public class MyActivityManager { private static MyActivityManager instance; private Stack<Activity> activityStack;//activity栈 private MyActivityManager() { } //单例模式 public static MyActivityManager getInstance() {     if (instance == null) {         instance = new MyActivityManager();     }     return instance; } //把一个activity压入栈中 public void pushOneActivity(Activity actvity) {     if (activityStack == null) {         activityStack = new Stack<Activity>();     }     activityStack.add(actvity);     Log.d("MyActivityManager ", "size = " + activityStack.size()); } //获取栈顶的activity，先进后出原则 public Activity getLastActivity() {     return activityStack.lastElement(); } //移除一个activity public void popOneActivity(Activity activity) {     if (activityStack != null && activityStack.size() > 0) {         if (activity != null) {             activity.finish();             activityStack.remove(activity);             activity = null;         }     } } //退出所有activity public void finishAllActivity() {     if (activityStack != null) {         while (activityStack.size() > 0) {             Activity activity = getLastActivity();             if (activity == null) break;             popOneActivity(activity);         }     } }}