cell实现跑马灯效果

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic ) IBOutlet UITableView *testTableView;
@property (weak, nonatomic ) IBOutlet NSLayoutConstraint *bottomLine;

@property (weak, nonatomic ) IBOutlet NSLayoutConstraint *topLine;
@property (weak, nonatomic ) IBOutlet NSLayoutConstraint *topLine2;
@property (weak, nonatomic ) IBOutlet NSLayoutConstraint *bottomLine2;


@property (strong, nonatomic ) CADisplayLink *displayLink;


@property (assign, nonatomic ) int count;

@property (strong, nonatomic ) NSArray *dataArray;
@end

@implementation ViewController

- ( void )viewDidLoad {
    [ super viewDidLoad];

    self .count = 0;
    self .testTableView.delegate = self ;
    self .testTableView.dataSource = self ;

    self .displayLink = [CADisplayLink displayLinkWithTarget: self selector: @selector (tick:)];
    [ self .displayLink addToRunLoop:[ NSRunLoop currentRunLoop]
                           forMode: NSDefaultRunLoopMode ];
    //测试数据----->将需要展示的数据进行拼接,比如需要展示的数据数组为 @[@"1",@"2",@"3",@"4",@"5"] 那么需要拼接新数组 为 @[@"1",@"2",@"3",@"4",@"5",@"1",@"2",@"3",@"4",@"5"],示例如下
    self .dataArray = [ NSArray arrayWithObjects: @"1" , @"2" , @"3" , @"4" , @"5" , @"1" , @"2" , @"3" , @"4" , @"5" , nil ];

    [ self .testTableView setContentOffset:CGPointMake(0, 0) animated: YES ];

    self .testTableView.userInteractionEnabled = NO ;

}

//CADisplayLink 定时器 系统默认每秒调用60次
- ( void ) tick:(CADisplayLink *)displayLink {

    self .count ++;
    //(25.0 / 30.0) * (float)self.count) ---> (tableview需要滚动的contentOffset / 一共调用的次数) * 第几次调用
    //比如该demo中 contentOffset最大值为 = cell的高度 * cell的个数 ,5秒执行一个循环则调用次数为 300,没1/60秒 count计数器加1,当count=300时,重置count为0,实现循环滚动.
    [ self .testTableView setContentOffset:CGPointMake(0, ((25.0 / 30.0) * ( float ) self .count)) animated: NO ];

    if ( self .count >= 300) {

        self .count = 0;
    }
}

- ( void )didReceiveMemoryWarning {
    [ super didReceiveMemoryWarning];
}


- ( NSInteger )tableView:(UITableView *)tableView numberOfRowsInSection:( NSInteger )section {

    return self .dataArray.count;

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:( NSIndexPath *)indexPath {

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: @"cell" ];

    if (cell == nil ) {

        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier: @"cell" ];
    }

    cell.textLabel.text = self .dataArray[indexPath.row];

    cell.backgroundColor = [UIColor clearColor];
    return cell;
}

- (CGFloat) tableView:(UITableView *)tableView heightForRowAtIndexPath:( NSIndexPath *)indexPath {

    return 50;
}

- ( void )dealloc {

    [ self .displayLink invalidate];
    self .displayLink = nil ;

}

@end