R cannot be resolved into a variable after declaration

Question

I have already declared the R into a variable. However, the error still remains there. I cleaned the project and restarted it but nothing changed. Im a beginner to eclipse android coding. Can someone help me out with the R variable?

Main.java

package com.example.smsmessaging;
import com.example.smsmessaging.R;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.telephony.gsm.SmsManager;


public class SMS extends Activity 
{

 Button btnSendSMS;
EditText txtPhoneNo;
EditText txtMessage;


@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();
        }
    });        
}    
public class SMS extends Activity 
{
    //...

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        //...
    }

    //---sends an SMS message to another device---
    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);        
    }    
  }
  //---sends an SMS message to another device---
  private void sendSMS(String phoneNumber, String message)
  {         
    String SENT = "SMS_SENT";
    String DELIVERED = "SMS_DELIVERED";

    PendingIntent sentPI = PendingIntent.getBroadcast(this, 0,
        new Intent(SENT), 0);

    PendingIntent deliveredPI = PendingIntent.getBroadcast(this, 0,
        new Intent(DELIVERED), 0);

    //---when the SMS has been sent---
    registerReceiver(new BroadcastReceiver(){
        @Override
        public void onReceive(Context arg0, Intent arg1) {
            switch (getResultCode())
            {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "SMS sent", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_GENERIC_FAILURE:
                    Toast.makeText(getBaseContext(), "Generic failure", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NO_SERVICE:
                    Toast.makeText(getBaseContext(), "No service", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NULL_PDU:
                    Toast.makeText(getBaseContext(), "Null PDU", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_RADIO_OFF:
                    Toast.makeText(getBaseContext(), "Radio off", 
                            Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }, new IntentFilter(SENT));

    //---when the SMS has been delivered---
    registerReceiver(new BroadcastReceiver(){
        @Override
        public void onReceive(Context arg0, Intent arg1) {
            switch (getResultCode())
            {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "SMS delivered", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case Activity.RESULT_CANCELED:
                    Toast.makeText(getBaseContext(), "SMS not delivered", 
                            Toast.LENGTH_SHORT).show();
                    break;                        
            }
        }
    }, new IntentFilter(DELIVERED));        

    SmsManager sms = SmsManager.getDefault();
    sms.sendTextMessage(phoneNumber, null, message, sentPI, deliveredPI);        
   }

xml:

    <receiver android:name=".SmsReceiver"> 
        <intent-filter> 
            <action android:name=
                "android.provider.Telephony.SMS_RECEIVED" /> 
        </intent-filter> 
    </receiver>

</application>
<uses-permission android:name="android.permission.SEND_SMS">
</uses-permission>
<uses-permission android:name="android.permission.RECEIVE_SMS">
</uses-permission>
</manifest>

Answer 1

You shouldn't import R or define it as a variable. Quoting from http://source.android.com/source/using-eclipse.html:

Note: Eclipse sometimes likes to add an import android.R statement at the top of your files > that use resources, especially when you ask eclipse to sort or otherwise manage imports. > This will cause your make to break. Look out for these erroneous import statements and delete them.

If there is no error in your resource xml files, then R should automatically be available. XML issues are usually reported in Eclipse. If you're not able to figure out the error, post your xml files here.

Answer 2

First Remove tour R.java file form gen folder. Now clean your project and import android.R;

Alternate import can be done by pressing Ctrl+Shift+O

Answer 3

Once check your imports and remove unused import in your code:
This line: import com.example.smsmessaging.R;
Then organize imports -> Ctrl+Shift+O

Thats it...

Answer 4

Remove line import com.example.smsmessaging.R; We should not import it in our .java.