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Android Build a Simple Android App (retired 2014) Getting Started with Android Adding an OnClickListener to a Button

App keeps crashing.

I can't keep it from crashing, I don't have any errors but it still happens.

Here is the LogCat:

03-20 01:53:15.393: D/AndroidRuntime(1317): Shutting down VM
03-20 01:53:15.393: W/dalvikvm(1317): threadid=1: thread exiting with uncaught exception (group=0xb2a77ba8)
03-20 01:53:15.403: E/AndroidRuntime(1317): FATAL EXCEPTION: main
03-20 01:53:15.403: E/AndroidRuntime(1317): Process: com.example.crystalball, PID: 131703-20 01:53:15.403: E/AndroidRuntime(1317): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.crystalball/com.example.crystalball.MainActivity}: java.lang.NullPointerException
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.os.Handler.dispatchMessage(Handler.java:102)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.os.Looper.loop(Looper.java:136)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread.main(ActivityThread.java:5017)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at java.lang.reflect.Method.invokeNative(Native Method)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at java.lang.reflect.Method.invoke(Method.java:515)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at dalvik.system.NativeStart.main(Native Method)
03-20 01:53:15.403: E/AndroidRuntime(1317): Caused by: java.lang.NullPointerException
03-20 01:53:15.403: E/AndroidRuntime(1317):     at com.example.crystalball.MainActivity.onCreate(MainActivity.java:26)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.Activity.performCreate(Activity.java:5231)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-20 01:53:15.403: E/AndroidRuntime(1317):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-20 01:53:15.403: E/AndroidRuntime(1317):     ... 11 more
03-20 01:53:18.553: I/Process(1317): Sending signal. PID: 1317 SIG: 9

My MainActivity.java generates a lot more code than what is in the video.

                    Here is my MainActivity.java file:

package com.example.crystalball;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

    protected void onCreate(Bundle savedInstanceState) {

        //Declare our View variables
        final TextView answerLabel = (TextView) findViewById(R.id.textView1);
        Button getAnswerButton = (Button) findViewById(R.id.button1);

        getAnswerButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                // The button was clicked, so update the answer label with an answer
                String answer = "Yes";


        if (savedInstanceState == null) {
                    .add(R.id.container, new PlaceholderFragment())

    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;

    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();
        if (id == R.id.action_settings) {
            return true;
        return super.onOptionsItemSelected(item);

     * A placeholder fragment containing a simple view.
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {

        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;

                    When going through the debugger line by line it fails in the ThreadGroup.class
     * Handles uncaught exceptions. Any uncaught exception in any {@code Thread}
     * is forwarded to the thread's {@code ThreadGroup} by invoking this
     * method.
     * <p>New code should use {@link Thread#setUncaughtExceptionHandler} instead of thread groups.
     * @param t the Thread that terminated with an uncaught exception
     * @param e the uncaught exception itself
    public void uncaughtException(Thread t, Throwable e) {
        if (parent != null) {
            parent.uncaughtException(t, e);                                      <--- This is the line it fails at
        } else if (Thread.getDefaultUncaughtExceptionHandler() != null) {
            // TODO The spec is unclear regarding this. What do we do?
            Thread.getDefaultUncaughtExceptionHandler().uncaughtException(t, e);
        } else if (!(e instanceof ThreadDeath)) {
            // No parent group, has to be 'system' Thread Group

     * Called by the Thread constructor.

4 Answers

I feel like an idiot, I didn't follow instructions after creating the new project and delete the fragment related code.


Under teachers notes the fourth bullet down is what needs to be done.

Looks like you having a problem with your main activity.. which is com.example.crystalball.MainActivity..

check if you have any problems outlined to u by eclipse

There were no errors with the red exclamation in the mainactivity.java file, I can't post my code at this time since I am not near my workstation right now.

Sage Elliott
Sage Elliott
30,003 Points

Did you figure this out? Mine crashes immediately.

No I did not, I tried searching and could not turn up anything. I just moved back to the web developers track. But will keep looking for a solution.

Sage Elliott
Sage Elliott
30,003 Points

Same here. If I figure it out first ill let you know.