title: How to check which radio button of a radio group is selected? [ANDROID]
body: <p>I am using two radio groups with multiple radio buttons, I want to check which radio button is selected so that I can call specific functions accordingly. I am using <strong><em>getCheckedRadioButtonId</em></strong> method to do this, but it's throwing null pointer exception. How this can be done in a correct way?  I have tried other methods too.
  Any help will be appreciated.
  Here is my code</p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
  private EditText et_name;
  private EditText et_age;
  private EditText et_contactno;
  
  private RadioGroup radioGroup_gender;
  private RadioButton radioButton_male;
  private RadioButton radioButton_female;
  private RadioGroup radioGroup_methods;
  private RadioGroup radioGroup_intent_methods;
  private RadioButton radioButton_textfile;
  private RadioButton radioButton_sharefpref;
  private RadioButton radioButton_database;
  private RadioButton radioButton_staticfields;
  private RadioButton radioButton_intents;
  private RadioButton radioButton_direct;
  private RadioButton radioButton_bundle;
  private RadioButton radioButton_parcelable;
  
  private String name;
  private String age;
  private String contact_no;
  private String gender;
  
  private int gender_selected_id;
  private int transfer_method_selected_id;
  private int selected_intent_method_id;
  
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
      setSupportActionBar(toolbar);
      findViewsByIds();
      FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
      fab.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {
              Snackbar.make(view, "FAB CLICKED", Snackbar.LENGTH_LONG)
                      .setAction("Action", null).show();
              executeSelectedMethod();
          }
      });
  }
  
  private void findViewsByIds() {
      et_name = (EditText) findViewById(R.id.et_name);
      et_age = (EditText) findViewById(R.id.et_age);
      et_contactno = (EditText) findViewById(R.id.et_contactno);
      radioGroup_gender = (RadioGroup) findViewById(R.id.rg_gender);
      radioButton_male = (RadioButton) findViewById(R.id.rb_male);
      radioButton_female = (RadioButton) findViewById(R.id.rb_female);
  
      radioGroup_methods = (RadioGroup) findViewById(R.id.rg_methods);
      radioGroup_intent_methods = (RadioGroup) findViewById(R.id.rg_intentmethods);
      radioButton_textfile = (RadioButton) findViewById(R.id.rb_textfile);
      radioButton_sharefpref = (RadioButton) findViewById(R.id.rb_sharefpref);
      radioButton_database = (RadioButton) findViewById(R.id.rb_database);
      radioButton_staticfields = (RadioButton) findViewById(R.id.rb_static);
      radioButton_intents = (RadioButton) findViewById(R.id.rb_intent);
      radioButton_direct = (RadioButton) findViewById(R.id.rb_intent_direct);
      radioButton_bundle = (RadioButton) findViewById(R.id.rb_intent_bundle);
      radioButton_parcelable = (RadioButton) findViewById(R.id.rb_intent_parcelable);
  }
  
  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.menu_main, menu);
      return true;
  }
  
  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
      // Handle action bar item clicks here. The action bar will
      // automatically handle clicks on the Home/Up button, so long
      // as you specify a parent activity in AndroidManifest.xml.
      int id = item.getItemId();
  
      //noinspection SimplifiableIfStatement
      if (id == R.id.action_settings) {
          return true;
      }
  
      return super.onOptionsItemSelected(item);
  }
  
  private void executeSelectedMethod() {
      try {
          name = et_name.getText().toString();
          age = et_age.getText().toString();
          contact_no = et_contactno.getText().toString();
          RadioButton rb = (RadioButton) findViewById(radioGroup_gender.getCheckedRadioButtonId());
          String selectedgender = rb.getText().toString();
          if (selectedgender.equalsIgnoreCase("Male")) {
              gender = radioButton_male.getText().toString();
          } else if (selectedgender.equalsIgnoreCase("Female")) {
              gender = radioButton_female.getText().toString();
          }
          RadioButton rb_selected_method = (RadioButton) findViewById(radioGroup_gender.getCheckedRadioButtonId());
          String selectedRadioButtontext = rb_selected_method.getText().toString();
          if (selectedRadioButtontext.equalsIgnoreCase("Text File")) {
              ConstantFile.TRANSFER_METHOD = radioButton_textfile.getText().toString();
              executeTextFileMethod();
          } else if (transfer_method_selected_id == R.id.rb_sharefpref) {
              ConstantFile.TRANSFER_METHOD = radioButton_sharefpref.getText().toString();
          } else if (transfer_method_selected_id == R.id.rb_database) {
              ConstantFile.TRANSFER_METHOD = radioButton_database.getText().toString();
          } else if (transfer_method_selected_id == R.id.rb_static) {
              ConstantFile.TRANSFER_METHOD = radioButton_staticfields.getText().toString();
          } else {
  
              selected_intent_method_id = radioGroup_intent_methods.getCheckedRadioButtonId();
              if (selected_intent_method_id == R.id.rb_intent_direct) {
                  ConstantFile.TRANSFER_METHOD = radioButton_direct.getText().toString();
              } else if (selected_intent_method_id == R.id.rb_intent_bundle) {
                  ConstantFile.TRANSFER_METHOD = radioButton_bundle.getText().toString();
  
              } else if (selected_intent_method_id == R.id.rb_intent_parcelable) {
                  ConstantFile.TRANSFER_METHOD = radioButton_parcelable.getText().toString();
  
              }
          }
      } catch (IOException e) {
          e.printStackTrace();
      }
  }
  
  private void executeTextFileMethod() throws IOException {
      File transfer_file = new File("/sdcard/" + name + ".txt");
      transfer_file.createNewFile();
      FileOutputStream fileoutputstrem = new FileOutputStream(transfer_file);
      OutputStreamWriter outstreamwriter = new OutputStreamWriter(fileoutputstrem);
      outstreamwriter.append(name + ":" + age + ":" + contact_no + ":" + gender);
      fileoutputstrem.close();
      outstreamwriter.close();
      Toast.makeText(this, "This is my Toast message!",
              Toast.LENGTH_LONG).show();
      ConstantFile.TXTFILENAME = transfer_file.getName();
      goToNextActivity();
  }
  
  private void goToNextActivity() {
      Intent intent = new Intent(MainActivity.this, Main2Activity.class);
      startActivity(intent);
  }}
  </code></pre>
  
  <p>This is the exception:</p>
  
  <pre><code>Process: com.phaseone_datatransferbetweenactivities, PID: 22385
  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.RadioButton.getText()' on a null object reference
  at com.phaseone_datatransferbetweenactivities.MainActivity.executeSelectedMethod(MainActivity.java:118)
  at com.phaseone_datatransferbetweenactivities.MainActivity.access$000(MainActivity.java:23)
  at com.phaseone_datatransferbetweenactivities.MainActivity$1.onClick(MainActivity.java:65)
  at android.view.View.performClick(View.java:5265)
  at android.view.View$PerformClick.run(View.java:21534)
  at android.os.Handler.handleCallback(Handler.java:815)
  at android.os.Handler.dispatchMessage(Handler.java:104)
  at android.os.Looper.loop(Looper.java:207)
  at android.app.ActivityThread.main(ActivityThread.java:5728)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
  </code></pre>