My goal right now is create a bitmap that is a non-rectangular shape, that I can also move. I have created a path that I can use as with canvas's clipPath method. Is it possible to move that clipPath around?
Also, am I doing this the best way, or is there a better way to accomplish this?
Here's my draw function:
public void draw(Canvas c){
// Paint object, for outline of clip Path.
Paint p = new Paint();
p.setStyle(Style.STROKE);
p.setColor(Color.RED);
// A currently defined path to clip the bitmap with
Path clipPath = new Path();
clipPath.moveTo(top_left.getX() + nodes.getNodeVals('L').getX(), top_left.getY() + nodes.getNodeVals('T').getY());
clipPath.addPath(outline);
c.save(); // Save the canvas (rotations, transformations, etc)
c.clipPath(clipPath); // Create a clip region
c.drawPath(clipPath, p); // Draw that clip region in red
c.drawBitmap(img, top_left.getX(), top_left.getY(), null); // Draw the bitmap in the clip
c.restore(); // Restore the canvas (rotations, transformations, etc)
}
The clipPath.moveTo line is where I'm having my problem, I believe. Basically, it should be creating a new path that is at the location defined with the x and y values of moveTo (I believe I have those set correctly elsewhere). The path is created beforehand, and stored into outline, and the addPath part should be adding the outline to clipPath.
Thanks in advance!
I'm not entirely sure if I understand exactly what it is you are trying to do, but if you simply want to offset the path from its original position, moveTo is not the way to go since the coordinates of a path you add will be retained.
Instead, you can add the offset coordinates in your addPath:
//clipPath.addPath(outline);
clipPath.addPath(outline, dx, dy);
where dx and dy are your offsets.
Related
I have a bitmap that spans the whole screen that will function as texture for a Path object that I need to draw to my canvas. I then have a background image that this textured path needs to be drawn on top of.
I tried using the PorterDuff modes, but nothing seemed to work correctly. I was having a hard time figuring out exactly how the PorterDuff modes act, because none of them seem to act the way I always thought they were supposed to function.
I've figured out a way to texture the path with this test code:
Paint paint = new Paint();
//draw the texture
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.texture),0,0,paint);
//construct the Path with an inverse even-odd fill
Path p = new Path();
p.setFillType(Path.FillType.INVERSE_EVEN_ODD);
p.addCircle(this.getHeight()/2, this.getWidth()/2, 200, Path.Direction.CCW);
//use CLEAR to remove inverted fill, thus showing only the originally filled section
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.CLEAR));
//draw path
canvas.drawPath(p, paint);
But I can't figure out how to then place that on top of a background image. Am I just using the PorterDuff modes wrong?
Maybe my questions could lead you to your solution:
The paint used in your drawPath call:
What is the paint style?
What is the paint stroke width?
What is the paint stroke/fill color?
If you are not using a stoke/fill color, but a texture instead, where is the call to the paint's setShader (using a BitmapShader)?
I try to do circle menu like in this app.
In "expanded" mode i draw this component like follows:
<RelativeLayout android:id="#+id/bigCircle">
<!--color full borders-->
<my.custom.component android:id="#+id/middleCircle">
<!--circle for buttons-->
<RelativeLayout android:id="#+id/smallCircle">
<!--minus button-->
</RelativeLayout>
</my.custom.component>
</RelativeLayout>
In onDraw method of my.custom.component i divide circle on 8 parts by using android.graphics.Path with android.graphics.Paint and some math.
Visually i have exactly as shown in the screenshot. But when i press on part of circle, i need redraw this part in another color to show user what something going on.
How i can redraw part of component's canvas cutting off from another part of canvas by android.graphics.Path for example. In another word i know what redraw canvas i should do in onDraw method, i know that i can show some bitmap from drawables painted in photoshop and have some "multiscreen trouble", i know how i can determine part which user pressed. But i don't know how i can select part of canvas and redraw it.
Developer of Catch here. If I'm understanding your issue, you're having trouble understanding how to specifically draw the highlight/selection indicator on a section of your circular menu.
While there are plenty of different ways one could implement it, what you're leaning towards (using android.graphics.Path) is how we did it. In the view hierarchy of our capture button, there's an element that serves as the canvas on which the selection highlight color (if there is an active selection) is drawn.
If you had a similar custom View in your layout, you could duplicate this behavior like so. First, you'll need the Path that defines the selection for a particular circle segment. Using Path.addArc(RectF, float, float) we can get the pizza-slice-shaped path we need:
private Path getPathForSegment(float startAngle, float sweep) {
Point center = new Point(getWidth() / 2, getHeight() / 2);
RectF rect = new RectF(0f, 0f, getWidth(), getHeight());
Path selection = new Path();
selection.addArc(rect, startAngle, sweep);
selection.lineTo(center.x, center.y);
selection.close();
return selection;
}
The getWidth() and getHeight() above are for the enclosing custom view object, so they define the bounding box that contains the circle on which the selection is drawn.
Then, in your custom view's onDraw(Canvas), if your code has determined a selection should be drawn for a segment:
#Override
protected void onDraw(Canvas canvas) {
// Assume one has the rest of these simple helper functions defined
if (shouldDrawSelection()) {
float startAngle = getStartAngleOfSelectedSegment();
float sweep = getSweepAngle();
Paint paint = getPaintStyleForSelectedSegment();
Path path = getPathForSegment(startAngle, sweep);
canvas.drawPath(path, paint);
}
// ...
super.onDraw(canvas);
}
In the other areas of your code that are tracking touches, just call invalidate() on the custom view so that it will redraw (or not) the selection path based on changes in input or state.
