Sunday, October 13, 2013

Tutorial for Drawing in Android - Views/layouts

This is a quick explanation to give context to my other post in SurfaceView and SurfaceHolder, which is really what I wanted to talk about :)

The fundamental way to set what we present in our Activity, in its surface, on what you see, is to call the Activity method setContentView(something) on the onCreate method of the activity. The "something" can change depending of the complexity/capabilities of what we want to do:
For simple stuff on the background, like buttons, horizontal or vertical lines, etc... the "something" will be a reference to a layout, like: R.layout.activity_main, which is created in xml. This is the typical way explained in many "hello world" tutorials to setup your Activity, more than to really "draw". 

For more advanced static views, the "something" is an object from a View class. We can then do calls to the View methods (like setbackground...) or in the onDraw method of the object use calls of the type canvas.drawsomething... The View class has callback methods for a bunch of things. onDraw is one of them, but others take care of window resizing (onSizeChanged), finger interactions with the window (onTouch), etc...

See the post here by Janusz or MuhammadAamirALi for simple layout examples, or from  DonGru, Hema or Vinay for a bit more advanced static views.

Anyhow, as I said, this is just an intro for the SurfaceView approach...


PS.: Please, click here to see an index of other posts on Android.

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