iOS Button 圖片互換：currentImage 屬性直接賦值

問題代碼

[btn2 setImage:[UIImage imageNamed:btn1.currentBackgroundImage] forState:UIControlStateNormal];
// 錯誤：currentBackgroundImage 是 UIImage，非 NSString

修正

[btn2 setImage:btn1.currentImage forState:UIControlStateNormal];
// 直接賦值 UIImage 對象

屬性區別

• currentImage：當前顯示的圖片（imageView.image）。
• currentBackgroundImage：當前背景圖片（backgroundImageView.image）。
• imageForState: / backgroundImageForState:：獲取指定狀態下的圖片。

完整示例

UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeCustom];
[btn1 setImage:[UIImage imageNamed:@"icon1.png"] forState:UIControlStateNormal];

UIButton *btn2 = [UIButton buttonWithType:UIButtonTypeCustom];
[btn2 setImage:[UIImage imageNamed:@"icon2.png"] forState:UIControlStateNormal];

[btn2 addTarget:self action:@selector(copyImage:) forControlEvents:UIControlEventTouchUpInside];

- (void)copyImage:(UIButton *)sender {
    [sender setImage:btn1.currentImage forState:UIControlStateNormal];
}