ios-尝试在图像上绘制点，然后通过线连接它们

Question

我可以使用 touchesbegan 中的代码在图像上绘制点。我将我的坐标存储在 NSMutable 数组中。我希望它在屏幕上标记点时画线..但我猜我的 drawRect 没有触发..你能告诉我该怎么做吗..

-(void) drawRect:(CGRect)rect
{

    int *count = 0;
    if([pointarray count]!=0)
    {
        float firstpointx= [[pointarray objectAtIndex:0]floatValue];
        float firstpointy= [[pointarray objectAtIndex:1]floatValue];
        float secondpointx= [[pointarray objectAtIndex:2]floatValue];
        float secondpointy= [[pointarray objectAtIndex:3]floatValue];

        //NSMutableArray *coordinates = [[NSMutableArray alloc] init];
        for (int i=0; i<=[pointarray count]; i++) {
            CGContextRef ctx = UIGraphicsGetCurrentContext();
            CGContextSetStrokeColorWithColor(ctx, [UIColor redColor].CGColor);
            CGContextSetLineWidth(ctx, 2.0);
            CGContextMoveToPoint(ctx, firstpointx, firstpointy);///move to ur first dot
            CGContextAddLineToPoint(ctx, secondpointx, secondpointy);//add line from first dot to second dot

            CGContextSetLineCap(ctx, kCGLineCapRound);
            CGContextStrokePath(ctx);
            [pointarray removeAllObjects];//remove first two points from ur array so that next line is not drawn in continuous with previous line
        }

        count++;

     }
}



-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{

    pointarray=[[NSMutableArray alloc]init];

    CGPoint curPoint = [[touches anyObject] locationInView:self.map];
    [pointarray addObject:[NSNumber numberWithFloat:curPoint.x]];
    [pointarray addObject:[NSNumber numberWithFloat:curPoint.y]];
    [_map setNeedsDisplay];

    [self logMessage:[NSString stringWithFormat:@"Sending : %@", pointarray]];
    NSLog(@"the point array is %@",pointarray);
    NSArray *coordinates = [[NSArray alloc]initWithArray:pointarray copyItems:YES];
    NSLog(@"the coordinate array %@",coordinates);

    //[self.map setNeedsDisplay]; // calls drawRectMethod

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(curPoint.x, curPoint.y, 10, 10)];
    view.backgroundColor = [UIColor redColor];
    [self.map addSubview:view];
}

Answer 1

在 touchedBegan:withEvent: 上，您只需在 _map 上调用 setNeedsDisplay，而不是在 self 上，这就是为什么 View 不会重绘。

此外，您只需添加两个点，但在 drawRect 中，如果确定数组包含四个点，您的代码就像这样。可能你想要做的是在touchesEnded:withEvent中添加两个点？如果是这样，您应该从那里调用 setNeedsDisplay。