Simple Android App Without XML

Question

I'm teaching a few colleagues Java with the intent to go into Android game programming. Is there a way to display a box on the screen, and when you touch it it changes colors, without creating an Activity (this is in Eclipse) and diving into the ugly world of XML?

Answer 1

Here is an example for programmatically creating UI in Android as you requested

public class MyActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Button changeColor = new Button(this);
        changeColor.setText("Color");
        changeColor.setLayoutParams(new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT));

        changeColor.setOnClickListener(new View.OnClickListener() {
            int[] colors = {Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW};
            @Override
            public void onClick(View view) {
                final Random random = new Random();
                view.setBackgroundColor(colors[random.nextInt(colors.length - 1) + 1]);
            }
        });
        setContentView(changeColor);
    }

However, I strongly encourage using XML for your layouts. It is much easier and quicker to use XML once your understand it, so here is a tutorial for you.

Answer 2

You can create widgets programmatically and add them to an layout which you set as the content view in onCreate. Something along the lines of this would work:

RelativeLayout layout = new RelativeLayout(this);
Button btnChangeColour = new Button(this);
btnChangeColour.setText("Change Colour");
btnChangeColour.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        v.setBackgroundColor(...);
    }
});
layout.addView(btnChangeColour);
setContentView(layout);