objective-c - 将填充更改为已绘制的 NSBezierPath

Question

我想更改我绘制的按钮的填充(我将 NSButton 子类化)

这是我已经得到的代码:

- (void)drawRect:(NSRect)dirtyRect {
// Drawing code here.
// Create the Gradient 
NSGradient *fillGradient = [[NSGradient alloc] initWithStartingColor:[NSColor lightGrayColor] endingColor:[NSColor darkGrayColor]];
// Create the path
aPath = [NSBezierPath bezierPath];

[aPath moveToPoint:NSMakePoint(10.0, 0.0)];
[aPath lineToPoint:NSMakePoint(85.0, 0.0)];
[aPath lineToPoint:NSMakePoint(85.0, 20.0)];
[aPath lineToPoint:NSMakePoint(10.0, 20.0)];
[aPath lineToPoint:NSMakePoint(0.0, 10.0)];
[aPath lineToPoint:NSMakePoint(10.0, 0.0)];

[fillGradient drawInBezierPath:aPath angle:90.0];
[fillGradient release];
}

- (void)mouseDown:(NSEvent *)theEvent {
    NSGradient *fillGradient = [[NSGradient alloc] initWithStartingColor:[NSColor lightGrayColor] endingColor:[NSColor darkGrayColor]];
    [fillGradient drawInBezierPath:aPath angle:-90.0];
}

我收到一个 EXC_BAD_ACCESS 信号。我该怎么做？

Answer 1

EXC_BAD_ACCESS 的原因是以下行:

aPath = [NSBezierPath bezierPath];

创建一个autoreleased bezierPath，它将在运行循环的当前迭代结束时释放。为了避免该错误，您需要将其更改为:

aPath = [[NSBezierPath bezierPath] retain];

但是，您正在从错误的方向解决问题。绘图只能在 -drawRect: 方法(或仅从 -drawRect: 调用的方法)中完成。您应该为您的类创建一个新的 BOOL 实例变量(例如，称为 mouseIsDown )并在 mouseDown: 中进行设置。然后使用该 bool 值来确定如何填充按钮:

- (void)drawRect:(NSRect)aRect {
    NSGradient *fillGradient = nil;
    if (mouseIsDown)
        fillGradient = [[NSGradient alloc] initWithStartingColor:[NSColor lightGrayColor] endingColor:[NSColor darkGrayColor]];
    else
        fillGradient = [[NSGradient alloc] initWithStartingColor:[NSColor lightGrayColor] endingColor:[NSColor darkGrayColor]];

    // Do the rest of your drawRect method

}

- (void)mouseDown:(NSEvent *)theEvent {
    mouseIsDown = YES;
    [self setNeedsDisplay:YES];
}

- (void)mouseUp:(NSEvent *)theEvent {
    mouseIsDown = NO;
    [self setNeedsDisplay:YES];
}