在应用程序关闭后保存BluetoothDevice对象

Question

我想保存我的应用程序连接到的最后一个蓝牙设备。如果之前有蓝牙连接，我希望根本不提示用户。他们可以选择连接到新设备，但他们不需要这样做。如果他们选择不选择连接，他们将定期使用应用程序，然后当需要蓝牙设备时，它将连接到最新的设备。

我已经尝试使用下面的Tudor Luca's answer中提供的代码，但对象不会写入文件。我要买一台NotSerializableException。我尝试保存的对象是用import android.bluetooth.BluetoothDevice导入的BluetoothDevice。

这就是我试图使蓝牙设备可序列化的方法：

import java.io.Serializable;
import android.bluetooth.BluetoothDevice;

public class SerializableObjects implements Serializable {
    private BluetoothDevice device;

    public SerializableObjects( BluetoothDevice device ) {
        this.device = device;
    }

    public BluetoothDevice getDevice() {
        return this.device;
    }
}

LogCat返回以下内容：

12-11 17:46:24.032: W/System.err(24641): java.io.NotSerializableException: android.bluetooth.BluetoothDevice
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1535)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:1143)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:413)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1241)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689)
12-11 17:46:24.032: W/System.err(24641):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653)
12-11 17:46:24.032: W/System.err(24641):    at my.eti.commander.LocalObjects.writeObjectToFile(LocalObjects.java:29)
12-11 17:46:24.032: W/System.err(24641):    at my.eti.commander.MainMenu$1.handleMessage(MainMenu.java:460)
12-11 17:46:24.032: W/System.err(24641):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-11 17:46:24.036: W/System.err(24641):    at android.os.Looper.loop(Looper.java:130)
12-11 17:46:24.036: W/System.err(24641):    at android.app.ActivityThread.main(ActivityThread.java:3687)
12-11 17:46:24.036: W/System.err(24641):    at java.lang.reflect.Method.invokeNative(Native Method)
12-11 17:46:24.036: W/System.err(24641):    at java.lang.reflect.Method.invoke(Method.java:507)
12-11 17:46:24.036: W/System.err(24641):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
12-11 17:46:24.036: W/System.err(24641):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
12-11 17:46:24.036: W/System.err(24641):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

没有办法直接序列化BluetoothDevice类。即使您序列化了它，我也不认为您能够在应用程序关闭后重用该对象。相反，我有一个helper类，它将存储设备的地址。您可以保存设备地址和名称，并在以后读取该信息。然后，您可以执行绑定设备的发现/搜索，并获得相应的设备。

下面是我通常使用的帮助器类

public class BluetoothState implements Serializable {
    public static final int STATE_NOT_CONNECTED = 1;
    public static final int STATE_CONNECTED = 1;

    public static final String filename = "btState.pref";

    public static int connectionState = STATE_NOT_CONNECTED;
    public static String deviceAddress = "00:00:00:00:00:00";
    public static String deviceName = "";

    public static void setConnectionState(boolean connected,BluetoothDevice device) {
        if(connected)
            connectionState = STATE_CONNECTED;
        else
            connectionState = STATE_NOT_CONNECTED;

        if(device != null) {
            deviceAddress = device.getAddress();
            deviceName = device.getName();
        }

    }

    public static void saveConnectionState(Context cxt) throws IOException {        
        FileOutputStream fos = cxt.openFileOutput(filename, Context.MODE_PRIVATE);
        ObjectOutputStream oos = new ObjectOutputStream(fos);       
        oos.writeInt(connectionState);
        oos.writeUTF(deviceAddress);
        oos.writeUTF(deviceName);
    }

    public static void loadConnectionState(Context cxt) throws IOException {        
        FileInputStream fis = cxt.openFileInput(filename);
        ObjectInputStream ois = new ObjectInputStream(fis);     
        connectionState = ois.readInt();
        deviceAddress = ois.readUTF();
        deviceName = ois.readUTF();
    }

    public static BluetoothDevice getDevice() {
        BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
        if(!btAdapter.isEnabled())
            btAdapter.enable();

        Set<BluetoothDevice> pairedDevices = btAdapter.getBondedDevices();

        for(BluetoothDevice d : pairedDevices)
            if(d.getAddress().equalsIgnoreCase(deviceAddress))
                return d;

        return null;        
    }

}

Answer 2

你可以把你的对象写到一个私有文件中，然后从那里加载它。你唯一需要对你的对象做的事情，就是让它成为implements Serializable。

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import android.app.Activity;
import android.content.Context;

/**
 *
 * Writes/reads an object to/from a private local file
 * 
 *
 */
public class LocalObjects{


    /**
     * 
     * @param context
     * @param object
     * @param filename
     */
    public static void witeObjectToFile(Context context, Object object, String filename) {

        ObjectOutputStream objectOut = null;
        try {

            FileOutputStream fileOut = context.openFileOutput(filename, Activity.MODE_PRIVATE);
            objectOut = new ObjectOutputStream(fileOut);
            objectOut.writeObject(object);
            fileOut.getFD().sync();

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (objectOut != null) {
                try {
                    objectOut.close();
                } catch (IOException e) {
                    // do nowt
                }
            }
        }
    }


    /**
     * 
     * @param context
     * @param filename
     * @return
     */
    public static Object readObjectFromFile(Context context, String filename) {

        ObjectInputStream objectIn = null;
        Object object = null;
        try {

            FileInputStream fileIn = context.getApplicationContext().openFileInput(filename);
            objectIn = new ObjectInputStream(fileIn);
            object = objectIn.readObject();

        } catch (FileNotFoundException e) {
            // Do nothing
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            if (objectIn != null) {
                try {
                    objectIn.close();
                } catch (IOException e) {
                    // do nowt
                }
            }
        }

        return object;
    }

}

所以基本上，你想做的就是得到最后一对设备，对吧？下面是代码应该是什么样子：

1. 所有蓝牙活动都需要BluetoothAdapter：

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

if (mBluetoothAdapter == null) {

//Then your device does not support Bluetooth

}

• Make确保蓝牙已启用

if (!mBluetoothAdapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); }

• Get以前配对的设备

Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); // If there are paired devices if (pairedDevices.size() > 0) { // Loop through paired devices for (BluetoothDevice device : pairedDevices) { // Add the name and address to an array adapter to show in a ListView mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); } }

有关如何使用蓝牙连接的完整教程，请查看this