I am trying to draw an animation. To do so I have extended View and overridden the onDraw() method. What I would expect is that each time onDraw() is called the canvas would be in the state that I left it in and I could choose to clear it or just draw over parts of it (This is how it worked when I used a SurfaceView) but each time the canvas comes back already cleared. Is there a way that I can not have it cleared? Or maybe save the previous state into a Bitmap so I can just draw that Bitmap and then draw over top of it?
I'm not sure if there is a way or not. But for my custom views I either redraw everything each time onDraw() is called, or draw to a bitmap and then draw the bitmap to the canvas (like you suggested in your question).
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Your expectations do not jib w/ reality :) The canvas will not be the way you left it, but it blank instead. You could create an ArrayList of objects to be drawn (canvas.drawCircle(), canvas.drawBitmap() etc.), then iterate though the ArrayList in the OnDraw(). I am new to graphics programming but I have used this on a small scale. Maybe there is a much better way.
I am trying to make an app using canvas and a surfaceview, and I am worrying that in the future I would have many problems with it because I am not sure if the canvas is proportional with every device. currently I can only use my emulator since my phone's usb cable doesn't work(I know.. I have to get a new one..).
anyways, i would like to know if the canvas would transfer my coordinates and make everything proportional, what I mean by that is that if i have something in point a, lets say (10, 10) on a device that the screen of it is 100 X 100 (this is just an example for easy calculation) it would be on point (1, 1) on a 10 X 10 device.
No, the unit on the screen (whether you are using canvas or OpenGL) is a pixel. You can get the size of your canvas using Canvas.getWidth() and Canvas.getHeight() if you need relative coordinates, but your Canvas drawing methods are also in Pixels, so I guess you will need to convert coordinates in OpenGL only and not while using Canvas.
I am just loving Clip Studio Paint. My work has really gotten better over the last 5-6 months using it, but I really want to know if there is a shortcut to flip my canvas so I can check my anatomy and also draw some things better. I know there has to be a way as I have accidentally done it twice now. I know about the flip under Edit>Transform, but that breaks my flow, and is not the same thing as that flip also flips the thumbnails in the layer view. When I accidentally flip the canvas, only the viewport is flipped, not the layers thumbnails. An on screen button like the undo or a gesture would be preferable.
I am drawing bitmaps, lines and shapes onto a Canvas inside the OnDraw(Canvas canvas) method of my view. I am looking for help on how to implement smooth scrolling in response to a drag by the user. I have searched but not found any tutorials to help me with this.
No need for the activity to be restarted! (Per prepbgg's Jan 27 10 reply to his Jan 17 10 'answer') Rather than recycling the bitmap and incurring the overhead of having the activity reloaded, you can avoid having the application loaded by putting the 'android:configChanges' attribute shown below, in the 'activity' element of the AndroidManifest.xml file for the app. This tells the system the the app will handle orientation changes and that it doesn't need to restart the app.
I'm using Android Studio and am aware that the size() method doesn't work, so I tried removing it altogether, but my canvas is super small within the emulator. Anyone know how to force it to be fullscreen?
I checked your project again and see that the problem is not with sprite. This time I started deleting all the sprites from the beginning and the canvas only started working when I got to the letter sprites. After that, I added 5-6 sprites and the canvas still worked.
Changing the canvas size will change the size of the canvas without changing the size of the image itself (if there is an image already on the canvas). Using this option is helpful if you need more space for drawing.From the Edit menu selecting Canvas Settings will bring up the option to edit the Canvas Size.
Drawing to a canvas is better when your app needs to regularly redraw itself. Apps, such as video games, should draw to the canvas on their own. This practical shows you how to create a canvas, associate it with a bitmap, and associate the bitmap with an ImageView for display.
The drawSomething() click handler responds to user taps by drawing an increasingly smaller rectangle until it runs out of room. Then it draws a circle with the text "Done!" to demonstrate basics of drawing on canvas.
