ios - "Saved photo"在用户允许照片库权限之前弹出警报？

Question

当用户点击该按钮时，它会立即触发“照片已保存”警告，然后再询问用户许可。如果用户单击否，则照片不会保存，但仍会显示警告。是否有一个 if else 语句可以用来让它在用户允许访问照片库之前不会弹出警报？

@IBAction func savePhotoClicked(_ sender: Any) {


    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)


    let alert = UIAlertController(title: "Saved!", message: "This wallpaper has been saved.", preferredStyle: .alert)
    let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil)
    alert.addAction(okAction)
    self.present(alert, animated: true, completion: nil)


}

Answer 1

您过早地展示了警报 Controller 。对 UIImageWriteToSavedPhotosAlbum 的调用是异步的。看到您传递给第二个、第三个和第四个参数的所有那些 nil 值了吗？将它们替换为适当的值，这样您就可以在调用 UIImageWriteToSavedPhotosAlbum 实际完成时调用警报，并且您可以正确确定图像是否实际保存。

@IBAction func savePhotoClicked(_ sender: Any) {
    UIImageWriteToSavedPhotosAlbum(image, self, #selector(image(_:didFinishSavingWithError:contextInfo:)), nil)
}

@objc func image(_ image: UIImage, didFinishSavingWithError error: Error?, contextInfo: UnsafeRawPointer) {
    if let error = error {
        // show error
    } else {
        let alert = UIAlertController(title: "Saved!", message: "This wallpaper has been saved.", preferredStyle: .alert)
        let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil)
        alert.addAction(okAction)
        self.present(alert, animated: true, completion: nil)
    }
}