如何获取UITableView单元格中的UIButton的绝对x，y

Question

In cellForRowAtIndexPath(), I allocate a UIButton in the cell. When button pressed, delegate is called that needs to allocate a UIImageView at the same absolute location on the screen as the button, in order to begin a drag of the UIImageView to elsewhere on the screen

But, when I read the x,y of delegate's 'sender' (the UIButton), the y is the relative y of the UIButton within the cell, and not the y of the UIButton on the iPad screen.

From within the delegate, how can I get absolute screen x,y of the UIButton that was allocated within the UITableView's cell?

THE CODE THAT MAKES THE UIBUTTON WITHIN cellForRowAtIndexPath()..................

                    // Put invisible UIButton on top of device icon, to detect start of drag:                    !!!
                    UIButton* invisible_drag_button = [UIButton buttonWithType:UIButtonTypeCustom];
                    invisible_drag_button.frame = CGRectMake    (x,y, w,h);        // location and size of device off icon
                    invisible_drag_button.tag = cell_record_index;      // store user device's record index
                    printf("%d  = invisible_drag_button.tag     aaaaaaaaaaaaaaaaa   \n", PWR_RX_status_index ); // !!!
                    printf("x=%d y=%d w=%d h=%d \n", x,y,w,h ); // !!!
                    [invisible_drag_button addTarget: self 
                                action:@selector( delegate_drag_start: )
                                forControlEvents: UIControlEventTouchDown ];
                    [cell.contentView addSubview: invisible_drag_button ];

THE DELEGATE THAT RESPONDS TO BUTTON PRESS...................

-(void)delegate_drag_start: (id)sender

{ int drag_record_index; // drag device's database record index

// Drag record index = database index of device:
    UIButton* invisible_drag_button = (UIButton*)sender;
    drag_record_index = invisible_drag_button.tag;      

printf("delegate_drag_start for drag_record_index %d.   \n", drag_record_index  );

// Lookup drag device's type from its record:
    int device_type = area_device_status[ device_area ][ drag_record_index ].device_type;

// Init UIImageView of drag device image:
    // Lookup its UIImage from its type, and allocate UIImageView of drag device image:
    self.device_drag_UIImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed: device_image_filename( device_type )]];

    self.device_drag_UIImageView.userInteractionEnabled = YES;
    // Get screen location of touched device icon image:
        CGRect drag_button_frame = [invisible_drag_button frame];
        //CGPoint drag_button_location = CGPointMake(invisible_drag_button.frame.origin.x, invisible_drag_button.frame.origin.y);

                    printf("x=%d y=%d w=%d h=%d \n",    (int)drag_button_frame.origin.x, 
                                                        (int)drag_button_frame.origin.y, 
                                                        (int)drag_button_frame.size.width, 
                                                        (int)drag_button_frame.size.height  ); // !!!

            // Start drag image at same location as touched device image:
            self.device_drag_UIImageView.frame = CGRectMake(    drag_button_frame.origin.x, 
                                                                drag_button_frame.origin.y, 
                                                                drag_button_frame.size.width * DRAG_IMAGE_BIGGER_FACTOR, 
                                                                drag_button_frame.size.height * DRAG_IMAGE_BIGGER_FACTOR );

    [self.view addSubview: self.device_drag_UIImageView];
    [self.view bringSubviewToFront: self.device_drag_UIImageView];

}

Answer 1

Try this one:

[view convertPoint:pointToConvert toView:nil]

it converts a point from the receiver's coordinate system to that of the specified view. If second parametr is nil, it converts to window coordinate system.

Answer 2

Here's solution:

    CGRect drag_button_CGRect = [invisible_drag_button.superview convertRect:invisible_drag_button.frame toView:self.view];

..which gives me the correct, absolute x,y: drag_button_CGRect.origin.x drag_button_CGRect.origin.y

Answer 3

您需要的代码行是：

self.device_drag_UIImageView.center = [self.view convertPoint: invisible_drag_button.center fromView: invisible_drag_button.superview];

Answer 4

对于在那里的Swift人。

    let buttonRect = sender.superview?.convertRect(sender.frame, toView: self.tableView);