Android中的蓝牙设备发现——startDiscovery()

Question

Android中的蓝牙设备发现——startDiscovery()

androidandroid-intentbluetoothandroid-adapterandroid-context

19

目标：构建一个Android应用程序，可以发现范围内的蓝牙设备名称和地址，并将其值提交到Web服务。蓝牙设备之前未与主机设备绑定，我只是想在走动时轮询所有设备。

已完成：

详细阅读了文档。
实现了主机设备BT适配器的本地实例。
实现了通知以启用BT（如果未启用）。
注册了Broadcast Receiver和Intents来解析startDiscovery()返回的ACTION_FOUNDs。
在清单中注册了BLUETOOTH和BLUETOOTH_ADMIN权限。

一切正常（经过增量控制台日志测试），直到startDiscovery()函数。

挫败感：

startDiscovery() -- 我怀疑我没有正确传递上下文。该方法需要放置在哪个上下文中才能正常工作？

如果您已经能够使此方法正常工作，我会非常感激您的指导。

更新 - 这里是引起我困扰的代码的简化版本; 这个简化重演了我的错误。这段代码可以运行，没有cat.log错误或其他错误，但它只是没有输出任何内容。

package aqu.bttest;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.Toast;

public class BT2Activity extends Activity {

private BluetoothAdapter mBTA;
private SingBroadcastReceiver mReceiver;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

  //register local BT adapter
    mBTA = BluetoothAdapter.getDefaultAdapter();
    //check to see if there is BT on the Android device at all
    if (mBTA == null){
        int duration = Toast.LENGTH_SHORT;
        Toast.makeText(this, "No Bluetooth on this handset", duration).show();
    }
    //let's make the user enable BT if it isn't already
    if (!mBTA.isEnabled()){
        Intent enableBT = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBT, 0xDEADBEEF);
    }
    //cancel any prior BT device discovery
    if (mBTA.isDiscovering()){
        mBTA.cancelDiscovery();
    }
    //re-start discovery
    mBTA.startDiscovery();

    //let's make a broadcast receiver to register our things
    mReceiver = new SingBroadcastReceiver();
    IntentFilter ifilter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
    this.registerReceiver(mReceiver, ifilter);
}

private class SingBroadcastReceiver extends BroadcastReceiver {

    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction(); //may need to chain this to a recognizing function
        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 Toast
            String derp = device.getName() + " - " + device.getAddress();
            Toast.makeText(context, derp, Toast.LENGTH_LONG);
        }
    }
}

}

- Lemminkainen

知道你遇到的错误会有所帮助……或者至少了解是什么让你相信 startDiscovery() 的功能存在问题。 - Alex Lockwood

1个回答

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可以查看英文原文，
原文链接

- Alex Lockwood · Accepted Answer

这个方法需要放在什么上下文中才能正常工作。

简单来说，当你想让你的应用发现本地蓝牙设备时，你应该使用startDiscovery() ...例如，如果你想实现一个ListActivity，它会扫描并动态添加附近的蓝牙设备到ListView（参见DeviceListActivity）。

你使用startDiscovery()方法应该像这样：

Define a class variable representing the local Bluetooth adapter.

BluetoothAdapter mBtAdapter = BluetoothAdapter.getDefaultAdapter();

Check to see if your device is already "discovering". If it is, then cancel discovery.
```
if (mBtAdapter.isDiscovering()) {
    mBtAdapter.cancelDiscovery();
}
```
Immediately after checking (and possibly canceling) discovery-mode, start discovery by calling,
```
mBtAdapter.startDiscovery();
```
Be very careful in general about accidentally leaving your device in discovery-mode. Performing device discovery is a heavy procedure for the Bluetooth adapter and will consume a lot of its resources. For instance, you want to make sure you check/cancel discovery prior to attempting to make a connection. You most likely want to cancel discovery in your onDestroy method too.

如果这个帮助到你了，请告诉我...如果你仍然有困难，请在回答中更新您的logcat输出和/或任何错误消息，并且也许我可以再帮助您一些。