title: I want to get text from radio button and store it in sqlite database but I am getting an error
body: <p>i want to get text from radio button but i am getting an error </p>
  
  <blockquote>
    <p>java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.RadioGroup.getCheckedRadioButtonId()' on a null object reference</p>
  </blockquote>
  
  <p>please tell me how can i get text from radio button and to remove <code>NullPointerException</code>.</p>
  
  <p>here is the code</p>
  
  <pre><code>public class BookActivity extends AppCompatActivity  {
  
      EditText editText4;
      EditText editText6;
      RadioGroup time;
      Button book;
      RadioButton radioButton;
  
      //RadioButton radioButton, radioButton2, radioButton3, radioButton4, radioButton5, radioButton6, radioButton7, radioButton8, radioButton9;
      Context context = this;
      UserDbHelper userDbHelper;
      SQLiteDatabase sqLiteDatabase;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.book);
  
          editText4 = (EditText) findViewById(R.id.editText4);
          editText6 = (EditText) findViewById(R.id.editText6);
          time=(RadioGroup)findViewById(R.id.time);
          book=(Button)findViewById(R.id.book);
  
          addListenerOnButton();
      }
  
  
      public void addListenerOnButton() {
          time = (RadioGroup) findViewById(R.id.radio);
          book = (Button) findViewById(R.id.book);
  
          book.setOnClickListener(new View.OnClickListener() {
  
              @Override
              public void onClick(View v) {
  
                  // get selected radio button from radioGroup
                  int selectedId = time.getCheckedRadioButtonId();
  
                  // find the radiobutton by returned id
                  radioButton = (RadioButton) findViewById(selectedId);
                  if (radioButton != null) {
                      String pname = editText4.getText().toString();
                      String rtime = radioButton.getText().toString();
  
                      userDbHelper = new UserDbHelper(context);
                      sqLiteDatabase = userDbHelper.getWritableDatabase();
                      userDbHelper.addInformations(pname, rtime, sqLiteDatabase);
                      Toast.makeText(BookActivity.this, "Data Saved", Toast.LENGTH_LONG).show();
                      userDbHelper.close();
                  }
  
                  //Toast.makeText(BookActivity.this,radioButton.getText(), Toast.LENGTH_SHORT).show();
              }
          });
      }
  }
  </code></pre>
  
  <p>here is the logcat</p>
  
  <pre><code>10-23 01:04:35.607 16858-16858/com.example.hp.appointit D/AndroidRuntime: Shutting down VM
  ---- Beginning of crash
  10-23 01:04:35.621 16858-16858/com.example.hp.appointit E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.example.hp.appointit, PID: 16858
  java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.RadioGroup.getCheckedRadioButtonId()' on a null object reference
      at com.example.hp.appointit.BookActivity$1.onClick(BookActivity.java:54)
      at android.view.View.performClick(View.java:4785)
      at android.view.View$PerformClick.run(View.java:19884)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:135)
      at android.app.ActivityThread.main(ActivityThread.java:5343)
      at java.lang.reflect.Method.invoke(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:372)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
  10-23 01:09:35.642 16858-16858/com.example.hp.appointit I/Process: Sending signal. PID: 16858 SIG: 9
  10-23 01:09:36.449 22673-22673/com.example.hp.appointit W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
  10-23 01:09:36.737 22673-22692/com.example.hp.appointit I/art: Background sticky concurrent mark sweep GC freed 8864(1707KB) AllocSpace objects, 1(16KB) LOS objects, 0% free, 16MB/16MB, paused 12.340ms total 74.187ms
  10-23 01:09:36.944 22673-22673/com.example.hp.appointit E/DATABASE OPERATIONS: Database created / opened
  10-23 01:09:36.985 22673-22714/com.example.hp.appointit D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
  10-23 01:09:36.996 22673-22673/com.example.hp.appointit D/Atlas: Validating map...
  10-23 01:09:37.034 22673-22714/com.example.hp.appointit I/Adreno-EGL: &lt;qeglDrvAPI_eglInitialize:410&gt;: EGL 1.4 QUALCOMM build: AU_LINUX_ANDROID_LA.BF.1.1.1_RB1.05.00.02.042.016_msm8226_LA.BF.1.1.1_RB1__release_AU ()
      OpenGL ES Shader Compiler Version: E031.25.03.00
      Build Date: 02/11/15 Wed
      Local Branch: 
      Remote Branch: quic/LA.BF.1.1.1_rb1.10
      Local Patches: NONE
      Reconstruct Branch: AU_LINUX_ANDROID_LA.BF.1.1.1_RB1.05.00.02.042.016 + 62ca4eb + acd831d + 9f8b442 + e027a02 + cba30ba + 53c303a + a649d79 + 23e16f8 + 5e97da7 + cbd2a44 + 33d072a + 7aacf06 + 72b33e7 + 28f6f60 + b4c13d8 +  NOTHING
  10-23 01:09:37.036 22673-22714/com.example.hp.appointit I/OpenGLRenderer: Initialized EGL, version 1.4
  10-23 01:09:37.060 22673-22714/com.example.hp.appointit D/OpenGLRenderer: Enabling debug mode 0
  </code></pre>