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 UIKit

class 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])
}
}