Créer son propre objet graphique sous Android

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="140sp"
        android:background="#FF555555"
        android:id="@+id/IdTextView"
        />

        // ajoute un texte dans le TextView
        m_tv = (TextView)findViewById(R.id.IdTextView);
 
        // ajoute un handler sur le TextView
        m_tv.setOnTouchListener(m_handler);

    private void RefreshText()
    {
        // affiche un texte ainsi que la position courante 
        m_tv.setText("Faites un balayage droite/gauche !!\n\nPosition=" + m_ctrl.WorkPos() + "/" + m_ctrl.WorkSize());
    }

    // le handler d'événements de la fenêtre texte
    private View.OnTouchListener m_handler = new View.OnTouchListener()
    {
        public boolean onTouch(View v, MotionEvent event)
        {
            Log.i("onTouchEvent", "event=" + event.toString());
            if(event.getX() > v.getWidth())
                return true;
            if(event.getY() > v.getHeight())
                return true;
 
            if(event.getAction() == MotionEvent.ACTION_DOWN)
            {
                Log.i("onTouchEvent", "DOWN");
                if(m_flag_swipe_is_on == true)
                    return true;
                m_flag_swipe_is_on = true;
                m_x_swipe = event.getX();
                return true;
            }
 
            if(event.getAction() == MotionEvent.ACTION_MOVE)
            {
                Log.i("onTouchEvent", "MOVE");
                if(m_flag_swipe_is_on == false)
                    return true;
 
                float delta_x = event.getX() - m_x_swipe;
                Log.i("onTouch", "Move, dx=" + delta_x);
 
                // seul un déplacement plus grand que 10 est pris en compte
                if(StrictMath.abs(delta_x) < m_move_sensibility_x)
                    return true;
                if(delta_x > 0)
                    m_ctrl.WorkPosNext();
                else
                    m_ctrl.WorkPosPrevious();
 
                m_x_swipe = event.getX();
                RefreshText();
                return true;
            }
 
            if(event.getAction() == MotionEvent.ACTION_UP)
            {
                Log.i("onTouchEvent", "UP");
                if(m_flag_swipe_is_on == false)
                    return true;
                m_flag_swipe_is_on = false;
                return true;
            }
 
            if(event.getAction() == MotionEvent.ACTION_CANCEL)
            {
                Log.i("onTouchEvent", "CANCEL");
                if(m_flag_swipe_is_on == false)
                    return true;
                m_flag_swipe_is_on = false;
                return true;
            }
 
            Log.i("onTouchEvent", "UNKNOWN");
            return true;
        }
    };
 
    // variable qui enregistre si un balayage est en cours
    private boolean m_flag_swipe_is_on;
 
    // variable qui enregistre la dernière position du balayage
    private float m_x_swipe;
 
    // variable qui permet de gérer la sensibilité du balayage. Plus cette valeur est petite, plus le balayage est sensible
    private final int m_move_sensibility_x = 25;

    <view
        class="fr.circitor.test.GuiPositionIndicator" 
        android:id="@+id/IdGuiPositionIndicator"
        android:layout_width="fill_parent"
        android:layout_height="40sp"
        />

    // Fonction appelée par Android pour redessiner l'objet graphique
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
 
        // verifie s'il y a quelque chose
        if(canvas == null) return;
        if(WorkSize() == 0) return;
        //Log.d("GuiPositionIndicator", "onDraw()");
 
        // paint color
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.RED);
        paint.setStyle(Paint.Style.STROKE);
 
        // get sizes of the object
        float width = getWidth();
        //Log.d("GuiPositionIndicator", "width=" + width);
        float height = getHeight();
        //Log.d("GuiPositionIndicator", "height=" + height);
 
        // check size to determine if horizontal or vertical view
        boolean flag_horizontal = true;
        if(width < height)
            flag_horizontal = false;
 
        // compute the radius
        float radius = width * radiusRatio();
        if(flag_horizontal == true)
            radius = height * radiusRatio();
 
        // compute the total size
        // 2 radius per circle to draw
        float size = WorkSize() * 2;
 
        // add space between circles
        if(WorkSize() > 1)
            size += (WorkSize() - 1) * nbRadiusBetweenCircle();
 
        // multiply by the size of the radius
        size *= radius;
 
        // and divide it by 2
        size /= 2;
 
        float x = width / 2;
        float y = height / 2;
        if(flag_horizontal == true)
            x -= size;
        else
            y -= size;
 
        // compute offset between circles
        float offset = (nbRadiusBetweenCircle() + 2) * radius;
 
        // draw circles
        for(int boucle = 0; boucle != WorkSize(); boucle++)
        {
            boolean fill_it = false;
            if(WorkPos() == boucle)
                fill_it = true;
            circle(canvas, x, y, radius, fill_it);
 
            if(flag_horizontal == true)
                x += offset;
            else
                y += offset;
        }
    }
 
    private final float radiusRatio() { return (float)0.20; }
    private final float nbRadiusBetweenCircle() { return (float)0.7; }
    private final int circleEmptyColor() { return Color.GRAY; }
    private final int circleFullColor() { return Color.WHITE; }
 
    private void circle(Canvas canvas, float X, float Y, float Radius, boolean Fill)
    {
        // paint color
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        if(Fill == false)
        {
            paint.setStyle(Paint.Style.STROKE);
            paint.setColor(circleEmptyColor());
        }
        else
        {
            paint.setStyle(Paint.Style.FILL_AND_STROKE);
            paint.setColor(circleFullColor());
        }
 
        // draw circle
        canvas.drawCircle(X, Y, Radius, paint);
    }

public class TestActivity extends Activity
{
    // l'objet GuiPositionIndicator
    private GuiPositionIndicator m_ctrl;
 
    public void onCreate(Bundle savedInstanceState)
    {
        ...
        // récupère l'indicateur de position
        m_ctrl = (GuiPositionIndicator)findViewById(R.id.IdGuiPositionIndicator);
 
        // initialise la taille et la position de l'indicateur (pour cet exemple, ces valeurs sont arbitraires)
        m_ctrl.WorkSize(10);
        m_ctrl.WorkPos(4);
        ...

                ...
                if(delta_x > 0)
                    m_ctrl.WorkPosNext();
                else
                    m_ctrl.WorkPosPrevious();
                ...