java - Error:(53, 43) error: cannot find symbol variable lumn

Question

I am new to android studio and learning to develop the android apps, I have got an error as stated above and am unable to resolve it. Any kind of help will be appreciated. Thank you!!

My ledControl.java code is as follow

package com.led.led;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.os.AsyncTask;

import java.io.IOException;
import java.util.UUID;


public class ledControl extends ActionBarActivity {

    Button btnOn, btnOff, btnDis;
    SeekBar brightness;
    TextView lumn;
    String address = null;
    private ProgressDialog progress;
    BluetoothAdapter myBluetooth = null;
    BluetoothSocket btSocket = null;
    private boolean isBtConnected = false;
    //SPP UUID. Look for it
    static final UUID myUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

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

        Intent newint = getIntent();
        address = newint.getStringExtra(DeviceList.EXTRA_ADDRESS); //receive the address of the bluetooth device

        //view of the ledControl
        setContentView(R.layout.activity_led_control);

        //call the widgtes
        btnOn = (Button)findViewById(R.id.button2);
        btnOff = (Button)findViewById(R.id.button3);
        btnDis = (Button)findViewById(R.id.button4);
        brightness = (SeekBar)findViewById(R.id.seekBar);
        lumn = (TextView)findViewById(R.id.lumn);

        new ConnectBT().execute(); //Call the class to connect

        //commands to be sent to bluetooth
        btnOn.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                turnOnLed();      //method to turn on
            }
        });

        btnOff.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                turnOffLed();   //method to turn off
            }
        });

        btnDis.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                Disconnect(); //close connection
            }
        });

        brightness.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if (fromUser==true)
                {
                    lumn.setText(String.valueOf(progress));
                    try
                    {
                        btSocket.getOutputStream().write(String.valueOf(progress).getBytes());
                    }
                    catch (IOException e)
                    {

                    }
                }
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
    }

    private void Disconnect()
    {
        if (btSocket!=null) //If the btSocket is busy
        {
            try
            {
                btSocket.close(); //close connection
            }
            catch (IOException e)
            { msg("Error");}
        }
        finish(); //return to the first layout

    }

    private void turnOffLed()
    {
        if (btSocket!=null)
        {
            try
            {
                btSocket.getOutputStream().write("TF".toString().getBytes());
            }
            catch (IOException e)
            {
                msg("Error");
            }
        }
    }

    private void turnOnLed()
    {
        if (btSocket!=null)
        {
            try
            {
                btSocket.getOutputStream().write("TO".toString().getBytes());
            }
            catch (IOException e)
            {
                msg("Error");
            }
        }
    }

    // fast way to call Toast
    private void msg(String s)
    {
        Toast.makeText(getApplicationContext(),s,Toast.LENGTH_LONG).show();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_led_control, menu);
        return true;
    }

    @Override
    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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private class ConnectBT extends AsyncTask<Void, Void, Void>  // UI thread
    {
        private boolean ConnectSuccess = true; //if it's here, it's almost connected

        @Override
        protected void onPreExecute()
        {
            progress = ProgressDialog.show(ledControl.this, "Connecting...", "Please wait!!!");  //show a progress dialog
        }

        @Override
        protected Void doInBackground(Void... devices) //while the progress dialog is shown, the connection is done in background
        {
            try
            {
                if (btSocket == null || !isBtConnected)
                {
                    myBluetooth = BluetoothAdapter.getDefaultAdapter();//get the mobile bluetooth device
                    BluetoothDevice dispositivo = myBluetooth.getRemoteDevice(address);//connects to the device's address and checks if it's available
                    btSocket = dispositivo.createInsecureRfcommSocketToServiceRecord(myUUID);//create a RFCOMM (SPP) connection
                    BluetoothAdapter.getDefaultAdapter().cancelDiscovery();
                    btSocket.connect();//start connection
                }
            }
            catch (IOException e)
            {
                ConnectSuccess = false;//if the try failed, you can check the exception here
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void result) //after the doInBackground, it checks if everything went fine
        {
            super.onPostExecute(result);

            if (!ConnectSuccess)
            {
                msg("Connection Failed. Is it a SPP Bluetooth? Try again.");
                finish();
            }
            else
            {
                msg("Connected.");
                isBtConnected = true;
            }
            progress.dismiss();
        }
    }
}

And the activity_led_control.xml is as below

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context="com.led.led.ledControl">

    <TextView android:text="LED Control" android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textview2" />

    <SeekBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/seekBar"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Brightness"
        android:id="@+id/textView3"
        android:layout_above="@+id/seekBar"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ON"
        android:id="@+id/button2"
        android:layout_above="@+id/button3"
        android:layout_centerHorizontal="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="OFF"
        android:id="@+id/button3"
        android:layout_above="@+id/button4"
        android:layout_alignLeft="@+id/button2"
        android:layout_alignStart="@+id/button2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Disconnect"
        android:id="@+id/button4"
        android:layout_above="@+id/textView3"
        android:layout_alignLeft="@+id/button3"
        android:layout_alignStart="@+id/button3" />

</RelativeLayout>

I know that this error is in text field statement but i dont know how to resolve it ?

Answer 1

You have no TextView identified by lumn in your activity_led_control.xml.

Therefore this line doesn't compile :

lumn = (TextView)findViewById(R.id.lumn);

since R.id.lumn is not generated.

You have TextViews identified by "@+id/textview2" and "@+id/textview3". If you rename one of them to "@+id/lumn", your code will compile.