Android 蓝牙教程

简介

Android 蓝牙技术可用于在 Android 手机和其他设备之间进行数据传输和通信。这个教程通过一个简单的示例来介绍如何在 Android 应用程序中使用蓝牙。

示例

这个示例将展示如何扫描蓝牙设备并与之建立连接，使用已配对的设备发送和接收数据。

步骤

1. 检查权限

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"/>

你还需要在代码中对权限进行检查和请求：

private void checkPermissions() {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH)
            != PackageManager.PERMISSION_GRANTED
            || ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_ADMIN)
            != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.BLUETOOTH, Manifest.permission.BLUETOOTH_ADMIN}, 1);
    }
}

2. 设置蓝牙

在代码中，你需要初始化 BluetoothAdapter，这是整个蓝牙 API 中最重要的类:

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

3. 扫描设备

扫描蓝牙设备需要开始搜索，代码如下：

mBluetoothAdapter.startDiscovery();

通过注册 BroadcastReceiver 来接收设备的扫描结果：

// Create a BroadcastReceiver for ACTION_FOUND.
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // Add the name and address to an array adapter to show in a ListView
            mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
        }
    }
};
// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter);

4. 连接设备

连接蓝牙设备需要一些步骤，主要有搜索设备、配对设备、连接设备等。下面是一个示例代码：

// Get the device MAC address, which is the last 17 chars in the View
String address = device.getAddress();
// Get the BluetoothDevice object
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
// Attempt to connect to the device
mBluetoothSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
bluetoothAdapter.cancelDiscovery();
mBluetoothSocket.connect();

5. 发送和接收数据

发送和接收数据也是相对简单的：

// Get the input and output streams, using temp objects because
// member streams are final
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
try {
    tmpIn = mBluetoothSocket.getInputStream();
    tmpOut = mBluetoothSocket.getOutputStream();
} catch (IOException e) {
    Log.e(TAG, "getStream() failed", e);
}
mInputStream = tmpIn;
mOutputStream = tmpOut;

// Read from the InputStream
byte[] buffer = new byte[1024];  // buffer store for the stream
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
    try {
        // Read from the InputStream
        bytes = mInputStream.read(buffer);
        // Send the obtained bytes to the UI activity
        mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
                .sendToTarget();
    } catch (IOException e) {
        Log.e(TAG, "disconnected", e);
        break;
    }
}

// Write to the OutputStream
byte[] bytes = message.getBytes();
try {
    mOutputStream.write(bytes);
} catch (IOException e) {
    Log.e(TAG, "write() failed", e);
}

总结

这篇教程仅仅是蓝牙技术的入门教学，希望能对想要学习和应用蓝牙技术的程序员有所帮助。