Android12中的相机使用的是camera2，在vendor下的Camera2进行修改，以下修改就是将相机的默认预览尺寸改为4:3。测试后可以成功调节。

--- vendor/mediatek/proprietary/packages/apps/Camera2/feature/setting/picturesize/src/com/mediatek/camera/feature/setting/picturesize/PictureSize.java  (版本 7713)
+++ vendor/mediatek/proprietary/packages/apps/Camera2/feature/setting/picturesize/src/com/mediatek/camera/feature/setting/picturesize/PictureSize.java  (版本 7735)
@@ -256,7 +256,7 @@
             // Default picture size is the max full-ratio size.
             List<String> entryValues = getEntryValues();
             for (String value : entryValues) {
-                if (PictureSizeHelper.getStandardAspectRatio(value) == fullRatio) {
+                if (PictureSizeHelper.getStandardAspectRatio(value) == PictureSizeHelper.RATIO_4_3) {//aadded by wxw 
                     valueInStore = value;
                     break;
                 }

以下链接有详细解读：https://blog.csdn.net/an_times/article/details/119876792

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