iOS 獲取 UIView 四個角座標：用 convertRect 簡單高效

需求

取得 UIView 在指定座標系（如父視圖或螢幕）中的四個頂點 CGPoint。

最佳方法：convertRect:fromView:

CGRect rect = [self.view convertRect:self.view.frame fromView:nil]; // 轉換到 self.view 座標系
// 或轉換到螢幕座標系
CGRect screenRect = [self.view convertRect:self.view.bounds toView:nil];

計算四個角

CGPoint topLeft     = rect.origin;
CGPoint topRight    = CGPointMake(rect.origin.x + rect.size.width, rect.origin.y);
CGPoint bottomLeft  = CGPointMake(rect.origin.x, rect.origin.y + rect.size.height);
CGPoint bottomRight = CGPointMake(rect.origin.x + rect.size.width, rect.origin.y + rect.size.height);

優點

• 一行取得位置與大小，自動處理視圖層級轉換
• 避免逐點 convertPoint: 繁瑣且易錯
• fromView:nil 表示轉換到視窗（螢幕）座標系

Swift 版本

let rect = view.convert(view.bounds, to: nil)
let corners = [
    rect.origin,
    CGPoint(x: rect.maxX, y: rect.minY),
    CGPoint(x: rect.minX, y: rect.maxY),
    CGPoint(x: rect.maxX, y: rect.maxY)
]