Xcode 使用单个按钮更改UIImage上的不同图像

我正在尝试编写一个UIButton，它可以更改UIImageView中的图像列表。下面列出了代码。但是，在更改所有图像并到达最后一个图像后，需要单击按钮两次才能返回到第一个图像。我可以知道如何修改它吗

谢谢大家

-(IBAction)changeimage:(id)sender{

if (currentimage ==0) {
    NSString *strTemp = [[NSString alloc]initWithString:@"stamp.png"];
    currentimage =1;
    aImage.image=[UIImage imageNamed:strTemp];
}
else if (currentimage ==1) {
    NSString *strTemp = [[NSString alloc]initWithString:@"yoda.jpg"];
    currentimage =2;
    aImage.image=[UIImage imageNamed:strTemp];
}
else if (currentimage ==2) {
    NSString *strTemp = [[NSString alloc]initWithString:@"44cents.jpg"];
    currentimage =3;
    aImage.image=[UIImage imageNamed:strTemp];
}
else (currentstamp =0);
}

很简单

-(IBAction)changeimage:(id)sender{

    if(currentimage == 3){
    currentimage  = 0;
    }

    if (currentimage ==0) {
        NSString *strTemp = [[NSString alloc]initWithString:@"stamp.png"];
        currentimage =1;
        aImage.image=[UIImage imageNamed:strTemp];
    }
    else if (currentimage ==1) {
        NSString *strTemp = [[NSString alloc]initWithString:@"yoda.jpg"];
        currentimage =2;
        aImage.image=[UIImage imageNamed:strTemp];
    }
    else if (currentimage ==2) {
        NSString *strTemp = [[NSString alloc]initWithString:@"44cents.jpg"];
        currentimage =3;
        aImage.image=[UIImage imageNamed:strTemp];
    }