ios - 强制刷新 UI 以更快地更改按钮颜色和内容

Question

我有以下代码从 CloudKit 获取数据，检查属性“Completed”是否为 false，如果是，则向 taskCount 添加 1。

迭代完任务后，它会更新按钮的内容和颜色。

问题是，代码全部执行后， View 需要几秒钟的时间才能真正更新，按钮上的数字以及颜色也会发生变化。

有没有办法在更新按钮颜色和内容后强制刷新或执行其他操作？

let taskManager = CloudKitTaskManager(database: CKContainer.defaultContainer().privateCloudDatabase)
    taskManager.getSummaryOfTasks {
        tasks in
        for index in 0...tasks.count-1 {
            if ("False" == tasks[index].completed){
                self.taskCount = self.taskCount + 1
            }
        }
        self.dueButton.setTitle(String(self.taskCount) + "\nOutstanding", forState: UIControlState.Normal)
        if (self.taskCount == 0) {
            self.dueButton.backgroundColor = UIColor(red:52/255, green:152/255, blue:219/255, alpha:1.0)
            self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
        }else if(self.taskCount > 0 && self.taskCount <= 5){
            self.dueButton.backgroundColor = UIColor(red:243/255, green:156/255, blue:18/255, alpha:1.0)
            self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
        }else if(self.taskCount > 5){
            self.dueButton.backgroundColor = UIColor(red:231/255, green:76/255, blue:60/255, alpha:1.0)
            self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
        }

    }

感谢您提前提供的任何帮助。

Answer 1

不保证 CloudKit 方法的完成处理程序在主队列上运行，因此您必须像这样将用户界面相关代码分派(dispatch)给它:

let taskManager = CloudKitTaskManager(database: CKContainer.defaultContainer().privateCloudDatabase)
    taskManager.getSummaryOfTasks {
        tasks in
        for index in 0...tasks.count-1 {
            if ("False" == tasks[index].completed){
                self.taskCount = self.taskCount + 1
            }
        }
        dispatch_async(dispatch_get_main_queue()) {
            self.dueButton.setTitle(String(self.taskCount) + "\nOutstanding", forState: UIControlState.Normal)
            if (self.taskCount == 0) {
                self.dueButton.backgroundColor = UIColor(red:52/255, green:152/255, blue:219/255, alpha:1.0)
                self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
            }else if(self.taskCount > 0 && self.taskCount <= 5){
                self.dueButton.backgroundColor = UIColor(red:243/255, green:156/255, blue:18/255, alpha:1.0)
                self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
            }else if(self.taskCount > 5){
                self.dueButton.backgroundColor = UIColor(red:231/255, green:76/255, blue:60/255, alpha:1.0)
                self.dueButton.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
            }
        }
    }