Fix the camera preview demo.

The preview size will be checked now in Camera HAL. So, we change the code to
get the supported preview sizes and find one of the size that match the
surface's width and height.

samples/ApiDemos/src/com/example/android/apis/graphics/CameraPreview.java

@@ -19,11 +19,14 @@ package com.example.android.apis.graphics;
 import android.app.Activity;
 import android.content.Context;
 import android.hardware.Camera;
+import android.hardware.Camera.Size;
 import android.os.Bundle;
 import android.view.SurfaceHolder;
 import android.view.SurfaceView;
 import android.view.Window;
+
 import java.io.IOException;
+import java.util.List;
 
 // ----------------------------------------------------------------------
 
@@ -82,11 +85,49 @@ class Preview extends SurfaceView implements SurfaceHolder.Callback {
         mCamera = null;
     }
 
+
+    private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
+        final double ASPECT_TOLERANCE = 0.05;
+        double targetRatio = (double) w / h;
+        if (sizes == null) return null;
+
+        Size optimalSize = null;
+        double minDiff = Double.MAX_VALUE;
+
+        int targetHeight = h;
+
+        // Try to find an size match aspect ratio and size
+        for (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);
+            }
+        }
+
+        // Cannot find the one match the aspect ratio, ignore the requirement
+        if (optimalSize == null) {
+            minDiff = Double.MAX_VALUE;
+            for (Size size : sizes) {
+                if (Math.abs(size.height - targetHeight) < minDiff) {
+                    optimalSize = size;
+                    minDiff = Math.abs(size.height - targetHeight);
+                }
+            }
+        }
+        return optimalSize;
+    }
+
     public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
         // Now that the size is known, set up the camera parameters and begin
         // the preview.
         Camera.Parameters parameters = mCamera.getParameters();
-        parameters.setPreviewSize(w, h);
+
+        List<Size> sizes = parameters.getSupportedPreviewSizes();
+        Size optimalSize = getOptimalPreviewSize(sizes, w, h);
+        parameters.setPreviewSize(optimalSize.width, optimalSize.height);
+
         mCamera.setParameters(parameters);
         mCamera.startPreview();
     }