dp和px相关

屏幕宽高：

DisplayMetrics metrics = context.getResources().getDisplayMetrics();
int screenWidth = metrics.widthPixels;

状态栏高度（24dp）：

@android:dimen/status_bar_height

public class DisplayUtils {

    /**
     * convert px to its equivalent dp
     * 
     * 将px转换为与之相等的dp
     */
    public static int px2dp(Context context, float pxValue) {
        final float scale =  context.getResources().getDisplayMetrics().density;
        return (int) (pxValue / scale + 0.5f);
    }


    /**
     * convert dp to its equivalent px
     * 
     * 将dp转换为与之相等的px
     */
    public static int dp2px(Context context, float dipValue) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dipValue * scale + 0.5f);
    }


    /**
     * convert px to its equivalent sp 
     * 
     * 将px转换为sp
     */
    public static int px2sp(Context context, float pxValue) {
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (pxValue / fontScale + 0.5f);
    }


    /**
     * convert sp to its equivalent px
     * 
     * 将sp转换为px
     */
    public static int sp2px(Context context, float spValue) {
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (spValue * fontScale + 0.5f);
    }
}

同时系统也提供了TypedValue类帮助我们转换

/**
* convert dp to its equivalent px
*/
protected int dp2px(int dp){
    return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,getResources().getDisplayMetrics());
}

/**
* convert sp to its equivalent px
*/
protected int sp2px(int sp){
    return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp,getResources().getDisplayMetrics());
}