Android 唯一識別碼

我們在專案過程中或多或少會使用到裝置的唯一識別碼，我們希望能夠得到一個穩定、可靠的裝置唯一識別碼。今天我們將介紹幾種方式。

       1. DEVICE_ID

        2. MAC ADDRESS

        3. Serial Number

在Android 2.3可以通過android.os.Build.SERIAL獲取，非手機裝置可以通過該介面獲取。

        4. ANDROID_ID

ANDROID_ID是裝置第一次啟動時產生和儲存的64bit的一個數，當裝置被wipe後該數重置

ANDROID_ID似乎是獲取Device ID的一個好選擇，但它也有缺陷：

• 它在Android <=2.1 or Android >=2.3的版本是可靠、穩定的，但在2.2的版本並不是100%可靠的
• 在主流廠商生產的裝置上，有一個很經常的bug，就是每個裝置都會產生相同的ANDROID_ID：9774d56d682e549c

        5. Installtion ID : UUID

以上四種方式都有或多或少存在的一定的侷限性或者bug，在這裡，有另外一種方式解決，就是使用UUID，該方法無需訪問裝置的資源，也跟裝置型別無關。

這 種方式是通過在程式安裝後第一次執行後生成一個ID實現的，但該方式跟裝置唯一標識不一樣，它會因為不同的應用程式而產生不同的ID，而不是裝置唯一 ID。因此經常用來標識在某個應用中的唯一ID（即Installtion ID），或者跟蹤應用的安裝數量。很幸運的，Google Developer Blog提供了這樣的一個框架：

public class Installation {
    private static String sID = null;
    private static final String INSTALLATION = "INSTALLATION";

    public synchronized static String id(Context context) {
        if (sID == null) {  
            File installation = new File(context.getFilesDir(), INSTALLATION);
            try {
                if (!installation.exists())
                    writeInstallationFile(installation);
                sID = readInstallationFile(installation);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        return sID;
    }

    private static String readInstallationFile(File installation) throws IOException {
        RandomAccessFile f = new RandomAccessFile(installation, "r");
        byte[] bytes = new byte[(int) f.length()];
        f.readFully(bytes);
        f.close();
        return new String(bytes);
    }

    private static void writeInstallationFile(File installation) throws IOException {
        FileOutputStream out = new FileOutputStream(installation);
        String id = UUID.randomUUID().toString();
        out.write(id.getBytes());
        out.close();
    }
}

   總結

綜 合以上所述，為了實現在裝置上更通用的獲取裝置唯一標識，我們可以實現這樣的一個類，為每個裝置產生唯一的UUID，以ANDROID_ID為基礎，在獲 取失敗時以TelephonyManager.getDeviceId()為備選方法，如果再失敗，使用UUID的生成策略。

重申下，以下方法是生成Device ID，在大多數情況下Installtion ID能夠滿足我們的需求，但是如果確實需要用到Device ID，那可以通過以下方式實現：

import android.content.Context;
import android.content.SharedPreferences;
import android.provider.Settings.Secure;
import android.telephony.TelephonyManager;

import java.io.UnsupportedEncodingException;
import java.util.UUID;

public class DeviceUuidFactory {
    protected static final String PREFS_FILE = "device_id.xml";
    protected static final String PREFS_DEVICE_ID = "device_id";

    protected static UUID uuid;

    public DeviceUuidFactory(Context context) {

        if( uuid ==null ) {
            synchronized (DeviceUuidFactory.class) {
                if( uuid == null) {
                    final SharedPreferences prefs = context.getSharedPreferences( PREFS_FILE, 0);
                    final String id = prefs.getString(PREFS_DEVICE_ID, null );

                    if (id != null) {
                        // Use the ids previously computed and stored in the prefs file
                        uuid = UUID.fromString(id);

                    } else {

                        final String androidId = Secure.getString(context.getContentResolver(), Secure.ANDROID_ID);

                        // Use the Android ID unless it's broken, in which case fallback on deviceId,
                        // unless it's not available, then fallback on a random number which we store
                        // to a prefs file
                        try {
                            if (!"9774d56d682e549c".equals(androidId)) {
                                uuid = UUID.nameUUIDFromBytes(androidId.getBytes("utf8"));
                            } else {
                                final String deviceId = ((TelephonyManager) context.getSystemService( Context.TELEPHONY_SERVICE )).getDeviceId();
                                uuid = deviceId!=null ? UUID.nameUUIDFromBytes(deviceId.getBytes("utf8")) : UUID.randomUUID();
                            }
                        } catch (UnsupportedEncodingException e) {
                            throw new RuntimeException(e);
                        }

                        // Write the value out to the prefs file
                        prefs.edit().putString(PREFS_DEVICE_ID, uuid.toString() ).commit();

                    }

                }
            }
        }

    }

    /**
     * Returns a unique UUID for the current android device.  As with all UUIDs, this unique ID is "very highly likely"
     * to be unique across all Android devices.  Much more so than ANDROID_ID is.
     *
     * The UUID is generated by using ANDROID_ID as the base key if appropriate, falling back on
     * TelephonyManager.getDeviceID() if ANDROID_ID is known to be incorrect, and finally falling back
     * on a random UUID that's persisted to SharedPreferences if getDeviceID() does not return a
     * usable value.
     *
     * In some rare circumstances, this ID may change.  In particular, if the device is factory reset a new device ID
     * may be generated.  In addition, if a user upgrades their phone from certain buggy implementations of Android 2.2
     * to a newer, non-buggy version of Android, the device ID may change.  Or, if a user uninstalls your app on
     * a device that has neither a proper Android ID nor a Device ID, this ID may change on reinstallation.
     *
     * Note that if the code falls back on using TelephonyManager.getDeviceId(), the resulting ID will NOT
     * change after a factory reset.  Something to be aware of.
     *
     * Works around a bug in Android 2.2 for many devices when using ANDROID_ID directly.
     *
     * @see http://code.google.com/p/android/issues/detail?id=10603
     *
     * @return a UUID that may be used to uniquely identify your device for most purposes.
     */
    public UUID getDeviceUuid() {
        return uuid;
    }
}

如何獲取Android手機的唯一標識？

注：android.os.SystemProperties的標籤被打上@hide了，所以sdk中並不會存在。如果需要使用，需要有android的source code支援。