iOS开发之UIPickView的循环显示内容

效果图：

UIPickerView实现循环滚动，需要实现UIPickerView的代理以及数据源方法，实现pickerViewLoaded方法！

原理是：是放大返回显示 numberOfRowsInComponent！的row数量，实现循环显示！

废话连篇直接上码：

@interface TimingController () 

@property (strong, nonatomic) UIPickerView *timePicker;
@property (nonatomic, strong) NSMutableArray *hoursArray;
@property (nonatomic, strong) NSMutableArray *secondArray;

-(UIPickerView *)timePicker{
    if (!_timePicker) {
        _timePicker = [[UIPickerView alloc] init];
        _timePicker.backgroundColor = [UIColor whiteColor];
        self.hoursArray = [NSMutableArray arrayWithArray:@[@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12",@"13",@"14",@"15",@"16",@"17",@"18",@"19",@"20",@"21",@"22",@"23"]];
        self.secondArray = [NSMutableArray arrayWithArray:@[@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12",@"13",@"14",@"15",@"16",@"17",@"18",@"19",@"20",@"21",@"22",@"23",@"24",@"25",@"26",@"27",@"28",@"29",@"30",@"31",@"32",@"33",@"34",@"35",@"36",@"37",@"38",@"39",@"40",@"41",@"42",@"43",@"44",@"45",@"46",@"47",@"48",@"49",@"50",@"51",@"52",@"53",@"54",@"55",@"56",@"57",@"58",@"59"]];
        self.timePicker.dataSource = self;
        self.timePicker.delegate = self;
        //在当前选择上显示一个透明窗口
        self.timePicker.showsSelectionIndicator = YES;
        //初始化，自动转一圈，避免第一次是数组第一个值造成留白
        [self.timePicker selectRow:[self.hoursArray count] inComponent:0 animated:YES];
        [self.timePicker selectRow:[self.secondArray count] inComponent:1 animated:YES];
        [self.view addSubview:_timePicker];
        
        [_timePicker mas_makeConstraints:^(MASConstraintMaker *make) {
            make.size.mas_equalTo(CGSizeMake(ScreenWidth,195.f));
            make.top.equalTo(self.view.mas_top).offset(20.f);
            make.centerX.equalTo(self.view.mas_centerX);
        }];
    }
    return _timePicker;
}

//自定义pick view的字体和颜色
-(UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{
    UILabel* pickerLabel = (UILabel*)view;
    if (!pickerLabel){
        pickerLabel = [[UILabel alloc] initWithFrame:CGRectMake(12.0f, 0.0f, [pickerView rowSizeForComponent:component].width-12, [pickerView rowSizeForComponent:component].height)];
        [pickerLabel setTextAlignment:NSTextAlignmentCenter];
        [pickerLabel setBackgroundColor:[UIColor clearColor]];
        [pickerLabel setFont:[UIFont boldSystemFontOfSize:18]];
        pickerLabel.textColor = [UIColor blackColor];
    }
    // Fill the label text here
    pickerLabel.text=[self pickerView:pickerView titleForRow:row forComponent:component];
    return pickerLabel;
}

#pragma mark - UIPickerViewDataSource

// 返回多少列
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 2;
}
//宽度
- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component __TVOS_PROHIBITED{
    return self.view.frame.size.width / 2;
}
//行高度
- (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component __TVOS_PROHIBITED {
    
    return 40;
}
// 返回多少行
- (NSInteger)pickerView:(UIPickerView *)pickerView  numberOfRowsInComponent:(NSInteger)component
{
    return 16384;
}

// 返回的是component列的行显示的内容
- (nullable NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    
    if (component == 0){
        return self.hoursArray[row % _hoursArray.count];
    }else{
        return self.secondArray[row % _secondArray.count];
    }
    
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component  {
    [self pickerViewLoaded:component];
}

-(void)pickerViewLoaded: (NSInteger)component {
    NSUInteger max = 16384;
    NSUInteger base10 = (max / 2) - (max / 2) % (component ? _secondArray.count : _hoursArray.count);
    [_timePicker selectRow:[_timePicker selectedRowInComponent:component] % (component ? _secondArray.count : _hoursArray.count) + base10 inComponent:component animated:NO];
}