRAIT) {
          targetRatio = (float) viewHeight / viewWidth;
      } else {
          targetRatio = (float) viewWidth / viewHeight;
      }
      
      // Find sizes with exact aspect ratio match
      for (Size size : choices) {
          float sizeRatio = (float) size.getWidth() / size.getHeight();
          if (Math.abs(sizeRatio - targetRatio) < 0.001f) {
              exactMatches.add(size);
          }
      }
      
      // Pick the largest exact match for best resolution
      if (!exactMatches.isEmpty()) {
          return Collections.max(exactMatches, (a, b) -> Long.compare(
              (long) a.getWidth() * a.getHeight(),
              (long) b.getWidth() * b.getHeight()
          ));
      }
      
      // Fallback to closest match if no exact fit
      Size bestFit = choices[0];
      float smallestDiff = Float.MAX_VALUE;
      for (Size size : choices) {
          float sizeRatio = (float) size.getWidth() / size.getHeight();
          float diff = Math.abs(sizeRatio - targetRatio);
          if (diff < smallestDiff) {
              smallestDiff = diff;
              bestFit = size;
          }
      }
      return bestFit;
  }
  

• Important: Pass the actual measured width/height of your TextureView (not the full screen resolution) to account for status/navigation bars.

If the above fixes fail, some Samsung Android 9 builds have bugs with TextureView hardware acceleration. Try disabling it:

• In your layout XML:

  <AutoFitTextureView
      android:id="@+id/textureView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:hardwareAccelerated="false" />
  

• Or programmatically:

  textureView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
  

Note: This may reduce preview performance, so only use it as a last resort.

内容的提问来源于stack exchange，提问作者Erum