问题
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 ?
回答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.
回答2:
Because you dont have a TextView with id lumn in your layout
来源：https://stackoverflow.com/questions/31018509/error53-43-error-cannot-find-symbol-variable-lumn