Question

我试图在UIView中绘制文字，＆＃39;擦除＆＃39;它，然后在不同的位置再次绘制它。（或者改为绘制不同的文字）

我有单页应用，故事板，Xcode 5，iOS 7。我已经为UIView创建了一个子类，并且可以使用＆＃39; drawRect＆＃39;来绘制一个单独的字符串。方法。但是，这只会被调用一次，因此无用。

我已经在我的子类中创建了另一个方法，但是调用它似乎不起作用。

如何创建一个可以反复调用以绘制文本的方法？

这是我的代码： MyView.h

#import <UIKit/UIKit.h>

@interface MyView : UIView

-(void)drawIt:(NSString *)inText;
@end

MyView.m

#import "MyView.h"

@implementation MyView

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

// This executes once and works
-(void)drawRect:(CGRect)myRect{
    UIFont *myFont=[UIFont fontWithName:@"Helvetica" size:30];
    NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
    paragraphStyle.alignment = NSTextAlignmentLeft;

    NSMutableDictionary *attributes = [[NSMutableDictionary alloc] init];
    [attributes setObject:myFont forKey:NSFontAttributeName];
    [attributes setObject:paragraphStyle forKey:NSParagraphStyleAttributeName];
    [attributes setObject:[UIColor blackColor] forKey:NSForegroundColorAttributeName];
    [@"TEST"  drawInRect:myRect withAttributes:attributes];
}

//This is what I'd like to call repeatedly with different text or clear, etc...
//However nothing shows when I call it
-(void)drawIt:(NSString *)inText{
    CGRect myRect=CGRectMake(0,0,self.bounds.size.width,self.bounds.size.height);
    UIFont *myFont=[UIFont fontWithName:@"Helvetica" size:30];

    NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
    paragraphStyle.alignment = NSTextAlignmentRight;

    NSMutableDictionary *attributes = [[NSMutableDictionary alloc] init];
    [attributes setObject:myFont forKey:NSFontAttributeName];
    [attributes setObject:paragraphStyle forKey:NSParagraphStyleAttributeName];
    [attributes setObject:[UIColor blackColor] forKey:NSForegroundColorAttributeName];
    [inText drawInRect:myRect withAttributes:attributes];
}
@end

在我的ViewController.m中：

#import "TextDrawViewController.h"
#import "MyView.h"

@interface TextDrawViewController ()

@end

@implementation TextDrawViewController

- (void)viewDidLoad{
    [super viewDidLoad];

    MyView *xView = [[MyView alloc] init];

    [xView drawIt:@"junk"];
}
@end

Answer 1

最好将所有绘图代码放到-(void)drawRect:(CGRect)myRect方法中更新文字和位置调用[self setNeedsDisplay];后，iOS会自动调用drawRect:方法。

在UIView中绘制文本然后清除它然后在另一个地方再次绘制

1 个答案: