当我点击我的Android应用程序中的打开按钮然后蓝牙连接，但当它在textview中显示值时，我的应用程序停止。 通过打开按钮，完成了Android手机和蓝牙模块的蓝牙连接 我在logcat中检查了它，然后我得到的错误是：
11-21 23:06:32.338 11949-12442/com.example.sugandhabansal.bluetooth_torch E/AndroidRuntime: FATAL EXCEPTION: Thread-520
Process: com.example.sugandhabansal.bluetooth_torch, PID: 11949
java.lang.StringIndexOutOfBoundsException: length=0; index=0
at java.lang.String.charAt(Native Method)
at com.example.sugandhabansal.bluetooth_torch.bluetooth_torch_Activity$5.run(bluetooth_torch_Activity.java:222)
at java.lang.Thread.run(Thread.java:818)
java代码是：
package com.example.sugandhabansal.bluetooth_torch;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AlertDialog;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.TextView;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;
public class bluetooth_torch_Activity extends Activity
{
TextView myLabel,mydata,myvalue;
BluetoothAdapter mBluetoothAdapter;
BluetoothSocket mmSocket;
BluetoothDevice mmDevice;
OutputStream mmOutputStream;
InputStream mmInputStream;
Thread workerThread;
byte[] readBuffer;
int readBufferPosition;
int counter;
volatile boolean stopWorker;
private CameraManager mCameraManager;
private String mCameraId;
private ImageButton mTorchOnOffButton;
private Boolean isTorchOn;
int min_data_onflash=-10;
int max_data_onflash=10;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
Log.d("bluetooth_torch", "onCreate()");
setContentView(R.layout.activity_bluetooth_torch_);
Button openButton = (Button)findViewById(R.id.open);
Button closeButton = (Button)findViewById(R.id.close);
myLabel = (TextView)findViewById(R.id.label);
myvalue = (TextView)findViewById(R.id.value);
mydata = (TextView)findViewById(R.id.data);
//Open Button
openButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
try
{
findBT();
openBT();
}
catch (IOException ex) { }
}
});
//Close button
closeButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
try
{
closeBT();
}
catch (IOException ex) { }
}
});
mTorchOnOffButton = (ImageButton) findViewById(R.id.button_on_off);
isTorchOn = false;
Boolean isFlashAvailable = getApplicationContext().getPackageManager()
.hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
if (!isFlashAvailable) {
AlertDialog alert = new AlertDialog.Builder(bluetooth_torch_Activity.this)
.create();
alert.setTitle("Error !!");
alert.setMessage("Your device doesn't support flash light!");
alert.setButton(DialogInterface.BUTTON_POSITIVE, "OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// closing the application
finish();
System.exit(0);
}
});
alert.show();
return;
}
mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
mCameraId = mCameraManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
e.printStackTrace();
}
mTorchOnOffButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
if (isTorchOn) {
turnOffFlashLight();
isTorchOn = false;
} else {
turnOnFlashLight();
isTorchOn = true;
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
void findBT()
{
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if(mBluetoothAdapter == null)
{
myLabel.setText("No bluetooth adapter available");
}
if(!mBluetoothAdapter.isEnabled())
{
Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBluetooth, 0);
}
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
if(pairedDevices.size() > 0)
{
for(BluetoothDevice device : pairedDevices)
{
if(device.getName().equals("HC-05"))
{
mmDevice = device;
break;
}
}
}
myLabel.setText("Bluetooth Device Found");
}
void openBT() throws IOException
{
UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); //Standard SerialPortService ID
mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid);
mmSocket.connect();
mmOutputStream = mmSocket.getOutputStream();
mmInputStream = mmSocket.getInputStream();
beginListenForData();
myLabel.setText("Bluetooth Connected");
}
void beginListenForData()
{
final Handler handler = new Handler();
final byte delimiter = 35; //This is the ASCII code for a newline character
stopWorker = false;
readBufferPosition = 0;
readBuffer = new byte[1024];
workerThread = new Thread(new Runnable()
{
public void run()
{
while(!Thread.currentThread().isInterrupted() && !stopWorker)
{
try
{
int bytesAvailable = mmInputStream.available();
if(bytesAvailable > 0)
{
byte[] packetBytes = new byte[bytesAvailable];
mmInputStream.read(packetBytes);
for(int i=0;i<bytesAvailable;i++)
{
byte b = packetBytes[i];
if(b == delimiter)
{
byte[] encodedBytes = new byte[readBufferPosition];
System.arraycopy(readBuffer, 0, encodedBytes, 0, encodedBytes.length);
final String DATA = new String(encodedBytes, "US-ASCII");
Log.d("SKY",DATA);
readBufferPosition = 0;
handler.post(new Runnable()
{
public void run()
{
mydata.setText(DATA);
}
});
if (DATA.charAt(i) == '#') {
String number_string = DATA.substring(1 /* data after # */, DATA.length());
int angle = Integer.getInteger(number_string);
if (angle > min_data_onflash && angle < max_data_onflash) {
turnOnFlashLight();
} else {
turnOffFlashLight();
}
}
}
else
{
readBuffer[readBufferPosition++] = b;
}
}
}
}
catch (IOException ex)
{
stopWorker = true;
}
}
}
});
workerThread.start();
}
void closeBT() throws IOException
{
stopWorker = true;
mmOutputStream.close();
mmInputStream.close();
mmSocket.close();
myLabel.setText("Bluetooth Closed");
}
public void turnOnFlashLight() {
try {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
mCameraManager.setTorchMode(mCameraId, true);
mTorchOnOffButton.setImageResource(R.drawable.on);
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void turnOffFlashLight() {
try {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
mCameraManager.setTorchMode(mCameraId, false);
mTorchOnOffButton.setImageResource(R.drawable.off);
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
protected void onStop() {
super.onStop();
if(isTorchOn){
turnOffFlashLight();
}
}
@Override
protected void onPause() {
super.onPause();
if(isTorchOn){
turnOffFlashLight();
}
}
@Override
protected void onResume() {
super.onResume();
if(isTorchOn){
turnOnFlashLight();
}
}
}
错误是什么，如何将其删除？.....请帮帮我