I can't just seem to figure it out. I am trying to draw a segmented circle (what looks like circle inside a circle). However I want the segments to have specific colors and to be transparent inside the smaller circle. Preferably , I would like to make the color of the segmented lines different than the circle
Here are the solutions I had in mind:
1- Draw arc with fill color for the bigger circle and draw a circle for the small circle. 2 problems with this. First one is that the inner circle area is no longer transparent as it takes the color from the bigger one. Second problem is that the segmentation lines of the outer circle is going all the way to the center (not only to the inner circle perimeter)
2) Draw arcs for the bigger outer circle and draw circle for the inner circle. Set it to be color filled but don't show strokes. Then draw another outer circle on top with no fill just to show strokes. And then draw lines between the inner and outer circle using the calculations ( angle and radius) to determine where the lines are... Very convoluted solution, there has to be another way. Even with this solution, still have problem with the color showing in the center but maybe playing with gradient can help.
I read so much on SO but I couldn't figure the right answer as many answers would remove the control of circle parameters
HEELP!!!
#Override
public void draw(Canvas canvas) {
float size = Math.min(getWidth(),getHeight());
paint.setStrokeWidth(size/4);
paint.setStyle(Paint.Style.STROKE);
final RectF oval = new RectF(0, 0, getWidth(), getHeight());
oval.inset(size/8,size/8);
paint.setColor(Color.RED);
Path redPath = new Path();
redPath.arcTo(oval, 0, 120, true);
canvas.drawPath(redPath, paint);
paint.setColor(Color.GREEN);
Path greenPath = new Path();
greenPath.arcTo(oval, 120, 120, true);
canvas.drawPath(greenPath, paint);
paint.setColor(Color.BLUE);
Path bluePath = new Path();
bluePath.arcTo(oval, 240, 120, true);
canvas.drawPath(bluePath, paint);
paint.setStrokeWidth(2);
paint.setColor(0xff000000);
canvas.save();
for(int i=0;i<360;i+=40){
canvas.rotate(40,size/2,size/2);
canvas.drawLine(size*3/4,size/2,size,size/2,paint);
}
canvas.restore();
final RectF ovalOuter = new RectF(0, 0, getWidth(), getHeight());
ovalOuter.inset(1,1);
canvas.drawOval(ovalOuter,paint);
final RectF ovalInner = new RectF(size/4, size/4, size*3/4,size*3/4);
canvas.drawOval(ovalInner,paint);
}
I'm drawing arcs using the Path class and strokes. Style.STROKE gives arcs without filling. Stroke width is set to size/4 which is a quarter of the view. Half of that stroke width goes outside and the second half goes inside, like this:
xxxxxxxx outer border of the arc of width 5
xxxxxxxx
------------ stroke
xxxxxxxx
xxxxxxxx inner border of the arc
That's why I'm using insets - I need to offset the stroke a bit in order to fit it in the view. Without insets the arcs are cut by all four sides of the view.
And why canvas rotation? Because it's easier to rotate the canvas with built-in methods than calculate lines manually. Rotation uses trigonometric functions and quickly becomes quite complex, hard to read and error prone. Basically I'm rotating the paper and drawing straight lines.
Related
I'm attempting to draw a rectangle around a custom view in Android. I mostly have it working except for one detail.
Here is my code...
Paint paint = new Paint();
paint.setColor(Color.BLACK);
paint.setStrokeWidth(14.5f);
paint.setStyle(Paint.Style.STROKE);
canvas.drawRoundRect(0, 0, getWidth(), getHeight(), 20.0f, 20.0f, paint);
And here is the resulting rectangle...
As you can see, the inside of the rectangle does have rounded corners, but the outside still draws pointed corners. How can I make it so that the outside corners are rounded as well?
You don't see corners rounded on the outside because part of the stroke is outside of the bounds of the Canvas. You can check this easily by adding a certain margin to the coordinates of the round rectangle to make sure it is drawn inside the Canvas.
In fact your best option is trying to optimize this margin depending on the selected stroke width.
I am trying to draw a heart shaped Canvas using Path in Android. The code is as follows :
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Fill the canvas with background color
canvas.drawColor(Color.WHITE);
// paint.setShader(null);
// Defining of the heart path starts
path.moveTo(left + WIDTH / 2, top + HEIGHT / 4); // Starting point
// Create a cubic Bezier cubic left path
path.cubicTo(left+WIDTH/5,top,
left+WIDTH/4,top+4*HEIGHT/5,
left+WIDTH/2, top+HEIGHT);
// This is right Bezier cubic path
path.cubicTo(left + 3 * WIDTH / 4, top + 4 * HEIGHT / 5,
left + 4 * WIDTH / 5, top,
left + WIDTH / 2, top + HEIGHT / 4);
paint.setShader(new LinearGradient(0, canvas.getHeight()/4, canvas.getWidth(), canvas.getHeight()/4, new int[]{Color.RED, Color.YELLOW, Color.GREEN}, new float[]{0, 0.6f, 1}, Shader.TileMode.CLAMP));
canvas.drawPath(path, paint);
heart_outline_paint.setColor(getResources().getColor(R.color.heart_outline_color)); // Change the boundary color
heart_outline_paint.setStrokeWidth(4);
heart_outline_paint.setStyle(Paint.Style.STROKE);
canvas.drawPath(path, heart_outline_paint);
}
I am able to draw heart without any issue and I am able to fill color inside the heart using the Fill option in Paint. But I should be able to fill the heart dynamically according to some data and it cannot be filled fully all the time. What I have achieved so far is as follows :
I have made an extensive search and came across a lot of things similar to this. Some of which includes :
Android fill in part of a path?
filling a circle gradually from bottom to top android
I also came across the concept of converting the canvas to bitmap and filling color inside the bitmap using Flood Fill Algorithm which lets users to fill colors inside the bitmap. However, I do not want the bitmap to fill the color while touching inside the heart but to fill while a button click action.
