iOS 抽奖轮盘效果实现思路

临近春节，相信不少app都会加一个新的需求——新年抽奖

不多废话，先上GIF效果图

DEMO链接：https://gitee.com/xudongxiang/LuckyDraw.git

1. 跑马灯效果

QQ20190117-153231.gif

2. 抽奖效果

QQ20190117-153345.gif

实现步骤：

一、跑马灯效果

其实很简单，就是通过以下两张图片，用NSTimer无限替换，达到跑马灯的效果

bg_lamp_1@2x.png

bg_lamp_2@2x.png

实现代码：

_rotaryTable = [[UIImageView alloc] initWithFrame:CGRectMake((kScreenWidth-366*XT)/2, 218*XT, 366*XT, 318*XT)];
_rotaryTable.tag = 100;
[_rotaryTable setImage:[UIImage imageNamed:@"bg_lamp_1"]];
[scrollView addSubview:_rotaryTable];

_itemBordeTImer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(itemBordeTImerEvent) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:_itemBordeTImer forMode:NSRunLoopCommonModes];

- (void)itemBordeTImerEvent
{
    if (_rotaryTable.tag == 100) {
        _rotaryTable.tag = 101;
        [_rotaryTable setImage:[UIImage imageNamed:@"bg_lamp_2"]];
    }else if (_rotaryTable.tag == 101){
        _rotaryTable.tag = 100;
        [_rotaryTable setImage:[UIImage imageNamed:@"bg_lamp_1"]];
    }
}

二、抽奖效果

初始化奖品数组，以及按照 从上到下，从左到右 的顺序布局UI界面

_itemTitleArray = @[@"3跳币",@"嘉年华门票",@"8跳币",@"10朵花",@"128朵花",@"2018跳币",@"528跳币",@"128跳币",@"28朵花",@"88跳币"];
for (int i = 0 ; i < 4; i ++) {
        UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(i*82*XT, 0, 78*XT, 80*XT)];
        [img setImage:[UIImage imageNamed:itemImgArray[i]]];
        [itemView addSubview:img];
        
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 63*XT, 78*XT, 13*XT)];
        label.textAlignment = NSTextAlignmentCenter;
        label.textColor = [UIColor whiteColor];
        label.font = [UIFont systemFontOfSize:13*XT];
        label.text = _itemTitleArray[I];
        [img addSubview:label];
    }
    
    for (int i = 0 ; i < 2; i ++) {
        UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(i*(78*XT+169*XT), 84*XT, 78*XT, 80*XT)];
        [img setImage:[UIImage imageNamed:itemImgArray[i+4]]];
        [itemView addSubview:img];
        
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 63*XT, 78*XT, 13*XT)];
        label.textAlignment = NSTextAlignmentCenter;
        label.textColor = [UIColor whiteColor];
        label.font = [UIFont systemFontOfSize:13*XT];
        label.text = _itemTitleArray[i+4];
        [img addSubview:label];
    }
    
    for (int i = 0 ; i < 4; i ++) {
        UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(i*82*XT, 168*XT, 78*XT, 80*XT)];
        [img setImage:[UIImage imageNamed:itemImgArray[i+6]]];
        [itemView addSubview:img];
        
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 63*XT, 78*XT, 13*XT)];
        label.textAlignment = NSTextAlignmentCenter;
        label.textColor = [UIColor whiteColor];
        label.font = [UIFont systemFontOfSize:13*XT];
        label.text = _itemTitleArray[i+6];
        [img addSubview:label];
    }

点击之后开始抽奖按钮后，先快速地将选中框 正时针 转三圈，再慢速地在 一圈之内 旋转至中奖位置，请注意是按照 正时针 的顺序旋转，和UI布局的顺序不一致，如图所示：

bg_lamp_2@2x.png

- (void)getLotteryInfo
{
    // 快速旋转计数，在NSTimer的方法下自增到29时结束，代表选中框快速旋转了三圈，结束快速旋转
    _fastIndex = 0;

