我是Objective-C和iOS的新手。我遇到了一些可能很容易纠正的问题，但我不知道为什么会发生这种情况。
我会尝试简要介绍一下我正在做的事情，并希望它有足够的信息来发现错误。
PolygonView.h是一个UIView类型的类，它像这样声明NSmutablearray：
@property(nonatomic, retain) NSMutableArray *polys;
我在PolygonView.m的initWithFrame：（CGRect）Frame方法中初始化它，如下所示：
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
polys = [[NSMutableArray alloc]init];
[self loadCsv];
return self;
}
在loadCSV中我加载一个csv用它来创建一些多边形对象并做一些其他的东西，但这里是它的要点：
poly* p;
p = [[poly alloc] init];
// here I set a few properties on p from the csv file and then add p to polys like this:
[polys addObject:p];
在方法结束时，我使用nslog打印计数，如下所示：
NSLog(@"polys size = %i", [polys count]);
这会在控制台上打印“polys size = 100”。
然后我决定做自己的drawRect。并且它的开头使用相同的nslog来打印大小/计数，但控制台上会打印“polys size = 0”。
我做错了什么？如何从drawRect方法访问我添加到此数组的对象？
编辑： 这是完整的polygonView.h文件：
#import <UIKit/UIKit.h>
@interface PolygonView : UIView{
NSMutableArray *polys;
}
@property(nonatomic, retain) NSMutableArray *polys;
-(void)loadCSV;
@end
编辑2：完整的多边形
//
// PolygonView.m
// Polygon2
//
#import "PolygonView.h"
#import "poly.h"
@implementation PolygonView
@synthesize polys;
-(id)init
{
NSLog(@"regular init");
self = [super init];
if (self) {
self.polys = [[NSMutableArray alloc]init];
[self loadCsv];
}
return self;
}
- (id)initWithFrame:(CGRect)frame
{
NSLog(@"init with frame");
self = [super initWithFrame:frame];
if (self) {
self.polys = [[NSMutableArray alloc]init];
[self loadCsv];
}
return self;
}
-(void)loadCsv
{
poly* p;
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"DivisoesEstaduais" ofType:@"csv"];
NSString *testString = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
NSString *newString = [testString stringByReplacingOccurrencesOfString:@"," withString:@"."];
if (newString) {
NSMutableArray *arrr = [newString componentsSeparatedByString:@"\n"];
for (int i = 0; i < [arrr count]; i++){
if ([[arrr objectAtIndex:i] length] > 0){
p = [[poly alloc] init];
NSMutableArray *arrayatual = [[arrr objectAtIndex:i] componentsSeparatedByString:@";"];
[p setPolyid:[arrayatual objectAtIndex:0]];
[p setPartid:[arrayatual objectAtIndex:1]];
[p setPointid:[arrayatual objectAtIndex:2]];
[p setx:[arrayatual objectAtIndex:3]];
[p sety:[arrayatual objectAtIndex:4]];
[self.polys addObject:p];
NSLog(@"polys size = %i", [self.polys count]); // this increases from 1 to 100
}
}
NSLog(@"polys size = %i", [self.polys count]); // this prints 100
}else{
NSLog(@"not");
}
}
- (void)drawRect:(CGRect)rect{
srandom( time( NULL ) );
CGContextRef context= UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, random() % 250, random() % 250, random() % 250, 1.0);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillPath(context);
int oldtemp = 0;
NSLog(@"drawRect polys pointer = %@", self.polys); // this is null
NSLog(@"polys size = %i", [self.polys count]); // this is zero
for (int i = 0; i < [polys count]; i++){
poly *p = [polys objectAtIndex:i];
int temp = p.getPolyid.intValue;
if (temp == oldtemp){
CGFloat hue = ( arc4random() % 256 / 256.0 ); // 0.0 to 1.0
CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from white
CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from black
UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
CGContextSetFillColorWithColor(context, color.CGColor);
CGContextFillPath(context);
NSLog(@"movetopoint");
CGContextMoveToPoint(context, [p.getx floatValue]+160, [p.gety floatValue]+160);
oldtemp++;
}else{
CGContextAddLineToPoint(context, [p.getx floatValue]+160, [p.gety floatValue]+160);
NSLog(@"addlinetopoint");
}
}
CGFloat hue = ( arc4random() % 256 / 256.0 ); // 0.0 to 1.0
CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from white
CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from black
UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
CGContextSetFillColorWithColor(context, color.CGColor);
CGContextFillPath(context);
}
@end
这里是viewController.m：
//
// ViewController.m
// Polygon2
//
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.view.multipleTouchEnabled = YES;
PolygonView * pv = [[PolygonView alloc] init];
[self.view addSubview:pv];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
EDIT3：
George Sachin的解决方案有效：使用viewDidAppear而不是viewDidLoad。但是为什么viewDidLoad会给我带来麻烦？这是拉链项目，以防有人想看一看并试图找出答案。 http://www.mediafire.com/download/b9ueqkqbmxswd7a/Polygon2_3.zip
对我来说，ViewDidload是我应该使用的。我应该从不使用它吗？
答案 0 :(得分：2)
最终修改：
当您为UIView创建初始化程序时，您应该始终调用super的initWithFrame：或initWithCoder：当您使用.xib时
将您的代码更改为：
-(id)init
{
NSLog(@"regular init");
self = [super initWithFrame:CGRectMake(0, 0, 20, 20)]; // Replace with the dimensions you want
if (self) {
self.polys = [[NSMutableArray alloc]init];
[self loadCsv];
}
NSLog(@"(init)polys size = %i", [self.polys count]);
return self;
}
答案 1 :(得分：0)
尝试这样做：
1）当您将@property(nonatomic, retain) myObj设置为对象时，您应该在.m文件中@synthesize myObj
2）因为HSNN说您应该通过self.myObj
访问它3）最好在这部分之间进行初始化
if (self) {
// Initialization code
}
短语“初始化代码”不是偶然放在那里））
问题的根源很可能被遗忘@synthesize，但最好覆盖所有3个步骤。