Android DisplayMetrics 获取和屏幕相关的信息
Android源码中是这样来描述DisplayMetrics的。
/** * A structure describing general information about a display, such as its * size, density, and font scaling. * <p>To access the DisplayMetrics members, initialize an object like this:</p> * <pre> DisplayMetrics metrics = new DisplayMetrics(); * getWindowManager().getDefaultDisplay().getMetrics(metrics);</pre> */
按照DisplayMetrics注释中的那样,我们直接写个例子来测试下,就什么都明白了。我用的是小米3:
DisplayMetrics metrics = new DisplayMetrics(); getActivity().getWindowManager().getDefaultDisplay().getMetrics(metrics); /** * The logical density of the display. This is a scaling factor for the * Density Independent Pixel unit, where one DIP is one pixel on an * approximately 160 dpi screen (for example a 240x320, 1.5"x2" screen), * providing the baseline of the system's display. Thus on a 160dpi screen * this density value will be 1; on a 120 dpi screen it would be .75; etc. * * <p>This value does not exactly follow the real screen size (as given by * {@link #xdpi} and {@link #ydpi}, but rather is used to scale the size of * the overall UI in steps based on gross changes in the display dpi. For * example, a 240x320 screen will have a density of 1 even if its width is * 1.8", 1.3", etc. However, if the screen resolution is increased to * 320x480 but the screen size remained 1.5"x2" then the density would be * increased (probably to 1.5). * * density 是逻辑上的屏幕密度,约定在160dpi的设备上,1px=1dip。 * density = densityDpi / 160 * * @see #DENSITY_DEFAULT */ float density = metrics.density; /** * The screen density expressed as dots-per-inch. May be either * {@link #DENSITY_LOW}, {@link #DENSITY_MEDIUM}, or {@link #DENSITY_HIGH}. * densityDpi 表示每英寸的点数(并不是像素数) */ int densityDpi = metrics.densityDpi; /** * The absolute height of the display in pixels. * 屏幕的绝对高度,以像素为单位。 */ int heightPixels = metrics.heightPixels; /** * The absolute width of the display in pixels. * 同样,这个是屏幕的绝对宽度,以像素为单位。 */ int widthPixels = metrics.widthPixels; /** * The exact physical pixels per inch of the screen in the X dimension. * 横向每一英寸确切的物理像素,我们可以尝试通过这个值和widthPixels 来计算屏幕的宽度英寸。 */ float xdpi = metrics.xdpi; /** * The exact physical pixels per inch of the screen in the Y dimension. * 横向每一英寸确切的物理像素,我们可以尝试通过这个值和heightPixels 来计算屏幕的高度英寸。 */ float ydpi = metrics.ydpi; /** * A scaling factor for fonts displayed on the display. This is the same * as {@link #density}, except that it may be adjusted in smaller * increments at runtime based on a user preference for the font size. * scaledDensity 这个值从上面的注释看,是和字体相关的factor,通常情况下这个值和density是相等的,但是假如用户手动的调整了 * 系统字体的大小,那么这个值就有可能改变(以小米3为例,标准字体,这个值=3,最大字体这个值=3.25)。 * 因此现在很多情况下,我们把字体单位写成dp,尽管Google建议的字体让写成sp。 */ float scaledDensity = metrics.scaledDensity; LogUtil.logd(TAG, "metrics.density = " + density); LogUtil.logd(TAG, "metrics.densityDpi = " + densityDpi); LogUtil.logd(TAG, "metrics.heightPixels = " +heightPixels); LogUtil.logd(TAG, "metrics.widthPixels = " +widthPixels); LogUtil.logd(TAG, "metrics.xdpi = " +xdpi); LogUtil.logd(TAG, "metrics.ydpi = " +ydpi); LogUtil.logd(TAG, "metrics.scaledDensity = " +scaledDensity); //来计算手机是几英寸的 float pixelsToDipWidth = widthPixels / xdpi; float pixelsToDipHeight = heightPixels / ydpi; LogUtil.logd(TAG, "pixelsToDipWidth = " + pixelsToDipWidth); LogUtil.logd(TAG, "pixelsToDipHeight = " + pixelsToDipHeight); double mobileInch = Math.sqrt(pixelsToDipHeight * pixelsToDipHeight + pixelsToDipWidth * pixelsToDipWidth); //我用的小米3,得到的值是4.917646062686045 LogUtil.logd(TAG, "mobileInch = " + mobileInch);
通过这个例子,我们明白了dip及px代表着什么,我们就可以来写出dip与px相互转换的方法。(dip = px / density)
/** * 根据手机的分辨率从 dp 的单位 转成为 px(像素) */ public static int dip2px(Context context, float dpValue) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (dpValue * scale + 0.5f); } /** * 根据手机的分辨率从 px(像素) 的单位 转成为 dp */ public static int px2dip(Context context, float pxValue) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (pxValue / scale + 0.5f); }
上面 加的这个0.5f的原因,Google官方文档中其实有介绍:
Then add 0.5f to round the figure up to the nearest whole number, when converting to an integer.
说白了就是为了四舍五入。。。
比如我上面的例子:
mobileInch = 4.917646062686045 ,我+0.5f(=5.417646062686045),然后再取整之后,就得到5。