写一个蓝牙spp通讯的app

以下是一个可以使用Java编写的蓝牙SPP通讯的简单Android应用程序示例：

1. 首先，在AndroidManifest.xml文件中添加以下权限：

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

2. 在MainActivity.java文件中，实现蓝牙初始化、搜索、连接和通讯的逻辑代码：

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter mBluetoothAdapter;
    private BluetoothSocket mBluetoothSocket;
    private InputStream mInputStream;
    private OutputStream mOutputStream;
    private ListView mMessageListView;
    private EditText mMessageEditText;
    private Button mSendButton;
    private List<String> mMessageList = new ArrayList<>();
    private MessageListAdapter mMessageListAdapter;

    private static final int MESSAGE_READ = 1;
    private static final int MESSAGE_WRITE = 2;
    private static final int MESSAGE_TOAST = 3;
    private static final String TOAST = "toast";

    private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MESSAGE_READ:
                    byte[] buffer = (byte[]) msg.obj;
                    String message = new String(buffer, 0, msg.arg1);
                    appendMessage("收到消息：" + message);
                    break;
                case MESSAGE_WRITE:
                    byte[] buffer2 = (byte[]) msg.obj;
                    String message2 = new String(buffer2);
                    appendMessage("发送消息：" + message2);
                    break;
                case MESSAGE_TOAST:
                    String message3 = msg.getData().getString(TOAST);
                    Toast.makeText(getApplicationContext(), message3, Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBluetoothAdapter == null) {
            Toast.makeText(this, "设备不支持蓝牙", Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        mMessageListView = (ListView) findViewById(R.id.message_list);
        mMessageEditText = (EditText) findViewById(R.id.message_edit);
        mSendButton = (Button) findViewById(R.id.send_button);

        mMessageListAdapter = new MessageListAdapter(this, mMessageList);
        mMessageListView.setAdapter(mMessageListAdapter);

        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String message = mMessageEditText.getText().toString();
                sendMessage(message);
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        if (!mBluetoothAdapter.isEnabled()) {
            mBluetoothAdapter.enable();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mBluetoothSocket == null || !mBluetoothSocket.isConnected()) {
            connectDevice();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        closeSocket();
    }

    private void connectDevice() {
        if (mBluetoothAdapter.isDiscovering()) {
            mBluetoothAdapter.cancelDiscovery();
        }

        BluetoothDevice device = mBluetoothAdapter.getRemoteDevice("设备地址");
        try {
            mBluetoothSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
            mBluetoothSocket.connect();
            mInputStream = mBluetoothSocket.getInputStream();
            mOutputStream = mBluetoothSocket.getOutputStream();
            startReading();
        } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(this, "连接失败", Toast.LENGTH_SHORT).show();
        }
    }

    private void startReading() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                byte[] buffer = new byte[1024];
                int bytes;
                while (true) {
                    try {
                        bytes = mInputStream.read(buffer);
                        mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer).sendToTarget();
                    } catch (IOException e) {
                        e.printStackTrace();
                        break;
                    }
                }
            }
        }).start();
    }

    private void sendMessage(String message) {
        if (mOutputStream == null) {
            Toast.makeText(this, "未连接设备", Toast.LENGTH_SHORT).show();
            return;
        }

        try {
            mOutputStream.write(message.getBytes());
            mHandler.obtainMessage(MESSAGE_WRITE, -1, -1, message.getBytes()).sendToTarget();
        } catch (IOException e) {
            e.printStackTrace();
            mHandler.obtainMessage(MESSAGE_TOAST, -1, -1, "发送失败").sendToTarget();
        }
    }

    private void closeSocket() {
        try {
            if (mBluetoothSocket != null) {
                mBluetoothSocket.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void appendMessage(String message) {
        mMessageList.add(message);
        mMessageListAdapter.notifyDataSetChanged();
        mMessageListView.smoothScrollToPosition(mMessageListAdapter.getCount() - 1);
    }
}

在该示例中，使用BluetoothAdapter获取蓝牙适配器，并创建一个BluetoothSocket对象来连接远程设备。连接成功后，使用InputStream读取数据，使用OutputStream发送数据。在MainActivity中，使用ListView和MessageListAdapter显示消息列表，并使用EditText和Button发送消息。使用Handler处理消息，以便在UI线程中更新UI。