参考链接
回调的思想
- 类A的a()方法调用类B的b()方法
- 类B的b()方法执行完毕主动调用类A的callback()方法
代码分析
public interface Callback {
public void tellAnswer(int answer);
}
public class Teacher implements Callback {
private Student student;
public Teacher(Student student) {
this.student = student;
}
public void askQuestion() {
student.resolveQuestion(this);
}
@Override
public void tellAnswer(int answer) {
System.out.println("知道了，你的答案是" + answer);
}
}
public interface Student {
public void resolveQuestion(Callback callback);
}
public class Ricky implements Student {
@Override
public voidresolveQuestion(Callback callback) {
// 模拟解决问题
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
}
// 回调，告诉老师作业写了多久
callback.tellAnswer(3);
}
}
测试
@Test
public void testCallBack() {
Student student = new Ricky();
Teacher teacher = new Teacher(student);
teacher.askQuestion();
}
Student也可以使用匿名类定义，更加简洁：
@Test
public void testCallBack2() {
Teacher teacher = new Teacher(new Student() {
@Override
public void resolveQuestion(Callback callback) {
callback.tellAnswer(3);
}
});
teacher.askQuestion();
}
分析
Teacher 中，有一个解决问题的对象：Student，在Student中解决问题之后，再通过引用调用Teacher中的tellAnswer接口，所以叫回调。
