I want to create a rounded graph that will display a range of values from my app. The values can be classified to 3 categories: low, mid, high - that are represented by 3 colors: blue, green and red (respectively).
Above this range, I want to show the actually measured values - in a form of a "thumb" over the relevant range part:
The location of the white thumb over the range arc may change, according to the measured values.
Currently, I'm able to draw the 3-colored range by drawing 3 arcs over the same center, inside the view's onDraw method:
width = (float) getWidth();
height = (float) getHeight();
float radius;
if (width > height) {
radius = height / 3;
} else {
radius = width / 3;
}
paint.setAntiAlias(true);
paint.setStrokeWidth(arcLineWidth);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStyle(Paint.Style.STROKE);
center_x = width / 2;
center_y = height / 1.6f;
left = center_x - radius;
float top = center_y - radius;
right = center_x + radius;
float bottom = center_y + radius;
oval.set(left, top, right, bottom);
//blue arc
paint.setColor(colorLow);
canvas.drawArc(oval, 135, 55, false, paint);
//red arc
paint.setColor(colorHigh);
canvas.drawArc(oval, 350, 55, false, paint);
//green arc
paint.setColor(colorNormal);
canvas.drawArc(oval, 190, 160, false, paint);
And this is the result arc:
My question is, how do I:
Create a smooth gradient between those 3 colors (I tried using
SweepGradient but it didn't give me the correct result).
Create the overlay white thumb as shown in the picture, so that I'll be able to control where to display it.
Animate this white thumb over my range arc.
Note: the 3-colored range is static - so another solution can be to just take the drawable and paint the white thumb over it (and animate it), so I'm open to hear such a solution as well :)
I would use masks for your first two problems.
1. Create a smooth gradient
The very first step would be drawing two rectangles with a linear gradient. The first
rectangle contains the colors blue and green while the second rectangle contains green
and red as seen in the following picture. I marked the line where both rectangles touch each other
black to clarify that they are infact two different rectangles.
This can be achieved using the following code (excerpt):
// Both color gradients
private Shader shader1 = new LinearGradient(0, 400, 0, 500, Color.rgb(59, 242, 174), Color.rgb(101, 172, 242), Shader.TileMode.CLAMP);
private Shader shader2 = new LinearGradient(0, 400, 0, 500, Color.rgb(59, 242, 174), Color.rgb(255, 31, 101), Shader.TileMode.CLAMP);
private Paint paint = new Paint();
// ...
#Override
protected void onDraw(Canvas canvas) {
float width = 800;
float height = 800;
float radius = width / 3;
// Arc Image
Bitmap.Config conf = Bitmap.Config.ARGB_8888; // See other config types
Bitmap mImage = Bitmap.createBitmap(800, 800, conf); // This creates a mutable bitmap
Canvas imageCanvas = new Canvas(mImage);
// Draw both rectangles
paint.setShader(shader1);
imageCanvas.drawRect(0, 0, 400, 800, paint);
paint.setShader(shader2);
imageCanvas.drawRect(400, 0, 800, 800, paint);
// /Arc Image
// Draw the rectangle image
canvas.save();
canvas.drawBitmap(mImage, 0, 0, null);
canvas.restore();
}
As your goal is having a colored arc with rounded caps, we next need to define the area of
both rectangles that should be visible to the user. This means that most of both rectangles
will be masked away and thus not visible. Instead the only thing to remain is the arc area.
The result should look like this:
In order to achieve the needed behavior we define a mask that only reveals the arc area within
the rectangles. For this we make heavy use of the setXfermode method of Paint. As argument
we use different instances of a PorterDuffXfermode.
private Paint maskPaint;
private Paint imagePaint;
// ...
