Question

我想要的是淡化第一张图片并显示下一张图片。我在资源中有3张图片 bundle我能够从第一个图像淡入到下一个然后然后appcrashes在控制台中发出错误..NSInvalidArgumentException- [NSCFString objectAtIndex：]：发送到实例0x5e的无法识别的选择器...下面是代码..你们伙计们帮助我。

标题

中的

UIImageView *imageViewBottom, *imageViewTop;

NSArray *imageArray;

实施

int topIndex = 0, prevTopIndex = 1; 
-(void)viewDidLoad
{
  imageViewBottom = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,480)];
  [self.view addSubview:imageViewBottom]; 

  imageViewTop = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,480)];
  [self.view addSubview:imageViewTop];

  imageArray = [NSArray arrayWithObjects:  
                  [UIImage imageNamed:@"lori.png"],
                  [UIImage imageNamed:@"miranda.png"],
                  [UIImage imageNamed:@"taylor.png"],
                  [UIImage imageNamed:@"ingrid.png"],
                  [UIImage imageNamed:@"kasey.png"], 
                  [UIImage imageNamed:@"wreckers.png"], nil];


  NSTimer *timer = [NSTimer timerWithTimeInterval:5.0 
                                              target:self 
                                            selector:@selector(onTimer) 
                                            userInfo:nil 
                                             repeats:YES];

  [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
  [timer fire];

  [super viewDidLoad];
}

-(void)onTimer
{    
  if(topIndex %2 == 0)
  {   
    [UIView animateWithDuration:5.0 animations:^    
    {
      imageViewTop.alpha = 0.0;
    }]; 
    imageViewTop.image = [imageArray objectAtIndex:prevTopIndex];

    imageViewBottom.image = [imageArray objectAtIndex:topIndex];
  }
  else
  {
    [UIView animateWithDuration:5.0 animations:^       
    {     
      imageViewTop.alpha = 1.0;
    }];        
    imageViewTop.image = [imageArray objectAtIndex:topIndex];

    imageViewBottom.image = [imageArray objectAtIndex:prevTopIndex];
  } 
  prevTopIndex = topIndex; 

  if(topIndex == [imageArray count] - 1)
  {
    topIndex = 0; 
  }
  else
  {
    topIndex++; 
  }
}

Answer 1

[NSArray arrayWithObjects:...]已自动释放，因此当您尝试访问时，您正在拾取垃圾

你需要

imageArray = [[NSArray arrayWithObjects:  
                  [UIImage imageNamed:@"lori.png"],
                  [UIImage imageNamed:@"miranda.png"],
                  [UIImage imageNamed:@"taylor.png"],
                  [UIImage imageNamed:@"ingrid.png"],
                  [UIImage imageNamed:@"kasey.png"], 
                  [UIImage imageNamed:@"wreckers.png"], nil] retain];

不要忘记在dealloc中发布

-(void)dealloc
{
[imageArray release];
[super dealloc];
}

[编辑]关于计时器和评论

尝试使用

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:5.0 
                                              target:self 
                                            selector:@selector(onTimer:) 
                                            userInfo:nil 
                                             repeats:YES];

而不是

NSTimer *timer = [NSTimer timerWithTimeInterval:5.0 
                                              target:self 
                                            selector:@selector(onTimer) 
                                            userInfo:nil 
                                             repeats:YES];

  [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
  [timer fire];

我感觉你的构造以某种方式锁定了线程。我可能错了。

-(void)onTimer:(NSTimer *)aTimer
{
...
}

也是首选签名。

从资源中淡化iphone中的图像

1 个答案: