Android quiz app error

Question

I am new to android programming so I am developing a quiz app for practice.. Every thing is working fine but there is one error and I can't find solution of it. The problem is when the first question appears and if I don't answer it and click next button it gives me error java.lang.nullpointerException. I have used sqlite for storing questions and I have used timer as time finishes all the radio buttons get disabled.

Here is my code:

    private TextView tv_timer;
    List<Question> question_list;
    int score = 0; 
    int qid = 0;
    Question currentQ;
    TextView tv_question;
    RadioButton rda,rdb,rdc,rdd,rde;
    Button btn_next;
    MyCount counter;
    RadioGroup rg;
    RadioButton answer;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_timer = (TextView)findViewById(R.id.tv_timer);
        counter = new MyCount(50000,1000);
        QuizHelper qh = new QuizHelper(this);
        question_list=qh.getAllQuestions();
        currentQ = question_list.get(qid);
        tv_question = (TextView)findViewById(R.id.tv_question);
        rda = (RadioButton)findViewById(R.id.radio1);
        rdb = (RadioButton)findViewById(R.id.radio2);
        rdc = (RadioButton)findViewById(R.id.radio3);
        rdd = (RadioButton)findViewById(R.id.radio4);
        rde = (RadioButton)findViewById(R.id.radio5);
        btn_next = (Button)findViewById(R.id.button1);
        setQuestionView();

       btn_next.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) 
            {  
                try{

                rda.setChecked(false);
                rdb.setChecked(false);
                rdc.setChecked(false);
                rdd.setChecked(false);
                rde.setChecked(false);

                rda.setClickable(true);
                rdb.setClickable(true);
                rdc.setClickable(true);
                rdd.setClickable(true);
                rde.setClickable(true);

                rg = (RadioGroup)findViewById(R.id.RadioGroup1);
                answer = (RadioButton)findViewById(rg.getCheckedRadioButtonId());

                if(currentQ.getANSWER().equals(answer.getText()))
                {
                score++;
                }
                if(qid < 5){
                currentQ = question_list.get(qid);
                setQuestionView();
                }
                else{
                    Intent i = new Intent(MainActivity.this,ResultActivity.class);
                    Bundle b = new Bundle();
                    b.putInt("score", score);
                    i.putExtras(b);
                    startActivity(i);
                    finish();
                }
                }catch(Exception e){
                    Log.d("Error","" + e);
                }
            }
        });
    }

    public void setQuestionView(){
        counter.start();
        tv_question.setText(currentQ.getQUESTION());
        rda.setText(currentQ.getOPTA());
        rdb.setText(currentQ.getOPTB());
        rdc.setText(currentQ.getOPTC());
        rdd.setText(currentQ.getOPTD());
        rde.setText(currentQ.getOPTE());
        qid++;
    }

    public class MyCount extends CountDownTimer{
        public MyCount(long millisInFuture, long countDownInterval) {
        super(millisInFuture, countDownInterval);
        }
        @Override
        public void onFinish() {
        rda.setClickable(false);
        rdb.setClickable(false);
        rdc.setClickable(false);
        rdd.setClickable(false);
        rde.setClickable(false);

        }

Somebody please help :)

Here is logcat:

09-02 01:13:58.958: D/AndroidRuntime(1348): Shutting down VM
09-02 01:13:58.958: W/dalvikvm(1348): threadid=1: thread exiting with uncaught exception (group=0xb1b0aba8)
09-02 01:13:59.018: E/AndroidRuntime(1348): FATAL EXCEPTION: main
09-02 01:13:59.018: E/AndroidRuntime(1348): Process: com.example.challengeyourself, PID: 1348
09-02 01:13:59.018: E/AndroidRuntime(1348): java.lang.NullPointerException
09-02 01:13:59.018: E/AndroidRuntime(1348):     at com.example.challengeyourself.MainActivity$1.onClick(MainActivity.java:84)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.view.View.performClick(View.java:4438)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.view.View$PerformClick.run(View.java:18422)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.os.Handler.handleCallback(Handler.java:733)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.os.Handler.dispatchMessage(Handler.java:95)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.os.Looper.loop(Looper.java:136)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at android.app.ActivityThread.main(ActivityThread.java:5017)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at java.lang.reflect.Method.invokeNative(Native Method)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at java.lang.reflect.Method.invoke(Method.java:515)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-02 01:13:59.018: E/AndroidRuntime(1348):     at dalvik.system.NativeStart.main(Native Method)
09-02 01:14:02.588: I/Process(1348): Sending signal. PID: 1348 SIG: 9
09-02 01:14:05.648: D/dalvikvm(1374): GC_FOR_ALLOC freed 58K, 5% free 3036K/3168K, paused 169ms, total 173ms
09-02 01:14:05.698: I/dalvikvm-heap(1374): Grow heap (frag case) to 8.390MB for 5622016-byte allocation
09-02 01:14:05.748: D/dalvikvm(1374): GC_FOR_ALLOC freed 2K, 2% free 8524K/8660K, paused 42ms, total 43ms
09-02 01:14:06.328: D/gralloc_goldfish(1374): Emulator without GPU emulation detected.

Answer 1

You are getting NullPointerException on

if(currentQ.getANSWER().equals(answer.getText()))

as you have not checked any radio button. Hence answer will be null at that time.

Put a check before you try to access answer's text:

if(answer != null){
   if(currentQ.getANSWER().equals(answer.getText())){
       //do something
   }
}

Hope this helps.

P.S: Always initialize all your views in onCreate. This way they are being initialized in onClick every time you click on Next. That's not a good practice.

Answer 2

initialize rg and answer in onCreate method i.e. before btn_next.setOnClickListener because those are part of activity layout.

i.e. Rewrite as

rg = (RadioGroup)findViewById(R.id.RadioGroup1);
answer = (RadioButton)findViewById(rg.getCheckedRadioButtonId());
btn_next.setOnClickListener(new View.OnClickListener() {

and don't forget to remove

rg = (RadioGroup)findViewById(R.id.RadioGroup1);
answer = (RadioButton)findViewById(rg.getCheckedRadioButtonId());

from setOnClickListener

Answer 3

Did you initialize these variable?

    Button btn_next;

like this

btn_next= (Button)findViewById(R.id.yourbutton); 

try to put this above code in OnCreate method of your activity orjust before you set the listinener of your button

btn_next= (Button)findViewById(R.id.yourbutton); 
btn_next.setOnClickListener(new View.OnClickListener()..........

and i think btn_next.setOnClickListiner is giving the nullpointer exception as you havent initialized it .