EdiText crash with button.setEnabled()

Question

I am trying to make an EditText with a listener that checks the length of the text entered. If the EditText is not empty then the button should be enabled, otherwise it is empty must be disabled. To do this I wrote this code.

        final EditText editText = new EditText(context);
        builder.setView(editText);
        builder.setTitle("TItle");

        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int i) {



            }
        });

        builder.setNegativeButton("No", null);

        editText.addTextChangedListener(new TextWatcher() {

              public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

              public void onTextChanged(CharSequence s, int start, int before, int count) 
              {
                  AlertDialog dialog = builder.create();
                  dialog.show();
                  String text = editText.getText().toString();

                  if(text.trim().length()>0) {
                     button = dialog.getButton(AlertDialog.BUTTON_POSITIVE);
                     button.setEnabled(false);
                  }
                  else {
                     button = dialog.getButton(AlertDialog.BUTTON_POSITIVE);
                     button.setEnabled(false);
                  }
              }


            @Override
            public void afterTextChanged(Editable arg0) {
                // TODO Auto-generated method stub

            }
           });

Just write something in EditText crashes with a NullPointerException here: button.setEnabled(false);

Why? how can i solve?

that only happens in the `if` case. Not in the `else` case. Look at my answer below. Should resolve it. :) — Amulya Khare, Jan 01 '14 at 07:45

score 2 · Accepted Answer · edited May 23 '17 at 12:20

2

Update

Seems like dialogo.getButton() is returning null in your case. I looked up, there is a similar issue related.

Basically you need dialogo.show() before you call getButton(). So update your code as:

builder.setNegativeButton("No", null);
final AlertDialog dialog = builder.create();
dialog.show();
editText.addTextChangedListener(new TextWatcher() {

    public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

    public void onTextChanged(CharSequence s, int start, int before, int count) 
    {

        String text = editText.getText().toString();
        ...
        ...
        button = dialog.getButton(AlertDialog.BUTTON_POSITIVE);
        if(button != null) {    
            if(text.trim().length()>0) {
                button.setEnabled(true);
            }
            else {
                button.setEnabled(false);
            }
        }
    }
    ...
...

Old Answer

Change your else to following:

...
...
else {
   button = dialogo.getButton(AlertDialog.BUTTON_POSITIVE);
   button.setEnabled(false);
}
...
...

edited May 23 '17 at 12:20

Community

1
1

answered Jan 01 '14 at 07:44

Amulya Khare

7,718
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Crash the same in the IF when i insert text. Always NullPointerException here: button.setEnabled(false); – Giovanni Mariotti Jan 01 '14 at 07:48
post your updated code.. also.. could you debug and check if `dialogo.getButton(AlertDialog.BUTTON_POSITIVE);` returns null? – Amulya Khare Jan 01 '14 at 07:49
If i remove button.setEnabled(false) when i insert text don't crash – Giovanni Mariotti Jan 01 '14 at 07:54
Are you talking about the `else` case? i dont see any other `setEnabled(false)`? See everyone is giving the same answer.. are you not giving us some info? – Amulya Khare Jan 01 '14 at 07:56
@GiovanniMariotti please see updated answer.. my question is why you never call `dialog.show()` you need that before `getButton` – Amulya Khare Jan 01 '14 at 08:09
Crash again at dialogo.show() with illegalstatexception the specified child already has a parent you must call removeView().. i update mu question with full code – Giovanni Mariotti Jan 01 '14 at 08:16
@GiovanniMariotti updated my answer again. I hope it resolves the problem now. Good Luck :) – Amulya Khare Jan 01 '14 at 08:25

score 1 · Answer 2 · answered Jan 01 '14 at 07:46

Initially when you click on the the edit text, the addTextChangedListener will be fired and since you have not entered and text text.trim().length()=0 so the control goes to the else block.

In your else block, you are not initializing the the button, hence the NPE.

You have write the following line in else block too

button = dialogo.getButton(AlertDialog.BUTTON_POSITIVE);

EdiText crash with button.setEnabled()

2 Answers2