我使用 BluetoothChat 示例中的代码从蓝牙秤发送和接收字节数据。 秤从设备接收命令，然后发回一个字节数组。 {2,198,48,48,48,48,199,3} 在我们的通信协议(protocol)中，2 = STX，198 = 数据包开始，199 = 数据包结束，3 = ETX。
一切正常，除了 BluetoothChatService.java 中的以下代码 react 异常，因为它丢弃了前两个字节。
/**
* This thread runs during a connection with a remote device.
* It handles all incoming and outgoing transmissions.
*/
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket, String socketType) {
Log.d(TAG, "create ConnectedThread: " + socketType);
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
Log.e(TAG, "temp sockets not created", e);
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
public void run() {
Log.i(TAG, "BEGIN mConnectedThread");
final byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true) {
try {
// Read from the InputStream
bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
connectionLost();
// Start the service over to restart listening mode
BluetoothChatService.this.start();
break;
}
}
}
我对以下代码部分有疑问:
bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
调试时，在执行之前查看 mmInStream.read(buffer) 中的缓冲区内容，缓冲区包含秤设备发回的正确数据，即:
{2,198,48,48,48,48,48,199,3}
但是一旦执行了代码，缓冲区的前两个字节就会被剥离，现在错误地包含:
{48,48,48,48,48,199,3}
消息处理程序最终将其传递给 Activity 。
为了更清楚，我必须补充一点，秤发送的字节流是 00 到 FF 范围内的十六进制字符。 由于某些奇怪的原因，字符串在调试器中实际上看起来像这样:
{2,-58,48,48,48,48,48,-57,3}
然后丢弃 2,-58。
我注意到当我通过套接字发送字节数组时，我需要执行以下操作:
byte[] sendBytes = {2,(byte)198,48,48,48,48,48,(byte)199,3}
当这个数组的内容被调试时它会给出 {2,-58,48,48,48,48,48,-57,3}
请理解我是 Android - java 的新手，还有很多东西要学。所有帮助将不胜感激。 谢谢 阿德里安
根据 Radu 的建议，我添加了 log.i 条目以更好地理解正在发生的事情。似乎在我通过蓝牙将数据写入我的设备后，它会响应，并且由于某种原因我们只读取前两个字节，然后将它们发送到消息处理程序，然后读取从设备发送的其余数据包，然后发送这交给消息处理程序，但在处理程序第一次响应之前，缓冲区已经被覆盖，因此当处理程序尝试读取前两个字节时，它正在读取响应的第三和第四字节数据包，然后立即再次响应并从 3-17th 位置读取整个数据包。 所以如果我可以简单地说.. 消息处理程序只在它被覆盖后响应发送的缓冲区。请参阅下面的日志:
09-05 13:16:52.093: V/BluetoothSocket.cpp(11279): writeNative
09-05 13:16:52.118: I/IN_BUFFER(11279): The entire buffer after read stream into buffer: 2
09-05 13:16:52.118: I/IN_BUF_AFTER(11279): 2
09-05 13:16:52.118: I/IN_BUF_AFTER(11279): -58
09-05 13:16:52.118: I/IN_BUF_AFTER(11279): 0
09-05 13:16:52.118: I/IN_BUF_AFTER(11279): 0
...truncated to save space ...
09-05 13:16:52.163: I/IN_BUF_AFTER(11279): 0
09-05 13:16:52.163: I/IN_BUFFER(11279): We now send to handler.
09-05 13:16:52.168: I/IN_BUFFER(11279): Read Stream into Buffer:
09-05 13:16:52.168: V/BluetoothSocket.cpp(11279): readNative
09-05 13:16:52.168: I/IN_BUFFER(11279): The entire buffer after read stream into buffer: 17
09-05 13:16:52.168: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.168: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.168: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.173: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.173: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.173: I/IN_BUF_AFTER(11279): 44
09-05 13:16:52.173: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.178: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.178: I/IN_BUF_AFTER(11279): 49
09-05 13:16:52.178: I/IN_BUF_AFTER(11279): 50
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 48
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 44
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 85
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 13
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): -57
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 3
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 6
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 0
...truncated to save space ...
09-05 13:16:52.188: I/IN_BUF_AFTER(11279): 0
09-05 13:16:52.188: I/IN_BUFFER(11279): We now send to handler.
