如何避免同时工作两个JButton

Question

I'm writing a simple paint program with Java. As all paint applications there are buttons for brushTool, sprayTool, sprayTool... This tools have their own class which extends to MouseAdapter. They are working as they should. However, the problem starts when I choose a tool after choose another tool, both buttons and their ActionListeners keep executing and they do what they are written for at the same time. I mean if I choose lineTool(which draws straight line) with rectangleTool I hava a diagonal too. here is example of my two button. What I'm tring to do is stop the current action when I click another button. Can you guys help me

brushBotton.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            pen = new PenTool(mainDrawArea);
            mainDrawArea.addMouseListener(pen);
            mainDrawArea.addMouseMotionListener(pen);
            }
    });

rectangleButton.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
                shapeToolbar.setVisible(false);
                rect = new RectangleTool(mainDrawArea);
                rect.setStrokeSize(strokeInt);
                mainDrawArea.addMouseListener(rect);
                mainDrawArea.addMouseMotionListener(rect);
            }
        });

Answer 1

You can't keep adding a MouseListener to the drawing area every time you click a button.

Instead you need to keep track of the current MouseListener. Then when you click a button you need to:

1. remove the current MouseListener
2. add the new MouseListener

Answer 2

I would replace the button action listener for a set of Toggle Buttons in a group

https://docs.oracle.com/javase/tutorial/uiswing/components/buttongroup.html

Then you move everything in a single mouse listener.

public void mousePressed(MouseEvent e) {
   this.drawingState = !this.drawingState
   if ( isRightCLick(e) ) resetAllPendingOperation();
   if (drawingState) {
      this.startPoint = getPointFromEvent(e);
      switch(toolbarGetCurrentTool()) {
          case "line":
            registerMouseLineListener(startPoint);//here you draw live preview
          break
          case "rectangle":
            registerMouseRectangleListener(startPoint); //here you draw live preview
          break;
      }
   } else {
     //user clicked the second time, commit changes
     //same switch as above
      this.endPoint = getPointFromEvent(e);
                switch(toolbarGetCurrentTool()) {
          case "line":
            commitLine(startPoint, endpoint);//here you draw live preview
          break
          case "rectangle":
            commitRectangle(startPoint, endpoint); //here you draw live preview
          break;
      }
   }
}

Answer 3

You are currently binding the listeners to the mainDrawArea, not setting an action for each individual button.

Note that the codes you write within actionPerformed() for each button's actionListener is the action you want to trigger everytime that button is clicked. You do not want to add a new listener to the mainDrawArea everytime we click the buttons.

You can a create a state for your current action, for example:

brushBotton.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            state = BRUSH;
        }
    });

lineBotton.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            state = LINE;
        }
    });

state can be an integer and BRUSH and LINE are constant such as 0 and 1.

Then in the listener (for the mainDrawArea), check the current state

switch (state){
    case BRUSH: //trigger action needed for brushing;
               break;
    case LINE: //trigger action needed for drawing line;
               break;
}