java - 无法读取蓝牙接收到的数据

Question

我无法读取通过蓝牙从 Arduino Uno 接收到的数据，但我知道 Arduino 正在向我发送一些数据。

我收到错误:

W/System.err:     at android.bluetooth.BluetoothSocket.read(BluetoothSocket.java:537)
    at android.bluetooth.BluetoothInputStream.read(BluetoothInputStream.java:96)
    at java.io.InputStream.read(InputStream.java:101)
    at bikit.chaptal.MainDisp$SendReceive.run(MainDisp.java:250)
    at bikit.chaptal.MainDisp$SendReceive.<init>(MainDisp.java:239)
    at bikit.chaptal.MainDisp$ConnectBT.doInBackground(MainDisp.java:200)
    at bikit.chaptal.MainDisp$ConnectBT.doInBackground(MainDisp.java:168)
    at android.os.AsyncTask$2.call(AsyncTask.java:345)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:257)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
    at java.lang.Thread.run(Thread.java:784)
java.io.IOException: bt socket closed, read return: -1
    at android.bluetooth.BluetoothSocket.read(BluetoothSocket.java:537)
    at android.bluetooth.BluetoothInputStream.read(BluetoothInputStream.java:96)
    at java.io.InputStream.read(InputStream.java:101)
    at bikit.chaptal.MainDisp$SendReceive.run(MainDisp.java:250)
    at bikit.chaptal.MainDisp$SendReceive.<init>(MainDisp.java:239)
    at bikit.chaptal.MainDisp$ConnectBT.doInBackground(MainDisp.java:200)
    at bikit.chaptal.MainDisp$ConnectBT.doInBackground(MainDisp.java:168)
    at android.os.AsyncTask$2.call(AsyncTask.java:345)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:257)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
    at java.lang.Thread.run(Thread.java:784)
java.io.IOException: bt socket closed, read return: -1

这是有问题的代码部分:

public  class SendReceive extends Thread
{
    private InputStream inputStream;
    private OutputStream outputStream;

    public SendReceive ( BluetoothSocket socket )
    {
        try {
            inputStream = mmSocket.getInputStream();
            outputStream = mmSocket.getOutputStream();
        }catch (IOException e ) {
            e.printStackTrace();
        }
        if(inputStream != null){
            run();
        }
    }

    public  void run()
    {
        byte[] buffer = new byte[1024];
        int bytes;

        while (true) {
            try {
                bytes = inputStream.read(buffer); 
                handler.obtainMessage(STATE_MESSAGE_RECEIVED, bytes, -1,buffer).sendToTarget();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    public void write (byte[] bytes)
    {
        try {
            outputStream.write(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

处理程序:

Handler handler = new Handler(new Handler.Callback() {
    @Override
    public boolean handleMessage(Message msg) {

        switch (msg.what)
        {
            case STATE_MESSAGE_RECEIVED:
                byte[]readBuff = (byte[]) msg.obj;
                if (bytes == 1){
                    Nbatt = readBuff[0];
                    bytes++;
                }
                else if (bytes == 2){
                    tempfloat = ByteBuffer.wrap(new byte[]{readBuff[1]}).getFloat();
                    temp = Float.toString(tempfloat);
                    resetbytes();   //bytes++;
                }
                else if (bytes == 3){
                    speed = readBuff[2];
                    resetbytes();
                }
                break;
        }
        return false;
    }
});

应用程序应该读取不同的字节并显示它们。我不明白这个错误，有人可以向我解释一下吗？

Answer 1

不深入分析代码，我们可以看出问题是由于IOException异常导致的InputStream.read()操作引起的，具体如下:bt socket closeed ，阅读 所以看起来连接已以某种方式断开。根据一些论坛的说法，这是因为该库太旧了，而且自 Android 4.2 以来，BT 堆栈已经发生了变化。

无论如何，有一个解决方法可以通过在出现此异常时实例化回退来使其工作:IOException: read failed, socket might closed - Bluetooth on Android 4.3