IOS 学习 PickView的使用

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@interface MJViewController ()

pragma mark - 数据源方法

/**
* 一共有多少列
*/
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return self.foods.count;
}

/**
* 第component列显示多少行
*/
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
NSArray *subfoods = self.foods[component];
return subfoods.count;
}

pragma mark - 代理方法

/**
* 第component列的第row行显示什么文字
*/
- (NSString )pickerView:(UIPickerView )pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return self.foods[component][row];
}

/**
* 选中了第component列的第row行
*/
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
if (component == 0) { // 水果
self.fruitLabel.text = self.foods[component][row];
} else if (component == 1) { // 主菜
self.mainLabel.text = self.foods[component][row];
} else if (component == 2) { // 饮料
self.drinkLabel.text = self.foods[component][row];
}
}

/**
* 随机选中某一种食物
*/
- (IBAction)randomFood {
for (int component = 0; component < self.foods.count; component++) {
// 第component列数组的总长度
int count = [self.foods[component] count];
// 之前的行号
int oldRow = [self.pickerView selectedRowInComponent:component];
// 第几行(默认新的行号跟旧的行号一样)
int row = oldRow;
// arc4random_uniform(count)

    // 保证行数跟上一次不一样    while (row == oldRow) {        row = arc4random()%count;    }    // 让pickerView主动选中第compoent列的第row行    [self.pickerView selectRow:row inComponent:component animated:YES];    // 设置label的文字    [self pickerView:nil didSelectRow:row inComponent:component];}

// [self.pickerView selectRow:arc4random()%[self.foods[0] count] inComponent:0 animated:YES];
// [self.pickerView selectRow:arc4random()%[self.foods[1] count] inComponent:1 animated:YES];
// [self.pickerView selectRow:arc4random()%[self.foods[2] count] inComponent:2 animated:YES];
}
@end

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