I'm guessing here..... CSS uses Android's Virtual Pixels, Canvas usesĀ
Physical?Have you set a meta viewport scale/width in your HTML, is that what isĀ
engaging the virtual pixel scale for CSS?As I said, pure guesses that maybe will help. I don't use canvas. (read:Ā
I hate canvas :) )-Dx
Most Canvas features will work and give the best user experience with the web browsers installed on the devices; however, mobile browsers are not officially supported by Canvas. Canvas has both iOS and Android mobile apps available (and different apps for student or faculty functionality), though the mobile apps are very limited and may not be able to display all content, assignments, quizzes, etc. To login to any of the mobile apps, please enter "canvas.umd.umich.edu" when prompted to select a school.
I have implemented a parking aid using an esp32 and 7 ultrasonic sensors via udp I send the data to android, and this works fine.
In implementing the graphic I have a problem, inserting an image with negative X and Y coordinate in a canvas, launching the app I see only a portion of the image (this is what I want), but varying only the X, also Y changes and places the image at Y coordinate 0.I enclose the two ScreenShot of what happens.
an someone help me understand what I'm doing wrong Thanks very much,
Yes, the canvas is not ordered as a regular graph would be, with 0,0 being the middle. Instead you kinda have to do some mathematical acrobatics to switch between the two. 0,0 is the top left of the canvas, with all the possible coords being positive. I don't know what else to offer other than that; Maybe a power user could give an even better explanation....
Good morning everyone and thanks for the informations you have given me.
I understand that canvas does not support negative coordinates even though the properties accept them.
At this point to get around the problem I will have to divide the image into n parts and enable / disable the visible parameter, In this way I will be able to make the image gradually enter in the canvas, once the entire image is in the canvas I can use the positive X Y coordinates , to move image .
I ask, if anyone has a better method?
Thanks very much Steve
I'll try to modify the app by replacing the ESP32 commands with up and down arrow keys.
Actually I could reduce the size of the image, as it does not give information on the distance from the sensors (it is purely a visual representation). To avoid impact with the sensors the ESP32 implements a hardware / firmware beep warning.
The same implementation is done on the android side (the sensor turns red and a beep sound is generated)
Greetings
Germano
I solved the problem by analyzing Scott's examples.
It was enough to increase the height and width of the canvas and transform the negative coordinates X, Y to the new reference system (X = 0, Y = 0 are now virtually out off the screen).
thank you very much
Germano
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The above code will draw a bitmap on a canvas that is rotated at 20 degrees. There are a few other functions on a Matrix that we can use such as scaling, rotating and skewing. The great part about using a Matrix over doing everything yourself manually with Canvas transformations, is that the Matrix holds cumulative information about the transformations that are applied to it.
A Matrix object can also provide us with the ability to perform perspective drawing, which is not possible to achieve with just standard Canvas transformation APIs. The function that allows perspective drawing or skewing of a canvas is Matrix#setPolyToPoly() . This method does sound a bit confusing at first, but once you wrap your head around how it works, it is not so bad!
The Android framework APIs provides a set 2D drawing APIs that allow you to render your owncustom graphics onto a canvas or to modify existing Views to customize their look and feel.When drawing 2D graphics, you'll typically do so in one of two ways:
In order to draw to the Surface Canvas from within your second thread, you must pass the thread your SurfaceHandlerand retrieve the Canvas with lockCanvas().You can now take the Canvas given to you by the SurfaceHolder and do your necessary drawing upon it.Once you're done drawing with the Canvas, callunlockCanvasAndPost(), passing ityour Canvas object. The Surface will now draw the Canvas as you left it. Perform this sequence of locking andunlocking the canvas each time you want to redraw.
The ShapeDrawable class (like many other Drawable types in the android.graphics.drawable package) allows you to define various properties of the drawable with public methods. Some properties you might want to adjust include alpha transparency, color filter, dither, opacity and color.
All existing posts will eventually be converted to canvases, and all of your content will be saved.If you use Slack on the free plan, your posts will be converted to read-only canvases. You can continue to edit your existing posts until they are converted.
Before canvases, Slack posts were a way to share long-form content in Slack. These were a specific file-type in your workspace, and if you made any, they'll be converted to canvases when the time comes. ff782bc1db