When I make a text field first responder it deletes my default text.I want this text to stay until the user enters something.
I\'m trying to work my way through an Objective-C tutorial. In the book there is this example: @interface
目录算法思路应用场景代码实现实验效果补充算法思路 1、求取源图I的平均灰度，并记录rows和cols；
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