观察者模式 android 更新UI
原来的网址:http://malong26.iteye.com/blog/1858724
android的app程序退出有几种方式:activity队列方式、广播方式。在这里介绍一下我实现该功能的方式--观察者模式。
方法的大概思路为:建立Activity基类,实现观察者接口,实现监听方法,finish掉本实例;在Application里面单例一个目标对象,当需要关闭程序的时候,调用目标对象的通知方法,通知所有观察者。
代码如下:
观察者接口
- public interface Observer {
- public void update(Subject subject);
- }
目标对象基类
- public class Subject {
- private List<Observer> observers = new ArrayList<Observer>();
- public void attach(Observer observer){
- observers.add(observer);
- }
- public void detach(Observer observer){
- observers.remove(observer);
- }
- protected void notifyObservers(){
- for(Observer observer : observers){
- observer.update(this);
- }
- }
- }
目标对象子类(实现具体退出方法)
- public class ApplicationSubject extends Subject {
- public void exit(){
- notifyObservers();
- }
- }
MyApplication类(在Manifest文件中将标签application的name改为本类的全限定名)
- public class MyApplication extends Application {
- private static ApplicationSubject applicationSubject;
- public ApplicationSubject getApplicationSubject() {
- if(applicationSubject == null) applicationSubject = new ApplicationSubject();
- return applicationSubject;
- }
- }
Activity基类
- public abstract class BaseActivity extends Activity implements Observer {
- public MyApplication app;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- app = (MyApplication) this.getApplication();
- app.getApplicationSubject().attach(this);
- }
- @Override
- public void finish() {
- // TODO Auto-generated method stub
- app.getApplicationSubject().detach(this);
- super.finish();
- }
- /**
- * 关闭程序
- */
- public void close() {
- app.getApplicationSubject().exit();
- };
- @Override
- public void update(Subject subject) {
- // TODO Auto-generated method stub
- this.finish();
- }
- }
写几个测试页面测试一下
- public class ATestActivity extends BaseActivity {
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- startActivity(new Intent(this, BTestActivity.class));
- }
- }
- public class BTestActivity extends BaseActivity {
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- close(); //在BTestActivity中调用close方法,发现A和B都关闭了
- }
- }
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