iPhone LineChart-优快云博客

本文介绍如何使用Objective-C实现简易折线图绘制。通过随机生成数据，并利用CGContext进行绘制，展示基本的坐标轴及数据点连线过程。文章包含完整的代码示例。

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说实话,OC代码写着真的很别扭,速度明显慢Ｎ倍.

下面是一个简单的line chart,虽然很难看,但是好歹照虎画猫也能弄个模子出来...

#define AXIS_Y_ITEM_COUNT 5
#define AXIS_X_ITEM_COUNT 5

NSMutableArray* radom_data() {
	srand((unsigned)time(NULL));
	
	float base = 30;
	
	NSMutableArray *array = [[NSMutableArray alloc] init];
	for (int i = 0; i < 100; i++) {
		NSLog(@"%f", (rand() % 1000) / 100.f + base);
		[array addObject:[NSNumber numberWithFloat:((rand() % 1000) / 100.f + base)]];
	}
	
	return array;
}

float _max(NSArray *data) {
	float max = [[data objectAtIndex:0] floatValue];
	for(NSNumber* num in data) {
		max = [num floatValue] > max ? [num floatValue] : max;
	}
	
	return max;
}

float _min(NSArray *data) {
	float min = [[data objectAtIndex:0] floatValue];
	for(NSNumber* num in data) {
		min = [num floatValue] < min ? [num floatValue] : min;
	}
	
	return min;
	
}


- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        viewFrame = frame;
    }
    return self;
}


- (void)drawRect:(CGRect)rect {
	NSLog(@"########################       %f    %f", viewFrame.size.width, viewFrame.size.height);
	
	NSNumberFormatter *numberFormatter = [NSNumberFormatter new];
	[numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
	[numberFormatter setMinimumFractionDigits:2];
	[numberFormatter setMaximumFractionDigits:2];
	
	
	NSMutableArray* data = radom_data();
	float max = _max(data);
	float min = _min(data);
	
	float offsetWidth = 80.0f; // 50 * 2 + 10 * 2
	float offsetHeight = 60.0f; // 20 * 2 + 10 * 2
	
	float stepY = (max - min) / AXIS_Y_ITEM_COUNT;
	float axisY_step = (viewFrame.size.height - offsetHeight) / (max - min);
	
	
	CGContextRef context = UIGraphicsGetCurrentContext();
	CGContextClearRect(context, rect);

	
	for (int i = 0; i < AXIS_Y_ITEM_COUNT + 1; i++) {
		CGFloat lineDash[2];
		lineDash[0] = 10.0f;
		lineDash[1] = 15.0f;

		CGContextSetLineDash(context, 0.0f,  lineDash, 2);
		CGContextSetLineWidth(context, 0.6f);
		
		CGPoint sPoint = CGPointMake(offsetWidth / 2, viewFrame.size.height - (offsetHeight / 2) - i * stepY * axisY_step);
		CGPoint ePoint = CGPointMake(viewFrame.size.width - offsetWidth / 2, viewFrame.size.height - (offsetHeight / 2) - i * stepY * axisY_step);
		
		
		
		CGContextMoveToPoint(context, sPoint.x, sPoint.y);
		CGContextAddLineToPoint(context, ePoint.x, ePoint.y);
		CGContextClosePath(context);
		CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
		CGContextStrokePath(context);
		

		UIFont *axisFont = [UIFont systemFontOfSize:[UIFont smallSystemFontSize]];
		NSNumber *axisValue = [NSNumber numberWithFloat:(min + i * stepY)];
		
		CGRect axisRect = CGRectMake(0.0f, sPoint.y - axisFont.capHeight, 50.0f, 20.0f);
		//CGRect axisRect = CGRectMake(0.0f, sPoint.y, 50.0f, 20.0f);
		
						
		[[UIColor redColor] set];
		
		NSLog(@"%@", [numberFormatter stringForObjectValue:axisFont]);
		[[numberFormatter stringForObjectValue:axisValue] drawInRect:axisRect withFont:axisFont
				  lineBreakMode:UILineBreakModeTailTruncation alignment:UITextAlignmentLeft];
		
	}
	
	
	float stepX = 100 / AXIS_X_ITEM_COUNT;
	float axisX_step = (viewFrame.size.width - offsetWidth) / 100;
	
	
	CGContextSetLineDash(context, 0.0f, NULL, 0);
    for(int i = 0; i < AXIS_X_ITEM_COUNT + 1; i++) {
		CGPoint sPoint = CGPointMake(offsetWidth / 2 + i * stepX * axisX_step, viewFrame.size.height - offsetHeight / 2);
		
		CGContextMoveToPoint(context, sPoint.x, viewFrame.size.height - offsetHeight / 2);
		CGContextAddLineToPoint(context, sPoint.x, viewFrame.size.height - offsetHeight / 2 + 10);
		CGContextClosePath(context);
		CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
		CGContextStrokePath(context);
		
		CGRect axisRect = CGRectMake(sPoint.x - 50 / 2, viewFrame.size.height - 20, 50.0f, 20.0f);
		UIFont *axisFont = [UIFont systemFontOfSize:[UIFont smallSystemFontSize]];
		NSNumber *axisValue = [NSNumber numberWithInt:(i * stepX)];
		
		NSLog(@"%f   %f  %@", axisRect.origin.x,  axisRect.origin.y, [axisValue stringValue]);
		[[UIColor yellowColor] set];
		[[axisValue stringValue] drawInRect:axisRect withFont:axisFont
							  lineBreakMode:UILineBreakModeTailTruncation alignment:UITextAlignmentCenter];
	}
	
	/*
	CGContextSetLineDash(context, 0.0f, NULL, 0);
	CGContextMoveToPoint(context, offsetWidth / 2, 0.0);
	CGContextAddLineToPoint(context, offsetWidth / 2, viewFrame.size.height - offsetHeight / 2 + 10);
	CGContextClosePath(context);
	CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
	CGContextStrokePath(context);
	*/
	
	int _x = 0;
	
	for (NSNumber *number in data) {
		float value = [number floatValue];
		CGPoint point = CGPointMake(_x++ * axisX_step + offsetWidth / 2, viewFrame.size.height - offsetHeight / 2 - (value - min) * axisY_step);
		if(_x == 1) {
			CGContextMoveToPoint(context, point.x, point.y);
		}
		else {
			CGContextAddLineToPoint(context, point.x, point.y);
		}
	}
	
	//CGContextSetLineCap(context, kCGLineCapRound);
	//CGContextSetLineJoin(context, kCGLineJoinRound);
	CGContextSetStrokeColorWithColor(context, [UIColor cyanColor].CGColor);
	CGContextStrokePath(context);
}



- (void)dealloc {
    [super dealloc];
}

@synthesize viewFrame;