iOS开发 点菜系统 使用UIPickerView

利用UIPickerView实现一个简单的点菜界面，如下图所示。源码地址：https://github.com/xiaoLong1010/iOSAppDemo.git



UIPickerView有两个协议UIPickerViewDataSource,UIPickerViewDelegate，它们为UIPickeView提供数据和代理。UIPickeView的三个component分别代表fruit，main，drink，选中某一行，菜名在下面显示。最上面的随机按钮，则实现随机点菜功能。

1.viewController实现两个协议，并且引用相关数据和控件。

@interface CsyViewController () <UIPickerViewDataSource,UIPickerViewDelegate>

@property (strong,nonatomic) NSArray *foodGroups;

@property (weak, nonatomic) IBOutlet UIPickerView *picker;
@property (weak, nonatomic) IBOutlet UILabel *fruitLabel;
@property (weak, nonatomic) IBOutlet UILabel *mainLabel;

@property (weak, nonatomic) IBOutlet UILabel *drinkLabel;
@property (weak, nonatomic) IBOutlet UIButton *randBtn;
@end

2.数据保存在plist文件中，由foodGroup引用，并且使用懒加载读取数据。

//重写getter方法，懒加载实现
- (NSArray *)foodGroups
{
if (!_foodGroups) {
NSString *path = [[NSBundle mainBundle] pathForResource:@"foods.plist" ofType:nil];

_foodGroups = [NSArray arrayWithContentsOfFile:path];

}

return _foodGroups;

}

3.UIPickerViewDataSource提供的相关信息：component数以及每个component有多少行

#pragma mark -- UIPickerViewDataSource

//返回component数
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return self.foodGroups.count;
}

//返回每个component有多少行
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
return [self.foodGroups[component] count];
}

4.UIPickerViewDelegate提供每一行显示的数据。

#pragma mark -- UIPickerViewDelegate

//每一行显示的数据，字符串数据

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return self.foodGroups[component][row];
}

5.在UIPickerView选中某一行后，需要动态更改下方的菜名。这个是通过UIPickerViewDelegate协议的didSelectRow:方法实现的，当选中某一行，会自动调用该方法。即在该方法中动态地改变菜名。

- (void)viewDidLoad
{
[super viewDidLoad];
//    for (NSArray *group in self.foodGroups) {
//        CsyLog(@"%@",group);
//    }

//初始化三个label，菜单名
for (int i = 0; i < self.foodGroups.count; i++) {
[self pickerView:self.picker didSelectRow:4 inComponent:i];
}

//    NSInteger row = [self.picker selectedRowInComponent:0];
//    CsyLog(@"selected row = %d",row);

//监听方法
[self.randBtn addTarget:self action:@selector(randBtnDidClick:) forControlEvents:UIControlEventTouchUpInside];

}

#pragma mark --randBtn Listener

- (void)randBtnDidClick:(UIButton *)button
{
//    CsyLog(@"click");

for (int i = 0; i < self.foodGroups.count; i++) {
NSArray *group = self.foodGroups[i];
NSInteger newRow = arc4random() % group.count;
//之前被选中的行
NSInteger currentRow = [self.picker selectedRowInComponent:i];
//        NSLog(@"currentRow = %d",currentRow);
//如果随机值和当前的值相当，随机的值加1
if (newRow == currentRow) {
newRow = (newRow + 1) % group.count;
}
//        NSLog(@"newRow = %d",newRow);
//选中某行某列
[self.picker selectRow:newRow inComponent:i animated:YES];
//调用didSecled方法,更新三个label
[self pickerView:self.picker didSelectRow:newRow inComponent:i];
}

}