Android观察者模式的简单实现demo

观察者模式就是：当一个对象的状态发送改变时，所有依赖于它的对象都能得到通知并被自动更新。

下面介绍一种简单的使用方法，（下面有demo链接）先看一下project的目录构成：



ObserverListener是观察者接口，SubjectListener是被观察者接口，ObserverManager是观察者的管理类。

1 /**
2  * Created by Administrator on 2016/9/28.
3  * 观察者接口
4  */
5
6 public interface ObserverListener {
7     void observerUpData(String content);//刷新操作
8 }

1 /**
2  * Created by Administrator on 2016/9/28.
3  * 被观察者接口
4  */
5
6 public interface SubjectListener {
7     void add(ObserverListener observerListener);
8     void notifyObserver(String content);
9     void remove(ObserverListener observerListener);
10 }

下面是比较重要的管理类：

1 public class ObserverManager implements SubjectListener {
2     private static ObserverManager observerManager;
3     //观察者接口集合
4     private List<ObserverListener> list = new ArrayList<>();
5
6     /**
7      * 单例
8      */
9     public static ObserverManager getInstance(){
10         if (null == observerManager){
11             synchronized (ObserverManager.class){
12                 if (null == observerManager){
13                     observerManager = new ObserverManager();
14                 }
15             }
16         }
17         return observerManager;
18     }
19
20     /**
21      * 加入监听队列
22      */
23     @Override
24     public void add(ObserverListener observerListener) {
25         list.add(observerListener);
26     }
27
28     /**
29      * 通知观察者刷新数据
30      */
31     @Override
32     public void notifyObserver(String content) {
33         for (ObserverListener observerListener : list){
34             observerListener.observerUpData(content);
35         }
36     }
37
38     /**
39      * 监听队列中移除
40      */
41     @Override
42     public void remove(ObserverListener observerListener) {
43         if (list.contains(observerListener)){
44             list.remove(observerListener);
45         }
46     }
47 }

效果是当点击ThirdActivity中的按钮时，执行ObserverManager.getInstance().notifyObserver("观察者请刷新信息");

然后所有添加到监听队列的Activity都会更新数据，ObserverManager.getInstance().add(this)就是添加到监听队列的方法，更新操作执行在observerUpData(String content)方法中。

下面是3个Activity，很简单：

1 public class MainActivity extends AppCompatActivity implements ObserverListener {
2     private TextView textView;
3     @Override
4     protected void onCreate(Bundle savedInstanceState) {
5         super.onCreate(savedInstanceState);
6         setContentView(R.layout.activity_main);
7         textView = (TextView) findViewById(R.id.tv);
8         findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
9             @Override
10             public void onClick(View v) {
11                 //ObserverManager.getInstance().notifyObserver("观察者请刷新信息");
12                 Intent intent = new Intent(MainActivity.this,SecondActivity.class);
13                 startActivity(intent);
14             }
15         });
16
17         //注册
18         ObserverManager.getInstance().add(this);
19
20     }
21
22     @Override
23     public void observerUpData(String content) {
24         Log.d("vvvvvvvvvvvvvvv","11111111111");
25         textView.setText(content);
26     }
27 }

1 public class SecondActivity extends AppCompatActivity implements ObserverListener {
2     private TextView textView;
3     @Override
4     protected void onCreate(Bundle savedInstanceState) {
5         super.onCreate(savedInstanceState);
6         setContentView(R.layout.activity_second);
7         textView = (TextView) findViewById(R.id.tv2);
8         findViewById(R.id.btn2).setOnClickListener(new View.OnClickListener() {
9             @Override
10             public void onClick(View v) {
11                 Intent intent = new Intent(SecondActivity.this,ThirdActivity.class);
12                 startActivity(intent);
13             }
14         });
15
16         //注册
17         ObserverManager.getInstance().add(this);
18     }
19
20     @Override
21     public void observerUpData(String content) {
22         Log.d("vvvvvvvvvvvvvvv","2222222222");
23         textView.setText(content);
24     }
25 }

1 public class ThirdActivity extends AppCompatActivity implements ObserverListener {
2     private TextView textView;
3     @Override
4     protected void onCreate(Bundle savedInstanceState) {
5         super.onCreate(savedInstanceState);
6         setContentView(R.layout.activity_third);
7         textView = (TextView) findViewById(R.id.tv3);
8         findViewById(R.id.btn3).setOnClickListener(new View.OnClickListener() {
9             @Override
10             public void onClick(View v) {
11                 ObserverManager.getInstance().notifyObserver("观察者请刷新信息");
12             }
13         });
14
15         //注册
16         ObserverManager.getInstance().add(this);
17     }
18
19     @Override
20     public void observerUpData(String content) {
21         Log.d("vvvvvvvvvvvvvvv","33333333333");
22         textView.setText(content);
23     }
24 }