    // 慢速旋转计数，在NSTimer的方法下自增到下面 _selectedIndex 的数字时，选中框到达中奖位置，结束慢速旋转
    _slowIndex = -1;

    // 中奖位置计数，按照顺时针的顺序，如上图所示，若 _selectedIndex = 9 则获得 9 所在位置的奖品
    _selectedIndex = arc4random()%10;
  
    // 根据奖品数组，获取中奖信息
    if (_selectedIndex<4) {
        _result = _itemTitleArray[_selectedIndex];
    }else if (_selectedIndex == 4){
        _result = @"2018跳币";
    }else if (_selectedIndex == 5){
        _result = @"88跳币";
    }else if (_selectedIndex == 6){
        _result = @"28朵花";
    }else if (_selectedIndex == 7){
        _result = @"128跳币";
    }else if (_selectedIndex == 8){
        _result = @"528跳币";
    }else if (_selectedIndex == 9){
        _result = @"128朵花";
    }
    _itemBorderView.hidden = NO;

    // 开启快速旋转，时间间隔为0.1秒
    _fastTimer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(fastTimerEvent) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:_fastTimer forMode:NSRunLoopCommonModes];
}

NSTimer 快速旋转事件

- (void)fastTimerEvent
{
    // _fastIndex 自增
    _fastIndex = _fastIndex + 1;

    // 顺时针移动选中框的位置
    if (_fastIndex % 10 == 0) {
        [_itemBorderView setFrame:CGRectMake(-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 1){
        [_itemBorderView setFrame:CGRectMake(82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 2){
        [_itemBorderView setFrame:CGRectMake(2*82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 3){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 4){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, 84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 5){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 6){
        [_itemBorderView setFrame:CGRectMake(2*82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 7){
        [_itemBorderView setFrame:CGRectMake(82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 8){
        [_itemBorderView setFrame:CGRectMake(-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_fastIndex % 10 == 9){
        [_itemBorderView setFrame:CGRectMake(-1*XT, 84*XT-1*XT, 80*XT, 82*XT)];
    }

    // _fastIndex = 29 时选中框结束快速旋转，开启慢速旋转，时间间隔为0.45秒
    if (_fastIndex >= 29) {
        [_fastTimer invalidate];
        _slowTimer = [NSTimer scheduledTimerWithTimeInterval:0.45 target:self selector:@selector(slowTimerEvent) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:_slowTimer forMode:NSRunLoopCommonModes];
    }
}

NSTimer 慢速旋转事件

// 慢速移动动画
- (void)slowTimerEvent
{
    // _slowIndex 自增
    _slowIndex = _slowIndex + 1;

    // 顺时针移动转中框的位置
    if (_slowIndex % 10 == 0) {
        [_itemBorderView setFrame:CGRectMake(-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 1){
        [_itemBorderView setFrame:CGRectMake(82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 2){
        [_itemBorderView setFrame:CGRectMake(2*82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 3){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, -1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 4){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, 84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 5){
        [_itemBorderView setFrame:CGRectMake(3*82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 6){
        [_itemBorderView setFrame:CGRectMake(2*82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 7){
        [_itemBorderView setFrame:CGRectMake(82*XT-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 8){
        [_itemBorderView setFrame:CGRectMake(-1*XT, 2*84*XT-1*XT, 80*XT, 82*XT)];
    }else if (_slowIndex % 10 == 9){
        [_itemBorderView setFrame:CGRectMake(-1*XT, 84*XT-1*XT, 80*XT, 82*XT)];
    }

    // 当  _slowIndex >= _selectedIndex 时选中框结束慢速旋转，开启中奖奖品界面
    if (_slowIndex >= _selectedIndex) {
        [_slowTimer invalidate];

        dispatch_time_t delayTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5/*延迟执行时间*/ * NSEC_PER_SEC));
        dispatch_after(delayTime, dispatch_get_main_queue(), ^{
            self.startButton.userInteractionEnabled = YES;
            [self showLotteryRlesultView];
        });
    }
}