Remember that it's good practice to avoid newing objects in onDraw(), so most of these building blocks (Paths, Paints, etc.) can be constructed ahead of time (or once, on first occurrence) and reused.
Hope this is close to what you were asking!
I want to draw a string say "stackoverflow" in circular view like below image can any one suggest how to do it. And also i need click event on each characer.
You need to make a customized view for this. in onDraw method, create a path object, add circle to that object, and then use Canvas Object to draw text on that path.
Path path = new Path();
path.addCircle(x, y, radius, Path.Direction.CW);
myCanvas.drawTextOnPath(myText, path, offset, 0, myPaint);
Edit:
use this line of code when using os 4.0 and above:
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
Take a look at both Path.addCircle and Canvas.drawTextOnPath API.
I am looking at one of the sample applications from Google, which deals with touch drawing using canvas:
http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/TouchPaint.html
I have a few doubts:
I am not able to understand what's the role of Canvas versus the role
of the bitmap.
In the drawPoint function, I am not able to
understand this code snippet:
mCanvas.drawCircle(x, y, radius, mPaint);
mRect.set((int) (x - radius - 2), (int) (y - radius - 2),
(int) (x + radius + 2), (int) (y + radius + 2));
invalidate(mRect);
If the circle is already drawn into the canvas above, then what happens in the onDraw function where the following code is given:
canvas.drawBitmap(mBitmap, 0, 0, null);
Canvas vs Bitmap
A Bitmap is what the name suggests: A normal image as a bitmap. The Canvas class is an editor for bitmaps. You use it to change the bitmap data, it holds all drawing methods. This principle behaves similar to the shared preferences (if you already worked with them), you have a SharedPreferences class that holds the preferences, and an Editor class to change things.
Drawing the circles
This code does something similar to double buffering. drawPoint() basically draws a circle into the mBitmap object¹. But this bitmap object is not yet visible. It exists in the memory. When onDraw() is called, it has a Canvas argument that represents the drawing surface of the view. All that drawBitmap() does here is use the prepared bitmap from the memory and draw it inside the views graphical representation to make it visible.
¹ The used canvas mCanvas is tied to mBitmap inside onSizeChanged()
if you go to the developper refference:
drawBitmap(Bitmap bitmap, float left, float top, Paint paint)
Draw the
specified bitmap, with its top/left corner at (x,y), using the
specified paint, transformed by the current matrix.
Then if you see that mBitmap doesn't exist in the class , thats cause that var comes from the extend from another activity .
Canvas also has a setBitmap(Bitmap bitmap) function . Then the solution is that that paint in canvas if you have set into it a bitmap object.
From the Android SDK:
The Canvas class holds the "draw" calls. To draw something, you need 4 basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls (writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap), and a paint (to describe the colors and styles for the drawing).
I'm assuming you're referring to this snippet:
#Override protected void onDraw(Canvas canvas) {
if (mBitmap != null) {
canvas.drawBitmap(mBitmap, 0, 0, null);
}
}
Well it looks like an override of an inherited onDraw method which by default probably 'does nothing', hence the override to actually give it some behaviour, in this case given a non-null Bitmap instance, make the canvas draw it.
This code was supposed to convert text to image
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.RED);
paint.setTextSize(16);
paint.setAntiAlias(true);
paint.setTypeface(Typeface.MONOSPACE);
Bitmap bm = Bitmap.createBitmap(16, 16, Bitmap.Config.ALPHA_8);
float x = bm.getWidth();
float y = bm.getHeight();
Canvas c = new Canvas(bm);
c.drawText("Test", x, y, paint);
}
Is this code ok? If yes, how can I make this new bitmap visible on screen? I tried this code which produced an error
setContentView(c); //<- ERROR!
I am confused with the element Canvas as there is not such element in XML which I can use in the code.
setContentView(View) takes a View and Canvas is not a View.
I am not sure that you want to create a Canvas on your own. There are ways to get a Canvas passed to you from the Android Framework though. One way you can do this is by creating a custom View. To do this, you will need to create a new class that extends View.
When overriding a View class, you will have the ability to override the onDraw(Canvas) method. This is probably where you want to do what you are attempting to do in your onCreate() method in the code you posted.
This link gives a good overview of what is required to create your own custom view.
First: If you draw your text at the x and y position you specified, you draw it
at the lower right corner, starting with exactly that pixel. Nothing will be drawn on your canvas. Try bm.getWidth()/2, for height the same for test drawing. You can optimize that later.
Second: Canvas is not a View (does not extend the View class). You can only set Views via set ContentView(). What I recommend here is writing a XML layout containing only a single ImageView and set that via setContentView(R.layout.mylayout).
After that, you can use findViewById() to grab that ImageView and use ImageView.setImageBitmap(bm) to show your bitmap on it.
You dont have to do anything with the canvas, once you created it with your bitmap. Everything you draw inside the canvas from that point on is found in the Bitmap immediately.
Therefore you can't specify the Canvas in XML. It's just an "Editor" to edit pictures, so to speak and not an actual UI element.