Question

drawtestViewController.m中的Button链接到ChalkBoard.m中的pushPoint操作。它使用CGpoint对象填充pointArray。除了从drawRect查看外，此数组到处都是对象。它似乎是从drawRect我以某种方式引用原始数组的空副本，但我找不到任何错误...

我已将整个项目上传到http://dl.dropbox.com/u/42099382/drawtest.zip

drawtestViewController.m中的按钮操作

- (IBAction)myDo {
   NSLog(@"-Button was pressed");    
  [self.board pushPoint:CGPointMake(100, 100 )];
  [self.board pushPoint:CGPointMake(10, 100 )];
  [self.graphicView setNeedsDisplay];
}

//  ChalkBoard.h
#import <UIKit/UIKit.h>

@interface ChalkBoard : UIView
-(void)pushPoint:(CGPoint)point;
@property (nonatomic,retain) NSMutableArray *pointArray;
@end

//ChalkBoard.m
#import "ChalkBoard.h"

@implementation ChalkBoard
@synthesize pointArray;

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor blackColor];
    }
    return self;
}

-(NSMutableArray *)pointArray 
{
    if(pointArray == nil) pointArray = [[NSMutableArray alloc]initWithCapacity:10];
    return pointArray;
}

-(void)pushPoint:(CGPoint)point{
    // this is called from drawtestViewController.m by button press
    // in here the array is full and growing by each button press
    [self.pointArray addObject:[NSValue valueWithCGPoint:point]];
   NSLog(@"-pushPoint executed, size is %u, array: %@",[self.pointArray count], pointArray);
}

- (void)drawRect:(CGRect)rect{
// here array is always empty
NSLog(@"-DrawRect executed, size is %u, array: %@",[pointArray count], pointArray);
    if ([pointArray count] >1){   
       ... some irrelevant code
    }
}

@end

NSLog output

2012-04-09 11:34:39.145 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)
2012-04-09 11:34:41.261 drawtest[5260:f803] -Button was pressed
2012-04-09 11:34:41.262 drawtest[5260:f803] -pushPoint executed, size is 1, array: (
    "NSPoint: {100, 100}"
)
2012-04-09 11:34:41.264 drawtest[5260:f803] -pushPoint executed, size is 2, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}"
)
2012-04-09 11:34:41.266 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)
2012-04-09 11:34:42.825 drawtest[5260:f803] -Button was pressed
2012-04-09 11:34:42.826 drawtest[5260:f803] -pushPoint executed, size is 3, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}",
    "NSPoint: {100, 100}"
)
2012-04-09 11:34:42.827 drawtest[5260:f803] -pushPoint executed, size is 4, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}",
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}"
)
2012-04-09 11:34:42.829 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)

Answer 1

在pointArray方法中将self.pointArray替换为drawRect。使用pointArray时，变量按原样使用（不使用getter方法调用）。当您使用self.pointArray时，将使用getter方法。

我还建议你将getter和setter留给编译器，在init方法中生成并初始化你的pointArray。

Answer 2

问题实际上不在您的Chalkboard课程中，而在于您的drawtestViewcontroller。您的myDo操作会将积分添加到self.board，但会将setNeedsDisplay邮件发送至self.graphicView，该Chalkboard也是{{1}}，但与您添加的{{1}}不同指向。

因此，您看到的第二条日志消息实际上来自一个完全不同的对象。

drawRect见空数组

2 个答案: