我正在尝试编程，当蓝牙设备（arduino uno）断开连接或超出范围时会显示通知。 当我测试时，关闭蓝牙设备，手机有延迟20秒显示通知。
我不知道为什么，希望有人帮助我弄清楚。
package com.example.arduinosensors;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;
import java.util.UUID;
import android.app.Activity;
import android.app.AlertDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Vibrator;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
Button btnOn, btnOff;
TextView txtArduino, txtString, txtStringLength, sensorView0, sensorView1, sensorView2, sensorView3;
Handler bluetoothIn;
public static final int handlerState = 0,MESSAGE_LOST_CONNECT = 1; //used to identify handler message
private BluetoothAdapter btAdapter = null;
private BluetoothSocket btSocket = null;
private StringBuilder recDataString = new StringBuilder();
private Vibrator mVibrator;
private ConnectedThread mConnectedThread;
// SPP UUID service - this should work for most devices
private static final UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
// Insert your bluetooth devices MAC address
private static String address = "20:14:12:03:11:31";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Link the buttons and textViews to respective views
btnOn = (Button) findViewById(R.id.buttonOn);
btnOff = (Button) findViewById(R.id.buttonOff);
txtString = (TextView) findViewById(R.id.txtString);
txtStringLength = (TextView) findViewById(R.id.testView1);
sensorView0 = (TextView) findViewById(R.id.sensorView0);
sensorView1 = (TextView) findViewById(R.id.sensorView1);
sensorView2 = (TextView) findViewById(R.id.sensorView2);
sensorView3 = (TextView) findViewById(R.id.sensorView3);
mVibrator=(Vibrator) getSystemService(VIBRATOR_SERVICE);
bluetoothIn = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == handlerState) { //if message is what we want
String readMessage = (String) msg.obj; // msg.arg1 = bytes from connect thread
recDataString.append(readMessage); //keep appending to string until ~
int endOfLineIndex = recDataString.indexOf("~"); // determine the end-of-line
if (endOfLineIndex > 0) { // make sure there data before ~
String dataInPrint = recDataString.substring(0, endOfLineIndex); // extract string
txtString.setText("Data Received = " + dataInPrint);
int dataLength = dataInPrint.length(); //get length of data received
txtStringLength.setText("String Length = " + String.valueOf(dataLength));
if (recDataString.charAt(0) == '#') //if it starts with # we know it is what we are looking for
{
String sensor0 = recDataString.substring(1, 5); //get sensor value from string between indices 1-5
String sensor1 = recDataString.substring(6, 10); //same again...
String sensor2 = recDataString.substring(11, 15);
String sensor3 = recDataString.substring(16, 20);
sensorView0.setText(" Sensor 0 Voltage = " + sensor0 + "V"); //update the textviews with sensor values
sensorView1.setText(" Sensor 1 Voltage = " + sensor1 + "V");
sensorView2.setText(" Sensor 2 Voltage = " + sensor2 + "V");
sensorView3.setText(" Sensor 3 Voltage = " + sensor3 + "V");
}
recDataString.delete(0, recDataString.length()); //clear all string data
}
}
if(msg.what == MESSAGE_LOST_CONNECT) { //
//Toast.makeText(getApplicationContext(), "", Toast.LENGTH_LONG).show();
mVibrator.vibrate(new long[]{10, 100, 100, 100}, -1);
new AlertDialog.Builder(MainActivity.this)
.setTitle("bluetooth disconnected")
.setIcon(R.drawable.blue1)
.setMessage("bluetooth out of range")
.setPositiveButton("yes", new
DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialogInterface, int i)
{
//finish();
}
})
.setNegativeButton("cancel", new
DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialogInterface, int i)
{
}
})
.show();
}
}
};
btAdapter = BluetoothAdapter.getDefaultAdapter(); // get Bluetooth adapter
checkBTState();
btnOff.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mConnectedThread.write("0"); // Send "0" via Bluetooth
Toast.makeText(getBaseContext(), "Turn off LED", Toast.LENGTH_SHORT).show();
}
});
btnOn.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mConnectedThread.write("1"); // Send "1" via Bluetooth
Toast.makeText(getBaseContext(), "Turn on LED", Toast.LENGTH_SHORT).show();
}
});
}
private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
return device.createRfcommSocketToServiceRecord(BTMODULEUUID);
//creates secure outgoing connecetion with BT device using UUID
}
@Override
public void onResume() {
super.onResume();
//Get MAC address from DeviceListActivity via intent
Intent intent = getIntent();
//Get the MAC address from the DeviceListActivty via EXTRA
//address = intent.getStringExtra(DeviceListActivity.EXTRA_DEVICE_ADDRESS);
//create device and set the MAC address
BluetoothDevice device = btAdapter.getRemoteDevice(address);
try {
btSocket = createBluetoothSocket(device);
} catch (IOException e) {
Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_LONG).show();
}
// Establish the Bluetooth socket connection.
try
{
btSocket.connect();
} catch (IOException e) {
try
{
btSocket.close();
} catch (IOException e2)
{
//insert code to deal with this
}
}
mConnectedThread = new ConnectedThread(btSocket);
mConnectedThread.start();
//I send a character when resuming.beginning transmission to check device is connected
//If it is not an exception will be thrown in the write method and finish() will be called
mConnectedThread.write("x");
}
@Override
public void onPause()
{
super.onPause();
try
{
//Don't leave Bluetooth sockets open when leaving activity
btSocket.close();
} catch (IOException e2) {
//insert code to deal with this
}
}
//Checks that the Android device Bluetooth is available and prompts to be turned on if off
private void checkBTState() {
if(btAdapter==null) {
Toast.makeText(getBaseContext(), "裝置並不支援藍芽", Toast.LENGTH_LONG).show();
} else {
if (btAdapter.isEnabled()) {
} else {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
}
}
}
//create new class for connect thread
private class ConnectedThread extends Thread {
private final InputStream mmInStream;
private final OutputStream mmOutStream;
//creation of the connect thread
public ConnectedThread(BluetoothSocket socket) {
InputStream tmpIn = null;
OutputStream tmpOut = null;
try {
//Create I/O streams for connection
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) { }
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
private void connectionLost() { //斷線通知副程式
// Send a failure message back to the Activity
Message msg = bluetoothIn.obtainMessage(MainActivity.MESSAGE_LOST_CONNECT);
bluetoothIn.sendMessage(msg);
}
public void run() {
byte[] buffer = new byte[256];
int bytes;
// Keep looping to listen for received messages
while (true) {
try {
bytes = mmInStream.read(buffer); //read bytes from input buffer
String readMessage = new String(buffer, 0, bytes);
// Send the obtained bytes to the UI Activity via handler
bluetoothIn.obtainMessage(handlerState, bytes, -1, readMessage).sendToTarget();
} catch (IOException e) {
connectionLost();
break;
}
}
}
//write method
public void write(String input) {
byte[] msgBuffer = input.getBytes(); //converts entered String into bytes
try {
mmOutStream.write(msgBuffer); //write bytes over BT connection via outstream
} catch (IOException e) {
//if you cannot write, close the application
Toast.makeText(getBaseContext(), "連線失敗", Toast.LENGTH_LONG).show();
finish();
}
}
}
}