java - 蓝牙启用会扰乱广播接收器

Question

我的应用程序旨在将所有扫描的蓝牙设备附加到textview。如果手机蓝牙已打开，此功能非常有用。但是，如果我的应用程序检查手机蓝牙是否关闭，如果关闭则将其打开，然后启动发现过程，我的 broadcastreciever 不会拾取事件，因此我的 textview 未填充。如有任何帮助，我们将不胜感激!

这是我的代码:

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

    txtResults = (TextView) this.findViewById(R.id.txtResults);
    mBlueToothAdapter = BluetoothAdapter.getDefaultAdapter();
    if (!(mBlueToothAdapter.isEnabled())) {
        mBlueToothAdapter.enable(); 

    }           

    mBlueToothAdapter.startDiscovery();

我的接收器:

public static class BlueToothBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        BluetoothDevice device = intent
                .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

        blueToothName = device.getName();
        blueToothAddress = device.getAddress();
        blueToothClass = device.getBluetoothClass();
        blueToothBondState = device.getBondState();
        GetBondStateStr(blueToothBondState);
        blueToothUUIDS = device.getUuids();

        paramsBlueTooth
                .add(new BasicNameValuePair("Name: ", blueToothName));
        paramsBlueTooth.add(new BasicNameValuePair("Address: ",
                blueToothAddress));
        paramsBlueTooth.add(new BasicNameValuePair("Class: ", String
                .valueOf(blueToothClass)));
        paramsBlueTooth.add(new BasicNameValuePair("Bond State: ",
                blueToothBondStateStr));
        paramsBlueTooth.add(new BasicNameValuePair("UUIDS: ", String
                .valueOf(blueToothUUIDS)));

        showBlueToothData();

    }

显示蓝牙数据():

    private void showBlueToothData() {
        StringBuilder results = new StringBuilder();

        results.append("-----BLUETOOTH DEVICE INFORMATION-----\n");
        results.append("Name: " + blueToothName + "\n");
        results.append("Address: " + blueToothAddress + "\n");
        results.append("Class: " + blueToothClass + "\n");
        results.append("Bond State: " + blueToothBondStateStr + "\n");
        results.append("UUIDS: " + blueToothUUIDS + "\n");

        txtResults.append(new String(results));
        txtResults.append("\n");
    }

Answer 1

您选择的通过 BluetoothAdapter.enable() 方法启用蓝牙 radio 的方法是异步调用。从 method's documentation 可以看出，您不能假设该方法一返回 radio 就已启动并处于 Activity 状态。您必须等待 ACTION_STATE_CHANGED 广播才能知道 radio 已准备好供您尝试扫描。

如果您阅读文档，还请注意，这样做的体验很差，因为没有向用户发出通知。更好的选择是将用户发送到“设置”以自行启用蓝牙。您可以将启动逻辑修改为更像这样的内容:

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

    txtResults = (TextView) this.findViewById(R.id.txtResults);
    mBlueToothAdapter = BluetoothAdapter.getDefaultAdapter();

    …
}

@Override
protected void onResume() {
    super.onResume();
    if (!(mBlueToothAdapter.isEnabled())) { 
        //Take the user to settings first!
        Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivity(intent);
    } else {
        mBlueToothAdapter.startDiscovery();
    }
}

此修改将在您每次来到前台时检查蓝牙，并且仅在您准备好时才触发扫描。