我正在使用Android应用程序，我需要通过蓝牙发送文本。我已经想出了一段代码来实现这一点。我的问题是它在将消息发送到设备抛出StringIndexOutOfBoundsException后崩溃了。我该如何解决这个问题。我的完整代码是：
package com.example.blueremote;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.UUID;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends Activity {
private BluetoothAdapter btadapter;
private BluetoothSocket socket;
private Button btnSend;
private ArrayList<BluetoothDevice> foundDevices;
private ArrayAdapter<BluetoothDevice> aa;
private Handler handler = new Handler();
private ListView list;
private TextView tvmsg;
private static int DISCOVERY_REQUEST = 1;
private UUID uuid = UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666");
ImageButton up;
private String address = "D8:50:E6:8A:16:0F";
private String text = "up";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btadapter = BluetoothAdapter.getDefaultAdapter();
Intent disc;
disc = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(disc, DISCOVERY_REQUEST);
up = (ImageButton) findViewById(R.id.btn_up);
registerReceiver(discoveryResult, new IntentFilter(
BluetoothDevice.ACTION_FOUND));
AsyncTask<Integer, Void, Void> connectTask = new AsyncTask<Integer, Void, Void>() {
@Override
protected Void doInBackground(Integer... params) {
// TODO Auto-generated method stub
try {
Log.v("Main Activity", " AsyncTask started");
BluetoothDevice device = btadapter.getRemoteDevice(address);
socket = device.createRfcommSocketToServiceRecord(uuid);
Log.v("Main Activity", "Socket Created");
socket.connect();
Log.v("Main Activity", "Socket Connected");
} catch (IOException e) {
Log.d("BLUETOOTH_CLIENT", e.getMessage());
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// Log.v("Main Activity", "Invoking switchUI");
// switchUI();
}
};
connectTask.execute();
up.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Log.v("Main Activity", "In up Button");
// Log.v("Main Activity", "Invoking switchUI");
switchUI();
}
});
}
private void switchUI() {
Log.v("Main Activity", "In SwitchUI Method");
Log.v("Main Activity", "Invoking sendMessage Method ");
sendMessage(socket, text);
Log.v("Main Activity", "Message Sent");
BluetoothSocketListener bsl = new BluetoothSocketListener(socket,
handler);
Thread messageListener = new Thread(bsl);
messageListener.start();
}
private void sendMessage(BluetoothSocket socket, String msg) {
msg = "UP";
OutputStream outStream;
try {
Log.v("Main Activity", "Inside sendMessage Method ");
outStream = socket.getOutputStream();
Log.v("Main Activity", "Outstream:" + outStream);
byte[] byteString = (msg + " ").getBytes();
Log.v("Main Activity", "byteString:" + byteString);
outStream.write(byteString);
Log.v("Main Activity", "outstream written:");
} catch (IOException e) {
Log.d("BLUETOOTH_COMMS", e.getMessage());
}
}
private class MessagePoster implements Runnable {
private TextView textView;
private String message;
public MessagePoster(String message) {
// this.textView = textView;
this.message = message;
}
public void run() {
// textView.setText(message);
}
}
private class BluetoothSocketListener implements Runnable {
private BluetoothSocket socket;
private TextView textView;
private Handler handler;
public BluetoothSocketListener(BluetoothSocket socket, Handler handler) {
this.socket = socket;
// this.textView = textView;
this.handler = handler;
}
public void run() {
int bufferSize = 2048;
byte[] buffer = new byte[bufferSize];
try {
InputStream instream = socket.getInputStream();
int bytesRead = -1;
String message = "";
while (true) {
message = "";
bytesRead = instream.read(buffer);
if (bytesRead != -1) {
while ((bytesRead == bufferSize)
&& (buffer[bufferSize - 1] != 0)) {
message = message
+ new String(buffer, 0, bytesRead);
bytesRead = instream.read(buffer);
}
message = message
+ new String(buffer, 0, bytesRead - 1);
handler.post(new MessagePoster(message));
socket.getInputStream();
}
}
} catch (IOException e) {
Log.d("BLUETOOTH_COMMS", e.getMessage());
}
}
}
BroadcastReceiver discoveryResult = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
BluetoothDevice remoteDevice;
remoteDevice = intent
.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (btadapter.getBondedDevices().contains(remoteDevice)) {
foundDevices.add(remoteDevice);
aa.notifyDataSetChanged();
}
}
};
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(discoveryResult);
}
}
logcat的：
E/AndroidRuntime(10360): FATAL EXCEPTION: Thread-1585
E/AndroidRuntime(10360): java.lang.StringIndexOutOfBoundsException: length=2048; regionStart=0; regionLength=65534
E/AndroidRuntime(10360): at java.lang.String.failedBoundsCheck(String.java:587)
E/AndroidRuntime(10360): at java.lang.String.<init>(String.java:247)
E/AndroidRuntime(10360): at java.lang.String.<init>(String.java:171)
E/AndroidRuntime(10360): at com.example.blueremote.MainActivity$BluetoothSocketListener.run(MainActivity.java:177)
答案 0 :(得分：0)
在参考String类时，我们发现当出现以下三种情况之一时，调用String (byte[] data, int offset, int byteCount)会抛出IndexOutOfBoundsException：
offset > 0 - 如果传递给方法的偏移量小于0，则抛出Exception。由于您将0而不是变量传递给方法调用，因此不会导致Exception。
offset + byteCount > data.length - 在这种情况下，当Exception加offset大于缓冲区的长度时，将引发byteCount。在您的代码中，offset总是0和byteCount，在您的示例中为bytesRead - 1，永远不会超过2048，因为instream.read(buffer)不能读取比buffer本身可以容纳的更多字节。这意味着offset（0）+ byteCount（-1≤byteCount≤2047）永远不会大于data.length（2048），所以这不是Exception。
byteCount < 0 - 当您传递小于Exception的{{1}}计数时，将抛出上述byte的第三种情况。在您的示例中，您将0作为bytesRead - 1计数传递。当您检查以确保byte（如果已到达流末尾时将会出现）时，您不会检查以确保至少读取了1 bytesRead != -1。这很可能是罪魁祸首...
根据您的示例，让我们考虑当byte返回bytesRead = instream.read(buffer);时会发生什么，这意味着没有读取0 ...
您执行的第一项检查byte将通过，因为if (bytesRead != -1)等于bytesRead。
0语句中的内容if当然也会失败，因为while ((bytesRead == bufferSize) && (buffer[bufferSize - 1] != 0)) bytesRead不等于0 }，这是bufferSize。
最终通话为2048，我们可以将其转换为message = message + new String(buffer, 0, bytesRead - 1);。如您所见，由于message = message + String(buffer, 0, -1)为0，因此上述调用将生成bytesRead。
要解决此问题，请确保在IndexOutOfBoundsException小于String(buffer, 0, bytesRead - 1)时不要致电bytesRead。