Question

我一直在尝试创建for循环，将UILabel.text合并为UIImage然后将其保存到实例中，然后进入for }第二次循环它会将结果保存在不同的实例中。

我面临的问题是它正在保存第一个UIImage，但质量低，并且跳过了第二个UIImage。我甚至尝试在按钮操作中执行-(void)CreateTheImage{ UIImage * img = [UIImage imageNamed:@"SquareBackground.jpg"]; UIGraphicsBeginImageContext(_imgView.bounds.size); int Counter = 0; for (UIView * view in [_imgView subviews]){ [view removeFromSuperview]; } NSString *txt1 = @"Test"; NSString *txt2 = @"Worked Well"; [array addObject:txt1]; [array addObject:txt2]; UILabel *lbl = [[UILabel alloc]init]; NSLog(@"%i",[array count]); NSLog(@"Before the loop"); for (int x = 0; x < [array count]; x++) { NSLog(@"Entered the loop"); NSLog(@"x = %i",x); lbl.text = [array objectAtIndex:x]; NSLog(@"lbl.text = %@",[array objectAtIndex:x]); lbl.textAlignment = NSTextAlignmentCenter; [lbl setBackgroundColor:[UIColor clearColor]]; lbl.font = [UIFont boldSystemFontOfSize:16]; [lbl setFrame:CGRectMake(20,112.5, 260, 75)]; [_imgView addSubview:lbl]; [_imgView bringSubviewToFront:lbl]; [_imgView setImage:img]; [_imgView.layer renderInContext:UIGraphicsGetCurrentContext()]; Counter = x+1; NSLog(@"counter = %i",Counter); switch (Counter) { case 1: NSLog(@"swintch case 1"); newImage1 = UIGraphicsGetImageFromCurrentImageContext(); break; case 2: NSLog(@"swintch case 2"); newImage2 = UIGraphicsGetImageFromCurrentImageContext(); break; default: break; } NSLog(@"after switch"); UIGraphicsEndImageContext(); } //To save the picture in the album UIImageWriteToSavedPhotosAlbum(newImage1, nil, nil, nil); UIImageWriteToSavedPhotosAlbum(newImage2, nil, nil, nil); NSLog(@"After the loop"); }保存代码，但仍然无效。

{{1}}

当我在iPhone上运行此方法时，它会给我一个警告

CreatingVideo [334]：CGContextSaveGState：无效的上下文0x0。这是一个严重的错误。该应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降低。此通知是礼貌的：请解决此问题。在即将到来的更新中，它将成为一个致命的错误。

Answer 1

您的代码没有意义。你有一个贯穿数组的for循环，将图像添加到图像视图，从当前的off-screnen上下文中捕获2个图像中的1个，然后在第一次通过数组后结束图像上下文。在第二次传递时，上下文不再存在，因此第二次结束上下文调用将失败。

将结束上下文移到for循环之外。这应该可以解决你的警告。

即便如此，我也不确定它是否能够从图像视图中删除子视图，添加新视图，将内容渲染到图形上下文，所有这些都无需返回。 UIKit视图绘图通常将更改排队到UI，直到您的代码返回，然后在下一次通过事件循环时呈现它。

Answer 2

感谢Duncan C帮助我找到答案并更正代码以便现在正常工作

-(void)CreateTheImage{

    UIImage * img = [UIImage imageNamed:@"SquareBackground.jpg"];

    UIGraphicsBeginImageContextWithOptions(CGSizeMake(320, 320), NO, 0.0f);

    int Counter = 0;


    NSString *txt1 = @"Test";
    NSString *txt2 = @"Worked Well";

    [array addObject:txt1];
    [array addObject:txt2];
    UILabel *lbl = [[UILabel alloc]init];

    NSLog(@"%i",[array count]);
    NSLog(@"Before the loop");

    for (int x = 0; x < [array count]; x++) {

        for (UIView * view in [_imgView subviews]){
            [view removeFromSuperview];
        }

        NSLog(@"Entered the loop");
        NSLog(@"x = %i",x);

        lbl.text = [array objectAtIndex:x];
        NSLog(@"lbl.text = %@",[array objectAtIndex:x]);

        lbl.textAlignment = NSTextAlignmentCenter;
        [lbl setBackgroundColor:[UIColor clearColor]];
        lbl.font = [UIFont boldSystemFontOfSize:25];
        [lbl setFrame:CGRectMake(20,122.5, 280, 75)];

        [_imgView addSubview:lbl];
        [_imgView bringSubviewToFront:lbl];
        [_imgView setImage:img];
        [_imgView.layer renderInContext:UIGraphicsGetCurrentContext()];


        Counter = x+1;
        NSLog(@"counter = %i",Counter);


        switch (Counter) {
            case 1:

                newImage1 = UIGraphicsGetImageFromCurrentImageContext();
                NSLog(@"swintch case 1");

                break;

            case 2:

                NSLog(@"swintch case 2");
                newImage2 = UIGraphicsGetImageFromCurrentImageContext();

                break;

            default:
                break;
        }

        NSLog(@"after switch");



    }

    UIGraphicsEndImageContext();

    //To save the picture in the album
    UIImageWriteToSavedPhotosAlbum(newImage1, nil, nil, nil);
    UIImageWriteToSavedPhotosAlbum(newImage2, nil, nil, nil);

    NSLog(@"After the loop");



}

绘图2 UIImage与不同的UILabel合并

2 个答案: