I let my user draw geometries on it. So I store all the data(ie. coordinates) required for each geometries(ie. line, triangle, quads, etc). Now, I'm implementing a paint/brush on it which I don't care about all the points that was inputted. My problem is I need to call canvas.drawColor(Color.WHITE); every time the user modify the geometry resulting to clearing also the paint which is gone now and I don't have access to.
Is there any way to actually separate the two in two canvas and combining it later? I mean, the paint is directly draw on one canvas and the geometry on other canvas and combine it.
Yout can set the backgroundcolor of your View to White.
mView.setBackgroundColor(Color.WHITE);
This way you dont need to use
canvas.drawColor(Color.WHITE);
Check out TouchPaint.java in the API demos included in the Android SDK, for an example of how you can do what you want to do.
Related
I am wondering if there is a way to draw filled areas (like a filled polygon) with the Android Canvas without using the Path class and call canvas.drawPath(...).
The reason I want to do this without Path is because I have to draw very large datasets and canvas.drawPath(...) is not hardware accelerated and therefore slow.
The performance when using canvas.drawLines(...) is much better because of hardware acceleration, however I have not found a way to draw the polygon filled using this approach (even when the lines are all connected).
Even calling paint.setStyle(Style.FILL) did not fill the polygon when using drawLines(...).
Is there a way to draw a filled-polygon without using the Path approach?
Or is there any other way to improve performance using the Canvas?
You might want to look at opengl view and use it for all the drawings you need. Definitely will be damn fast. Still, all your drawing code needs to be re-written.
You probably need to do something like :
Paint red = new Paint();
red.setColor(android.graphics.Color.RED);
red.setStyle(Paint.Style.FILL);
And use this color for your path, instead of your ARGB. Make sure the last point of your path ends on the first one, it makes sense also.
Im looking for Android 2D framework which allows me to create canvas layer on which I can draw simple shapes like rect, oval atc (raster graphics). The canvas have to PERSIST everything I draw on it.
I found many engines (libgdx, andengine ...) but if they have capability to draw shapes, its only for one screen update. Reason becouse I dont store drawn shapes to some kind of List is becouse in app, the drawing occurs every screen update so I just want to modify canvas and dont remember anything.
Thanks for every answer.
As far as I know, android doesn't support something like that. Android uses double-buffering which means 2 alternatives "screens" that alternate each other so if you draw on one the next would be on random state.
There are tricks you can use to achieve what you want like draw both screens and then stop drawing, but android doesn't support such behavior because when you get hold of a canvas it's not certain that it returned exactly as what you did last frame, it doesn't specify what could cause an error, but if you ask me it could be anything that pops up on screen.
You don't really need an engine to do that, you can use a SurfaceView and draw on it (it supports shapes like the ones you want)
I'm currently attempting to make a simple 2D CAD-type viewer app for Android. Basically the input file contains a bunch of primitives (rectangles, lines, circles, octagons, that type of thing), and the goal is to draw these to the screen at whatever coordinates/sizes they offer.
My initial instinct is to use a Canvas to draw these to, using a quadtree or some similar structure to track which items will show up on the screen at any given time.
Does anyone have any recommendations here for a better way to implement this (my graphics programming experience is minimal, and hence I'm having problems even finding a starting point to Google from)?
Thanks in advance,
-Ross
That's a very broad question so my answer will only point at classes that you should be looking at.
Extend a surfaceView to be your cadView, that way you'll be all the calculation outside the main thread.
you'll still have to draw on the canvas.
from the canvas you can getWidth() and getHeight() and use those values for base comparison on your positions.
Canvas have some primitives drawings types like arc, circle, point.
Further you can use Path to draw full figures, line, filling, quadratic, etc.
for backgrounds you can create color drawables and draw it on the canvas.
and that's pretty much it.
I am working on application in which i am drawing a image on the canvas now i want o draw the second image in that canvas.
for example see the image ......
the first image s looking as follow ....
when i click on some place then it will show as follow
but the other thing which is shown in the image (thymin) it should display as fadein in the canvas
how to do it i am not getting any thing can any one help me .....
That's quite complicated by the sounds of it though not impossible to achieve. I think it would take more than the standard View class to achieve this, more like you would need to use the SurfaceView class where you have greater control over what gets drawn and where and when. If you're not familiar with Android 2D graphics then a good place to start would be here.
For drawing the bitmap, you could use canvasObject.drawBitmap() method of Canvas class. drawBitmap takes a paint object as one of its parameters, you could programmatically vary the alpha value of the paint object to create a fade-in effect. Paint class has a setAlpha(value) method to do this. I haven't tried this out myself but this should work.
I have been searching all evening for some way to implement an eraser function for my drawing app. The most common answer is to simply paint the background color or image in, but this solution will not work for my application because I am implementing multiple layers (Gimp/Photoshop style).
The user should be able to draw a line with the brush tools provided in as many layers as they like (the onDraw method of my drawingview draws layer0...layerX on top of each other). Then if they choose the eraser tool it should cause any area of the current layer that they trace over to become transparent.
I cannot seem to find an appropriate class/function built in and am unsure how I could write it myself. I tried to do something like
Paint paint = new Paint();
paint.setAlpha(0);
and then use that Paint object to draw with, but that only draws an 'invisible' line.
I also attempted to use
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
but that just seemed to draw as normal and without effect. I'm probably using it incorrectly, but the Android documentation does not contain a clear description of what it does. I just happened to see it in some examples about modifying bitmaps.
I can supply code as needed, I am just not sure what would be helpful to solve my problem. Being pointed in the right direction would be the biggest help as I have not been successful with Google.
You can find the implementation of eraser function, create new canvas, brush function and save function, on this link :
create android drawing interface
it's have very good tutorial for making drawing app on android using motion event.