在使用MJRefresh實(shí)現(xiàn)下拉刷新時(shí)，經(jīng)常有自定義刷新動(dòng)畫樣式的需求，那么我們就要在MJRefresh庫(kù)的基礎(chǔ)上代碼改造，并盡量做到改動(dòng)工作量最小。

1、新建一個(gè)對(duì)象，繼承自MJRefreshGifHeader

#import "MJRefreshGifHeader.h"

@interface YtGifHeader : MJRefreshGifHeader

@end

2、然后重寫方法- (void)prepare，重寫后記得實(shí)現(xiàn)[super prepare]

#pragma mark - 重寫父類的方法
- (void)prepare{
    [super prepare];
    
    // 設(shè)置普通狀態(tài)的動(dòng)畫圖片
    NSMutableArray *idleImages = [NSMutableArray array];
    for (NSUInteger i = 1; i<8; i++) {
        UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"load%lu", (unsigned long)i]];
        // 設(shè)置Gif的size 對(duì)image等比例壓縮
        UIImage *newImage = [image imageByScalingToSize:CGSizeMake(75, 65)];
        [idleImages addObject:newImage];
    }
    [self setImages:idleImages forState:MJRefreshStateIdle];
    
    // 設(shè)置即將刷新狀態(tài)的動(dòng)畫圖片（一松開就會(huì)刷新的狀態(tài)）
    NSMutableArray *refreshingImages = [NSMutableArray array];
    for (NSUInteger i = 1; i<8; i++) {
        UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"load%lu", (unsigned long)i]];
        // 設(shè)置Gif的size 對(duì)image等比例壓縮
        UIImage *newImage = [image imageByScalingToSize:CGSizeMake(75, 65)];
        [refreshingImages addObject:newImage];
    }
    [self setImages:refreshingImages forState:MJRefreshStatePulling];
    
    // 設(shè)置正在刷新狀態(tài)的動(dòng)畫圖片
    [self setImages:refreshingImages forState:MJRefreshStateRefreshing];
    
    //隱藏時(shí)間
    self.lastUpdatedTimeLabel.hidden = YES;
    //隱藏狀態(tài)
    self.stateLabel.hidden = YES;
}

3、在需要下拉刷新的控制器這樣實(shí)現(xiàn)既可

#import "YtGifHeader.h"

self.tableView.mj_header = [YtGifHeader headerWithRefreshingBlock:^{
        //刷新請(qǐng)求
    }];

注意事項(xiàng)：

mj_header視圖展示出來的是GIF原圖的大小，如果美工給的切圖稍大則效果很丑，那么我們就要在程序中控制GIF動(dòng)圖的Size，思路是對(duì)image等比例縮放

1、新建類別UIImage+Extras繼承自UIImage

#import <UIKit/UIKit.h>

@interface UIImage (Extras)

- (UIImage *)imageByScalingToSize:(CGSize)targetSize;

@end

2、配置對(duì)Image等比例縮放的代碼

#import "UIImage+Extras.h"

@implementation UIImage (Extras)

- (UIImage *)imageByScalingToSize:(CGSize)targetSize {
    
    UIImage *sourceImage = self;
    UIImage *newImage = nil;
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
    
    if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;
        if (widthFactor < heightFactor)
            scaleFactor = widthFactor;
        else
            scaleFactor = heightFactor;
        scaledWidth  = width * scaleFactor;
        scaledHeight = height * scaleFactor;
        // center the image
        if (widthFactor < heightFactor) {            
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
        } else if (widthFactor > heightFactor) {
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }
    // this is actually the interesting part:
    UIGraphicsBeginImageContext(targetSize);
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    [sourceImage drawInRect:thumbnailRect];
    newImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    if(newImage == nil) 
        NSLog(@"could not scale image");   
    return newImage ; 
}

@end

3、調(diào)用方法

        // 設(shè)置Gif的size 對(duì)image等比例壓縮
        UIImage *newImage = [image imageByScalingToSize:CGSizeMake(75, 65)];