蓝牙连接总是失败，为什么?

main = plus.android.runtimeMainActivity();  
    BluetoothAdapter = plus.android.importClass("android.bluetooth.BluetoothAdapter");  
    UUID = plus.android.importClass("java.util.UUID");  
    uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");  
    BAdapter = BluetoothAdapter.getDefaultAdapter();  
    device = BAdapter.getRemoteDevice(mac_address);  
    plus.android.importClass(device);  
    bluetoothSocket = device.createInsecureRfcommSocketToServiceRecord(uuid);  
    plus.android.importClass(bluetoothSocket);  

    if (!bluetoothSocket.isConnected()) {  
        console.log('检测到设备未连接，尝试连接中....');  
        bluetoothSocket.connect();  
    }  

    console.log('设备已连接成功');  

    if (bluetoothSocket.isConnected()) {  
        var outputStream = bluetoothSocket.getOutputStream();  
        plus.android.importClass(outputStream);  
        var string = "我我你你他他我我你你他他我我你你他他我我你你他他我我你你他他我我你你他他我我你你他他";  
        var bytes = plus.android.invoke(string, 'getBytes', 'gbk');  
        outputStream.write(bytes);  
        outputStream.flush();  
        device = null //这里关键  
        bluetoothSocket.close(); //必须关闭蓝牙连接否则意外断开的话打印错误  

    }

这个代码一直都会走下面这个里面，然后每次都是失败，偶尔会有一次成功的

 if (!bluetoothSocket.isConnected()) {  
        console.log('检测到设备未连接，尝试连接中....');  
        bluetoothSocket.connect();  
    }