objective-c - Animated loader like Snapchat

Question

I was wonder how snapchat animates that ghost thing when you pull down to refresh? I wanted to implement that in my app and was wondering how it was done.

Answer 1

我认为您需要编写自己的解决方案。但这真的没那么难。

您需要创建一个包含可拉伸图像的自定义表头视图，并在UITableViewDelegate. 下面是自定义刷新控件处理的一个相当通用的实现。

1）创建一个自定义 UIView 作为您的下拉指示器视图：

头文件：

#import <UIKit/UIKit.h>

typedef enum UpdateListViewState
{
    UpdateListViewStatePull,
    UpdateListViewStateRelease,
    UpdateListViewStateUpdate

}UpdateListViewState;


@interface UpdateListView : UIView
@property (nonatomic,readwrite) UpdateListViewState state;
@property (nonatomic,strong) UIImageView imageView;
@end

2）将 headerView 分配为 tableView 标题：

self.header = [[UpdateListView alloc] init];
self.table.tableHeaderView = self.header;

3）在你的UITableViewDelegate，实现表格滚动处理：

const int UPDATE_DRAG_HEIGHT = -70; 

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset 
{
    if (self.header.state == UpdateListViewStateRelease) {
       //Perform update stuff here & perhaps refresh animation
       self.header.state = UpdateListViewStateInitial;

    }
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //adjust size of self.header.imageView here according to scrollView.ContentOffset
    if (scrollView.contentOffset.y < UPDATE_DRAG_HEIGHT && self.header.state != UpdateListViewStateUpdate) {
            self.header.state = UpdateListViewStateRelease;
    }
}