5.用户接口UI布局----View控件的概述之Button

Button(textview 子类)----控件能向用户展现文本信息
// With text
<Button 
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button_text"
    ... />
// With an icon ( ImageView 子类)

<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/button_icon"
    ... />
// With text and an icon

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button_text"
android:drawableLeft="@drawable/button_icon"
    ... />

android:onClick="sendMessage"

publicvoid sendMessage(View view){
// Do something in response to button click
}

sendMessage 应该满足

• Be public
• Return void
• Define a View as its only parameter (this will be the View that was clicked)