Android icons集合：
Be aware that the style changes occur fairly regularly with each major release, so it‘s always worth checking current guidelines!
Pixel DensitiesAndroid icons require five separate sizes for different screen pixel densities. Icons for lower resolution are created automatically from the baseline. |
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| mdpi (Baseline): | 160 dpi | 1× |
| hdpi: | 240 dpi | 1.5× |
| xhdpi: | 320 dpi | 2× |
| xxhdpi: | 490 dpi | 3× |
| xxxhdpi: | 640 dpi | 4× |
| Sizes (px) | Format and naming | Notes |
|---|---|---|
Launcher icons |
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| 48 × 48 (mdpi) 72 × 72 (hdpi) 96 × 96 (xhdpi) 144 × 144 (xxhdpi) 192 × 192 (xxxhdpi) 512 × 512 (Google Play store) |
.png | Three-dimensional, front view, with a slight perspective as if viewed from above, so that users perceive some depth. |
Action bar, Dialog & Tab icons |
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| 24 × 24 area in 32 × 32 (mdpi) 36 × 36 area in 48 × 48 (hdpi) 48 × 48 area in 64 × 64 (xhdpi) 72 × 72 area in 96 × 96 (xxhdpi) 96 × 96 area in 128 × 128 (xxxhdpi) |
.png | These icons are used in the action bar menu. The first number is the size of the icon area, and the second is file size. |
Small Contextual Icons |
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| 16 × 16 (mdpi) 24 × 24 (hdpi) 32 × 32 (xhdpi) 48 × 48 (xxhdpi) 64 × 64 (xxxhdpi) |
.png |
Small icons are used to surface actions and/or provide status for specific items. For example, in the Gmail app, each message has a star icon that marks the message as important. |
Notification icons
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| 22 × 22 area in 24 × 24 (mdpi) 33 × 33 area in 36 × 36 (hdpi) 44 × 44 area in 48 × 48 (xhdpi) 66 × 66 area in 72 × 72 (xxhdpi) 88 × 88 area in 96 × 96 (xxxhdpi) |
.png | These are used to represent application notifications in the status bar. They should be flat (no gradients), white and face-on perspective |
原文：http://www.cnblogs.com/spring87/p/5390432.html