Question

This is the manifest file

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="net.learn2develop.SMSMessaging"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="10" />
    <uses-permission android:name="android.permission.SEND_SMS"></uses-permission>
    <uses-permission android:name="android.permission.RECEIVE_SMS"></uses-permission>

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".SMS"
                  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>

This is the XML file (main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <TextView  
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:text="Enter the phone number of recipient"
        />     
    <EditText 
        android:id="@+id/txtPhoneNo"  
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"        
        />
    <TextView  
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"         
        android:text="Message"
        />     
    <EditText 
        android:id="@+id/txtMessage"  
        android:layout_width="fill_parent" 
        android:layout_height="150px"
        android:gravity="top"         
        />          
    <Button 
        android:id="@+id/btnSendSMS"  
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
        android:text="Send SMS"
        />    
</LinearLayout>

This is the java file (SMS.java):-

package net.learn2develop.SMSMessaging;

import android.app.Activity;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.telephony.SmsManager;

public class SMS extends Activity 
{
    Button btnSendSMS;
    EditText txtPhoneNo;
    EditText txtMessage;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);        

        btnSendSMS = (Button) findViewById(R.id.btnSendSMS);
        txtPhoneNo = (EditText) findViewById(R.id.txtPhoneNo);
        txtMessage = (EditText) findViewById(R.id.txtMessage);


        btnSendSMS.setOnClickListener(new View.OnClickListener() 
        {
            public void onClick(View v) 
            {                
                String phoneNo = txtPhoneNo.getText().toString();
                String message = txtMessage.getText().toString();                 
                if (phoneNo.length()>0 && message.length()>0) {
                    sendSMS(phoneNo, message);
                } else {
                    Toast.makeText(getBaseContext(), 
                        "Please enter both phone number and message.", 
                        Toast.LENGTH_SHORT).show();
                }
            }
        });        
    } 
    private void sendSMS(String phoneNumber, String message)
    {        
        PendingIntent pi = PendingIntent.getActivity(this, 0,
            new Intent(this, SMS.class), 0);                
        SmsManager sms = SmsManager.getDefault();
        sms.sendTextMessage(phoneNumber, null, message, pi, null);        
    }   
}

The error portion :-

08-26 23:06:41.040: ERROR/AndroidRuntime(411): FATAL EXCEPTION: main
08-26 23:06:41.040: ERROR/AndroidRuntime(411): java.lang.RuntimeException: Unable to start activity ComponentInfo{net.learn2develop.SMSMessaging/net.learn2develop.SMSMessaging.SMS}: java.lang.NullPointerException
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.os.Looper.loop(Looper.java:123)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at java.lang.reflect.Method.invokeNative(Native Method)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at java.lang.reflect.Method.invoke(Method.java:507)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at dalvik.system.NativeStart.main(Native Method)
08-26 23:06:41.040: ERROR/AndroidRuntime(411): Caused by: java.lang.NullPointerException
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at net.learn2develop.SMSMessaging.SMS.onCreate(SMS.java:31)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-26 23:06:41.040: ERROR/AndroidRuntime(411):     ... 11 more

Answer 1

YOu’re getting a NullPointerException at line 31 which is where btnSendSMS.setOnClickListener(

Probably the view with the id wasn’t found.

as a workaround add

if (btnSendSMS != null) {
   btnSendSMS.setOnClickLi......
}