- java lang NullPointerException - setText on null object reference

Question

This is what I m trying to do for several hours  I ve got a MainActivity java file  listing below  and a fragment start xml file with a start button  Tapping the start-button should display the activity main xml file with points- round- and countdown-Textviews  It doesn t work and this is what is happening   The logcat tells me  PID  1240 java lang NullPointerException  Attempt to invoke virtual method  void android widget TextView setText java lang CharSequence   on a null object reference  The emulator displays  Unfortunately  GAME has stopped   Necessary to mention that I m rather new in programming   Thanks for any advice   import android app Activity  import android os Bundle  import android view View  import android view ViewGroup  import android widget TextView    public class MainActivity extends Activity implements View OnClickListener    private int points  private int round  private int countdown    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout activity main       showStartFragment       private void newGame          points 0      round 1      initRound       private void initRound         countdown   10      update       private void update          fillTextView R id points  Integer toString points        fillTextView R id round  Integer toString round        fillTextView R id countdown  Integer toString countdown   1000       private void fillTextView  int id  String text        TextView tv    TextView  findViewById id       tv setText text      private void showStartFragment         ViewGroup container    ViewGroup  findViewById R id container       container removeAllViews        container addView              getLayoutInflater   inflate R layout fragment start  null         container findViewById R id start  setOnClickListener this       Override public void onClick View view        if view getId      R id start            startGame             public void startGame         newGame

User · Answer

The problem is the tv setText text   The variable tv is probably null and you call the setText method on that null  which you can t  My guess that the problem is on the findViewById method  but it s not here  so I can t tell more  without the code

User · Answer

private void fillTextView  int id  String text        TextView tv    TextView  findViewById id       tv setText text       If this is where you re getting the null pointer exception  there was no view found for the id that you passed into findViewById    and the actual exception is thrown when you try to call a function setText   on null  You should post your XML for R layout activity main  as it s hard to tell where things went wrong just by looking at your code   More reading on null pointers  What is a NullPointerException  and how do I fix it

User · Answer

Here lies your problem   private void fillTextView  int id  String text        TextView tv    TextView  findViewById id       tv setText text      tv is null     --   TextView  findViewById id      returns null But from your code  I can t find why this method returns null  Try to track down  what id you give as a parameter and if this view with the specified id exists   The error message is very clear and even tells you at what method  From the documentation   public final View findViewById  int id      Look for a child view with the given id  If this view has the given id  return this view      Parameters         id  The id to search for      Returns         The view that has the given id in the hierarchy or null   http   developer android com reference android view View html findViewById 28int 29  In other words  You have no view with the id you give as a parameter

[java] - java.lang.NullPointerException - setText on null object reference

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