学步园

Android能够展现给用户的界面都是继承来自Activity,虽然Android操作系统能根据当前Activity的状态通过维护一个栈来进行管理，但是

开发人员只能在每个activity的所在的state改变的事件中进行相关的操作。而且，如果一个activity想去获得某个activity的时候，也是比较

麻烦的。还有，比如我想给当前如果是Home的界面，需要校验是否需要显示登录窗口，那如何去处理将不会让校验代码出现在Home的Activity中。因为本身显示登录窗口与否和当前的Activity没多大关系。下面就给出一些项目中的真实案例的代码，供大家去看看。

ActivityManager.这个类除了模拟栈的行为，还添加一些额外的功能。比如用户是否身份有效。

public class ActivityManager {<br /> private ActivityManager() {<br /> }<br /> private static ActivityManager instance = new ActivityManager();<br /> public static ActivityManager getInstance() {<br /> return instance;<br /> }<br /> private List<Activity> activities = new ArrayList<Activity>();<br /> private Activity topActivity;<br /> private boolean topAcitivityActivited;<br /> private boolean waitingForDialogContainer = true;<br /> private boolean logining = false;<br /> private String loginPrompt;<br /> public void addActivity(Activity activity) {<br /> if (!activities.contains(activity)) {<br /> activities.add(activity);<br /> }<br /> }<br /> public void removeActivity(Activity activity) {<br /> activities.remove(activity);<br /> }<br /> public void setTopActivity(Activity topActivity) {<br /> this.topActivity = topActivity;<br /> }<br /> public Activity getTopActivity() {<br /> return topActivity;<br /> }<br /> public void setTopAcitivityActivited(boolean topAcitivityActivited) {<br /> this.topAcitivityActivited = topAcitivityActivited;<br /> if (waitingForDialogContainer) {<br /> waitingForDialogContainer = false;<br /> new Handler().post(new Runnable() {<br /> public void run() {<br /> showLoginDialog(loginPrompt);<br /> }<br /> });<br /> }<br /> }<br /> public boolean isTopAcitivityActivited() {<br /> return topAcitivityActivited;<br /> }<br /> public void showLoginDialog(String initialMessage) {<br /> if (logining) {<br /> return;<br /> }<br /> if (topActivity != null && topAcitivityActivited == true) {<br /> logining = true;<br /> new LoginView(topActivity, initialMessage).show();<br /> } else {<br /> waitingForDialogContainer = true;<br /> loginPrompt = initialMessage;<br /> }<br /> }</p> <p> @SuppressWarnings("unchecked")<br /> public <T extends Activity> T getActivity(Class<T> cls){<br /> for(Activity act : activities){<br /> if(act.getClass() == cls){<br /> return (T)act;<br /> }<br /> }<br /> return null;<br /> }</p> <p> private void quit() {<br /> for (Activity activity : activities) {<br /> activity.finish();<br /> }<br /> waitingForDialogContainer = true;<br /> loginPrompt = null;<br /> }<br /> public void onLoginReturned(boolean result) {<br /> logining = false;<br /> if (!result) {<br /> quit();<br /> }<br /> }<br /> }<br />

ManagedActivity:这个类继承来自Activity.为了方便让ActivityManager的管理，每个Activity都继承来自该类。代码如下。

public class ManagedActivity extends Activity{<br /> @Override<br /> protected void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> ActivityManager.getInstance().addActivity(this);<br /> }</p> <p> @Override<br /> protected void onPause() {<br /> super.onPause();<br /> ActivityManager.getInstance().setTopAcitivityActivited(false);<br /> }</p> <p> @Override<br /> protected void onDestroy() {<br /> super.onDestroy();<br /> ActivityManager.getInstance().removeActivity(this);<br /> }</p> <p> @Override<br /> protected void onStart() {<br /> super.onStart();<br /> ActivityManager.getInstance().setTopActivity(this);<br /> ActivityManager.getInstance().setTopAcitivityActivited(true);<br /> }<br /> }<br />

ActivityManager的showLoginDialog可用来根据登录窗台来检测是否当前需要弹出登录框。而且这只是一部分小的作用，更多的大家

可以想想，这个ActivityManager中还可以处理很多你想处理的功能，当那些界面状态发生变化。