objective-c - 绘制 NSRect 时出现问题

Question

我的问题是，当 Action UpdateRect 调用drawRect方法时，我的矩形没有更新高度!

当我点击按钮时，我期望看到我的矩形高度为 20，但它仍然是 10。为什么？

@implementation Graphic_view

int height = 10; //The height of my rect.

-(IBAction)updateRect:(id)sender {
    height += 10;
    //Calling the drawrect method
    [self performSelector:@selector(drawRect:)];
}

-(void)drawRect:(NSRect)dirtyRect {
    NSLog(@"DrawRect has been called !");
    // Drawing code here.
    NSRect viewBounds = [self bounds];
    NSColor *color = [NSColor orangeColor];
    [colore set];
    NSRectFill(viewBounds);
    NSRect myRect;
    myRect.origin.x = 20;
    myRect.origin.y = 20;
    myRect.size.height = height;
    myRect.size.width = 100;
    NSColor *whiteColor = [NSColor whiteColor];
    [whiteColor set];
    NSRectFill(myRect);
} 

@end

Answer 1

你永远不应该自己调用drawRect:。而是调用 setNeedsDisplay:

-(IBAction)updateRect:(id)sender {
    height += 10;
    // Schedule the drawrect method
    [self setNeedsDisplay:YES];
}

注意:iOS 等效项是不带参数的 setNeedsDisplay。