Apps Understanding Canvas and Bitmap

[Moynzy]

Hello!

I am new to Android Studio/ development.

I have worked with XCode + Swift, and I have managed to implement a simple scribble application.

However, I'm finding it difficult to do it in Android.

I have checked the documentation and YouTube for answers regarding to the graphics API.

The application captures touch input from the user and must display it on to the screen.

Now can you paint directly to the canvas, or must you create a bitmap containing what the user drew, then display it on to the bitmap?
If so, doesn't the canvas takes priority in the layer, i.e if you have a button and your canvas is full screen then the button will not appear.

How does the drawing functionality work (sorry, i'm lost for words and can't quite clearly explain)/

 

[Deleted User]

You can draw directly on to a Canvas. The Canvas API contains methods such as drawRect(), drawLine() etc to allow you to do this.

You can create a class which extends View. Then override certain methods, primarily onDraw(), which takes as a parameter, a Canvas object. You can then directly render your content on the Canvas.

 

[Moynzy]

You can draw directly on to a Canvas. The Canvas API contains methods such as drawRect(), drawLine() etc to allow you to do this.

You can create a class which extends View. Then override certain methods, primarily onDraw(), which takes as a parameter, a Canvas object. You can then directly render your content on the Canvas.

Hi, cheers for the explanation.

I have extended my custom class to extend View. onDraw has been implemented, however, if i set the content view to my custom view class, then I am unable to view the buttons.

If I am to have a button that increases a brushes opacity/ size ect. Then it would be impossible, since the content view isn't r.layout.view (I believe that's the code).

 

[Deleted User]

Are there any sample applications in Android Studio which use 2D graphics?

 

[Moynzy]

Are there any sample applications in Android Studio which use 2D graphics?

To be honest with you. I am not sure. However, I have managed to create a scribble application, but as I said, setting the content view to my draw class, that extends view, makes the buttons dissapear.

 

[Deleted User]

Sorry, I've not actually used graphics before in an app, so just suggesting some things. I believe there's a 'layering' capability that could be what you need to look at. Sounds like the canvas is obscuring everything else.
But do have a look through the sample apps in Android Studio, as something there may be able to help you.

 

[Moynzy]

From my understanding, most applications do not really need to use the core graphics API right, since images are made in a different application like photoshop, and then imported into the application.

Yeah, my thoughts are the same, the view on the GUI builder is not appearing due to the custom view being at the top.

I'll look through the sample applications, many thanks for your time though.

 

[Deleted User]

Well you can render bitmaps, but it sounds like you are taking input from the user, and wanting to draw vector graphics on the screen directly? This would mean that performance is critical, and introducing a bitmap might cause delays.
Just thinking out loud here, I might be talking a load of rubbish.