本文介绍了这个错误是什么无效的上下文0x0?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我在ViewDidLoad中编写了以下代码
//在加载视图后执行viewDidLoad进行额外的设置,笔尖。
- (void)viewDidLoad {
[super viewDidLoad];
NSString * str = [NSString stringWithFormat:@Veer];
CGColorSpaceRef rgbColorspace = CGColorSpaceCreateDeviceRGB();
CGFloat values [4] = {55.0,0.0,0.0,1.0};
CGColorRef glowColor = CGColorCreate(rgbColorspace,values);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetShadowWithColor(context,CGSizeMake(5.0,0.0),20.0f,glowColor);
[str drawAtPoint:CGPointMake(10.5f,0.5f)withFont:[UIFont fontWithName:@Helveticasize:100.0f]];
UILabel * label = [[UILabel alloc] initWithFrame:CGRectMake(60,200,250,100)];
[label setBackgroundColor:[UIColor clearColor]];
label.font = [UIFont fontWithName:@DBLCDTempBlacksize:50.0];
label.textColor = [UIColor colorWithRed:0.0 green:1.0 blue:0.0 alpha:1.0];
[label setText:str];
[self.view addSubview:label];
}
在控制台中我看到了
测试时钟[3286]<错误> ;: CGContextSetStyle:无效的上下文0x0
测试时钟<错误> ;: CGContextSetFont:无效的上下文0x0
测试时钟CGContextSetTextMatrix:无效的上下文0x0
测试时钟:CGContextSetFontSize:无效的上下文0x0
测试时钟<错误>:CGContextSetTextPosition :invalid context 0x0
测试时钟[3286]<错误> ;: CGContextShowGlyphsWithAdvances:无效的上下文0x0
CGContextRef上下文= UIGraphicsGetCurrentContext();
if(context){
//做你的东西
}
I wrote the following code in ViewDidLoad
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
-(void)viewDidLoad {
[super viewDidLoad];
NSString *str = [NSString stringWithFormat:@"Veer"];
CGColorSpaceRef rgbColorspace = CGColorSpaceCreateDeviceRGB();
CGFloat values[4] = {55.0, 0.0, 0.0, 1.0};
CGColorRef glowColor = CGColorCreate(rgbColorspace, values);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetShadowWithColor( context, CGSizeMake( 5.0, 0.0 ), 20.0f, glowColor);
[str drawAtPoint:CGPointMake(10.5f, 0.5f) withFont:[UIFont fontWithName:@"Helvetica" size:100.0f]];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(60, 200, 250, 100)];
[label setBackgroundColor:[UIColor clearColor]];
label.font=[UIFont fontWithName:@"DBLCDTempBlack" size:50.0];
label.textColor = [UIColor colorWithRed:0.0 green:1.0 blue:0.0 alpha:1.0];
[label setText:str];
[self.view addSubview:label];
}
In Console I saw as
Testing Clock[3286] <Error>: CGContextSetStyle: invalid context 0x0
Testing Clock[3286] <Error>: CGContextSetFont: invalid context 0x0
Testing Clock[3286] <Error>: CGContextSetTextMatrix: invalid context 0x0
Testing Clock[3286] <Error>: CGContextSetFontSize: invalid context 0x0
Testing Clock[3286] <Error>: CGContextSetTextPosition: invalid context 0x0
Testing Clock[3286] <Error>: CGContextShowGlyphsWithAdvances: invalid context 0x0
解决方案
You just have to check if context exist before drawing :
CGContextRef context = UIGraphicsGetCurrentContext();
if (context) {
// Do your stuff
}
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08-14 12:31