An Android view that responds to gamepad events

DotView.java

package com.riskcompletefailure.happydot;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;

public class DotView extends View {

    private final Rect mRect = new Rect();
    private static final double DOT_SIZE = 0.025;
    private static final double BUTTON_SIZE = 0.05;
    private static final double BASE_DOT_Y = 0.5;
    private static final double BASE_DOT_X = 0.5;
    private double mDoty = 0;
    private double mDotx = 0;
    private int mHeightInPixels;
    private int mWidthInPixels;
    private boolean mDrawA = false;
    private boolean mDrawB = false;
    private Paint mPaint = new Paint();
    public Context mActivity;

    public DotView(Context context, AttributeSet attrs) {
        super(context, attrs);

        setFocusable(true);

        mActivity = context;
    }

    // Convert back from screenspace
    public int spy(double screenSpaceCoordinate) {
        return (int) Math.round(screenSpaceCoordinate * mHeightInPixels);
    }

    // Convert back from screenspace
    public int spx(double screenSpaceCoordinate) {
        return (int) Math.round(screenSpaceCoordinate * mWidthInPixels);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        mHeightInPixels = this.getHeight();
        mWidthInPixels = this.getWidth();

        // Draw Background.
        mRect.top = 0;
        mRect.bottom = mHeightInPixels;
        mRect.left = 0;
        mRect.right = mWidthInPixels;
        mPaint.setColor(0xFF000000);
        canvas.drawRect(mRect, mPaint);

        // Draw Dot
        mPaint.setColor(0xFFFFFFFF);
        canvas.drawCircle(
                spx(BASE_DOT_X + mDotx),
                spy(BASE_DOT_Y + mDoty),
                spx(DOT_SIZE),
                mPaint);

        // Draw Buttons
        if (mDrawA) {
            mPaint.setColor(0xFFFF00FF);
            canvas.drawCircle(spx(0.8), spy(0.9), spx(BUTTON_SIZE), mPaint);
        }

        if (mDrawB) {
            mPaint.setColor(0xFFFFFF00);
            canvas.drawCircle(spx(0.9), spy(0.8), spx(BUTTON_SIZE), mPaint);
        }
    }

    public boolean onGenericMotionEvent(MotionEvent e) {
        if ((e.getDevice().getSources() & InputDevice.SOURCE_CLASS_JOYSTICK) != 0) {
            mDotx = e.getX() / 4.0;
            mDoty = e.getY() / 4.0;
            // Debug: Log.d("JOY", e.toString());
            // Trigger a redraw.
            invalidate();
            return true;
        }
        return false;
    }

    public boolean onKeyDown(int keyCode, KeyEvent event) {
        //Debug: Log.d("JOY", event.toString());
        if(event.getAction() == KeyEvent.ACTION_DOWN) {
            if(keyCode == KeyEvent.KEYCODE_BUTTON_A) {
                mDrawA = !mDrawA;
            } else if(keyCode == KeyEvent.KEYCODE_BUTTON_B) {
                mDrawB = !mDrawB;
            }
            // Trigger a redraw.
            invalidate();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }
}