Android 低版本sdk中没有getSupportedPreviewSizes和getSupportedPictureSizes函数怎么办？

在做camera和SurfaceView做摄像头程序时，需要获取camera支持的相片大小，在低版本sdk中没有getSupportedPictureSizes函数，怎么办呢，请参阅下面的关键代码：

1、定义Size类

public class Size {

    /***

     * Sets the dimensions for pictures.

     *

     * @param w the photo width (pixels)

     * @param h the photo height (pixels)

     */

    public Size(int w, int h) {
        width = w;
        height = h;
    }

    /***

     * Compares {@code obj} to this size.

     *

     * @param obj the object to compare this size with.

     * @return {@code true} if the width and height of {@code obj} is the

     *         same as those of this size. {@code false} otherwise.

     */

    @Override

    public boolean equals(Object obj) {
        if (!(obj instanceof Size)) {
            return false;
        }
        Size s = (Size) obj;
        return width == s.width && height == s.height;
    }

    @Override

    public int hashCode() {
        return width *  + height;
    }

    /*** width of the picture */
    public int width;

    /*** height of the picture */
    public int height;
}

2、定义CameraHelper类

import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import android.hardware.Camera;
public class CameraHelper {
    private static final String KEY_PREVIEW_SIZE = "preview-size";
    private static final String KEY_PICTURE_SIZE = "picture-size";
    private static final String SUPPORTED_VALUES_SUFFIX = "-values";
    private Camera.Parameters mParms;

    public CameraHelper(Camera.Parameters parm) {
        this.mParms = parm;
    }

    public List<Size> GetSupportedPreviewSizes() {
        String str = mParms.get(KEY_PREVIEW_SIZE + SUPPORTED_VALUES_SUFFIX);
        return splitSize(str);
    }

    public List<Size> GetSupportedPictureSizes() {
        String str = mParms.get(KEY_PICTURE_SIZE + SUPPORTED_VALUES_SUFFIX);
        return splitSize(str);
    }    

    private ArrayList<Size> splitSize(String str) {
        if (str == null)
            return null;
        StringTokenizer tokenizer = new StringTokenizer(str, ",");
        ArrayList<Size> sizeList = new ArrayList<Size>();
        while (tokenizer.hasMoreElements()) {
            Size size = strToSize(tokenizer.nextToken());
            if (size != null)
                sizeList.add(size);
        }
        if (sizeList.size() == )
            return null;
        return sizeList;
    }

    private Size strToSize(String str) {
        if (str == null)
            return null;
        int pos = str.indexOf('x');
        if (pos != -) {
            String width = str.substring(, pos);
            String height = str.substring(pos + );
            return new Size(Integer.parseInt(width), Integer.parseInt(height));
        }
        return null;
    }

}

其实，主要是通过Camera.Parameters的get方法，然后再解析获取的字符串来代替那些不存在的api。