TimmahhTimmahh TimmahhTimmahh - 1 month ago 7
Java Question

java.lang.NullPointerException in MainAcitivity setOnClickListener

When I run my application, I keep getting a NullPointerException on line 56 as shown in the debug log below. I am relatively new to programming android applications, so I can't figure out what's going on here. Can someone please help me out with this?
My MainActivity.java:

package com.termite.pockettube;

import java.util.Locale;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends FragmentActivity implements View.OnClickListener{

/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;

/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;

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

// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());

// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);

button = (Button) findViewById(R.id.button);
button.setOnClickListener(this); //this is line 56
}
public void countryOnClick() {
startActivity(new Intent("com.termite.pockettube.COUNTRY"));
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.button:
countryOnClick();
break;
}
}
@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;
}

/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {

public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}

@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
switch (position) {
case 0:
Fragment1 fragment1 = new Fragment1();
return fragment1;
case 1:
Fragment2 fragment2 = new Fragment2();
return fragment2;
case 2:
Fragment3 fragment3 = new Fragment3();
return fragment3;
case 3:
Fragment4 fragment4 = new Fragment4();
return fragment4;
case 4:
Fragment5 fragment5 = new Fragment5();
return fragment5;
}
return null;
}

@Override
public int getCount() {
// Show 5 total pages.
return 5;
}

@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
case 3:
return getString(R.string.title_section4).toUpperCase(l);
case 4:
return getString(R.string.title_section5).toUpperCase(l);
}
return null;
}
}

}


This is my debug log when attempting to run the application:

12-20 01:13:26.898: D/AndroidRuntime(6539): Shutting down VM
12-20 01:13:26.906: W/dalvikvm(6539): threadid=1: thread exiting with uncaught exception (group=0x40af21f8)
12-20 01:13:26.906: E/AndroidRuntime(6539): FATAL EXCEPTION: main
12-20 01:13:26.906: E/AndroidRuntime(6539): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.termite.pockettube/com.termite.pockettube.MainActivity}: java.lang.NullPointerException
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2035)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2060)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.access$600(ActivityThread.java:127)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1181)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.os.Handler.dispatchMessage(Handler.java:99)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.os.Looper.loop(Looper.java:137)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.main(ActivityThread.java:4558)
12-20 01:13:26.906: E/AndroidRuntime(6539): at java.lang.reflect.Method.invokeNative(Native Method)
12-20 01:13:26.906: E/AndroidRuntime(6539): at java.lang.reflect.Method.invoke(Method.java:511)
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-20 01:13:26.906: E/AndroidRuntime(6539): at dalvik.system.NativeStart.main(Native Method)
12-20 01:13:26.906: E/AndroidRuntime(6539): Caused by: java.lang.NullPointerException
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.termite.pockettube.MainActivity.onCreate(MainActivity.java:56)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.Activity.performCreate(Activity.java:4635)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1999)
12-20 01:13:26.906: E/AndroidRuntime(6539): ... 11 more


Manifest xml code:



<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />

<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>

</manifest>


activity_main.xml:

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

<android.support.v4.view.PagerTabStrip
android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_gravity="top"
android:background="#33b5e5"
android:paddingBottom="4dp"
android:paddingTop="4dp"
android:textColor="#fff"
>

</android.support.v4.view.PagerTabStrip>



</android.support.v4.view.ViewPager>


fragment1.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity$DummySectionFragment" >

<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_alignParentTop="true"
android:text="@string/button" />

</RelativeLayout>

Answer

Thank you all for your input, and it all worked to end the NPE, yet it didn't perform the task I wanted it to complete. I added the button to ,y Fragment1.java file and then it worked.

package com.termite.pockettube;

import com.termite.pockettube.MainActivity.SectionsPagerAdapter;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;

public class Fragment1 extends Fragment implements View.OnClickListener {
 Button button;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Get the view from fragmenttab1.xml
        View view = inflater.inflate(R.layout.fragment1, container, false);
        button = (Button)view.findViewById(R.id.button);
        button.setOnClickListener(this);
        return view;
    }
   /* @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


    }*/
    public void countryOnClick() {
        startActivity(new Intent("com.termite.pockettube.COUNTRY"));
    }
    @Override
public void onClick(View v) {
    switch (v.getId()){
    case R.id.button:
        countryOnClick();
        break;
    }
}
}