绘图视图在drawRect Objective-c OSX中无限地实例化新的子视图

Question

我正在绘制一个非结构化的二叉树。我现在遇到的问题是，当我构建应用程序时，它会进入一个无限循环，一直在创建新的 nodeView 对象。

我是编程绘图的新手。我知道我犯了一些可能相当明显的基本错误。在不不断地重新实例化这些的情况下，绘制我的 NSView 树的最佳方法是什么。

理想情况下，我希望能够拖放 NSView 节点。我稍后可以弄清楚，这些信息只是以防万一它以某种方式有所帮助。

- (void)drawRect:(NSRect)dirtyRect {
    if (!hasSetUp) [self setUp];
    [super drawRect:dirtyRect];

    DTNodeView *nodeView = [[DTNodeView alloc] initWithFrame:NSMakeRect(200, 200, 100, 100)];
    //[self addSubview:nodeView];


    [[NSColor yellowColor] set];
    NSRectFill([self frame]);

    //NSLog(@"Subviews are: %@", [self.window.contentView subviews]);

    NSLog(@"Left tree height: %i", leftTree.treeHeight);

    double deltaY = (self.window.frame.size.height / 2) / ([leftTree treeHeight] + 1);
    [self drawSubtreeFromNode:[leftTree root] yValue:self.window.frame.size.height - 100 yDecrement:deltaY leftBound:0 rightBound:self.window.frame.size.width / 2];

    // Drawing code here.
}

-(void)drawSubtreeFromNode:(DTNode *)node yValue:(double)y yDecrement:(double)deltaY leftBound:(double)left rightBound:(double)right {

    double x = (left + right) / 2; // Draw the node in between the parents

    DTNodeView *selfRoot = [[DTNodeView alloc] initWithFrame:NSMakeRect(x, y, 100, 50) andNode:node];
    [self addSubview:selfRoot];

    if ([node hasLeft]) {
        double y2 = (y - deltaY);
        double x2 = (left + ((left + right)/2))/2;


        [[NSColor redColor] set];
        NSBezierPath *line = [[NSBezierPath alloc] init];
        [line setLineWidth:2];
        [line moveToPoint:NSMakePoint(x, y)];
        [line lineToPoint:NSMakePoint(x2, y2)];
        [line stroke];

        //drawSubtree(node.getLeft(), y-yDecrement, yDecrement, left, ((left + right)/2));
        [self drawSubtreeFromNode:[node left] yValue:(y - deltaY) yDecrement:deltaY leftBound:left rightBound:((left + right) / 2)];

    }

    if ([node hasRight]) {
        double x2 = (right + ((left + right)/2))/2;
        double y2 = (y - deltaY);

        [[NSColor redColor] set];
        NSBezierPath *line = [[NSBezierPath alloc] init];
        [line setLineWidth:2];
        [line moveToPoint:NSMakePoint(x, y)];
        [line lineToPoint:NSMakePoint(x2, y2)];
        [line stroke];


        //drawSubtree(node.getRight(), y-yDecrement, yDecrement, ((left + right)/2), right);
        [self drawSubtreeFromNode:[node right] yValue:(y - deltaY) yDecrement:deltaY leftBound:((left + right) / 2) rightBound:right];

    }

}

Answer 1

在 drawRect 方法中，你应该绘制而不是别的。它不是创建视图并将它们添加到他们的超级视图的地方。很明显，添加子视图意味着需要重新绘制视图，然后会创建新的子视图等等等等。