14.UIPickerView

UIPickerView

UIPickerView就是一个滑动选择控件,下面我们学习如何使用它

1. UIPickerView的创建

let pickerView = UIPickerView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: 500))self.view.addSubview(pickerView)

运行程序

我们发现,就一条横线,什么都没有, UIPickerView和前面学习的控件有那么不一样,它的数据是在dataSource中设置的

2. UIPickerView的dataSource

我们设置pickerView的dataSource为自身

pickerView.dataSource = self

我们在Xcode会发现一个提示,说我们的ViewController没有实现UIPickerViewDataSource,那么我们实现它

class ViewController: UIViewController, UIPickerViewDataSource {    ...}

然后Xcode又报错,说我们没有实现UIPickerViewDataSource的方法
我们查看一下UIPickerViewDataSource的定义

public protocol UIPickerViewDataSource : NSObjectProtocol {    // returns the number of 'columns' to display.    @available(iOS 2.0, *)    public func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int // UIPickerView的列数    // returns the # of rows in each component..    @available(iOS 2.0, *)    public func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int // UIPickerView的行数}

我们实现这两个方法:

// MARK: - UIPickerViewDataSource// MARK: 列数func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {    return 3}// MARK: 行数func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {    return 3}

运行程序:

我们发现确实出现了3行3列的数据, 但是全是问号, 这说明我们还没有给UIPickerView设置数据,它是在delegate中设置的

3. UIPickerView的delegate

有了上面的dataSource的经验, 我们给UIPickerView实现UIPickerViewDelegate代理

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {    override func viewDidLoad() {        ...        pickerView.delegate = self    }    ...}

然后我们查看UIPickerViewDelegate的定义:

public protocol UIPickerViewDelegate : NSObjectProtocol {    // 下面的两个方法设置一个内容的宽高     @available(iOS 2.0, *)    optional public func pickerView(pickerView: UIPickerView, widthForComponent component: Int) -> CGFloat    @available(iOS 2.0, *)    optional public func pickerView(pickerView: UIPickerView, rowHeightForComponent component: Int) -> CGFloat    // 设置内容    @available(iOS 2.0, *)    optional public func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?    @available(iOS 6.0, *)    optional public func pickerView(pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? // attributed title is favored if both methods are implemented    @available(iOS 2.0, *)    optional public func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusingView view: UIView?) -> UIView // 设置的内容可以是UIView    // 获取选中的行列的值    @available(iOS 2.0, *)    optional public func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)}

我们发现UIPickerViewDelegate中的方法都是可选的
下面我们实现一个需求:
韦小宝 22岁 老婆7个
西门吹雪 30岁 老婆1个
魏忠贤 44岁 没老婆

let contents = [    ["韦小宝", "西门吹雪", "魏忠贤"],    ["22岁", "30岁", "44岁"],    ["老婆7个", "老婆1个", "没老婆"]]// MARK: - UIPickerViewDelegate// MARK: 内容func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {    return self.contents[component][row]}

现在我们希望默认选中的是中间的西门吹雪 30岁 老婆1个

pickerView.selectRow(1, inComponent: 0, animated: true)pickerView.selectRow(1, inComponent: 1, animated: true)pickerView.selectRow(1, inComponent: 2, animated: true)

运行程序:

我们再实现一个需求, 将选中的内容在控制台打印出来

// MARK: 选中行列func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {    print(self.contents[component][row])}

由此,我们发现: 实力很重要,但还得能说会道,要不然,没老婆!

4. 完整代码

import UIKitclass ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {    let contents = [        ["韦小宝", "西门吹雪", "魏忠贤"],        ["22岁", "30岁", "44岁"],        ["老婆7个", "老婆1个", "没老婆"]    ]    override func viewDidLoad() {        super.viewDidLoad()        let pickerView = UIPickerView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: 500))        self.view.addSubview(pickerView)        pickerView.dataSource = self        pickerView.delegate = self        pickerView.selectRow(1, inComponent: 0, animated: true)        pickerView.selectRow(1, inComponent: 1, animated: true)        pickerView.selectRow(1, inComponent: 2, animated: true)    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }    // MARK: - UIPickerViewDataSource    // MARK: 列数    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {        return 3    }    // MARK: 行数    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {        return 3    }    // MARK: - UIPickerViewDelegate    // MARK: 内容    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {        return self.contents[component][row]    }    // MARK: 选中行列    func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {        print(self.contents[component][row])    }}