I want to create a shape like this on a canvas. I know how to draw a circle with a stroke but I want a crescent moon kind of an effect on the circle.
Here is the code of the circle:
Bitmap bitmap = Bitmap.createBitmap(50, 50, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
float mid1;
float min1,fat1,half1,rad1;
mid1 = ImageWidth / 2;
min1 = Math.min(ImageWidth, ImageHeight);
fat1 = min1 / 17;
half1 = min1 / 2;
rad1 = half1 - fat1;
mid1 = mid1 - half1;
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setStyle(Paint.Style.FILL);
paint.setColor(color);
canvas.drawCircle(mid1 + half1, half1, rad1, paint);
The code is working perfectly for the circle. I know how to draw a stroke too but I cant create a crescent moon effect.
Set a circular clip path and then draw a second circle displaced by some quantity in both x and y.
You can refer to this view，Use Bezier curve to draw, use PorterDuff.Mode.DST_OUT to get the correct partial view (moon view).
While searching for results I came across this
How can I convert a View to a Drawable?
The idea behind this is I can convert TextView into a bitmap first and then combine the two bitmaps. But by converting the TextView into Bitmap, it would make it lose it's transparency which I don't want. I want the TextView over my ImageView but as one image using canvas.
My idea is to create images like these:
Here I want to enclose the text with a drawable shape for that white border.
And then place this Textview on an image and then save everything as a bitmap.
Please help
You can try to draw text and lines on canvas.
Below is example method which draws text on drawable image and returns Bitmap.
You can set custom font by calling .setTypeface() on Paint object.
Call canvas.drawLine() to draw line. To customize your line you can create new Paint object, set its color and width by .setColor() and .setStrokeWidth() and pass it in drawLine() together with line coordinates.
public Bitmap drawTextOnBitmap(Context context, int resId, String text) {
// prepare canvas
Resources resources = context.getResources();
float scale = resources.getDisplayMetrics().density;
Bitmap bitmap = BitmapFactory.decodeResource(resources, resId);
android.graphics.Bitmap.Config bitmapConfig = bitmap.getConfig();
// set default bitmap config if none
if (bitmapConfig == null) {
bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888;
}
// resource bitmaps are immutable, so we need to convert it to mutable one
bitmap = bitmap.copy(bitmapConfig, true);
Canvas canvas = new Canvas(bitmap);
// new antialiased Paint
TextPaint paint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
// text color - #3D3D3D
paint.setColor(Color.rgb(61, 61, 61));
// text size in pixels
paint.setTextSize((int) (bitmap.getHeight() / 10 * scale));
// text shadow
paint.setShadowLayer(1f, 0f, 1f, Color.WHITE);
// set text width to canvas width minus 16dp padding
int textWidth = canvas.getWidth() - (int) (16 * scale);
// init StaticLayout for text
StaticLayout textLayout = new StaticLayout(text, paint, textWidth,
Layout.Alignment.ALIGN_CENTER, 1.0f, 0.0f, false);
// get height of multiline text
int textHeight = textLayout.getHeight();
// get position of text's top left corner
float x = (bitmap.getWidth() - textWidth) / 2;
float y = (bitmap.getHeight() - textHeight) / 2;
// draw text to the Canvas center
canvas.save();
canvas.translate(x, y);
textLayout.draw(canvas);
canvas.restore();
return bitmap;
}
Update:
To draw rectangle add this to the method:
Paint p = new Paint();
p.setStyle(Paint.Style.STROKE);
p.setStrokeWidth(24);
RectF rectF = new RectF(80, 150, 200, 350);
canvas.drawRect(rectF, p);
Parameters for new RectF():
left
The X coordinate of the left side of the rectangle
top
The Y coordinate of the top of the rectangle
right
The X coordinate of the right side of the rectangle
bottom
The Y coordinate of the bottom of the rectangle
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
Starting with Android 6 the drawOval method seems to draw a rectangle instead of a circle when paint style is set to Paint.Style.STROKE.
If paint style is set to the Paint.Style.FILL or FILL_AND_STROKE everything seems to be fine.
See how it looks in next pictures.
Pre Android 6
Android 6
The green rectangle is supposed to be the green circle from the scale
Note that the drawing is made in a rectangle with 1.0f by 1.0f dimensions.
Everything works fine on all Android versions excepting 6.0.
Thank you
I manage it by using helper function that re-scale the canvas to a bigger rectangle (100x100), draws the circle and the scale back the canvas to original size.
public static void drawOval(Canvas canvas, RectF rectangle, Paint paint, float scale) {
float originalStrokeWidth = paint.getStrokeWidth();
float upScaling = 100f;
paint.setStrokeWidth(originalStrokeWidth * upScaling);
canvas.save();
RectF newRect = new RectF();
newRect.left = rectangle.left*upScaling;
newRect.top = rectangle.top*upScaling;
newRect.right = rectangle.right*upScaling;
newRect.bottom = rectangle.bottom*upScaling;
canvas.scale(scale/upScaling, scale/upScaling);
canvas.drawOval(newRect, paint);
canvas.restore();
paint.setStrokeWidth(originalStrokeWidth);
}
public static void drawOval(Canvas canvas, RectF rectangle, Paint paint) {
drawOval(canvas, rectangle, paint, 1f);
}
So, where I had canvas.drawOval(rect, paint) I replace it with
CanvasUtils.drawOval(canvas, rect, paint);
I have notice that "bug" happens only when I use a bitmap as canvas and draw that bitmap as background of the gauge.
I have drawn a circle filled with black color in the canvas and I have set the background color of the canvas to red.
I want only the circle which is black color to appear as my view but I get the red color as well.
I tried using canvas.clipPath() it dint work. I searched the net and found out we need to disable hardware acceleration to get it work. I tried that but it still dint work.
Tried disabling the Hardware Acceleration for particular view:
view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
And also to whole application:
android:hardwareAccelerated="false"
Dint work in both the cases.
Any ideas on how to make it work ?
Code:
And here I am clipping
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
this.canvas = canvas;
path.reset();
left = 50;
top = 50;
right = getWidth()- 50;
bottom = getHeight()-50;
RectF rectf = new RectF(left, top, right, bottom);
path.arcTo(rectf, startAngle, sweepAngle);
path.lineTo(linex, liney);
canvas.clipPath(path);
canvas.drawPath(path, paint);
//canvas.restore();
}
This is not what clip path is for. When you draw a path and then clip it - it means that the rest of the things you will draw on the canvas from that point will be masked by the path.
In your case you draw a red background before clipping the canvas - so it went all over the canvas, then you clipped it but draw only inside the path, so the clipping was useless.
you can get what you need that in that code:
// Do not set any background to the view before
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
this.canvas = canvas;
path.reset();
left = 50;
top = 50;
right = getWidth()- 50;
bottom = getHeight()-50;
RectF rectf = new RectF(left, top, right, bottom);
path.arcTo(rectf, startAngle, sweepAngle);
path.lineTo(linex, liney);
canvas.clipPath(path);
canvas.drawRect(0, 0, getWidth(), getHeight(), Red Paint in here);
canvas.drawPath(path, paint);
//canvas.restore();
}
That way you draw the background after pathClip
You will not see any red color because you draw all over the path right after it, if I am guessing right - you want to be able to draw a part of a circle in one color and the rest in other - you can achieve it if your path that you will clip will be the full circle and the path that you draw will be the part that you want to draw