android中Activity的管理及程序的退出

public class ScreenManager {
private static Stack<Activity> activityStack;
private static ScreenManager instance;


private ScreenManager() {


}


public static ScreenManager getScreenManager() {
if (null == instance) {
instance = new ScreenManager();
}
return instance;
}


/**
* 彈出最後一個Activity
*/
public void popActivity() {
Activity activity = activityStack.lastElement();
if (null != activity) {
activity.finish();
activity = null;
}
}


/**
* 關閉指定的Activity
* 
* @param activity
*/
public void popActivity(Activity activity) {
if (null != activity) {
activity.finish();
activityStack.remove(activity);
activity = null;
}
}


/**
* 獲取當前的Activity
* 
* @return
*/
public Activity currentActivity() {
return activityStack.lastElement();
}


/**
* 將當前Activity入棧
* 
* @param activity
*/
public void pushActivity(Activity activity) {
if (null == activityStack) {
activityStack = new Stack<Activity>();
}
activityStack.add(activity);
}


/**
* 關閉除指定之外的所有Activity
* 
* @param activity
*/
public void popOtherActivity(Activity activity) {
while (true) {
Activity tmpActivity = currentActivity();
if (null == tmpActivity) {
break;
}
if (!tmpActivity.equals(activity)) {
popActivity(tmpActivity);
}
if (activityStack.size() == 1) {
if (activityStack.lastElement() == activity) {
break;
}
}
}
}


/**
* 關閉所有Activity
* 
* @param cls
*/
public void popAllActivityExceptOne(Class cls) {
while (true) {
Activity activity = currentActivity();
if (null == activity) {
break;
}
if (activity.getClass().equals(cls)) {
break;
}
popActivity(activity);
}
}
}