ios 根據圖片大小設置button的尺寸

// 添加一個加號按鈕
    UIButton *addButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [addButton setImage:[UIImage imageNamed:@"tag_add_icon"] forState:UIControlStateNormal];
    addButton.x = TbTopicCellMargin;
    addButton.size = addButton.currentImage.size;
    [addButton addTarget:self action:@selector(add) forControlEvents:UIControlEventTouchUpInside];
    [self.topView addSubview:addButton];
    self.addButton = addButton;

1>咱們知道imageNamed是有緩存的，從新再次拿到同一個圖片名稱，內存地址打印是相同的，沒必要擔憂又加載了一次圖片

addButton.size = [UIImage imageNamed:@"tag_add_icon"].size;

2>根據狀態獲取圖片大小

addButton.size = [addButton imageForState:UIControlStateNormal].size;

3>根據當前圖片獲取圖片大小

addButton.size = addButton.currentImage.size;