点餐系统思路

点餐系统思路

步骤一：遵守和实现UIPickerView的数据源。

步骤二：加载 plist 文件，把数据存放在 NSArray 数组中。
- (NSArray *)foodArray
{
    if (_foodArray == nil ) {
        _foodArray = [NSArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"foods.plist" ofType: nil ]];
        for ( int i = 0 ; i < self .foodArray.count; i++) {
            [ self pickerView: nil didSelectRow: 0 inComponent:i];
        }
    }
    return _foodArray;
}

步骤三：遵守和实现 UIPickerView 的代理方法，监听选中每一行的方法。
#pragma mark - 实现代理方法

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

/** 一组有多少行 */
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    NSArray *foods = self .foodArray[component];
    return foods.count;
}

/** 一行显示什么内容 */
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return   self .foodArray[component][row];
}

/** 选中 */
- ( void )pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if (component == 0 ) {
        self .fruitLabel.text = self .foodArray[component][row];
    } else if (component == 1 ){
        self .mainFoodLabel.text = self .foodArray[component][row];
    } else if (component == 2 ){
        self .drinkLabel.text = self .foodArray[component][row];
    }
}

步骤四：监听 UIBarButtonItem 随机的事件
- ( IBAction )randomClickBtn
{
    for ( int i = 0 ;i < self .foodArray.count;i++) {
        // 根据组算出有多少行
        int cou = [ self .foodArray[i] count];
        // 取得被选中的
        int oldRow = [ self .picker selectedRowInComponent:i];
        int row = oldRow;
        // 如果上一个和下一个相等，就随机
        while (row == oldRow) {
            row = arc4random_uniform(cou);
        }
       
        [ self .picker selectRow:row inComponent:i animated: YES ];
        [ self pickerView: nil didSelectRow:row inComponent:i];
    }
}