前言
问题：mipmap&drawable 为什么会存在两个放图片的地方
答案：mipmap放icon，其他图片都放在drawable下
引用了：https://segmentfault.com/a/1190000009045864
另外很多人对图片是放在mipmap下面还是drawable下面总是有疑问，对放在什么文件夹下面没有什么概念，对此官方有个解释：
Drawables may be stripped out as part of dp-specific resource optimisation. But mipmaps will not be stripped. So it's best to put app icons under mipmaps.
Here is more detail written on google documentation page:
Different home screen launcher apps on different devices show app launcher icons at various resolutions. When app resource optimization techniques remove resources for unused screen densities, launcher icons can wind up looking fuzzy because the launcher app has to upscale a lower-resolution icon for display. To avoid these display issues, apps should use the mipmap/ resource folders for launcher icons. The Android system preserves these resources regardless of density stripping, and ensures that launcher apps can pick icons with the best resolution for display.
总结下：
上面话就是想表达放在drawable的图片会对不适用真机屏幕密度的资源进行移除，
放在mipmap依然会保留下各个密度的图片，所以为了保证桌面图标的显示质量因此放在mipmap下面，其他的图标建议都放在drawable文件夹下面吧。
icon尺寸
| 密度 | 建议尺寸 |
|---|---|
| mipmap-mdpi | 48 * 48 |
| mipmap-hdpi | 72 * 72 |
| mipmap-xhdpi | 96 * 96 |
| mipmap-xxhdpi | 144 * 144 |
| mipmap-xxxhdpi | 192 * 192 |
结语
作者：知乎用户
链接：https://www.zhihu.com/question/29265243/answer/102971363
来源：知乎
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
谷歌官方：
drawable/For bitmap files (PNG, JPEG, or GIF), 9-Patch image files, and XML files that describe Drawable shapes or Drawable objects that contain multiple states (normal, pressed, or focused). See the Drawable resource type.
翻译:drawable/用于位图文件（PNG，JPEG，或GIF），9补丁图像文件，和XML文件，描述可绘制形状或可绘制对象包含多个状态（正常，按下或聚焦）。请参阅可绘制资源类型。
mipmap/For app launcher icons. The Android system retains the resources in this folder (and density-specific folders such as mipmap-xxxhdpi) regardless of the screen resolution of the device where your app is installed. This behavior allows launcher apps to pick the best resolution icon for your app to display on the home screen. For more information about using the mipmap folders, see Managing Launcher Icons as mipmap Resources.
