Android Drawable 几个目录对应不同的分辨率

res/drawable-ldpi/  (240x320 and nearer resolution)
res/drawable-mdpi/  (320x480 and nearer resolution)
res/drawable-hdpi/  (480x800 540x960 and nearer resolution)
res/drawable-xhdpi/  (720x1280 )
res/drawable-xxhdpi/ (1080x1920）  nexus 5 就是使用的这个目录下的图片资源