Question

我是初学者。我只是想在不使用IB的情况下绘制一条简单的线条。我用的代码是

lineViewController.m

-(id)init
{
    if(self = [super init])
    {
        myView = [[UIView alloc]initWithFrame:CGRectMake(0,0,320,440)];
        myView.backgroundColor = [UIColor grayColor];
        mView = [[UIView alloc]initWithFrame:CGRectMake(0,0,200,200)];

        self.view = myView;
        [myView addSubView:mView];          
    }
    return self;
}

-(void)viewWillAppear:(BOOL)animated
{
    line = [[MyView alloc]init];
    [line setNeedsDisplay];         
}

MyView.m

#import "MyView.h"

@implementation MyView

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        // Initialization code
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    CGFloat red[4] = {1.0f, 0.0f, 0.0f, 1.0f};
    CGContextSetStrokeColor(c, red);
    CGContextBeginPath(c);
    CGContextMoveToPoint(c, 150.0f, 200.0f);
    CGContextSetLineWidth(c, 5.0f);
    CGContextAddLineToPoint(c, 50,300);
    CGContextAddLineToPoint(c, 260,300);
    CGContextClosePath(c);
}

但我无法画画。你能帮我么。提前谢谢。

Answer 1

viewWillAppear中的代码不执行任何操作，因为行永远不会添加到视图层次结构中。由于上述原因，MyView drawRect从未被调用，而“myView”被分配为UIView而不是MyView。尝试在视图控制器init中更改alloc。

myView = [[MyView alloc]initWithFrame:CGRectMake(0,0,320,440)];

此外，代码将按写入方式泄漏。留意保留＆amp;释放内存管理。

如何在不使用Interface Builder的情况下绘制简单的线条？

1 个答案: