Android 实现下载时主界面与详细界面一致更新

1、创建监听管理类

public class ObserverManager {
    private List observers = new ArrayList();

    public interface Observer {
        public void update();
        public void updateState();
    }

    public void addObserver(Observer observer) {
        if (observer == null) {
            throw new RuntimeException();
        }
        synchronized (this) {
            if (!observers.contains(observer)) {
                observers.add(observer);
            }
        }
    }

    public void notifyObservers() {
        for (Observer observer : observers) {
            observer.update();
        }
    }

    public void notifyState() {
        for (Observer observer : observers) {
            observer.updateState();
        }
    }

}

2、创建详细界面

public class DetailView extends View  implements Observer {

    public DetailView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public DetailView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public DetailView(Context context) {
        super(context);
    }

    @Override
    public void update() {
        System.out.println("update");
    }

    @Override
    public void updateState() {
        System.out.println("updateState");
    }

}

3、创建主界面
1)在初始化时添加监听

    mObserverManager.addObserver(new DetailView(this));

2)在主界面点击下载时通知详细界面更新

public class MainActivity extends Activity {

    private ObserverManager mObserverManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mObserverManager = new ObserverManager();
        mObserverManager.addObserver(new DetailView(this));
    }

    public void click(View v) {
        //TODO 比如开始下载
        mObserverManager.notifyUpdate();// 
    }
}