Question

我想在我的UITextView中绘制线条。经过一番研究后我发现了这个：

UITextView ruled line background but wrong line height

我在我的代码中尝试过，调用了drawRect但是没有绘制线条。有人可以帮助我吗？

#import "FacebookViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface MyViewController (){
UITextView *text;
}

@end

@implementation MyViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    // Do any additionnal customisation
}
return self;
}

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
text.contentMode = UIViewContentModeRedraw;
//TextView init
text = [[UITextView alloc]initWithFrame:CGRectMake(0,44,320,380)];
[self.view addSubview:text];
text.delegate = self;
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

- (void)drawRect:(CGRect)rect {
NSLog(@"TEST");
//Get the current drawing context
CGContextRef context = UIGraphicsGetCurrentContext();
//Set the line color and width
CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
CGContextSetLineWidth(context, 1.0f);
//Start a new Path
CGContextBeginPath(context);

//Find the number of lines in our textView + add a bit more height to draw lines in the empty part of the view
NSUInteger numberOfLines = (text.contentSize.height + text.bounds.size.height) / text.font.leading;

//Set the line offset from the baseline. (I'm sure there's a concrete way to calculate this.)
CGFloat baselineOffset = 6.0f;

//iterate over numberOfLines and draw each line
for (int x = 0; x < numberOfLines; x++) {
    //0.5f offset lines up line with pixel boundary
    CGContextMoveToPoint(context, text.bounds.origin.x, text.font.leading*x + 0.5f + baselineOffset);
    CGContextAddLineToPoint(context, text.bounds.size.width, text.font.leading*x + 0.5f + baselineOffset);
}

CGContextClosePath(context);
CGContextStrokePath(context);
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
[text setNeedsDisplay];
}

@end

可能是一个愚蠢的错误，但我找不到它

由于

Answer 1

当我看着你的代码时，一切都很好。也许有颜色的东西？可能与背景颜色相同或类似。

可能忘了设置内容模式：

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.contentMode = UIViewContentModeRedraw;
    }
    return self;
}

修改

我想我知道：您在显示后忘记设置[myTextView setNeedsDisplay];。 Read here

修改

首先创建视图：

t = [[[MyTextView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, 200)] autorelease]; [self.view addSubview:t]; t.delegate = self;

使你的viewcontroller实现UITextViewDelegate并在那之后

- (void)scrollViewDidScroll:(UIScrollView *)scrollView { [t setNeedsDisplay]; }

这应该有效

Answer 2

我有同样的问题.. 我认为你不是UITextView的子类

由于UIViewController没有实现此方法，只有UITextView执行

所以只需将其子类化..您的代码将起作用

Answer 3

您是否有可能成功绘制但是被匹配的背景颜色遮挡了？我注意到你选择的颜色的alpha非常小。如果只是为了排除这一点，请更改：

CGContextSetStrokeColorWithColor(context, [UIColor colorWithWhite:0.5f alpha:0.15f].CGColor);

到

CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);

在UITextView中绘制线条

3 个答案: