"Unfortunately, 'App name' has stopped working." : Android Eclipse

Question

I am a begginner trying to build android apps.I just copy pasted the code in the Eclipse software.But I dont know what is going wrong here.The application isnt getting opened.Hope my doubts will be cleared.Thanks in advance.

Here is my fragment_main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<EditText
    android:id="@+id/my_text"
    android:layout_width="fill_parent"
    android:layout_height="60dp"
    android:ems="10"
    android:inputType="textPersonName" />

<Button
    android:id="@+id/button1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/button_text" />

Here is my MainActivity.java:

package com.MyButtonApp.mybuttonapp;

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

 public class MainActivity extends ActionBarActivity {
Button myButton;
EditText myText;
int count=0;

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

    myButton=(Button)findViewById(R.id.button1);
    myText=(EditText)findViewById(R.id.my_text);

    myText.setSingleLine();
    myText.setInputType(InputType.TYPE_NULL);

    setContentView(R.layout.activity_main);

    myButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            myButton.setText("You hav clicked"+ ++count+ "times.!!!");
            }
        });

Here is the logCat:

07-03 05:45:46.860: D/AndroidRuntime(991): Shutting down VM.
07-03 05:45:46.860: W/dalvikvm(991): threadid=1: thread exiting with uncaught exception        
(group=0xb2a23ba8)07-03 05:45:46.880: E/AndroidRuntime(991): FATAL EXCEPTION:main
07-03 05:45:46.880: E/AndroidRuntime(991): Process: com.MyButtonApp.mybuttonapp,PID:991
07-03 05:45:46.880: E/AndroidRuntime(991): java.lang.RuntimeException:Unable to start
activityComponentInfo{com.MyButtonApp.mybuttonapp/com.MyButtonApp.mybuttonapp.
MainActivity}
:java.lang.NullPointerException
07-03 05:45:46.880: E/AndroidRuntime(991):at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
07-03 05:45:46.880: E/AndroidRuntime(991):  at  
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
07-03 05:45:46.880: E/AndroidRuntime(991):  at   

android.app.ActivityThread.access$800(ActivityThread.java:135)
07-03 05:45:46.880: E/AndroidRuntime(991):  at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
07-03 05:45:46.880: E/AndroidRuntime(991):  at      
android.os.Handler.dispatchMessage(Handler.java:102) 
07-03 05:45:46.880: E/AndroidRuntime(991):  at android.os.Looper.loop(Looper.java:136)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
android.app.ActivityThread.main(ActivityThread.java:5017)
07-03 05:45:46.880: E/AndroidRuntime(991):  at   
java.lang.reflect.Method.invokeNative(Native Method)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
java.lang.reflect.Method.invoke(Method.java:515)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
07-03 05:45:46.880: E/AndroidRuntime(991):  at dalvik.system.NativeStart.main(Native  
Method)
07-03 05:45:46.880: E/AndroidRuntime(991): Caused by: java.lang.NullPointerException
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
com.MyButtonApp.mybuttonapp.MainActivity.onCreate(MainActivity.java:28)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
android.app.Activity.performCreate(Activity.java:5231)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
07-03 05:45:46.880: E/AndroidRuntime(991):  at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
07-03 05:45:46.880: E/AndroidRuntime(991):  ... 11 more
07-03 05:45:52.400: I/Process(991): Sending signal. PID: 991 SIG: 9
07-03 05:52:10.125: D/AndroidRuntime(1302): Shutting down VM
07-03 05:52:10.125: W/dalvikvm(1302): threadid=1: thread exiting with uncaught 
exception (group=0xb2a23ba8)
07-03 05:52:10.135: E/AndroidRuntime(1302): FATAL EXCEPTION: main
07-03 05:52:10.135: E/AndroidRuntime(1302): Process: com.MyButtonApp.mybuttonapp, PID:  
1302
07-03 05:52:10.135: E/AndroidRuntime(1302): java.lang.RuntimeException: Unable to start   
activity 
ComponentInfo{com.MyButtonApp.mybuttonapp/com.MyButtonApp.mybuttonapp.MainActivity}: 
java.lang.NullPointerException
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread.access$800(ActivityThread.java:135)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.os.Handler.dispatchMessage(Handler.java:102)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.os.Looper.loop(Looper.java:136)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread.main(ActivityThread.java:5017)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
java.lang.reflect.Method.invokeNative(Native Method)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
java.lang.reflect.Method.invoke(Method.java:515)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
dalvik.system.NativeStart.main(Native Method)
07-03 05:52:10.135: E/AndroidRuntime(1302): Caused by: java.lang.NullPointerException
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
com.MyButtonApp.mybuttonapp.MainActivity.onCreate(MainActivity.java:28)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.Activity.performCreate(Activity.java:5231)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
07-03 05:52:10.135: E/AndroidRuntime(1302):     at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
07-03 05:52:10.135: E/AndroidRuntime(1302):     ... 11 more

Here is AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.MyButtonApp.mybuttonapp"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    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.MyButtonApp.mybuttonapp.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>
     </application>
    </manifest>

Answer 1

You should change the order like

 setContentView(R.layout.activity_main);

 myButton=(Button)findViewById(R.id.button1);
 myText=(EditText)findViewById(R.id.my_text);

First you need to setContentView(R.layout.activity_main); and then reference your View.

Answer 2

I think you are initialising wrong layout.Change setContentView(R.layout.activity_main); to setContentView(R.layout.fragment_main);

then put setContentView(R.layout.fragment_main) before findViewById(); like:

setContentView(R.layout.fragment_main);
myButton=(Button)findViewById(R.id.button1);
myText=(EditText)findViewById(R.id.my_text);

Answer 3

Move the findViewById() to the fragment onCreateView() or onViewCreated() after you've inflated the fragment_main layout you posted.

The views you're attempting to find are in the fragment layout and activity onCreate() is too early to find them. (Finding activity views before setContentView() would be a problem in case the views were in your activity layout.)

See NullPointerException accessing views in onCreate() for more.