CorePlot学习六---点击scatterPlot中的symbol点时弹出对应的凝视

因为项目须要用到用户点击 symbol时，弹出对应的具体信息，发现国内解说的比較少，经过一番搜索验证最终解决，先看效果图：

详细须要改动的代码例如以下：

首先要引用托付方法：CPTScatterPlotDelegate、CPTPlotSpaceDelegate

完毕例如以下：

#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
//当我们选择对应的点时。弹出凝视：
<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);
}

千万别忘记了依据自定义的设置对应的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，该点很重要。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干触发以下的方法，这多难啊，有个參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。以用来检測手指的触摸

ok搞定

其它的看凝视。不想再多加说明了

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