Android 根据屏幕尺寸适配控件尺寸（按比例缩放）

在做facebook登录时，正好看到其SDK中一段代码，可以根据屏幕像素适配自己的控件的大小，虽然自己以前也做过类似的逻辑，但不如人家的逻辑来的严谨，这里贴出来学习一下：

    // width below which there are no extra margins
    private static final int NO_PADDING_SCREEN_WIDTH = 480;
    // width beyond which we're always using the MIN_SCALE_FACTOR
    private static final int MAX_PADDING_SCREEN_WIDTH = 800;
    // height below which there are no extra margins
    private static final int NO_PADDING_SCREEN_HEIGHT = 800;
    // height beyond which we're always using the MIN_SCALE_FACTOR
    private static final int MAX_PADDING_SCREEN_HEIGHT = 1280;

private void calculateSize() {
        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();
        DisplayMetrics metrics = new DisplayMetrics();
        display.getMetrics(metrics);
        // always use the portrait dimensions to do the scaling calculations so we always get a portrait shaped
        // web dialog
        int width = metrics.widthPixels < metrics.heightPixels ? metrics.widthPixels : metrics.heightPixels;
        int height = metrics.widthPixels < metrics.heightPixels ? metrics.heightPixels : metrics.widthPixels;

        int dialogWidth = Math.min(
                getScaledSize(width, metrics.density, NO_PADDING_SCREEN_WIDTH, MAX_PADDING_SCREEN_WIDTH),
                metrics.widthPixels);
        int dialogHeight = Math.min(
                getScaledSize(height, metrics.density, NO_PADDING_SCREEN_HEIGHT, MAX_PADDING_SCREEN_HEIGHT),
                metrics.heightPixels);

        getWindow().setLayout(dialogWidth, dialogHeight); 
    }

    // the minimum scaling factor for the web dialog (50% of screen size)
    private static final double MIN_SCALE_FACTOR = 0.5;
/**
     * Returns a scaled size (either width or height) based on the parameters passed.
     * @param screenSize a pixel dimension of the screen (either width or height)
     * @param density density of the screen
     * @param noPaddingSize the size at which there's no padding for the dialog
     * @param maxPaddingSize the size at which to apply maximum padding for the dialog
     * @return a scaled size.
     */
    private int getScaledSize(int screenSize, float density, int noPaddingSize, int maxPaddingSize) {
        int scaledSize = (int) ((float) screenSize / density);
        double scaleFactor;
        if (scaledSize <= noPaddingSize) {
            scaleFactor = 1.0;
        } else if (scaledSize >= maxPaddingSize) {
            scaleFactor = MIN_SCALE_FACTOR;
        } else {
            // between the noPadding and maxPadding widths, we take a linear reduction to go from 100%
            // of screen size down to MIN_SCALE_FACTOR
            scaleFactor = MIN_SCALE_FACTOR +
                    ((double) (maxPaddingSize - scaledSize))
                            / ((double) (maxPaddingSize - noPaddingSize))
                            * (1.0 - MIN_SCALE_FACTOR);
        }
        return (int) (screenSize * scaleFactor);
    }