callback是回调的意思，一般我们需要2个类需要相互掉用，一个类把数据动态传递给另外一个类的时候，可以用这种方式，比如Android里面的Launcher类和LauncherModel类，LauncherModel里面有接口很多没有实现的方法，Launcher实现LauncherModel的接口，实现方法，传递数据给LauncherModel类。

1）CallBack.java文件内容如下

package leetcode.chenyu.test;public class CallBack {private Callback mCallback;public CallBack(Callback callback) {this.mCallback = callback;}public static interface Callback {public void before();public void after();}public void doThing() {mCallback.before();System.out.println("hello chenyu");mCallback.after();}
}

2）TestCallBack.java文件如下

package leetcode.chenyu.test;public class TestCallBack implements CallBack.Callback{public CallBack mCallback;public TestCallBack() {mCallback = new CallBack(this);}@Overridepublic void before() {System.out.println("hello before");}@Overridepublic void after() {System.out.println("hello before");}public void doThing() {mCallback.doThing();}public static void main(String[] args) {new TestCallBack().doThing();}}

 

hello before
hello chenyu
hello before