09-05 13:16:52.193: I/IN_BUFFER(11279): Read Stream into Buffer:
09-05 13:16:52.208: V/BluetoothSocket.cpp(11279): readNative
09-05 13:16:52.208: I/MESSAGE_READ(11279): I am reading 2 bytes
09-05 13:16:52.208: I/Content(11279): The entire array:
09-05 13:16:52.208: I/some hardcoded tag(11279): 0
09-05 13:16:52.208: I/some hardcoded tag(11279): 0
09-05 13:16:52.273: I/MESSAGE_READ(11279): I am reading 17 bytes
09-05 13:16:52.273: I/Content(11279): The entire array:
09-05 13:16:52.273: I/some hardcoded tag(11279): 0
...truncated to save space ...
09-05 13:16:52.283: I/some hardcoded tag(11279): 0
09-05 13:16:52.283: I/some hardcoded tag(11279): 0
09-05 13:16:54.528: V/BluetoothSocket.cpp(11279): writeNative
09-05 13:16:54.553: I/IN_BUFFER(11279): The entire buffer after read stream into buffer: 2
09-05 13:16:54.553: I/IN_BUF_AFTER(11279): 2
09-05 13:16:54.553: I/IN_BUF_AFTER(11279): -58
09-05 13:16:54.558: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.558: I/IN_BUF_AFTER(11279): 0
...truncated to save space ...
09-05 13:16:54.618: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.618: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.618: I/IN_BUFFER(11279): We now send to handler.
09-05 13:16:54.618: I/IN_BUFFER(11279): Read Stream into Buffer:
09-05 13:16:54.618: V/BluetoothSocket.cpp(11279): readNative
09-05 13:16:54.623: I/IN_BUFFER(11279): The entire buffer after read stream into buffer: 17
09-05 13:16:54.623: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.623: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.623: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.623: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.628: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.628: I/IN_BUF_AFTER(11279): 44
09-05 13:16:54.628: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.628: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.633: I/IN_BUF_AFTER(11279): 49
09-05 13:16:54.633: I/IN_BUF_AFTER(11279): 50
09-05 13:16:54.638: I/IN_BUF_AFTER(11279): 48
09-05 13:16:54.638: I/IN_BUF_AFTER(11279): 44
09-05 13:16:54.638: I/IN_BUF_AFTER(11279): 85
09-05 13:16:54.638: I/IN_BUF_AFTER(11279): 13
09-05 13:16:54.638: I/IN_BUF_AFTER(11279): -57
09-05 13:16:54.648: I/IN_BUF_AFTER(11279): 3
09-05 13:16:54.648: I/IN_BUF_AFTER(11279): 6
09-05 13:16:54.648: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.648: I/IN_BUF_AFTER(11279): 0
...truncated to save space ...
09-05 13:16:54.653: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.653: I/IN_BUF_AFTER(11279): 0
09-05 13:16:54.653: I/IN_BUFFER(11279): We now send to handler.
09-05 13:16:54.653: I/IN_BUFFER(11279): Read Stream into Buffer:
09-05 13:16:54.653: V/BluetoothSocket.cpp(11279): readNative
09-05 13:16:54.658: I/MESSAGE_READ(11279): I am reading 2 bytes
09-05 13:16:54.658: I/Content(11279): The entire array:
09-05 13:16:54.658: I/some hardcoded tag(11279): 0
09-05 13:16:54.663: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/MESSAGE_READ(11279): I am reading 17 bytes
09-05 13:16:54.723: I/Content(11279): The entire array:
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.723: I/some hardcoded tag(11279): 0
09-05 13:16:54.728: I/some hardcoded tag(11279): 0
09-05 13:16:54.728: I/some hardcoded tag(11279): 0
09-05 13:16:54.728: I/some hardcoded tag(11279): 0
我的新代码还在读取最新流之前将缓冲区重置为 0，因此消息处理程序只看到 0，在我这样做之前，日志显示如下:
09-05 13:06:20.508: V/BluetoothSocket.cpp(10176): writeNative
09-05 13:06:20.533: I/IN_BUFFER(10176): The entire buffer after read stream into buffer: 2
09-05 13:06:20.533: I/IN_BUF_AFTER(10176): 2
09-05 13:06:20.533: I/IN_BUF_AFTER(10176): -58
09-05 13:06:20.533: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.533: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.538: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.538: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.548: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.548: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.548: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.553: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.553: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.568: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.573: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.573: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.573: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.573: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.573: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.578: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.578: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.578: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.578: I/IN_BUFFER(10176): We now send to handler.
