无法更改 UIImageView 中的图像

Question

我有一个图像视图，每次方向改变时我都试图改变图像视图的图像，但图像没有改变任何人都可以帮助我吗

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {


if (!mainBackgroundImageView) {
    mainBackgroundImageView=[[UIImageView alloc] init];
}
    if (interfaceOrientation==UIInterfaceOrientationPortrait || interfaceOrientation==UIInterfaceOrientationPortraitUpsideDown) {
    UIImage *tempImage=[UIImage imageNamed:@"dart-login-image.png"];
    [mainBackgroundImageView setImage:tempImage];
    [tempImage release];
}
else {
    [mainBackgroundImageView setImage:[UIImage imageNamed:@"background-and-header-integerated.png"]];
}

return YES;

}

Answer 1

// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    NSLog(@"interfaceOrientation");
    return (interfaceOrientation == UIInterfaceOrientationLandscapeRight,UIInterfaceOrientationLandscapeLeft,UIInterfaceOrientationPortrait, UIInterfaceOrientationPortraitUpsideDown);
    // take out the ones you DON'T want to be available
}

// if you want to change things based on orientation
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation duration:(NSTimeInterval)duration 
{
    switch (interfaceOrientation) 
    {
        case UIInterfaceOrientationPortrait:
        {       
            //changes for Portait
            NSLog(@"Portait");
            [imgView setFrame:CGRectMake(0,0,768,1024)];
            [imgView setImage:[UIImage imageNamed:@"1.jpg"]];
        }
            break;

        case UIInterfaceOrientationPortraitUpsideDown: 
        {
            //changes for PortaitUpsideDown
            NSLog(@"PortaitUpsideDown");
            [imgView setFrame:CGRectMake(0,0,768,1024)];
            [imgView setImage:[UIImage imageNamed:@"1.jpg"]];
        }
            break;


        case UIInterfaceOrientationLandscapeRight: 
        {
            //changes for LandscapeRight
            NSLog(@"LandscapeRight");
            [imgView setFrame:CGRectMake(0,0,1024,768)];
            [imgView setImage:[UIImage imageNamed:@"2.jpg"]];

        }
            break;

        case UIInterfaceOrientationLandscapeLeft: 
        {
            //changes for LandscapeRight
            NSLog(@"LandscapeRight");
            [imgView setFrame:CGRectMake(0,0,1024,768)];
            [imgView setImage:[UIImage imageNamed:@"2.jpg"]];
        }
            break;          
    }
}

Answer 2

您在错误的位置更改了图像，

-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation 

对于支持的界面旋转，应该只返回 YES 或 NO。

实施：

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration

并更改那里的图像。
另外，如果您使用 imageNamed: 创建 tempImage，则不需要释放它，它已经自动释放了。

Answer 3

有趣的代码...

您在此处创建一个 UIImageView 对象：

if (!mainBackgroundImageView) {
    mainBackgroundImageView=[[UIImageView alloc] init];
}

没有证据表明它已添加到视图中的任何位置。例如：

[self.view addSubView:mainBackgroundImageView];

此外，您支持所有旋转，因此只需在此处返回 yes

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
  return YES;
}

将工作放在这里...

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation duration:(NSTimeInterval)duration 
{
   if (interfaceOrientation==UIInterfaceOrientationPortrait || interfaceOrientation==UIInterfaceOrientationPortraitUpsideDown)
   {
    mainBackgroundImageView.frame = portraitFrame; // set frame size here
    [mainBackgroundImageView setImage:[UIImage imageNamed:@"dart-login-image.png"]];

   } else {

    mainBackgroundImageView.frame = landscapeFrame; // set frame size here
    [mainBackgroundImageView setImage:[UIImage imageNamed:@"background-and-header-integerated.png"]];

}
}

所有这一切都假设您已经将 mainBackgroundImageView 添加到视图中的某个位置，例如 -(void)viewDidLoad 中。

[self.view addSubView:mainBackgroundImageView];