Button to trigger drawRect to redraw a view

问题

I have a VC with a subview. At the subview level I have a button. I want the button to result in the view being updated.

The IBAction code is in the VC. All it currently does is toggle a BOOL value.

Back in the subview drawRect: method is the code that tests the BOOL and changes the view accordingly.

My observation is that when the button is pressed, the IBAction code runs, toggles the BOOL, but the drawRect: method doesn't get called.

I tried calling drawRect manually (not good practice and didn't work). I tried calling setNeedsDisplay but that too didn't work (couldn't figure out how to reference the subview, which is created programmatically).

Suggestions welcome.

IBAction code is trivial but included below:

- (IBAction)rotateWindowButtonWasPressed:(id)sender
{
    // just flip the boolean here. Need to make the code change in drawRect: in top2View.m
    if ([myGlobals gWinVertical])
        [myGlobals setGWinVertical:NO];
    else
        [myGlobals setGWinVertical:YES];
    // Hoping this would force a redraw, but bounds have to change...:(
    //_top2ViewOutlet.contentMode = UIViewContentModeRedraw;
}

回答1:

to issue a drawRect call, call setNeedsDisplay on the view you changed.. the OS will call drawRect on it and affected overlapping views automatically.

in your case I think

[self.view setNeedsDisplay]

回答2:

Not sure what happened - there was an answer above that solved my issue but now it's gone? Anyway - the answer is to create the button programmatically and then I can include the method at the subview level where drawRect: is, and using setNeedsDisplay to repaint the screen. That vs. using IB and having the IBAction code at the VC level.

来源：https://stackoverflow.com/questions/15084270/button-to-trigger-drawrect-to-redraw-a-view

标签

ios

xcode

drawrect

ibaction

setneedsdisplay