获取当前栈顶的activity

/**
 * 得到栈顶的activity
 * 路径+类名
 * 需要在清单文件中添加权限 
 */
public static String getTopActivity(Activity context) {

    ActivityManager manager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);

    List runningTaskInfos = manager.getRunningTasks(1);
    ComponentName componentName;
    if (runningTaskInfos != null) {
        componentName = runningTaskInfos.get(0).topActivity;
        String result = componentName.getPackageName() + "." + componentName.getClassName();
        return result;
    } else {
        return null;
    }
}