ios 折线图绘制 总结一下最近项目中需要使用到的折线图的展示，首先说下折线图演示的一下几种情况 1 当数据出现有正数和负数，那么折现就要x 轴的上方和下面都要展示 2 当数据只为正数，折线只在x轴上方演示 3 当数据只为负数 ，折现则只在x轴下方演示 4 当数据全为0 ，那么就只显示一条横线（具体演示如下图所示）
需求大致了解，那么我先把需求细化（这个demo 上下方最多只画两条线） 1 如何画数据分割线呢，每一条线应该标多大呢
(1)首先我们分析画线会有大体几种情况，如果有可能会有如下几种情形 先拿一正一负来举例c 12 个月的数据10，200,-3000,400,1300,-801,650 12个月的数据10，200,-3000,400,1600,-801,650 12个月的数据10，200,3000,400,-1600,-801,650 12 个月的数据10，200,3000,400,-1300,-801,650
我们要根据不同的情况画出y轴显示对应的分割线如下图
因此该显示多少条分割线是根据数据来判断来看看具体实现的代码
-(void)calMaxValueAndMinValue{
float max = -100000000;
float min = 100000000;
downYdivsion = 2;
upYdivsion = 2;
for (int i = 0; i < _dataArr.count; i++) {
NSString *value = _dataArr[i];
if (max < [value floatValue]) {
max = [value floatValue];
}
if (min > [value floatValue]){
min = [value floatValue];
}
}
maxValue = [NSString stringWithFormat:@"%.0f",max];
minValue = [NSString stringWithFormat:@"%.0f",min];
int max_val = [maxValue intValue];
int min_val = [minValue intValue];
int maxV = -1;
if (abs(min_val) <= max_val) {
maxV = [maxValue intValue];
absMax_value = [maxValue floatValue];
}
if (abs(min_val) > max_val) {
maxV = abs([minValue intValue]);
absMax_value = fabsf([minValue floatValue]);
}
moneySep = (maxV)/2;
if (max_val < moneySep) {
upYdivsion = upYdivsion -1;
}else if (abs(min_val)<moneySep ){
downYdivsion = downYdivsion -1;
}
if (min_val >= 0) {
downYdivsion = 0;
}
if (max_val <= 0) {
upYdivsion = 0;
}
if(maxV == 0){
upYdivsion = 2;
downYdivsion = 0;
moneySep = 100;
}
Ydivision = upYdivsion+downYdivsion;
}上面的代码主要是计算x轴上下方该显示的分割线，这里我用两个变量downYdivsion upYdivsion ; 来记录x轴上下方的分割线的数量，当所有数据都不大于分割线的所标的数值，则不显示这条分割线。
接下来再看看绘画折线的部分，先上一下代码段
- (void)dravLine{
//计算每条分割线的距离
float sep = (self.frame.size.height-bounceY*2)/Ydivision;
//计算出x轴的y坐标
float xDivison_y = self.frame.size.height-bounceY*2-sep*downYdivsion;
UILabel * label = (UILabel*)[self viewWithTag:1000];
UIBezierPath * path = [[UIBezierPath alloc]init];
path.lineWidth = 1.0;
self.path1 = path;
UIColor * color = [UIColor greenColor];
[color set];
CGFloat value = [self.dataArr[0] floatValue];
float max_v = absMax_value;
int floor_max_v = floor(absMax_value);
//x坐标是x轴标注的位置
float x1 = label.frame.origin.x ;
//y坐标 是根据当前高度对比坐标轴高度的比例算出y坐标
float y1 ;
if(value > 0){
y1 = xDivison_y+bounceY-(value) /max_v*2*sep;
}else{
y1 = (fabs(value)) /max_v*2*sep+xDivison_y+bounceY;
}
if (floor_max_v == 0) {
y1 = xDivison_y+bounceY;
}
[path moveToPoint:CGPointMake( x1 - bounceX, y1-bounceY )];
UIView *circle1 = [[UIView alloc]initWithFrame:CGRectMake(x1-2.5, y1-2.5, 5, 5)];
circle1.tag = 3000+0; // circle.center = CGPointMake(x, y);
circle1.backgroundColor = [UIColor whiteColor];
circle1.layer.cornerRadius = 2.5;
circle1.layer.masksToBounds = YES;
[self addSubview:circle1];
//创建折现点标记
for (NSInteger i = 1; i< self.dataArr.count; i++) {
UILabel * label1 = (UILabel*)[self viewWithTag:1000 + i];
CGFloat value = [self.dataArr[i] floatValue];
float x = label1.frame.origin.x;
float y ;
if(value > 0){
y = xDivison_y+bounceY-(value) /max_v*2*sep;
}else{
y = (fabs(value)) /max_v*2*sep+xDivison_y+bounceY;
}
if (floor_max_v == 0) {
y = xDivison_y+bounceY;
}
[path addLineToPoint:CGPointMake(x-bounceX,y-bounceY )];
//画圆点
UIView *circle = [[UIView alloc]initWithFrame:CGRectMake(x-2.5, y-2.5, 5, 5)];
circle.tag = 3000+i;
circle.backgroundColor = [UIColor whiteColor];
circle.layer.cornerRadius = 2.5;
circle.layer.shadowColor = [UIColor redColor].CGColor;
circle.layer.shadowOffset = CGSizeMake(3, 0);
circle.layer.shadowRadius = 100;
circle.layer.shadowOpacity = 0.5;
circle.clipsToBounds = YES;
// circle.layer.masksToBounds = YES;
[self addSubview:circle];
}
// [path stroke];
//根据路径划线
self.lineChartLayer = [CAShapeLayer layer];
self.lineChartLayer.path = path.CGPath;
self.lineChartLayer.strokeColor = [UIColor whiteColor].CGColor;
self.lineChartLayer.fillColor = [[UIColor clearColor] CGColor];
// 默认设置路径宽度为0，使其在起始状态下不显示
self.lineChartLayer.lineWidth = 0;
self.lineChartLayer.lineCap = kCALineCapRound;
self.lineChartLayer.lineJoin = kCALineJoinRound;
[self.gradientBackgroundView.layer addSublayer:self.lineChartLayer];//直接添加导视图上
// self.gradientBackgroundView.layer.mask = self.lineChartLayer;//添加到渐变图层
}
上面代码主要根据数据算出对应的x，y坐标，来描绘出路径