I thought that filling a circle gradually from bottom to top android
would give help me but it makes use of a circle and I am not well-versed in Canvas which makes me very weak in adapting the circle code to such a shape.
If anybody has some ideas or any insights on how to achieve this, it will be really helpful. Cheers. Thanks in advance.
P.S : I also tried some tricks using setShader in Paint but nothing would give me what I want.
EDIT :
I just stumbled upon a idea of drawing a rectangle over the heart with another color same as the background of the canvas so that it will look like its half filled !! I am still working on the idea and not sure how accurate this is gonna be for me. If someone has a better idea, you're most welcome.
I used clipPath function available in Canvas to achieve what I needed. I draw the heart by above method and draw a rectangle over it, and I use the clipPathfunction to clip out the region that is outside the heart.
public static double filled_amount = .90;
path.moveTo(left_x_moveto, left_y_moveto);
path.cubicTo(left_x1, left_y1, left_x2, left_y2, left_x3, left_y3);
path.cubicTo(right_x2, right_y2, right_x1, right_y1, left_x_moveto, left_y_moveto);
path.close();
Rect rect = new Rect((int)(canvas.getWidth()*.10),(int)(canvas.getHeight()*filled_amount),(int) canvas.getWidth(), (int) canvas.getHeight());
canvas.clipPath(path);
paint.setColor(Color.WHITE);
paint.setStyle(Paint.Style.FILL);
canvas.drawPath(path, paint);
canvas.drawRect(rect, rect_paint);
heart_outline_paint.setColor(getResources().getColor(R.color.heart_outline_color)); // Change the boundary color
heart_outline_paint.setStrokeWidth(15);
heart_outline_paint.setStyle(Paint.Style.STROKE);
canvas.drawPath(path, heart_outline_paint);
This will give me the desired result of filling the heart dynamically. Changing the value of filled_amount dynamically and calling invalidate() will make it look like the heart is being filled dynamically.
#Henry's answer might be a better one but this did the trick for me and I dont look deeply in to the edges so a bit of zig-zags here and there is all right.
You could use Bitmap Masking to get a partially filled Heart. What you ideally do here is use one bitmap to mask the other.
In your case you could have a filled rectangle in the canvas and you have then have the heart shape in a new bitmap to act as the mask. You could then dynamically change the filling of the heart by changing the height of the background rectangle.
Refer this: https://stackoverflow.com/a/33483600/4747587. This contains the implementation of partially filling a Star. The idea is the same.
I want to be able to draw text and rectangles to the canvas after I have rotated them along their center. So I am making a test case where I have a blue square that does not get rotated, and a red square that should be rotated. THey are the same size, and should share the same center "pivot point". I have the following code:
Paint p = new Paint();
p.setColor(Color.CYAN);
p.setAlpha(200);
canvas.drawRect(new Rect(100,100,300,300), p);
canvas.save();
canvas.rotate(45,250,250);// 250,250 is the center of the blue rectangle
p.setColor(Color.RED);
p.setAlpha(100);
canvas.drawRect(new Rect(100,100,300,300), p);
canvas.restore();
It gives me a result close to what I want, but I am missing some math, because it looks like the canvas also needs a translation applied. Here is the result:
What I am missing so that I can rotate the red rectangle along the center of the blue one, and they end up sharing the same center point like this:
The center of the blue rectangle is wrong.
center(x,y) = (left + (width/2), top + (height/2))
Note: width = 200, height = 200 so, center(x,y) = (200,200)
Change to this, and it works:
canvas.rotate(45,200,200);// 200,200 is the center of the blue rectangle
Is it possible to realize the following picture in Android with canvas?
I want to have a hole and not only a Circle over the red layer which is yellow colored. I tried this (and failed) with the following Code in my onDraw()-Method:
canvas.drawBitmap(yellow, 0, 0, paint);
canvas.drawBitmap(red, 0, 200, paint);
Paint p = new Paint();
p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawCircle(300, 300, radius, p);
But when I use this code, it makes a hole through both bitmap's. At the end, this App should be a Maze with a ball, holes and other stuff. When the ball would fall into a hole it should appear under the red-Bitmap. Is it possible to realize this?
Answer:
If someone should have the same problem: use View and not SurfaceView. That was my fault, because the bg of a SurfaceView could not be set transparent.
I think you're misunderstanding how the canvas/bitmaps work. There aren't layers or objects stored (unless you store them). It's just a pixel by pixel representation of the image displayed. A yellow circle over a red square is what you have shown in the above picture.
If you truly want a red layer, you have to composite two bitmaps. Draw the hole over the red square in one bitmap, draw the yellow layer in one bitmap. On the canvas, draw the yellow bitmap, then the "red square with a hole" bitmap on top.
How can I draw rectangle at start and end points but still maintain the same width? ie 10 pixels width.
Rect simplr = new Rect();
simplr.set(start.x, start.y, end.x, end.y);
thank you
Thickness is normally something you set in the Paint, not in the Rect.
See http://developer.android.com/reference/android/graphics/Paint.html#setStrokeWidth(float)