09-05 13:06:20.578: I/IN_BUFFER(10176): Read Stream into Buffer:
09-05 13:06:20.578: V/BluetoothSocket.cpp(10176): readNative
09-05 13:06:20.578: I/IN_BUFFER(10176): The entire buffer after read stream into buffer: 17
09-05 13:06:20.578: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.578: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.583: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.583: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.583: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 44
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 49
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 51
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 48
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 44
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 85
09-05 13:06:20.593: I/IN_BUF_AFTER(10176): 13
09-05 13:06:20.598: I/IN_BUF_AFTER(10176): -57
09-05 13:06:20.598: I/IN_BUF_AFTER(10176): 3
09-05 13:06:20.613: I/IN_BUF_AFTER(10176): 6
09-05 13:06:20.613: I/IN_BUF_AFTER(10176): 0
...truncated to save space ...
09-05 13:06:20.623: I/IN_BUF_AFTER(10176): 0
09-05 13:06:20.623: I/IN_BUFFER(10176): We now send to handler.
09-05 13:06:20.623: I/IN_BUFFER(10176): Read Stream into Buffer:
09-05 13:06:20.623: V/BluetoothSocket.cpp(10176): readNative
09-05 13:06:20.628: I/MESSAGE_READ(10176): I am reading 2 bytes
09-05 13:06:20.628: I/Content(10176): The entire array:
09-05 13:06:20.628: I/some hardcoded tag(10176): 48
09-05 13:06:20.628: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/MESSAGE_READ(10176): I am reading 17 bytes
09-05 13:06:20.688: I/Content(10176): The entire array:
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.688: I/some hardcoded tag(10176): 44
09-05 13:06:20.688: I/some hardcoded tag(10176): 48
09-05 13:06:20.693: I/some hardcoded tag(10176): 48
09-05 13:06:20.693: I/some hardcoded tag(10176): 49
09-05 13:06:20.693: I/some hardcoded tag(10176): 51
09-05 13:06:20.693: I/some hardcoded tag(10176): 48
09-05 13:06:20.693: I/some hardcoded tag(10176): 44
09-05 13:06:20.693: I/some hardcoded tag(10176): 85
09-05 13:06:20.693: I/some hardcoded tag(10176): 13
09-05 13:06:20.693: I/some hardcoded tag(10176): -57
09-05 13:06:20.693: I/some hardcoded tag(10176): 3
09-05 13:06:20.693: I/some hardcoded tag(10176): 6
09-05 13:06:21.788: V/BluetoothSocket.cpp(10176): writeNative
09-05 13:06:21.803: I/IN_BUFFER(10176): The entire buffer after read stream into buffer: 2
09-05 13:06:21.803: I/IN_BUF_AFTER(10176): 2
09-05 13:06:21.803: I/IN_BUF_AFTER(10176): -58
09-05 13:06:21.803: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.803: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.808: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.808: I/IN_BUF_AFTER(10176): 44
09-05 13:06:21.818: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.818: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.818: I/IN_BUF_AFTER(10176): 49
09-05 13:06:21.823: I/IN_BUF_AFTER(10176): 51
09-05 13:06:21.823: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.828: I/IN_BUF_AFTER(10176): 44
09-05 13:06:21.828: I/IN_BUF_AFTER(10176): 85
09-05 13:06:21.833: I/IN_BUF_AFTER(10176): 13
09-05 13:06:21.848: I/IN_BUF_AFTER(10176): -57
09-05 13:06:21.848: I/IN_BUF_AFTER(10176): 3
09-05 13:06:21.848: I/IN_BUF_AFTER(10176): 6
09-05 13:06:21.853: I/IN_BUF_AFTER(10176): 0
...truncated to save space ...
09-05 13:06:21.853: I/IN_BUF_AFTER(10176): 0
09-05 13:06:21.853: I/IN_BUFFER(10176): We now send to handler.
