Android Class cast exception with radio group widget?

Question

Building a small quiz application and have some issues with the code, it worked on a previous version but that got delete during a fresh install of windows, when i try open up the a activity for a quiz i keep getting an unexpected error and the log says after a few lines

Java.lang.classexception : android.widget.Radio Group

the code for the activity looks like this

    package com.example.quizzards;
import java.io.FileNotFoundException;
import java.util.Arrays;
import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;


@SuppressLint("NewApi")
public class GamesActivity extends Activity {

    boolean rightWrong;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_games);
        try {
            @SuppressWarnings("unused")
            Questions questions = new Questions(getApplicationContext());
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        update();

        Button answer = (Button) findViewById(R.id.AnswerButton);

        answer.setOnClickListener(new OnClickListener()
        {
            public void onClick(View V)
            {
                RadioGroup allOptions = (RadioGroup) findViewById(R.id.questions);
                int toCheck = allOptions.getCheckedRadioButtonId();
                if (toCheck == -1) {
                    Toast.makeText(GamesActivity.this, "Please select an option.",
                            Toast.LENGTH_SHORT).show();
                } else {
                    RadioButton selected = (RadioButton) findViewById(allOptions
                            .getCheckedRadioButtonId());
                    rightWrong = Questions.checkAnswer(selected.getText()
                            .toString());
                    if (rightWrong == true) {
                        Toast.makeText(GamesActivity.this, "Right!!!",
                                Toast.LENGTH_SHORT).show();
                        Questions.addPoint();
                        update();
                    } else {
                        Questions.incorrectTry();
                        int remainingTries = Questions.getRemainingTries();
                        if (remainingTries == 0) {
                            //                      Toast.makeText(MainActivity.this,
                            //                              "Your final score is " + Questions.getScore() + ".",
                            //                              Toast.LENGTH_SHORT).show();
                            Intent i = new Intent(GamesActivity.this,
                                    ResultsActivity.class);
                            startActivity(i);
                        } else {
                            Toast.makeText(
                                    GamesActivity.this,
                                    "Wrong!!! " + remainingTries
                                            + " tries left.",
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                    allOptions.clearCheck();
                }
            }
        });

    }

    @Override
    public void onBackPressed() {
        Intent i = new Intent(GamesActivity.this, PlayActivity.class);
        startActivity(i);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.games, menu);
        return true;
    }

    public void update()
    {
        if (Questions.finished()) {
            Intent i = new Intent(GamesActivity.this,
                    ResultsActivity.class);
            startActivity(i);
        } else {
            String[] aQuestion = Questions.getNextQuestion();
            String[] temp = Arrays.copyOfRange(aQuestion, 1, aQuestion.length);
            for (int i = 0; i < temp.length; i++) {
                int r = (int) (Math.random() * (i + 1));
                String swap = temp[r];
                temp[r] = temp[i];
                temp[i] = swap;
            }
            TextView textViewQuestion = (TextView) findViewById(R.id.questions);
            textViewQuestion.setText(aQuestion[0]);
            TextView textViewOption1 = (TextView) findViewById(R.id.option1);
            textViewOption1.setText(temp[0]);
            TextView textViewOption2 = (TextView) findViewById(R.id.option2);
            textViewOption2.setText(temp[1]);
            TextView textViewOption3 = (TextView) findViewById(R.id.option3);
            textViewOption3.setText(temp[2]);
            TextView textViewOption4 = (TextView) findViewById(R.id.option4);
            textViewOption4.setText(temp[3]);
            TextView runningTotal = (TextView) findViewById(R.id.runningTotal);
            runningTotal.setText("Total: " + Questions.getScore());
        }
    }
}

The XML file contains a radio group and few radio buttons, when i try to run the code without any sort of radio buttons and comment out the code, works perfectly

Answer 1

1. Make sure all your RadioButtons and RadioGroup have different id's in the layout file.

2. Another small optimization would be to look for the RadioButtons inside RadioGroup as following.

    RadioButton selected = (RadioButton) allOptions.findViewById( allOptions.getCheckedRadioButtonId());