dp转px的工具类DisplayUtil

/**
* 屏幕显示相关工具类
* （px ，sp， dp 等转换）
*/
public class DisplayUtil {
private static Map screenMap = new HashMap<>();
/**
* 将px值转换为dip或dp值，保证尺寸大小不变
*
* @param pxValue
* @return
*/
public static int px2dip(float pxValue, Activity activity) {
   return (int) (pxValue / getScreenMsg(activity).get(ScreenEnum.Density) + 0.5f);
}
/**
* 将dip或dp值转换为px值，保证尺寸大小不变
* @return
*/
public static int dip2px(float dipValue, Activity activity) {
   return (int) (dipValue * getScreenMsg(activity).get(ScreenEnum.Density) + 0.5f);
}
/**
* 将px值转换为sp值，保证文字大小不变
*
* @return
*/
public static int px2sp(float pxValue, Activity activity) {
   return (int) (pxValue / getScreenMsg(activity).get(ScreenEnum.ScaledDensity) + 0.5f);
}
/**
* 将sp值转换为px值，保证文字大小不变
* @return
*/
public static int sp2px(float spValue, Activity activity) {
   return (int) (spValue * getScreenMsg(activity).get(ScreenEnum.ScaledDensity) + 0.5f);
}
/**
* 获取屏幕尺寸等信息
*/
public static Map getScreenMsg(Activity activity){
   DisplayMetrics metric = new DisplayMetrics();
   activity.getWindowManager().getDefaultDisplay().getMetrics(metric);
   int width = metric.widthPixels;
   int height = metric.heightPixels;
   float density = metric.density;///屏幕密度（0.75, 1.0 . 1.5）
   int densityDpi = metric.densityDpi;///屏幕密度DPI（120/160/240/320/480）
   float scaledDensity = metric.scaledDensity;
   if (screenMap==null) screenMap = new HashMap<>();

   screenMap.clear();
   screenMap.put(ScreenEnum.Width,width);
   screenMap.put(ScreenEnum.Height,height);
   screenMap.put(ScreenEnum.Density,(int)density);
   screenMap.put(ScreenEnum.DendityDpi,densityDpi);
   screenMap.put(ScreenEnum.ScaledDensity, (int)scaledDensity);
   return screenMap;
}
enum ScreenEnum{
   Width,Height,Density,DendityDpi,ScaledDensity
}
}

转自：http://www.jianshu.com/p/10ab0154c507