Android - Handling screen with 'joysticks'

I implemented this one myself over the weekend from an adaptation of this[^] code:

/*Copyright Edward Nutting. This may be adapted but all adaptations must at least credit myself and http://blog.trostalex.com/?p=114 as the original sources.*/
import android.graphics.Point;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class GameControls implements OnTouchListener{

	public enum ControlModes
	{
		Game,
		Menu
	}
	
        //The centre x/y coordinates of the joystick thumb pad
	public static int initx = 550;
	public static int inity = 400;

        //The min x/y and max x/y coordinates for the joystick touching point - defines the box surrounds the joystick basically
	public static int minx = 0;
	public static int miny = 0;
	public static int maxx = 0;
	public static int maxy = 0;
	
        //The exact x/y coordinates of the latest point being touched on the screen
	public Point _touchingPoint = new Point(initx,inity);
        //The angle the thumb pad is from the centre of the joystick in degrees.
        //Where 0 = south on the screen or in other words 1 unit in the direction of 0 degrees would mean an increase of 1 in the y coordinates
	public double ControllerAngle = 0.0;
        //Distance from the centre of the joystick to the thumb pad - set to a maximum of maxx - minx so that the thumb pad actually follows a circle round.
	private double ControllerDistance = 0.0;
        //The percentage (as decimal number so 0.97 not 97%) distance of the the thumb pad from the centre of the joystick
        //Calculated by (ControllerDistance / ((maxx - minx) / 2)) or in simplified form (ControllerDistance * 2 / maxx - minx)
	public float ControllerPercentage = 0.0f;
	private Boolean _dragging = false;
	
        //The x/y coordinates and width/height of the fire button
	public static int FireButtonX = 0;
	public static int FireButtonY = 0;
	public static int FireButtonWidth = 0;
	public static int FireButtonHeight = 0;
        //Whether the fire button is currently being pressed or not
	public boolean FireButton_Pressed = false;

        //The current control mode - default is Game (see constructor below)
	public ControlModes ControlsMode;
	
	public GameControls()
	{
		super();
		ControlsMode = ControlModes.Game;
	}
	
	public boolean onTouch(View v, MotionEvent event) {
		update(event);
		return true;
	}

	private MotionEvent lastEvent;
	public void update(MotionEvent event){

		if (event == null && lastEvent == null)
		{
			return;
		}else if(event == null && lastEvent != null){
			event = lastEvent;
		}else{
			lastEvent = event;
		}
		
		if(ControlsMode == ControlModes.Game)
		{
			for(int i = 0; i < event.getPointerCount(); i++)
			{
				int x = (int)event.getX(i);
				int y = (int)event.getY(i);
				
				boolean IsFireButton = false;
				if(x > FireButtonX - 30 && x < FireButtonX + FireButtonWidth + 30 &&
						y > FireButtonY - 30 && y < FireButtonY + FireButtonHeight + 30)
					IsFireButton = true;
				
				//drag drop 
				if (event.getActionIndex() == i && (event.getAction() == MotionEvent.ACTION_DOWN || 
						event.getAction() == MotionEvent.ACTION_POINTER_2_DOWN)){
					if(IsFireButton)
						FireButton_Pressed = true;
					else
						_dragging = true;
				}else if (event.getActionIndex() == i && (event.getAction() == MotionEvent.ACTION_UP || 
						event.getAction() == MotionEvent.ACTION_POINTER_2_UP)){
					if(IsFireButton)
						FireButton_Pressed = false;
					else
						_dragging = false;
				}
				
				if(!IsFireButton)
				{
					_touchingPoint = new Point();
					
					if ( _dragging ){
						// get the pos
						_touchingPoint.x = x;
						_touchingPoint.y = y;
			
						// bound to a box
						if( _touchingPoint.x < minx){
							_touchingPoint.x = minx;
						}
						if ( _touchingPoint.x > maxx){
							_touchingPoint.x = maxx;
						}
						if (_touchingPoint.y < miny){
							_touchingPoint.y = miny;
						}
						if ( _touchingPoint.y > maxy ){
							_touchingPoint.y = maxy;
						}
			
						//get the angle
						ControllerAngle = Math.atan2(_touchingPoint.x - initx,_touchingPoint.y - inity)/(Math.PI/180);
						//Atan2 returns negative values for northen hemisphere angles and positive for below. 
                                                //I wanted all positive with a range of 0-360 so this code sorts that out.
                                                ControllerAngle += 360;
						if(ControllerAngle > 360)
						{
							ControllerAngle = ControllerAngle - 360;
						}
						
					}else if (!_dragging)
					{
						// Snap back to center when the joystick is released
						_touchingPoint.x = (int) initx;
						_touchingPoint.y = (int) inity;
					}
				
                                        //Using Pythagoras to calculate distance from centre.
					double a = _touchingPoint.x - initx;
					double b = _touchingPoint.y - inity;
                                        //Use the absolute (i.e. non-negative) value
					ControllerDistance = Math.abs(Math.sqrt((a * a) + (b * b)));
					ControllerDistance = ControllerDistance > (maxx - minx) / 2 ? (maxx - minx) / 2 : ControllerDistance;
					ControllerPercentage = (float)(ControllerDistance * 2) / (maxx - minx);
				}
			}
		}
		else if(ControlsMode == ControlModes.Menu)
		{
			if((event.getAction() == MotionEvent.ACTION_DOWN || 
						event.getAction() == MotionEvent.ACTION_POINTER_2_DOWN))
			{
				_touchingPoint = new Point((int)event.getX(), (int)event.getY());
			}
			else if((event.getAction() == MotionEvent.ACTION_UP || 
						event.getAction() == MotionEvent.ACTION_POINTER_2_UP))
			{
				_touchingPoint = null;
			}
		}
	}
}

This will handle direction and acceleration in joystick where direction is based on where the user points it (0 degrees is south not north as you may expect but it worked for my application) and acceleration is based on the (calculated by my code and provided value of) the percentage distance of the joystick thumb pad from the centre of the game pad. The code does not include rendering but this can easily be done from the given variables. All static variables must be set up properly before calling update etc. The code also allows a second button which is just a push button which I used (and called) FireButton, hence FireButton_IsPressed. The code successfully handles multi-touch input of up to two pointers.

Finally note the code also allows input mode to be set to menu, in which case the _touchingPoint is simply set, reducing computation and simplifying other code (also handles multi-touch on a menu of up to 2 pointers, eliminating most of the risk of hitting two menu items at once).

Hope this helps,
Ed