Android EditText:触摸时选择所有文本，并在用户开始输入时清除.

我的应用程序中有一个编辑文本.当用户触摸编辑文本时，应选择整个文本，并且当他开始键入文本时应清除.一个示例是浏览器地址栏.有什么办法吗?请帮帮我.

I have a edit text in my app. When the user touches the edit text the whole text should be selected and when he starts typing text should be cleared. An example is browser address bar. Is there any way to do this?Please help me.