android:onClick attribute

本文以Button为例进行介绍

1》XML文件代码如下：

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_send"
    android:onClick="sendMessage" />

The android:onClick attribute’s value, "sendMessage", is the name of a method in your activity that the system calls when the user clicks the button.

2》Open the Activity class (located in the project'ssrc/ directory) and add the corresponding method:

/** Called when the user clicks the Send button */
public void sendMessage(View view) {
    // Do something in response to button
}

注意：

In order for the system to match this method to the method name given to android:onClick, the signature must be exactly as shown. Specifically, the method must:（该方法必须全部满足以下三个条件：）
•Be public.(public)
•Have a void return value.(返回值为void)
•Have a View as the only parameter (this will be the View that was clicked).(ps:有且仅有一个参数类型为View的参数，这一点特别重要，否则点击该按钮时，不会调用该方法。)

这也是有时候明明指定了android:onClick属性，并且Activity中也实现了对应的方法，但是实际执行的时候就是没有执行指定的方法的原因。仔细看一下你的方法是否同时满足以上三个条件！！！