Android 实现双击退出的功能

 public void onBackPressed() {

    //Preferences 中获取是否双击退出
    boolean isDoubleClick = true;
    //BaseApplication.get("ifDoubleClickedBack", true);

    if (isDoubleClick) {
      long curTime = SystemClock.uptimeMillis();
      if ((curTime - mBackPressedTime) < (2 * 1000)) {
        finish();
        //activity栈管理
        AppManager.getAppManager().AppExit();
      } else {
        mBackPressedTime = curTime;
        Toast.makeText(this, "再次点击退出", Toast.LENGTH_SHORT).show();
      }
    } else {
      finish();
    }

  }

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

  private AppManager() {
  }

  /**
   * 单一实例
   */
  public static AppManager getAppManager() {
    if (instance == null) {
      instance = new AppManager();
    }

    if (activityStack == null) {
      activityStack = new Stack<Activity>();
    }

    return instance;
  }

  /**
   * 获取指定的Activity
   *
   * @author kymjs
   */
  public static Activity getActivity(Class<?> cls) {
    if (activityStack != null)
      for (Activity activity : activityStack) {
        if (activity.getClass().equals(cls)) {
          return activity;
        }
      }
    return null;
  }

  /**
   * 添加Activity到堆栈
   */
  public void addActivity(Activity activity) {
    activityStack.add(activity);
  }

  /**
   * 获取当前Activity（堆栈中最后一个压入的）
   */
  public Activity currentActivity() {
    Activity activity = activityStack.lastElement();
    return activity;
  }

  /**
   * 结束当前Activity（堆栈中最后一个压入的）
   */
  public void finishActivity() {
    Activity activity = activityStack.lastElement();
    finishActivity(activity);
  }

  /**
   * 结束指定的Activity
   */
  public void finishActivity(Activity activity) {
    if (activity != null && activityStack.contains(activity)) {
      activityStack.remove(activity);
      activity.finish();
    }
  }

  /**
   * 结束指定的Activity
   */
  public void removeActivity(Activity activity) {
    if (activity != null && activityStack.contains(activity)) {
      activityStack.remove(activity);
    }
  }

  /**
   * 结束指定类名的Activity
   */
  public void finishActivity(Class<?> cls) {
    for (Activity activity : activityStack) {
      if (activity.getClass().equals(cls)) {
        finishActivity(activity);
        break;
      }
    }
  }

  /**
   * 结束所有Activity
   */
  public void finishAllActivity() {
    for (int i = 0, size = activityStack.size(); i < size; i++) {
      if (null != activityStack.get(i)) {
        finishActivity(activityStack.get(i));
      }
    }
    activityStack.clear();
  }

  /**
   * 退出应用程序
   */
  public void AppExit() {
    try {
      finishAllActivity();
      // System.exit(0);
    } catch (Exception e) {
    }
  }
}