4

我最近下载了 GLPaint 示例代码并查看了其中一个非常有趣的部分。有一个 RecordedPaths NSMutableArray，其中有点，然后由 GLPaint 读取和绘制。

它在这里声明：

NSMutableArray *recordedPaths;
recordedPaths = [NSMutableArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"Recording" ofType:@"data"]];
if([recordedPaths count])
     [self performSelector:@selector(playback:) withObject:recordedPaths afterDelay:0.2];

这是播放的代码：

 - (void) playback:(NSMutableArray*)recordedPaths {

     NSData*                    data = [recordedPaths objectAtIndex:0];

     CGPoint*               point = (CGPoint*)[data bytes];

     NSUInteger               count = [data length] / sizeof(CGPoint),

                              i;



     //Render the current path

     for(i = 0; i < count - 1; ++i, ++point)

          [self renderLineFromPoint:*point toPoint:*(point + 1)];



     //Render the next path after a short delay 

     [recordedPaths removeObjectAtIndex:0];

     if([recordedPaths count])

          [self performSelector:@selector(playback:) withObject:recordedPaths afterDelay:0.01];

}

由此我了解到，recordedPaths 是一个可变数组，他在其中构造了 CGPoint 的 c 数组，然后读取和渲染。我想放入自己的数组，但我一直遇到麻烦。

我尝试将recordedPaths声明更改为：

      NSMutableArray *myArray = [[NSMutableArray alloc] init];

      CGPoint* points;

      CGPoint a = CGPointMake(50,50);

      int i;

      for (i=0; i<100; i++,points++) {

           a = CGPointMake(i,i);

           points = &a;

      }

      NSData *data = [NSData dataWithBytes:&points length:sizeof(*points)];

      [myArray addObject:data];

这没有用......有什么建议吗？

4

3 回答 3

6

如果您查看 Recording.data，您会注意到每一行都是它自己的数组。要捕获墨迹并播放它，您需要有一个数组数组。出于本演示的目的 - 声明一个可变数组 - writRay

    @synthesize writRay;
//init in code
 writRay = [[NSMutableArray alloc]init];

捕捉墨水

// Handles the continuation of a touch.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{  

 CGRect    bounds = [self bounds];
 UITouch*   touch = [[event touchesForView:self] anyObject];

 // Convert touch point from UIView referential to OpenGL one (upside-down flip)
 if (firstTouch) {
  firstTouch = NO;
  previousLocation = [touch previousLocationInView:self];
  previousLocation.y = bounds.size.height - previousLocation.y;
  /******************* create a new array for this stroke's points **************/
  [writRay addObject:[[NSMutableArray alloc]init]];
  /***** add 1st point *********/
  [[writRay objectAtIndex:[writRay count] -1]addObject:[NSValue valueWithCGPoint:previousLocation]];
 } else {
  location = [touch locationInView:self];
     location.y = bounds.size.height - location.y;
  previousLocation = [touch previousLocationInView:self];
  previousLocation.y = bounds.size.height - previousLocation.y;
  /********* add additional points *********/
  [[writRay objectAtIndex:[writRay count] -1]addObject:[NSValue valueWithCGPoint:previousLocation]];
 }

 // Render the stroke
 [self renderLineFromPoint:previousLocation toPoint:location];

}

播放墨水。 

- (void)playRay{

 if(writRay != NULL){

  for(int l = 0; l < [writRay count]; l++){
    //replays my writRay -1 because of location point
   for(int p = 0; p < [[writRay objectAtIndex:l]count] -1; p ++){
    [self renderLineFromPoint:[[[writRay objectAtIndex:l]objectAtIndex:p]CGPointValue] toPoint:[[[writRay objectAtIndex:l]objectAtIndex:p + 1]CGPointValue]];
   }
  }
 }
}

为了获得最佳效果，请摇动屏幕以清除并从 AppController 中的 changeBrushColor 调用 playRay。

于 2010-12-09T16:20:20.100 回答
1

我只是在阅读这篇文章，因为我正试图实现类似的目标。通过 Apple 对原始项目的修改，我能够通过相应地修改代码来创建一个新的“形状”。

请注意，它只画了一条对角线......几次。但该理论可以创建您自己的绘图。

我已经从 KennyTM 的帖子中获取了代码并将其合并到“回报”函数中，这可以适用于在 initWithCoder 函数中创建数组，然后像原始代码一样发送它，但现在 - 这会给你一个结果.

    CGPoint* points = malloc(sizeof(CGPoint)*100);
CGPoint a;
int iter;
for (iter=0; iter<200; iter++) {
    a = CGPointMake(iter,iter);
    points[iter] = a;
}
NSData *data = [NSData dataWithBytes:points length:sizeof(*points)*100];
free(points);

CGPoint*            point = (CGPoint*)[data bytes];
NSUInteger      count = [data length] / sizeof(CGPoint),
                    i;

for(i = 0; i < count - 1; ++i, ++point)
    [self renderLineFromPoint:*point toPoint:*(point + 1)];

[recordedPaths removeObjectAtIndex:0];
if([recordedPaths count])
    [self performSelector:@selector(playback:) withObject:recordedPaths afterDelay:0.01];

我仍处于 openGL 编码的第一周，所以请原谅任何明显的错误/糟糕的方法，并感谢您的帮助！

希望这可以帮助

于 2010-04-08T22:44:07.420 回答
1 
  CGPoint* points;
  CGPoint a = CGPointMake(50,50);
  int i;
  for (i=0; i<100; i++,points++) {
       a = CGPointMake(i,i);
       points = &a;
  }
  NSData *data = [NSData dataWithBytes:&points length:sizeof(*points)];

错误代码。

(1)你需要一个点数组。简单地声明CGPoint* points;不会创建一个点数组，只是一个未初始化的 CGPoint 指针。您需要为数组分配空间

CGPoint points[100];

或者

CGPoint* points = malloc(sizeof(CGPoint)*100);

free如果您选择方式，请记住要点malloc。

(2)复制值到需要使用的指针内容

*points = a;

但我建议您在循环中保持指针points不变，因为您稍后将重用它。使用数组语法points[i]。

(3)

sizeof(*points)

由于*points只是一个 CGPoint，所以 sizeof 总是 8 个字节。您需要将结果乘以 100 才能得到正确的长度。

(4)

 [NSData dataWithBytes:&points ...

points已经是指向实际数据的指针。您无需再次获取它的地址。直接通过就好了points。

所以最终的代码应该是这样的

  CGPoint* points = malloc(sizeof(CGPoint)*100); // make a cast if the compiler warns.
  CGPoint a;
  int i;
  for (i=0; i<100; i++) {
       a = CGPointMake(i,i);
       points[i] = a;
  }
  NSData *data = [NSData dataWithBytes:points length:sizeof(*points)*100];
  free(points);
于 2010-02-28T06:50:44.067 回答