大神Github：https://github.com/JessYanCoding/AndroidAutoSize.git

px = density*dp; //像素

density = dpi/160;//像素密度

dpi = √(x2+y2)/屏幕尺寸;//dot per inch 每英寸像素點數(shù)

width_dp = width_px/density;//寬度dp

height_dp = height_px/density;//高度dp

由于px = density*dp，dp為設計圖固定值，想要px寬度/高度恒定，那么只有改變density變量。

DisplayMetrics displayMetrics = getResources().getDisplayMetrics();

? ? ? ? int densityDpi = displayMetrics.densityDpi;

? ? ? ? float scaledDensity = displayMetrics.scaledDensity;

? ? ? ? int widthPixels = displayMetrics.widthPixels;

? ? ? ? int heightPixels = displayMetrics.heightPixels;

? ? ? ? float xdpi = displayMetrics.xdpi;

? ? ? ? float ydpi = displayMetrics.ydpi;

? ? ? ? double size = Math.sqrt((widthPixels / xdpi) * (widthPixels / xdpi) + (heightPixels / ydpi) * (heightPixels / ydpi));

? ? ? ? double dpi = Math.sqrt(widthPixels * widthPixels + heightPixels * heightPixels) / size;

Log.i("Simon","densityDpi = " + densityDpi

+"? scaledDensity = " + scaledDensity

+"? widthPixels = " + widthPixels

+"? heightPixels = " + heightPixels

+"? screenSize = " + screenSize

+"? screenDpi = " + screenDpi

);