回调的概念

回调

1、接口回调

interface People{
void peopleList();  //回调函数
}
class Student implements People{
public void peopleList(){
System.out.println("I’m a student.")；
}
}
class Teacher implements People{
public void peopleList(){
System.out.println("I’m a teacher.");
}
}
public class Example{
public static void main(String args[]){
People a;             //声明接口变量
a=new Student();      //实例化，接口变量中存放对象的引用
a.peopleList();        //接口回调
a=new Teacher();     //实例化，接口变量中存放对象的引用
a.peopleList();       //接口回调
}
}

android接口回调

1．定义接口
public interface OnClickListener {

public void OnClick(Button b);

}
2． 定义Button
public class Button {
OnClickListener listener;

public void click() {
listener.OnClick(this);
}
public void setOnClickListener(OnClickListener listener) {
this.listener = listener;
}
}
3． 将接口对象OnClickListener 赋给 Button的接口成员
public class Activity {
public Activity() {
}
public static void main(String[] args) {
Button button = new Button();
'   button.setOnClickListener(new OnClickListener(){  '
@Override
'       public void OnClick(Button b) {               '
'                System.out.println("clicked");       '
}
});
button.click(); //user click,System call button.click();
}
}