Implementing the color selection

The ColorPicker class is much easier to implement than it looks. The basic idea is to show a large color palette where the user can pick the desired color by touching the color palette area: you draw an image of the color palette on the screen, and when the user touches it, you use the Graphics class to identify the color under the user's finger.

Figure: Changing the color

To implement the color selection:

1. Use the pointerDragged and pointerReleased methods to grab the touch event while the color palette is shown.

       public void pointerDragged(int x, int y, int id) {
           if (!drawingAllowed && colorpicker.isVisible()) {
               colorpicker.dragged(x, y);
           }
           // ...
       }
   
       public void pointerReleased(int x, int y, int id) {
           if (!drawingAllowed) {
               if (colorpicker.isVisible()) {
                   colorpicker.pressed(x, y);
               }
               else if (savedialog.isVisible()) {
                   savedialog.pointerUnpressed(x, y);
               }
           }
           // ...
       }

2. The MIDlet grabs the touch event when the finger is lifted from the screen, because the same action is used to close the ColorPicker when a color has been selected. The pressed method checks which color is at the touch event’s coordinates.

   The background variable (the color palette image) is used to determine which RGB value is at the point where the user pressed, and then that new color is emitted to all the classes that implement the ColorChangeListener interface and have been registered to listen to it. If the touch event is outside the ColorPicker, the color palette view is simply closed.

       public void dragged(int x, int y) {
           selectColor(x, y);
       }
   
       public void pressed(int x, int y) {
           selectColor(x, y);
           // hide me
           Main.getInstance().getDrawArea().hideColorPicker();
       }
   
       // ...
   
       private void selectColor(int x, int y) {
           if (area.isPointInside(x, y)) {
               int[] argb = new int[1];
               palette.getRGB(argb, 0, 1, x - this.x, y - this.y, 1, 1);
               int rgb = argb[0] & 0x00FFFFFF;
               int l = listeners.size();
               for (int i = 0; i < l; i++) {
                   ColorChangeListener listener = (ColorChangeListener) listeners.elementAt(i);
                   listener.colorChanged(rgb);
               }
           }
   
       }