我正在尝试读取从外部蓝牙模块发送到我的 HTC Sensation 的串行数据,但是当我调用 InputStream.available() 时 - 它返回 0,因此我无法遍历接收到的字节并调用 InputStream.read(字节数组)。
有人可以帮我解决这个问题吗?
我需要在读取之前检查可用字节吗?
对于我在技术上不准确的帖子,我深表歉意。
这是我的代码:
public class BluetoothTest extends Activity
{
TextView myLabel;
TextView snapText;
EditText myTextbox;
BluetoothAdapter mBluetoothAdapter;
BluetoothSocket mmSocket;
BluetoothDevice mmDevice;
OutputStream mmOutputStream;
InputStream mmInputStream;
Thread workerThread;
byte[] readBuffer;
int readBufferPosition;
int counter;
volatile boolean stopWorker;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button openButton = (Button)findViewById(R.id.open);
Button closeButton = (Button)findViewById(R.id.close);
Button chkCommsButton = (Button)findViewById(R.id.chkCommsButton);
Button offButton = (Button)findViewById(R.id.offButton);
myLabel = (TextView)findViewById(R.id.mylabel);
snapText = (TextView)findViewById(R.id.snapText);
//Open Bluetooth
openButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
try
{
findBT();
openBT();
}
catch (IOException ex) { }
}
});
//Close Bluetooth
closeButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
try
{
closeBT();
}
catch (IOException ex) { }
}
});
// Check Comms - multicast all SNAP nodes and pulse their BLUE led
chkCommsButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try {
chkcommsButton();
} catch (Exception e) {
// TODO: handle exception
}
}
});
//Off Button - set strip to all OFF
offButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try {
offButton();
} catch (Exception e) {
// TODO: handle exception
}
}
});
}
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("BTNODE25")) // Change to match RN42 - node name
{
mmDevice = device;
Log.d("ArduinoBT", "findBT found device named " + mmDevice.getName());
Log.d("ArduinoBT", "device address is " + mmDevice.getAddress());
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("BT << " + mmDevice.getName() + " >> is now open ");
}
void closeBT() throws IOException
{
stopWorker = true;
mmOutputStream.close();
mmInputStream.close();
mmSocket.close();
myLabel.setText("Bluetooth Closed");
}
void beginListenForData()
{
final Handler handler = new Handler();
final byte delimiter = 10; //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");
readBufferPosition = 0;
handler.post(new Runnable()
{
public void run()
{
snapText.setText(data);
}
});
}
else
{
readBuffer[readBufferPosition++] = b;
}
}
}
}
catch (IOException ex)
{
stopWorker = true;
}
}
}
});
workerThread.start();
}
void offButton() throws IOException
{
mmOutputStream.write("0".getBytes());
}
void chkcommsButton() throws IOException
{
mmOutputStream.write("1".getBytes());
}
最佳答案
InputStream.read()
方法是阻塞的,这意味着它将阻塞您的代码,直到某些数据到达,或者某些东西破坏了管道(例如主机断开连接或关闭流)。
阻塞是 CPU 友好的,因为线程处于 WAIT 状态( sleep )直到中断将其置于 READY 状态,因此它将被安排在 CPU 上运行;所以你不会在等待数据时使用 cpu,这意味着你会使用更少的电池(或者你将 CPU 时间留给其他线程)!
available()
给出了实际可用的数据,因为串行通信真的很慢(115200 波特在 8n1 意味着 11520 字节/秒)并且你的循环运行速度至少快一到两个数量级,您将读取很多 0,并使用大量 cpu 来请求该零...这意味着您使用了大量电池。
可用循环在 arduino 上不是问题,因为您只有一个线程/进程:您的代码。但是在多线程系统中循环检查数据(称为“轮询”)总是一个坏主意,只有在您别无选择时才应该这样做,并且总是添加一点 sleep() 这样您的代码就不会t 窃取 CPU 给系统和其他线程。好主意是使用阻塞调用(对于初学者来说很容易使用)或像你为图形事件所做的那样的事件系统(你使用的库并不总是支持它,并且需要同步,所以它很棘手但你不会在其中产生其他线程你自己的代码,但请记住,来自串行和图形的数据以及你的应用程序可能在不同的线程中,并且应该同步)
关于java - Android 蓝牙读取输入流,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22846076/