如何在NSmutableArray中保存和读取CGLayerRef [英] How to save and read a CGLayerRef, in a NSmutableArray

问题描述

我对CGLayerRef elements有疑问（因为它们不是对象！）

i have a question about the CGLayerRef "elements" ( because they are not object !)

在我的应用程序中，我想存储从中创建的CGLayerRef列表位图，以便在DrawRect上获得良好的帧率。

In my app, i want to store a list of CGLayerRef created from bitmaps, for obtain a good framerate on my DrawRect.

我如何存储和读取此代码中的CGLayerRef？

how can i store and read the CGLayerRef in this code ?

这是存储在NSMutableArray中的代码

This is the code for store in the NSMutableArray

    CGLayerRef imageLayer;
// create my layer...
// init  my NSMutableArray
if (layerTable == nil) {
    layerTable = [[NSMutableArray alloc] init];
}
// and store my CGCLayer in this array with NSValue
[layerTable addObject:[[NSValue alloc] initWithBytes:imageLayer objCType:"CGLayerRef"]];

现在在我看来是DrawRect的代码：

Now the code for DrawRect in my view :

actualIdp是用于标识要绘制的图层的整数。

"actualIdp" is a int for identify the layer to draw.

-(void)drawInContext:(CGContextRef)context{
// other code...

// here I want to read my CGLayerRef


//test with NSValue, but i don't know NSValue

NSValue *val = [layerTable objectAtIndex:actualIdp];
CGLayerRef layerToShow;
[val getValue:layerToShow]; // maybe an error

CGContextDrawLayerInRect(context, imageRect, layerToShow );

}

在这里，更改我的ID的代码：

Here, the code for change my id :

-(void)showThisId:(int)idp{
actualIdp = idp;
[self setNeedsDisplay];

};

推荐答案

您忽略了 @编码指令：

[layerTable addObject:[[NSValue alloc] initWithBytes:imageLayer objCType:"CGLayerRef"]];

应读为：

[layerTable addObject:[[NSValue alloc] initWithBytes:imageLayer objCType:@encode(CGLayerRef)]];

您需要将缓冲区的地址传递给 [NSValue getValue：] 。所以这行：

You need to pass the address of a buffer to [NSValue getValue:]. So this line:

[val getValue:layerToShow];

应为：

[val getValue:&layerToShow];

我认为应该可以。

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