09-05 13:06:21.858: I/IN_BUFFER(10176): Read Stream into Buffer:
09-05 13:06:21.858: V/BluetoothSocket.cpp(10176): readNative
09-05 13:06:21.858: I/IN_BUFFER(10176): The entire buffer after read stream into buffer: 17
09-05 13:06:21.858: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.863: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.863: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.863: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.863: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.863: I/IN_BUF_AFTER(10176): 44
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 49
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 51
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 48
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 44
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 85
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 13
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): -57
09-05 13:06:21.868: I/IN_BUF_AFTER(10176): 3
09-05 13:06:21.873: I/IN_BUF_AFTER(10176): 6
09-05 13:06:21.873: I/IN_BUF_AFTER(10176): 0
...truncated to save space ...
09-05 13:06:21.893: I/IN_BUF_AFTER(10176): 0
09-05 13:06:21.893: I/IN_BUFFER(10176): We now send to handler.
09-05 13:06:21.893: I/IN_BUFFER(10176): Read Stream into Buffer:
09-05 13:06:21.898: V/BluetoothSocket.cpp(10176): readNative
09-05 13:06:21.903: I/MESSAGE_READ(10176): I am reading 2 bytes
09-05 13:06:21.903: I/Content(10176): The entire array:
09-05 13:06:21.903: I/some hardcoded tag(10176): 48
09-05 13:06:21.903: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/MESSAGE_READ(10176): I am reading 17 bytes
09-05 13:06:21.958: I/Content(10176): The entire array:
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 44
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 49
09-05 13:06:21.958: I/some hardcoded tag(10176): 51
09-05 13:06:21.958: I/some hardcoded tag(10176): 48
09-05 13:06:21.958: I/some hardcoded tag(10176): 44
09-05 13:06:21.958: I/some hardcoded tag(10176): 85
09-05 13:06:21.958: I/some hardcoded tag(10176): 13
09-05 13:06:21.958: I/some hardcoded tag(10176): -57
09-05 13:06:21.963: I/some hardcoded tag(10176): 3
09-05 13:06:21.963: I/some hardcoded tag(10176): 6
我希望这没有把事情弄糊涂，但实际上证明了很多人在添加 BluetoothChat 演示代码以供自己使用时遇到的问题。 在消息处理程序读取之前，我们需要以某种方式防止缓冲区被覆盖？ 问候
阿德里安·雷福德
由于 Sleep，更新后的代码运行得更好!
public void run() {
Log.i(TAG, "BEGIN IN mConnectedThread");
byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true) {
try {
try {
sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
bytes = mmInStream.available();
Log.i("IN_BUFFER", "mmInStream-available bytes: " + Integer.toString(bytes)+ " ");
if (bytes>0){
for(int i=0; i<30; i++){
buffer[i] = 0;}
// Read from the InputStream
Log.i("IN_BUFFER", "Read Stream into Buffer:");
bytes = mmInStream.read(buffer);
Log.i("IN_BUFFER", "The entire buffer after read stream into buffer: " + Integer.toString(bytes)+ " ");
for(int i=0; i<30; i++)
Log.i("IN_BUF_AFTER", buffer[i] + " ");
// Send the obtained bytes to the UI Activity
Log.i("IN_BUFFER", "We now send to handler.");
mHandler.obtainMessage(BluetoothScale.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();}
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
connectionLost();
// Start the service over to restart listening mode
BluetoothScaleService.this.start();
break;
}
}
}
现在日志如下所示:
09-05 20:57:15.833: V/BluetoothSocket.cpp(25368): availableNative
09-05 20:57:15.838: I/IN_BUFFER(25368): mmInStream-available bytes: 0
09-05 20:57:15.888: V/BluetoothSocket.cpp(25368): availableNative
09-05 20:57:15.888: I/IN_BUFFER(25368): mmInStream-available bytes: 0
09-05 20:57:15.943: V/BluetoothSocket.cpp(25368): availableNative
09-05 20:57:15.943: I/IN_BUFFER(25368): mmInStream-available bytes: 0
09-05 20:57:15.958: V/BluetoothSocket.cpp(25368): writeNative
09-05 20:57:15.988: V/BluetoothSocket.cpp(25368): availableNative
09-05 20:57:15.993: I/IN_BUFFER(25368): mmInStream-available bytes: 2
09-05 20:57:15.993: I/IN_BUFFER(25368): Read Stream into Buffer:
09-05 20:57:15.993: V/BluetoothSocket.cpp(25368): readNative
09-05 20:57:15.998: I/IN_BUFFER(25368): The entire buffer after read stream into buffer: 19
09-05 20:57:15.998: I/IN_BUF_AFTER(25368): 2
09-05 20:57:15.998: I/IN_BUF_AFTER(25368): -58
09-05 20:57:16.003: I/IN_BUF_AFTER(25368): 48
...truncated to save space ...
