How to draw a curved line in android?
I am new to android and I am developing a sample line drawing project. I want to draw a curved or raised line connecting two points (x1, y1 and x2, y2). I tried the canvas.drawArc () method, but the RectF values inside the drawArc method are only the x, y center points of the circle. This gives me an arc between my two points. But I want the curved line to connect my two points exactly. Can anyone help me? Thanks in advance.
source to share
Declare this method inside the onDraw method:
private void drawOvalAndArrow(Canvas canvas){
Paint circlePaint = new Paint();
circlePaint.setStyle(Paint.Style.FILL_AND_STROKE);
circlePaint.setAntiAlias(true);
circlePaint.setStrokeWidth(2);
circlePaint.setColor(Color.CYAN);
float centerWidth = canvas.getWidth()/2; //get center x of display
float centerHeight = canvas.getHeight()/2; //get center y of display
float circleRadius = 20; //set radius
float circleDistance = 200; //set distance between both circles
//draw circles
canvas.drawCircle(centerWidth, centerHeight, circleRadius, circlePaint);
canvas.drawCircle(centerWidth+circleDistance, centerHeight, circleRadius, circlePaint);
//to draw an arrow, just lines needed, so style is only STROKE
circlePaint.setStyle(Paint.Style.STROKE);
circlePaint.setColor(Color.RED);
//create a path to draw on
Path arrowPath = new Path();
//create an invisible oval. the oval is for "behind the scenes" ,to set the path´
//area. Imagine this is an egg behind your circles. the circles are in the middle of this egg
final RectF arrowOval = new RectF();
arrowOval.set(centerWidth,
centerHeight-80,
centerWidth + circleDistance,
centerHeight+80);
//add the oval to path
arrowPath.addArc(arrowOval,-180,180);
//draw path on canvas
canvas.drawPath(arrowPath, circlePaint);
//draw arrowhead on path start
arrowPath.moveTo(centerWidth,centerHeight ); //move to the center of first circle
arrowPath.lineTo(centerWidth-circleRadius, centerHeight-circleRadius);//draw the first arrowhead line to the left
arrowPath.moveTo(centerWidth,centerHeight );//move back to the center
arrowPath.lineTo(centerWidth+circleRadius, centerHeight-circleRadius);//draw the next arrowhead line to the right
//same as above on path end
arrowPath.moveTo(centerWidth+circleDistance,centerHeight );
arrowPath.lineTo((centerWidth+circleDistance)-circleRadius, centerHeight-circleRadius);
arrowPath.moveTo(centerWidth+circleDistance,centerHeight );
arrowPath.lineTo((centerWidth+circleDistance)+circleRadius, centerHeight-circleRadius);
//draw the path
canvas.drawPath(arrowPath,circlePaint);
}
Also this will find the two sides of the screen (landscape mode) and draw a perfect curve on the screen
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
PointF mPoint1 = new PointF(w/1.2F, h/1.2F);
PointF mPoint2 = new PointF(w/24, h/1.2F);
Path myPath1 = new Path();
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setStyle(Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.WHITE);
myPath1 = drawCurve(canvas, paint, mPoint1, mPoint2);
canvas.drawPath(myPath1, paint);
}
private Path drawCurve(Canvas canvas, Paint paint, PointF mPointa, PointF mPointb) {
Path myPath = new Path();
myPath.moveTo(63*w/64, h/10);
myPath.quadTo(mPointa.x, mPointa.y, mPointb.x, mPointb.y);
return myPath;
}
Useful links for drawing in android:
source to share
This may not be what you want, but take a look at http://developer.android.com/reference/android/graphics/Path.html for more precisely moveTo, lineTo, quadTo and cubTo. (The last 2 methods will draw Bézier curves, quadratic or cubic. If you don’t know what these are, take a look at http://en.wikipedia.org/wiki/B%C3%A9zier_curve You only need to understand the funcion parameters, not math behind it). For your purpose, you can do the following:
Path mPath;
Paint paint;
mPath = new Path();
mPath.moveTo(x1, y1);
mPath.cubicTo(anchor1_x, anchor1_y, anchor2_x, anchor2_y, x2, y2); /*the anchors you want, the curve will tend to reach these anchor points; look at the wikipedia article to understand more */
paint = new Paint();
paint.setColor(0xFFFFFFFF);
paint.setAntiAlias(true);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(width); //the width you want
canvas.drawPath(mPath, paint);
source to share