How do I display numbers in JTextField after tap on any number from calculator?

Question

I know that I should use "actionlistener", so I suppose that the below code should work but it doesn't.

if (e.getSource() == "but0") { // but0 is name of button with number "0"
    String aaa = but0.getText();
    field.setText(aaa);
}

[Don't compare strings with '=='](http://stackoverflow.com/questions/995918/java-string-comparison). — Bernhard Barker, Jul 15 '13 at 08:23
How can i check it? I'm new in Java, i tryind to create simple calculator. I think that getText() method must return "0" from the JButton but0=new JButton("0"); — Shell Scott, Jul 15 '13 at 08:29

Sandiip Patil · Answer 1 · 2013-07-15T08:52:08.550

0

The button caption should be read using .equals(). == won't work here.

Try e.getSource().getText().equals("0")

Or compare the object directly as e.getSource()==but0

edited Jul 15 '13 at 08:52

answered Jul 15 '13 at 08:33

Sandiip Patil

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no, "==" works, for example functionality of button "C" (Clean) work correctly with next code if (e.getSource()==clean){ field.setText(null);} wen I tap on "C" button all text is deleted from JTextfield!! but I can input any text only from keyboard – Shell Scott Jul 15 '13 at 08:35
@redavlr You should only ever compare strings for equality using `equals()`, not `==`, because `==` will only work with string literals known at compile time. – Theodoros Chatzigiannakis Jul 15 '13 at 08:37
clean is your button's caption?? I am sure it is the object name. Fo C you are comparing object not string. e.getSource() gives action button. – Sandiip Patil Jul 15 '13 at 08:43
Yes, but but0 is also object name for button 0 ( ... Can somebody write part of code which create jtextfield, one button and alction listener method which help to display value of this button in textfield after tapping? (( need help) – Shell Scott Jul 15 '13 at 08:48
I have edited my answer. and if but0 is name of the object than you should not compare it as =="but0"; just do ==but0. – Sandiip Patil Jul 15 '13 at 08:51

score 0 · Answer 2 · answered Jul 15 '13 at 08:50

Add button in array when creating it

ArrayList<JButton> buttonA = new ArrayList();
for(int i=0;i<=9;i++) {
 String num_ = String.valueOf(i);
 JButton button = new JButton(num_);
 button.setName(num_);
 buttonA.add(button);
  // do remaining stuff
}

In action

 public void actionPerformed(ActionEvent e) {
   if(buttonA.contains(e.getSource())) {
            JButton btn = (JButton) e.getSource();
            display.setText(display.getText() + btn.getName());
   } else if() { // operations like +,- etc.,

   }

score 0 · Answer 3 · edited Jun 20 '20 at 09:12

0

From the JavaDocs, on java.awt.event.EventObject:

public Object getSource()

The object on which the Event initially occurred.

Instead of comparing with a String, try comparing with the button itself:

if (e.getSource() == but0) {
    String aaa = but0.getText();
    field.setText(aaa);
}

edited Jun 20 '20 at 09:12

Community

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answered Jul 15 '13 at 08:52

afsantos

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How do I display numbers in JTextField after tap on any number from calculator?

3 Answers3