09-05 20:57:16.033: I/IN_BUF_AFTER(25368): 85
09-05 20:57:16.033: I/IN_BUF_AFTER(25368): 13
09-05 20:57:16.033: I/IN_BUF_AFTER(25368): -57
09-05 20:57:16.033: I/IN_BUF_AFTER(25368): 3
09-05 20:57:16.038: I/IN_BUF_AFTER(25368): 6
09-05 20:57:16.038: I/IN_BUF_AFTER(25368): 0
...truncated to save space ...
09-05 20:57:16.043: I/IN_BUF_AFTER(25368): 0
09-05 20:57:16.043: I/IN_BUFFER(25368): We now send to handler.
09-05 20:57:16.058: I/MESSAGE_READ(25368): I am reading 19 bytes
09-05 20:57:16.058: I/Content(25368): The entire array:
09-05 20:57:16.058: I/some hardcoded tag(25368): 2
09-05 20:57:16.058: I/some hardcoded tag(25368): -58
09-05 20:57:16.058: I/some hardcoded tag(25368): 48
...truncated to save space ...
09-05 20:57:16.063: I/some hardcoded tag(25368): 13
09-05 20:57:16.063: I/some hardcoded tag(25368): -57
09-05 20:57:16.063: I/some hardcoded tag(25368): 3
09-05 20:57:16.063: I/some hardcoded tag(25368): 6
09-05 20:57:16.093: V/BluetoothSocket.cpp(25368): availableNative
09-05 20:57:16.093: I/IN_BUFFER(25368): mmInStream-available bytes: 0
请注意，mmInStream.available() 返回 2 个字节，然后在我们读取缓冲区时的下一行代码中，读取了 19 个字节......真的很奇怪，它是如何在这两个假定的直接步骤之间填满的。在缓冲区被重写之前， sleep 似乎允许处理程序有足够的时间从传递的缓冲区中读取消息。
我本来希望 handler.obtainmessage... 发送一个唯一的缓冲区，但似乎发送了对线程缓冲区的引用，因此很麻烦。 我怎样才能每次发送一个唯一的缓冲区？ 谢谢 阿德里安
最佳答案
我以前见过有人在使用蓝牙聊天示例时遇到过此类问题。示例代码的问题在于，发送到 Handler 的消息对象仅包含对用于每个后续 的实际 操作。这意味着一旦 byte[] 数组的引用>read()Handler 获取消息并开始检查数组，随后对蓝牙套接字的 read() 操作已经有机会写入更新的数据到那个数组。
在这行代码中:
mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget()
数组没有被复制；而是消息只是传达对同一数组的对象引用。
Bluetooth Chat 示例能够实现其最初目的的唯一原因是因为它的目的是以人类打字速度传送短串字符。如果您发送的速度比这快，Handler 从该数组中读取的内容将变成垃圾。
答案是发送数组的副本(例如 System.arraycopy())或使用简单的循环缓冲区，这是我自己的蓝牙应用程序所使用的。
前两个字节被破坏这一事实很奇怪，但它可能只是特定设备上蓝牙堆栈中底层读取操作的具体实现。一个简单的事实是，一旦您使用该缓冲区调用了 read()，您不应同时接触该缓冲区或关心其中的内容。也许您设备上特定的蓝牙套接字读取实现会对缓冲区中的前几个字节执行某些操作，因为与其内部操作有关。但是当 read() 阻塞时，您不应该关心缓冲区处于何种有趣的中间状态，因为此时没有其他线程应该试图理解它。您所关心的只是当 read() 返回时缓冲区是否处于具有有效数据的有效状态。
之所以使用 sleep() 操作显然部分地“解决”了这个问题，是因为它是让您的 Handler 有时间在之前查看数组的粗略方法随后的 read() 操作会处理数组。但这不是一个好的解决方案。
第二个问题是因为在 Java 中，byte 是有符号的。这就是调试器将字节显示为有符号值的原因。在您的应用程序中，如果您需要将给定字节用作 int 并且该字节最初是无符号的，您可以执行以下操作:
int someValue = myByteArray[someIndex] & 0xff;
关于Android InputStream 丢弃前两个字节(修改后的 BluetoothChat)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12239692/