objective-c – 停止绘制CATiledLayer

发布时间：2020-12-16 05:38:24 所属栏目：百科来源：网络整理

导读：是否可以停止CATiledLayer绘制(drawLayer：inContext)？它异步绘制,当我尝试释放CATiledLayer使用的CGPDFDocumentRef时,应用程序崩溃(EXC_BAD_ACCESS). 这是我的看法 @implementation TiledPDFView- (id)initWithFrame:(CGRect)frame andScale:(CGFloat)sca

是否可以停止CATiledLayer绘制(drawLayer：inContext)？
它异步绘制,当我尝试释放CATiledLayer使用的CGPDFDocumentRef时,应用程序崩溃(EXC_BAD_ACCESS).

这是我的看法

@implementation TiledPDFView

- (id)initWithFrame:(CGRect)frame andScale:(CGFloat)scale{
    if ((self = [super initWithFrame:frame])) {

        CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
        tiledLayer.levelsOfDetail = 4;
        tiledLayer.levelsOfDetailBias = 4;
        tiledLayer.tileSize = CGSizeMake(512.0,512.0);
        myScale = scale;
    }
    return self;
}

// Set the layer's class to be CATiledLayer.
+ (Class)layerClass {
    return [CATiledLayer class];
}

- (void)stopDrawing{
    CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
    [tiledLayer removeFromSuperlayer];
    tiledLayer.delegate = nil;
}
// Set the CGPDFPageRef for the view.
- (void)setPage:(CGPDFPageRef)newPage
{
    CGPDFPageRelease(self->pdfPage);
    self->pdfPage = CGPDFPageRetain(newPage);

    //self->pdfPage = newPage;
}


-(void)drawRect:(CGRect)r
{
}


// Draw the CGPDFPageRef into the layer at the correct scale.
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{   

    // First fill the background with white.
    CGContextSetRGBFillColor(context,1.0,1.0);
    CGContextFillRect(context,self.bounds);

    CGContextSaveGState(context);
    // Flip the context so that the PDF page is rendered
    // right side up.
    CGContextTranslateCTM(context,0.0,self.bounds.size.height);
    CGContextScaleCTM(context,-1.0);

    // Scale the context so that the PDF page is rendered 
    // at the correct size for the zoom level.
    CGContextScaleCTM(context,myScale,myScale);    
    CGContextDrawPDFPage(context,pdfPage);
    CGContextRestoreGState(context);

}

// Clean up.
- (void)dealloc {
    CGPDFPageRelease(pdfPage);

    [super dealloc];
}

这是我试图在视图控制器中停止和发布PDF的地方：
v是TiledPDFView的实例

-(void) stopDwaring {
     [v stopDrawing];
     [v removeFromSuperview];
     [v release];
     [self.view removeFromSuperview];
     self.view = nil;
     CGPDFDocumentRelease(pdf);

 }

解决方法

这篇文章帮助我解决了我自己的麻烦与CATiledLayer.我以Apple的文档中的TiledPDFview.m为例.
由于我需要在某个时候重绘整个视图和所有的图块,所以我使用CATiledLayer作为属性.
当退出并取消分配视图控制器时,它使用[CATiledLayer retain]：发送到释放的实例的消息崩溃.
这是我的dealloc方法的视图控制器：

- (void)dealloc {
    self.tiledLayer.contents=nil;
    self.tiledLayer.delegate=nil;
    [self.tiledLayer removeFromSuperlayer];

    // note: releasing the layer still crashes- 
    // I guess removeFromSuperlayer releases it already,// but couldn't find documentation so far.
    // So that's why it's commented out:
    // [self.tiledLayer release],self.tiledLayer=nil;

    //release the other viewcontroller stuff... 
    [super dealloc];
}

这对我行得通.希望它有助于某人.

（编辑：李大同）

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