iOS开发渐变导航条升级版(判断滚动的方向和改变方向时的位置)

释放双眼,带上耳机,听听看~!

上一篇渐变导航条的,地址:iOS开发渐变导航栏

但是在中部滚动的时候不能实现渐变,类似的好的效果在百度贴吧里出现过,所以博主对那个Demo进行了改进,看下效果:

这里加上了对向上向下和改变方向时的位置的判断,下面看下代码:

#import "ViewController.h"
@interface ViewController ()<UIScrollViewDelegate,UITableViewDelegate,UITableViewDataSource>
{
UIImageView *barImageView;
UITableView *myTableView;
float _lastPosition;
float currentPostion;
float stopPosition;
}
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.view.backgroundColor=[UIColor whiteColor];
//    [self.navigationController.navigationBar setBackgroundImage:[UIImage new]
//                                                  forBarMetrics:UIBarMetricsDefault];
//    self.navigationController.navigationBar.shadowImage = [UIImage new];
_lastPosition = 0;
stopPosition = 0;
[[NSUserDefaults standardUserDefaults]setObject:@"1" forKey:@"first"];
[[NSUserDefaults standardUserDefaults]synchronize];
self.navigationController.navigationBar.barTintColor=[UIColor orangeColor];
self.title=@"This is my title!";
self.navigationController.navigationBar.tintColor = [UIColor blackColor];
myTableView=[[UITableView alloc]initWithFrame:self.view.bounds];
myTableView.delegate=self;
myTableView.dataSource=self;
[self.view addSubview:myTableView];
UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 320, 270)];
imageView.image=[UIImage imageNamed:@"1.png"];
myTableView.tableHeaderView=imageView;
barImageView = self.navigationController.navigationBar.subviews.firstObject;
NSString *str=@"122222";
}
#pragma mark - UITableViewDelaget
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 40;
}
-(CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 44;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:@"cell"];
if (!cell) {
cell=[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"];
}
cell.textLabel.text=[NSString stringWithFormat:@"%ld",indexPath.row];
return cell;
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{
[NSObject cancelPreviousPerformRequestsWithTarget:self];
stopPosition = currentPostion + 64;
NSLog(@"滑动停止:%f",stopPosition);
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
currentPostion = scrollView.contentOffset.y;
if (currentPostion > 0) {
if (currentPostion - _lastPosition >= 0) {
if ([[NSUserDefaults standardUserDefaults]objectForKey:@"first"]!=nil) {
[[NSUserDefaults standardUserDefaults]removeObjectForKey:@"first"];
[[NSUserDefaults standardUserDefaults]synchronize];
//                [NSObject cancelPreviousPerformRequestsWithTarget:self];
//                [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:nil afterDelay:0.00001];
[[NSUserDefaults standardUserDefaults]setObject:@"1" forKey:@"second"];
[[NSUserDefaults standardUserDefaults]synchronize];
stopPosition = currentPostion + 64;
}
_lastPosition = currentPostion;
NSLog(@"ScrollUp now    current:%f    last:%f    stop:%f",currentPostion,_lastPosition,stopPosition);
self.navigationController.navigationBar.alpha = 1 - currentPostion / 400;
}
else
{
if ([[NSUserDefaults standardUserDefaults]objectForKey:@"second"]!=nil) {
[[NSUserDefaults standardUserDefaults]removeObjectForKey:@"second"];
[[NSUserDefaults standardUserDefaults]synchronize];
//                [NSObject cancelPreviousPerformRequestsWithTarget:self];
//                [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:nil afterDelay:0.00001];
[[NSUserDefaults standardUserDefaults]setObject:@"1" forKey:@"first"];
[[NSUserDefaults standardUserDefaults]synchronize];
stopPosition = currentPostion + 64;
}
_lastPosition = currentPostion;
NSLog(@"ScrollDown now    current:%f   last:%f    stop:%f",currentPostion,_lastPosition,stopPosition);
self.navigationController.navigationBar.alpha = (stopPosition - currentPostion)/200;
}
}
}

这里有一个关于滚动停止的判断,但是博主注释了代码,在下一篇博客中,会针对滚动停止,和改变方向,以及滚动未停止时改变方向的情况作说明。

代码很简单,需要Demo的点击下载:下载

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