我在文档中读到 @property(nonatomic, copy) NSString *restorationIdentifier
能够保留 UIImageView
属性的状态,例如位置、角度、等我尝试添加方法
-(BOOL)applicationUIApplication *)application shouldRestoreApplicationStateNSCoder *)coder
{
return YES;
}
-(BOOL)applicationUIApplication *)application shouldSaveApplicationStateNSCoder *)coder
{
return YES;
}
到 View Controller 。我已经在IB中将 View Controller 的恢复ID设置为@"myFirstViewController
。
我也在 View Controller 中添加了以下方法。
-(void)encodeRestorableStateWithCoderNSCoder *)coder
{
[coder encodeObject:_myImageView.image forKey"UnsavedImage"];
[super decodeRestorableStateWithCoder:coder];
}
-(void)decodeRestorableStateWithCoderNSCoder *)coder
{
_myImageView.image = [coder decodeObjectForKey"UnsavedImage"];
[super encodeRestorableStateWithCoder:coder];
}
我应该在 appDelegate
或 View Controller 中添加前两个方法吗?
UIImageView 没有得到保留。这里有什么问题?
要使状态保存和恢复工作,始终需要两个步骤:
您还应该为需要保存和恢复状态的 View 和 View Controller 实现 encodeRestorableStateWithCoder:
和 decodeRestorableStateWithCoder:
。
将以下方法添加到 UIImageView
的 View Controller 中。
-(void)encodeRestorableStateWithCoderNSCoder *)coder
{
[coder encodeObject:UIImagePNGRepresentation(_imageView.image)
forKey"YourImageKey"];
[super decodeRestorableStateWithCoder:coder];
}
-(void)decodeRestorableStateWithCoderNSCoder *)coder
{
_imageView.image = [UIImage imageWithData:[coder decodeObjectForKey"YourImageKey"]];
[super encodeRestorableStateWithCoder:coder];
}
状态保存和恢复是一项可选功能,因此您需要通过实现两种方法让应用程序委托(delegate)选择加入:
- (BOOL)applicationUIApplication *)application shouldSaveApplicationStateNSCoder *)coder
{
return YES;
}
- (BOOL)application:(UIApplication *)application shouldRestoreApplicationState:(NSCoder *)coder
{
return YES;
}
关于状态保存的有用文章: http://useyourloaf.com/blog/2013/05/21/state-preservation-and-restoration.html
关于ios - iOS6中使用restoreIdentifier保存UIImageView的状态,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15872738/
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