<uses-feature

        android:name="android.hardware.bluetooth_le"

        android:required="true" />

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

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

package myapplication.com.myapplicationble;

import android.app.Service;

import android.bluetooth.BluetoothAdapter;

import android.bluetooth.BluetoothDevice;

import android.bluetooth.BluetoothServerSocket;

import android.bluetooth.BluetoothSocket;

import android.content.Context;

import android.content.Intent;

import android.os.AsyncTask;

import android.os.Handler;

import android.os.IBinder;

import android.os.Message;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.PopupMenu;

import android.widget.PopupWindow;

import android.widget.TextView;

import android.widget.Toast;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.Socket;

import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter BA;

    BluetoothServerSocket mmServerSocket;

    private static String address = "20:16:09:26:81:80"; // <==应填写蓝牙串口模块的蓝牙地址。

    private BluetoothSocket btSocket = null;

    private OutputStream outStream = null;

    public InputStream inStream = null;

    EditText editText;

    TextView textView;

    Button button, button1;

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

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initView();

    }

    /**

     * 连接蓝牙

     * **/

    public void connect() {

        BA = BluetoothAdapter.getDefaultAdapter();

        BluetoothDevice device = BA.getRemoteDevice(address);

//          pairedDevices = BA.getBondedDevices();

        try {

            btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);

           // new  ReceiveDatas(btSocket).start();

        } catch (IOException e) {

        }

        BA.cancelDiscovery();

        try {

            btSocket.connect();

         //   String s="sm";

            outStream = btSocket.getOutputStream();

          //  outStream.write(s.getBytes());

            //outStream.write(0x41);

            inStream = btSocket.getInputStream();

            while (true){

                byte[] buffer = new byte[100];

                int count = inStream.read(buffer);

               int a= inStream.available();

                String ss= new String(buffer, 0, count, "utf-8");

                System.out.println("***A"+ss);
　　　　　　// 输出信息缺少……不全，占时不会

            }

        } catch (IOException e) {

        }

        try {

          //  btSocket.close();

        } catch (Exception e2) {

            // Log .e(TAG,"ON RESUME: Unable to close socket during connection failure", e2);

        }

    }

    public void initView() {

        editText = (EditText) findViewById(R.id.edit);

        textView = (TextView) findViewById(R.id.textView);

        button = (Button) findViewById(R.id.button);

        button1 = (Button) findViewById(R.id.button1);

        BA = BluetoothAdapter.getDefaultAdapter();

       /**

        * 连接蓝牙

        * */

        button1.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                System.out.println("***11");

                as();

            }

        });

        /**

         * 发送信息

         * **/

        button.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                String s = editText.getText().toString();

                try {

　　　　　　　　　　//   outStream.write(s.getBytes()); 发送数据

                    outStream = btSocket.getOutputStream();

                    inStream=btSocket.getInputStream();

                    outStream.write("sm".getBytes());

                    outStream.write("\r\n".getBytes());

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        });

    }

/**

 *

 *   连接蓝牙

 * **/

    public void as() {

        new AsyncTask() {

            @Override

            protected String doInBackground(Object[] params) {

                connect();

                return null;

            }

            @Override

            protected void onPreExecute() {

                super.onPreExecute();

            }

            @Override

            protected void onPostExecute(Object o) {

                super.onPostExecute(o);

                Toast.makeText(getApplicationContext(), "2", Toast.LENGTH_SHORT).show();

            }

        }.execute();

    }

}

private class ConnectedThread extends Thread {

       private final BluetoothSocket socket;

       private final InputStream inputStream;

       private final OutputStream outputStream;

       public ConnectedThread(BluetoothSocket socket) {

           this.socket = socket;

           InputStream input = null;

           OutputStream output = null;

           try {

               input = socket.getInputStream();

               output = socket.getOutputStream();

           } catch (IOException e) {

               e.printStackTrace();

           }

           this.inputStream = input;

           this.outputStream = output;

       }

       public void run() {

           byte[] buff = new byte[1024];

           int bytes;

           while (true) {

               try {

                   bytes = inputStream.read(buff);

                   String str = new String(buff, "ISO-8859-1");

                   str = str.substring(0, bytes);

                   Log.e("recv", str);

                   Message message=handler.obtainMessage();

                   message.obj=str;

                   handler.sendMessage(message);

               } catch (IOException e) {

                   e.printStackTrace();

                   break;

               }

           }

       }

       public void write(byte[] bytes) {

           try {

               outputStream.write(bytes);

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

       public void cancel() {

           try {

               socket.close();

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

   }

    <uses-feature

        android:name="android.hardware.bluetooth_le"

        android:required="true" />

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

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

package myapplication.com.myapplicationble;

import android.app.Service;

import android.bluetooth.BluetoothAdapter;

import android.bluetooth.BluetoothDevice;

import android.bluetooth.BluetoothServerSocket;

import android.bluetooth.BluetoothSocket;

import android.content.Context;

import android.content.Intent;

import android.os.AsyncTask;

import android.os.Handler;

import android.os.IBinder;

import android.os.Message;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.PopupMenu;

import android.widget.PopupWindow;

import android.widget.TextView;

import android.widget.Toast;

import java.io.BufferedReader;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.net.Socket;

import java.util.ArrayList;

import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter BA;

    BluetoothServerSocket mmServerSocket;

    String message="";

    private static String address = "20:16:09:26:81:80"; // <==应填写蓝牙串口模块的蓝牙地址。

    private BluetoothSocket btSocket = null;

    private OutputStream outStream = null;

    public InputStream inStream = null;