// To be called within all constructors
private void init() {
// I encourage you to research what this does in detail for a better understanding
maskPaint = new Paint();
maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
imagePaint = new Paint();
imagePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OVER));
}
#Override
protected void onDraw(Canvas canvas) {
// #step1
// Mask
Bitmap mMask = Bitmap.createBitmap(800, 800, conf);
Canvas maskCanvas = new Canvas(mMask);
paint.setColor(Color.WHITE);
paint.setShader(null);
paint.setStrokeWidth(70);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setAntiAlias(true);
final RectF oval = new RectF();
center_x = 400;
center_y = 400;
oval.set(center_x - radius,
center_y - radius,
center_x + radius,
center_y + radius);
maskCanvas.drawArc(oval, 135, 270, false, paint);
// /Mask
canvas.save();
// This is new compared to step 1
canvas.drawBitmap(mMask, 0, 0, maskPaint);
canvas.drawBitmap(mImage, 0, 0, imagePaint); // Notice the imagePaint instead of null
canvas.restore();
}
2. Create the overlay white thumb
This solves your first problem. The second one can be achieved using masks again, though this
time we want to achieve something different. Before, we wanted to show only a specific area (the arc)
of the background image (being the two rectangles). This time we want to do the opposite:
We define a background image (the thumb) and mask away its inner content, so that only
the stroke seems to remain. Applied to the arc image the thumb overlays the colored arc with
a transparent content area.
So the first step would be drawing the thumb. We use an arc for this with the same radius as
the background arc but different angles, resulting in a much smaller arc. But becaus the
thumb should "surround" the background arc, its stroke width has to be bigger than the
background arc.
#Override
protected void onDraw(Canvas canvas) {
// #step1
// #step2
// Thumb Image
mImage = Bitmap.createBitmap(800, 800, conf);
imageCanvas = new Canvas(mImage);
paint.setColor(Color.WHITE);
paint.setStrokeWidth(120);
final RectF oval2 = new RectF();
center_x = 400;
center_y = 400;
oval2.set(center_x - radius,
center_y - radius,
center_x + radius,
center_y + radius);
imageCanvas.drawArc(oval2, 270, 45, false, paint);
// /Thumb Image
canvas.save();
canvas.drawBitmap(RotateBitmap(mImage, 90f), 0, 0, null);
canvas.restore();
}
public static Bitmap RotateBitmap(Bitmap source, float angle)
{
Matrix matrix = new Matrix();
matrix.postRotate(angle);
return Bitmap.createBitmap(source, 0, 0, source.getWidth(), source.getHeight(), matrix, true);
}
The result of the code is shown below.
So now that we have a thumb that is overlaying the background arc, we need to define the mask
that removes the inner part of the thumb, so that the background arc becomes visible again.
To achieve this we basically use the same parameters as before to create another arc, but
this time the stroke width has to be identical to the width used for the background arc as
this marks the area we want to remove inside the thumb.
Using the following code, the resulting image is shown in picture 4.
#Override
protected void onDraw(Canvas canvas) {
// #step1
// #step2
// Thumb Image
// ...
// /Thumb Image
// Thumb Mask
mMask = Bitmap.createBitmap(800, 800, conf);
maskCanvas = new Canvas(mMask);
paint.setColor(Color.WHITE);
paint.setStrokeWidth(70);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
final RectF oval3 = new RectF();
center_x = 400;
center_y = 400;
oval3.set(center_x - radius,
center_y - radius,
center_x + radius,
center_y + radius);
maskCanvas.drawBitmap(mImage, 0, 0, null);
maskCanvas.drawArc(oval3, 270, 45, false, paint);
// /Thumb Mask
canvas.save();
canvas.drawBitmap(RotateBitmap(mMask, 90f), 0, 0, null); // Notice mImage changed to mMask
canvas.restore();
}
3. Animate the white thumb
The last part of your question would be animating the movement of the arc. I have no solid
solution for this, but maybe can guide you in a useful direction. I would try the following:
First define the thumb as a ImageView that is part of your whole arc graph. When changing
the selected values of your graph, you rotate the thumb image around the center of the background
arc. Because we want to animate the movement, just setting the rotation of the thumb image would
not be adequate. Instead we use a RotateAnimation kind of like so:
final RotateAnimation animRotate = new RotateAnimation(0.0f, -90.0f, // You have to replace these values with your calculated angles
RotateAnimation.RELATIVE_TO_SELF, // This may be a tricky part. You probably have to change this to RELATIVE_TO_PARENT
0.5f, // x pivot
RotateAnimation.RELATIVE_TO_SELF,
0.5f); // y pivot
animRotate.setDuration(1500);
animRotate.setFillAfter(true);
animSet.addAnimation(animRotate);
thumbView.startAnimation(animSet);
This is far from final I guess, but it very well may aid you in your search for the needed
solution. It is very important that your pivot values have to refer to the center of your
background arc as this is the point your thumb image should rotate around.
