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 }
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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：
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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 }
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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 }
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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 }
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布局都是一个TextView和一个Button。
demo链接http://yun.baidu.com/share/link?shareid=2719259515&uk=1969594477Android---观察者模式的简单实现demo
原文：http://www.cnblogs.com/mafeng/p/6255592.html
