Api 25新功能，原生支持在软键盘中选取图片,这个项目clone自谷歌官方示例，但是原示例有缺陷，已经向官方提issue,我自己已经修复.可以使用Api25的模拟器中自带的Goole Mesager测试
Note: After installing it, you will need to enable this app as a keyboard by navigating to Settings > Languages & Input > Virtual Keyboard > Manage Keyboards. This keyboard can then be accessed by pressing the virtual keyboard icon in the lower-right hand corner of the display while in a text field.