I have tested my (full) code with API Level 16 and 22, 23, so I hope that this answer at least
gives you new ideas on how to solve your problems.
Please note that allocation operations within the onDraw method are a bad idea and should
be avoided. For simplicity I failed to follow this advise. Also the code is to be used as
a guide in the right direction and not to be simply copy & pasted, because it makes heavy
use of magic numbers and generally does not follow good coding standards.
I would change a bit of the way you draw your view, by looking on the original design, instead of drawing 3 caps I would draw just 1 line, that way the SweepGradient will work.
This migth be a bit tricky, you have 2 options:
create a Path with 4 arcs
draw 2 arcs- one is the big white (filled with white so you still want to use Paint.Style.STROKE) and another on top of that make it fill transparent, you can achieve it with PorterDuff xfermode, it probably take you couple of tries until you get that without clearing the green circle too.
I imagine you want to animate thumb position, so just use simple Animation that invalidate the view and draw the thumb view position accordingly.
Hopes this helps
Create a gradient than follow a path is not so simple.
So I can suggest you to use some libraries than already did it.
Include the library:
dependencies {
...
compile 'com.github.paroca72:sc-gauges:3.0.7'
}
Create the gauge in XML:
<com.sccomponents.gauges.library.ScArcGauge
android:id="#+id/gauge"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal" />
Your code:
ScArcGauge gauge = this.findViewById(R.id.gauge);
gauge.setAngleSweep(270);
gauge.setAngleStart(135);
gauge.setHighValue(90);
int lineWidth = 50;
ScCopier baseLine = gauge.getBase();
baseLine.setWidths(lineWidth);
baseLine.setColors(Color.parseColor("#dddddd"));
baseLine.getPainter().setStrokeCap(Paint.Cap.ROUND);
ScCopier progressLine = gauge.getProgress();
progressLine.setWidths(lineWidth);
progressLine.setColors(
Color.parseColor("#65AAF2"),
Color.parseColor("#3EF2AD"),
Color.parseColor("#FF2465")
);
progressLine.getPainter().setStrokeCap(Paint.Cap.ROUND);
Your result:
You can find something more complex on this site:
ScComponents
I have the following code to delimit the area of a view to be drawn:
Rect rect = new Rect();
rect.set(0, 0, 100, 100);
View.setClipBounds(rect);
This will draw my view only on the specified rectangle (or square, in this case). However, I wanted the view to be clipped to a circle. Is there any way to somehow round the corners of a Rect object?
In this case, you've to subclass that view and add some extra logic to it.
Add these codes to its constructor method, or wherever you would like to initialize the view.
final Path path = new Path();
path.addRoundRect(new RectF(0,0,getWidth(),getHeight()),10,10,Direction.CW);
Using these codes, you're defining a path along which your view is going to be drawn (the area inside the boundaries of the patch).
Add this method to the class to apply this mask on your view.
#Override
protected void dispatchDraw(Canvas canvas){
canvas.clipPath(path);
super.dispatchDraw(canvas);
}
Credits: https://stackoverflow.com/a/7559233/1841194
Try to use
RectF r = new RectF(10,100,200,400);
canvas.drawRoundRect(r, 0, 0, mPaint);
about
or square case of it.
The other approach is to use clipping mask. The concept of this idea is to use PorterDuffXfermode or PorterDuff .
This is an example for the rounded corner view. I don't know what directly you want that's why I just can give to base methods I've used. The other example.
Try this:
val circlePath = Path().apply {
addCircle(x, y, radius, Path.Direction.CW)
}
canvas.clipPath(circlePath)
I have a path that is a serie of arc with first arc clockwise, next arc
is counterclockwise, etc.... The last arc join the first in a circle way.
Somthing like this:
(
)
(
)
(
But in circle and each arc touch perfectly the next.