    EditText editText;

    TextView textView;

    Button button, button1;

    boolean BluetoothFlag;

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

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initView();

    }

    /**

     * 连接蓝牙

     **/

    public void connect() {

        BA = BluetoothAdapter.getDefaultAdapter();

        BluetoothDevice device = BA.getRemoteDevice(address);

//          pairedDevices = BA.getBondedDevices();

        try {

            btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);

        } catch (IOException e) {

        }

        BA.cancelDiscovery();

        try {

            btSocket.connect();

           // String s="sm";

            outStream = btSocket.getOutputStream();

            //outStream.write(s.getBytes());

            //outStream.write(0x41);

            inStream = btSocket.getInputStream();

//            while (true){

//                byte[] buffer = new byte[1];

//                int length = 0;

//                byte bb = 0;

//                String line = null;

//                ArrayList<Byte> list = new ArrayList<Byte>();

//                while (inStream.read(buffer) == -1) {

//                    try {

//                        Thread.sleep(100);

//                    } catch (InterruptedException e) {

//                        e.printStackTrace();

//                    }

//                    System.out.print("-->"   +inStream.read(buffer));

//                }

//            }

            /***

             * 1

             * **/

//            while (true) {

//

//                if(inStream.available()>=0){

//                    byte[] buffer = new byte[1024];

//                    int count = inStream.read(buffer);

//                    // System.out.println("***MAX:" + a);

//                    String ss = new String(buffer, 0, count, "utf-8");

//                    System.out.println("*--" + ss);

//                }

//

//            }

            /****

             *  2

             * */

//            BluetoothFlag = true;

//            MyThread bluetoothThread = new MyThread();

//            bluetoothThread.start();

            /***

             *

             *  3

             *  */

            ConnectedThread connectedThread = new ConnectedThread(btSocket);

            connectedThread.start();

        } catch (IOException e) {

        }

        try {

            //  btSocket.close();

        } catch (Exception e2) {

            // Log .e(TAG,"ON RESUME: Unable to close socket during connection failure", e2);

        }

    }

    public void initView() {

        editText = (EditText) findViewById(R.id.edit);

        textView = (TextView) findViewById(R.id.textView);

        button = (Button) findViewById(R.id.button);

        button1 = (Button) findViewById(R.id.button1);

        BA = BluetoothAdapter.getDefaultAdapter();

        /**

         * 连接蓝牙

         * */

        button1.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                System.out.println("***11");

                as();

            }

        });

        /**

         * 发送信息

         * **/

        button.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                String s = editText.getText().toString();

                try {

                    outStream = btSocket.getOutputStream();

                    inStream = btSocket.getInputStream();

                   // outStream.write("\r\n".getBytes());

                   outStream.write("sm".getBytes());

                  outStream.write("\r\n".getBytes());

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        });

    }

    /**

     * 连接蓝牙

     **/

    public void as() {

        new AsyncTask() {

            @Override

            protected String doInBackground(Object[] params) {

                connect();

                return null;

            }

            @Override

            protected void onPreExecute() {

                super.onPreExecute();

            }

            @Override

            protected void onPostExecute(Object o) {

                super.onPostExecute(o);

                Toast.makeText(getApplicationContext(), "2", Toast.LENGTH_SHORT).show();

            }

        }.execute();

    }

   /**

    * 在接受不到数据

    * **/

   private class ConnectedThread extends Thread {

       private final BluetoothSocket socket;

       private final InputStream inputStream;

       private final OutputStream outputStream;

       public ConnectedThread(BluetoothSocket socket) {

           this.socket = socket;

           InputStream input = null;

           OutputStream output = null;

           try {

               input = socket.getInputStream();

               output = socket.getOutputStream();

           } catch (IOException e) {

               e.printStackTrace();

           }

           this.inputStream = input;

           this.outputStream = output;

       }

       public void run() {

           byte[] buff = new byte[1024];

           int bytes;

           while (true) {

               try {

                   bytes = inputStream.read(buff);

                   String str = new String(buff, "ISO-8859-1");

                   str = str.substring(0, bytes);

                   Log.e("recv", str);

                   Message message=handler.obtainMessage();

                   message.obj=str;

                   handler.sendMessage(message);

               } catch (IOException e) {

                   e.printStackTrace();

                   break;

               }

           }

       }

       public void write(byte[] bytes) {

           try {

               outputStream.write(bytes);

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

       public void cancel() {

           try {

               socket.close();

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

   }

    Handler  handler=new Handler(){

        @Override

        public void handleMessage(Message msg) {

            String s= (String) msg.obj;

            message=message+s;

            if(message.contains("RTS_Mon->")){

                textView.setText(message);

            }

        }

    };

}

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="myapplication.com.myapplicationble.MainActivity">

    <TextView

        android:id="@+id/textView"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Hello World!" />

    <EditText

        android:layout_below="@+id/textView"

        android:id="@+id/edit"

        android:layout_width="match_parent"

        android:textColor="@color/hei"

        android:layout_height="wrap_content"/>

    <Button

        android:layout_height="wrap_content"

        android:layout_width="match_parent"

        android:id="@+id/button"

        android:layout_below="@+id/edit"

        android:text="send"

        />

    <Button

        android:layout_height="wrap_content"

        android:layout_width="match_parent"

        android:id="@+id/button1"

        android:layout_below="@+id/button"

        android:text="lianjie"

        />

</RelativeLayout>