NSPopUpButton, NSComboBox similar menu

问题:

I'm trying to create a menu with a drop down menu with a custom background for every cell. First i tried to adapt NSPopUpButton but i couldn't find a way to change the cells background image. Using setImage: would slide the text to the right of the background. Next I stopped at NSComboBox but i couldn't find a way to change the arrow button. Can someone please help with and idea? Next thing would be to create a custom controller but i would like to use something already done.

回答1:

To customise the arrow button in NSComboBox, you need to create a subclass of NSComboBoxCell and set your combo box to use that cell. If you've configured your control in IB, you can easily change the class of your cell there. If you're programmatically creating your combo box, create a subclass of NSComboBox, override + (Class)cellClass and return your custom NSComboBoxCell subclass from that method.

Now for the drawing. In your NSComboBoxCell subclass, you need to override - (void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView.

(I've tried overriding - (void)drawInteriorWithFrame:(NSRect)cellFrame inView:(NSView *)controlView but the cell frame it provides stops short of drawing the actual button area, i.e. it only covers the text input area.)

Your custom - (void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView should look something like this:

- (void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView {
    [super drawWithFrame:cellFrame inView:controlView];

    // Constrain to the far right of the provided frame to draw the button
    NSRect bounds = NSMakeRect(cellFrame.origin.x + cellFrame.size.width - cellFrame.size.height, cellFrame.origin.y, cellFrame.size.height, cellFrame.size.height);

    // Draw your custom button inside the bounds rect
}

回答2:

I'm not sure if I understood your question correctly. If you want to show a menu at an arbitrary position somewhere in your UI: NSMenu provides convenience methods for achieving that. Have a look at the documentation for + popUpContextMenu:withEvent:forView:, + popUpContextMenu:withEvent:forView:withFont: and – popUpMenuPositioningItem:atLocation:inView: to find the one that best fits your needs. Like that you can display a menu at whatever position you like.

If you instead want to display arbitrary content inside a menu, have a look at the documentation of NSMenuItem's - setView:. This allows you to insert views inside menus. Together with the above method of displaying menus wherever you want, you can create all sorts of solutions for "PopOver" needs.