Cannot identify the problem (java.lang.NullPointerException)

[Lovro Bajc]

Hi Everyone,

everything was working fine till yesterday, and that out of nowhere appeared following problem. Once the main activity is started there are two buttons which based on the selection initiate new activity. The onClick method checkStats works normally, however method startHappinessMeter (uppon click) results in "Unfortunately, Happy App has stopped":

Main Activity code:

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.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();
        return id == R.id.action_settings || super.onOptionsItemSelected(item);
    }

    public void startHappinessMeter(View view) {
        Intent intent = new Intent(this, happinessMeterMeassurement.class);
        startActivity(intent);
    }

    public void checkStats(View view) {
        Intent intent = new Intent(this, checkStats.class);
        startActivity(intent);
    }
}

Error which is returned when I press the button:

  E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sportelitemanagement.animus.happyapp/com.sportelitemanagement.animus.happyapp.happinessMeterMeassurement}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2266)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
            at android.app.ActivityThread.access$600(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:213)
            at android.app.ActivityThread.main(ActivityThread.java:5225)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.sportelitemanagement.animus.happyapp.happinessMeterMeassurement.onCreate(happinessMeterMeassurement.java:26)
            at android.app.Activity.performCreate(Activity.java:5133)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
            at android.app.ActivityThread.access$600(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:213)
            at android.app.ActivityThread.main(ActivityThread.java:5225)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
            at dalvik.system.NativeStart.main(Native Method)

I checked the line 26 in below provided java file and I cant understand why it guides me to the greatBtn onClick listener?

package com.sportelitemanagement.animus.happyapp;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;


public class happinessMeterMeassurement extends ActionBarActivity implements View.OnClickListener {


    private static final String GREAT_COUNTER = "great_counter";
    private static final String NORMAL_COUNTER = "normal_counter";
    private static final String SAD_COUNTER = "sad_counter";
    Button greatBtn, normalBtn, sadBtn;
    int greatCounter, normalCounter, sadCounter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

       //Initiate variables from XML and for counting
        greatBtn = (Button) findViewById(R.id.great);
        greatBtn.setOnClickListener(this);
        normalBtn = (Button) findViewById(R.id.feelingNormal);
        sadBtn = (Button) findViewById(R.id.feelingSad);
        normalBtn.setOnClickListener(this);
        sadBtn.setOnClickListener(this);

        greatCounter = 0;
        normalCounter = 0;
        sadCounter = 0;


    }

    //Save the current values when the screen changes
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt(GREAT_COUNTER, greatCounter);
        outState.putInt(NORMAL_COUNTER, normalCounter);
        outState.putInt(SAD_COUNTER, sadCounter);
    }


    //Recall values when activity is recreated.
    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

        //repopulate values when the activity is resumed and private static final needs to be created

        greatCounter = savedInstanceState.getInt(GREAT_COUNTER);
        normalCounter = savedInstanceState.getInt(NORMAL_COUNTER);
        sadCounter = savedInstanceState.getInt(SAD_COUNTER);

    }

    public void showStats(View view) {
        Intent intent = new Intent(this, checkStats.class);

        //Converts the obtained clicks to String for transfer
        String feelingGreat = String.valueOf(greatCounter);
        String feelingNormal = String.valueOf(normalCounter);
        String feelingBad = String.valueOf(sadCounter);

        //Sends the values to the new intent
        intent.putExtra("greatCounter", feelingGreat);
        intent.putExtra("normalCounter", feelingNormal);
        intent.putExtra("sadCounter", feelingBad);
        startActivity(intent);


    }
}

Help would me much appreciated!

best regards

[Lovro Bajc]

Found the solution In the OnCreate the setContentView was missing.