CorePlot学习六---点击scatterPlot中的symbol点时弹出相应的注释

由于项目需要用到用户点击 symbol时，弹出相应的详细信息，发现国内讲解的比较少，经过一番搜索验证终于解决，先看效果图：





具体需要修改的代码如下：

首先要引用委托方法：CPTScatterPlotDelegate、CPTPlotSpaceDelegate

完成如下：

#pragma mark -
#pragma mark CPTPlotSpaceDelegate methods
-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceCancelledEvent:(UIEvent *)event
{
return YES;
}
-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceUpEvent:(UIEvent *)event atPoint:(CGPoint)point
{
return YES;
}
-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceDownEvent:(UIEvent *)event atPoint:(CGPoint)point
{
NSLog(@"you putdown at point:%@",[NSValue valueWithCGPoint:point]
);
return YES;
}
-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceDraggedEvent:(UIEvent *)event atPoint:(CGPoint)point
{
return YES;
}

#pragma mark -
#pragma mark CPTScatterPlotDelegate
//当我们选择相应的点时，弹出注释：
<span style="color:#FF0000;">-(void)scatterPlot:(CPTScatterPlot *)plot plotSymbolWasSelectedAtRecordIndex:(NSUInteger)idx withEvent:(UIEvent *)event
{
</span>    if ( symbolTextAnnotation ) {
[xyGraph.plotAreaFrame.plotArea removeAnnotation:symbolTextAnnotation];
symbolTextAnnotation = nil;
}
// Setup a style for the annotation
CPTMutableTextStyle *hitAnnotationTextStyle = [CPTMutableTextStyle textStyle];
hitAnnotationTextStyle.color    = [CPTColor greenColor];
hitAnnotationTextStyle.fontSize = 10.0f;
hitAnnotationTextStyle.fontName = @"Helvetica-Bold";

// Determine point of symbol in plot coordinates
NSNumber *x          =
[[datasForPlot objectAtIndex:idx] valueForKey:@"x"];
NSNumber *y          = [[datasForPlot objectAtIndex:idx] valueForKey:@"y"];
NSString *date = [[datasForPlot objectAtIndex:idx]valueForKey:@"date"];

NSArray *anchorPoint = [NSArray arrayWithObjects:x, y, nil];
// Add annotation
// First make a string for the y value
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setMaximumFractionDigits:2];
NSString *yString = [formatter stringFromNumber:y];
NSString *myString = [NSString stringWithFormat:@"温度：%@\n日期：%@\n事件：%@",yString,date,nil];

// Now add the annotation to the plot area
CPTTextLayer *textLayer = [[CPTTextLayer alloc] initWithText:myString/*yString*/ style:hitAnnotationTextStyle];
symbolTextAnnotation              = [[CPTPlotSpaceAnnotation alloc] initWithPlotSpace:xyGraph.defaultPlotSpace anchorPlotPoint:anchorPoint];
symbolTextAnnotation.contentLayer = textLayer;
symbolTextAnnotation.displacement = CGPointMake(0.0, 20.0);
[xyGraph.plotAreaFrame.plotArea addAnnotation:symbolTextAnnotation];

// NSLog(@"index:%lu,event:%@",(unsigned long)idx,event);
}

千万别忘记了根据自己定义的设置相应的delegate = self；

红色标注的就是我们实现该功能的重点

对了，忘记说一点，该点非常重要，不然你手指点击不灵活。我们的symbol那么小，还要点击到它的中心才能触发下面的方法，这多难啊，有个参数设置一下就搞定了，设置它的触发范围：

CPTScatterPlot *boundLinePlot = [[CPTScatterPlot alloc]init];
boundLinePlot.<span style="color:#FF0000;">plotSymbolMarginForHitDetection</span> = 5.0f;//设置symbol点的外沿范围，以用来检测手指的触摸
ok搞定

其他的看注释，不想再多加说明了

代码传送门：http://download.csdn.net/detail/u012951123/7521733