我正在尝试构建一个 Android 应用程序以使用 Kotlin 连接到 HC-05 蓝牙设备，但我无法连接

Question

这是 MainActivity.Kt 文件，我正在关注 Android 开发人员文档，我无法弄清楚为什么它无法连接，我是一个绝对新手，请帮助。

我已经尝试了可发现性和绑定并获取所有绑定的设备，它工作正常，但我无法连接，我直接使用设备的 MAC 地址来帮助简化事情，但仍然没有任何工作，所有权限也是在 Manifest、BT、BT_ADMIN 和 LOCATION 中设置。谢谢

package com.example.btconnection

import android.app.Activity
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothDevice
import android.bluetooth.BluetoothSocket
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.core.view.isVisible
import kotlinx.android.synthetic.main.activity_main.*
import java.io.IOException
import java.util.*

class MainActivity : AppCompatActivity() {

    val bluetoothAdapter: BluetoothAdapter? = BluetoothAdapter.getDefaultAdapter()
    val REQUEST_ENABLE_BT = 1
    val MY_UUID: UUID = UUID.fromString("00000000-0000-1000-8000-00805F9B34FB")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        if (bluetoothAdapter == null) {
            Toast.makeText(this, "Device Doesn't support BT", Toast.LENGTH_SHORT).show()
        }
        else{
            if (!bluetoothAdapter.isEnabled) {
                val enableBtIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
                startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT)
            }
        }

        connectbutton.setOnClickListener {
            ConnectThread(bluetoothAdapter!!.getRemoteDevice("00:19:10:08:4D:F0"))
        }
    }

    private inner class ConnectThread(device: BluetoothDevice) : Thread() {

        private val mmSocket: BluetoothSocket? by lazy(LazyThreadSafetyMode.NONE) {
            device.createRfcommSocketToServiceRecord(MY_UUID)
        }

        override fun run() {
            // Cancel discovery because it otherwise slows down the connection.
            bluetoothAdapter?.cancelDiscovery()

            mmSocket?.use { socket ->
                // Connect to the remote device through the socket. This call blocks
                // until it succeeds or throws an exception.
                socket.connect()
                Toast.makeText(this@MainActivity, "Connected", Toast.LENGTH_SHORT).show()
                // The connection attempt succeeded. Perform work associated with
                // the connection in a separate thread.
               // manageMyConnectedSocket(socket)
            }
        }

        // Closes the client socket and causes the thread to finish.
        fun cancel() {
            try {
                mmSocket?.close()
            } catch (e: IOException) {
                Log.e("Error", "Could not close the client socket", e)
            }
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if(requestCode == REQUEST_ENABLE_BT){
            if (resultCode == Activity.RESULT_OK){
                if(bluetoothAdapter!!.isEnabled){
                    Toast.makeText(this,"BT Enabled", Toast.LENGTH_SHORT).show()
                }
                else{
                    Toast.makeText(this,"BT Disabled", Toast.LENGTH_SHORT).show()
                }
            }
            else if(resultCode == Activity.RESULT_CANCELED){
                Toast.makeText(this,"BT Enable Cancelled", Toast.LENGTH_SHORT).show()
            }
        }
   
    }
}

Answer 1

我终于弄明白了，我仔细观察了 HC-05，发现它连接了 500 毫秒然后断开连接，我发现它在很短的时间后连接然后断开连接，当我检查代码中，函数 'fun cancel()' 在连接后立即关闭套接字。

So the socket remain open for the data stream to be sent out.
now the button only does this


 connectbutton.setOnClickListener {
            btSocket = bluetoothAdapter!!.getRemoteDevice("00:19:10:08:4D:F0").createRfcommSocketToServiceRecord(MY_UUID)
//            ConnectThread(bluetoothAdapter!!.getRemoteDevice("00:19:10:08:4D:F0"))
            try {
            bluetoothAdapter.cancelDiscovery()
            btSocket!!.connect()
                Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show()
            }
            catch (e: Exception){
                Toast.makeText(this, "Can't Connect", Toast.LENGTH_SHORT).show()
            }

        }
    }