Alert Dialog on work thread

Question

I have a class "MessageParser" which extends

AbstractParser

and a method "onMessagePacketReceived" which calls a method:

conversation.add(message);

add is a method of entity "Conversation" which extends

AbstractEntity

and adds messages received like below:

public void add(Message message) {
    message.setConversation(this);
    synchronized (this.messages) {
        this.messages.add(message);
    }
}

What I want to do is to display an alert dialog which has an input like below:

 AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle(R.string.input_pass);
        View dialogView = getLayoutInflater().inflate(R.layout.set_password_dialog, null);
        builder.setView(dialogView);
        builder.setNegativeButton(R.string.cancel, null);
        builder.setPositiveButton(R.string.next, null);
        final AlertDialog dialog = builder.create();
        dialog.show();

        dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(
                new View.OnClickListener() {

                    @Override
                    public void onClick(final View v) {
                        EditText edit = (EditText) dialog.findViewById(R.id.account_password);
                        String pass = edit.getText().toString();
                        if (pass.equals(accountList.get(0).getPassword())) {
                            conversation.add(message);
                            dialog.dismiss();
                        } else {
                            edit.setError(getString(R.string.incorrect_pass));
                        }
                    }
                });

which replaces conversation.add(message). I am having troubles with this. It displays

Can't create handler inside thread that has not called Looper.prepare()

I have seen this answer but doesn't help me.

Answer 1

The problem is that you are trying the create and show the dialog within a non-UI thread (that's what the error says, as usually only the main UI Thread calls Looper.prepare()). To fix it, use this code:

activity.runOnUiThread(new Runnable() {
    @Override public void run() {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle(R.string.input_pass);
        View dialogView = getLayoutInflater().inflate(R.layout.set_password_dialog, null);
        builder.setView(dialogView);
        builder.setNegativeButton(R.string.cancel, null);
        builder.setPositiveButton(R.string.next, null);
        final AlertDialog dialog = builder.create();
        dialog.show();
        dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(final View v) {
                        EditText edit = (EditText) dialog.findViewById(R.id.account_password);
                        String pass = edit.getText().toString();
                        if (pass.equals(accountList.get(0).getPassword())) {
                            conversation.add(message);
                            dialog.dismiss();
                        } else {
                            edit.setError(getString(R.string.incorrect_pass));
                        }
                    }
                });
    }});

EDIT:
In the code above, the activity variable should be passed by an activity at the creation.

If that doesn't work, please post the whole log cat.