When i use fill, it fill only aproximately the half part of each circle, like if i stoke a line between the start and end point of each circle. The filled part is internal to every arc.
What i want is to fill the inner part of this shape composed of all this arc. Is there some params i have miss ?
Some code:
Path path = new Path();
// for simplicity let's say i have a couple of
path.addArc(rect, (float)startingAngle, sweepAngle);
Paint paintPath = new Paint();
paintPath.setColor(0xFFFFFFFF);
paintPath.setStyle(Paint.Style.FILL);
Bitmap tempBitmap = Bitmap.createBitmap(this.getMeasuredWidth(), this.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(tempBitmap);
canvas.drawPath(path, paintPath);
canvas.drawBitmap(tempBitmap, 0, 0, paintPath);
imageViewackground.setImageBitmap(tempBitmap);
Try using
path.arcTo(rect, (float)startingAngle, sweepAngle);
or
path.arcTo(rect, (float)startingAngle, sweepAngle,true);
In my Android application I will retrieve data from a server where some coordinates will be returned back. Then I use these coordinates to create lines and draw them in the view.
I want a line rendered in different manners. For example: line rendering
The line at the top is the original line, and I want it rendered as the shapes at the below.
And there are some lines which intersect with each other. Then the intersection may be rendered as follows:
The manner of intersection rendering at the left is what I want.
So I wonder whether the Android graphics api supports these kinds of operations?
If you're using the Android Canvas to do this drawing your path twice, with a different stroke size and color. Here's an example which creates a Bitmap with an image similar to what you want :
// Creates a 256*256 px bitmap
Bitmap bitmap = Bitmap.createBitmap(256, 256, Config.ARGB_8888);
// creates a Canvas which draws on the Bitmap
Canvas c = new Canvas(bitmap);
// Creates a path (draw an X)
Path path = new Path();
path.moveTo(64, 64);
path.lineTo(192, 192);
path.moveTo(64, 192);
path.lineTo(192, 64);
// the Paint to draw the path
Paint paint = new Paint();
paint.setStyle(Style.STROKE);
// First pass : draws the "outer" border in red
paint.setColor(Color.argb(255, 255, 0, 0));
paint.setStrokeWidth(40);
c.drawPath(path, paint);
// Second pass : draws the inner border in pink
paint.setColor(Color.argb(255, 255, 192, 192));
paint.setStrokeWidth(30);
c.drawPath(path, paint);
// Use the bitmap in the layout
((ImageView) findViewById(R.id.image1)).setImageBitmap(bitmap);
I'm having trouble setting an alpha value of a region path drawn on a bitmap, using SurfaceView.
I'm creating my bitmap and erase with a black color (and 255 as alpha)
bitmap = Bitmap.createBitmap(480, 724, Bitmap.Config.ARGB_8888);
bitmap.eraseColor(0xFF000000);
Canvas canvas = new Canvas(bitmap);
Next, in my onDraw method I draw a path on the bitmap with his own alpha, white color as stroke, black as fill color and 1 as alpha value :
Paint border = new Paint();
border.setStyle(Paint.Style.STROKE);
border.setStrokeWidth(1);
border.setStrokeCap(Paint.Cap.BUTT);
border.setStrokeJoin(Paint.Join.MITER);
border.setColor(Color.WHITE);
Paint inside = new Paint();
inside.setAntiAlias(false);
inside.setStyle(Paint.Style.FILL);
int alpha = 1<<24;
inside.setColor(alpha);
canvas.drawBitmap(bitmap,0,0, null);
canvas.drawPath(path, border);
canvas.drawPath(path, inside);
Finally, in my onTouchEvent method, i'm doing this :
int index = bitmap.getPixel((int)event.getX(), (int)event.getY());
int alpha = index >>> 24;
Log.v("TAG", " Region path alpha :"+ String.valueOf(alpha));
So, when I click inside the path region, I'm expecting to have 1 (0x01) as alpha value,
but instead I'm still have 255 (0xFF). What's wrong with that ? Thanks in advance.
I am trying this in usual Java, and getting no errors ! probably you should try debugging the value of index. Output the value of index and check, or just try
Color.alpha(index)
http://developer.android.com/reference/android/graphics/Color.html#alpha(int)