IOS uses CGContextRef to dynamically draw a line chart

IOS uses CGContextRef to dynamically draw a line chart

-(Void) drawRect :( CGRect) rect {CGContextRef context = UIGraphicsGetCurrentContext (); CGContextClearRect (context, rect); CGContextSetLineWidth (context, _ lineWidth ); // set the paint brush width CGContextSetFillColorWithColor (context, [[self backgroundColor] CGColor]); // set the background fill color CGContextFillRect (context, rect); // fill the background CGContextSetStrokeColorWithColor (context, _ lineColor. CGColor); // set the paint brush color // arr to the dynamic data array obtained in real time for (int I = 0; I <_ arr. count; I ++) {if (I <_ arr. count-1) {CGPoint pp [2]; [_ arr [I] getBytes: & pp [0] length: sizeof (CGPoint)]; [_ arr [I + 1] getBytes: & pp [1] length: sizeof (CGPoint)]; CGContextMoveToPoint (context, pp [0]. x, pp [0]. y); CGContextAddLineToPoint (context, pp [1]. x, pp [1]. y); CGContextStrokePath (context) ;}}- (void) addDataToArr :( CGFloat) data {if (! _ Arr) _ arr = [[NSMutableArray alloc] init]; CGPoint point; // MAX_X_COUNT indicates the maximum number displayed on the X axis. If it is exceeded, the X axis moves to the left, move one unit each time if (_ arr. count> = MAX_X_COUNT) {// move the X axis CGRect frame = self. frame; frame. origin. x-= (self. frame. size. width/MAX_X_COUNT); frame. size. width + = (self. frame. size. width/MAX_X_COUNT); self. frame = frame;} point. x = _ arr. count * (self. frame. size. width/MAX_X_COUNT); // if the current value is greater than the maximum value represented by the Y axis, the maximum value of the Y axis is expanded to 2 times that of the current value if (data> _ maxYPower) {// change the maximum value of y to currentPower _ maxYPower = data * 2;} point. y = data; // Save the data obtained in real time to _ arr [_ arr addObject: [NSData dataWithBytes: & point length: sizeof (CGPoint)];}

You only need to dynamically call addDataToArr: And then call [self. view setNeedDisplay ].