问题
I'm using actionsheet to display lists of data for the user to choose from. The problem is that showing the actionsheet using [self.actionSheet showInView:self.view]; is causing several CGContext errors. The same code worked well in iOS 6.
Code:
self.actionSheet = [[UIActionSheet alloc] initWithTitle:nil
delegate:nil
cancelButtonTitle:nil
destructiveButtonTitle:nil
otherButtonTitles:nil];
[self.actionSheet setActionSheetStyle:UIActionSheetStyleBlackOpaque];
CGRect tableFrame = CGRectMake(0, 40, 320, 214);
self.tableView = [[UITableView alloc] initWithFrame:tableFrame style:UITableViewStylePlain];
self.tableView.dataSource = self;
self.tableView.delegate = self;
[self.actionSheet addSubview:self.tableView];
UISegmentedControl *closeButton = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObject:@"Done"]];
closeButton.momentary = YES;
closeButton.frame = CGRectMake(260, 7.0f, 50.0f, 30.0f);
closeButton.tintColor = [UIColor redColor];
[closeButton addTarget:self action:@selector(dismissActionSheet:) forControlEvents:UIControlEventValueChanged];
[self.actionSheet addSubview:closeButton];
[self.actionSheet showFromView:self.view];
[UIView beginAnimations:nil context:nil];
[self.actionSheet setBounds:CGRectMake(0, 0, 320, 485)];
[UIView commitAnimations];
Errors:
CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextSetStrokeColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextSaveGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextSetFlatness: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextAddPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextDrawPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
CGContextRestoreGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Update:
The workaround to set cancelButtonTitle to @"" results in this UI problem for me:
The original code came from another stackoverflow answer, see https://stackoverflow.com/a/2074451/654870.
回答1:
I believe the answer here is that UIActionSheet is not intended to be used this way, and as a result may have side effects like these. From the Apple ActionSheet documentation, "UIActionSheet is not designed to be subclassed, nor should you add views to its hierarchy."
While this didn't cause problems for me in iOS 6, something has clearly changed in iOS 7 and I am more in favor of going down another route than trying to do something that contradicts the docs. Note that a workaround may be to pass @"" for the cancelButtonTitle rather than nil, but this causes other UI problems and may not be approved by Apple.
Alternative solutions:
- Create your own view and present it modally - I made a simple example project showing one way to do this.
- https://github.com/gpambrozio/BlockAlertsAnd-ActionSheets (no update for iOS 7 yet)
回答2:
Kyle, What other UI problem that you have after using @""?
After I used the following code, it works fine for me. I dont use tableview though, I use pickerview as the subview.
self.startSheet=[[UIActionSheet alloc]initWithTitle:nil
delegate:nil
cancelButtonTitle:@""
destructiveButtonTitle:nil
otherButtonTitles:nil];
回答3:
Here is an answer i gave on a similar question that works well
self.actionSheet = [[UIActionSheet alloc] initWithTitle:@""
delegate:nil
cancelButtonTitle:nil
destructiveButtonTitle:nil
otherButtonTitles:nil];
However that will mess up the graphic/drawing at the top of your action sheet so if you dont already have a background your adding just add this code to give you the default action sheet look.
UIView *background = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
background.backgroundColor = [UIColor colorWithRed:204.0/255.0 green:204.0/255.0 blue:204.0/255.0 alpha:1];
[self.actionSheet addSubview:background];
then add whatever else you want to your custom action sheet.
来源：https://stackoverflow.com/questions/19129091/showing-actionsheet-causes-cgcontext-invalid-context-errors