在API 26中，getDeviceId()被贬低了，所以你可以使用下面的代码来满足API 26和更早的版本

TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
String imei="";
if (android.os.Build.VERSION.SDK_INT >= 26) {
  imei=telephonyManager.getImei();
}
else
{
  imei=telephonyManager.getDeviceId();
}

不要忘记为READ_PHONE_STATE添加使用上述代码的权限请求。

更新: 从Android 10开始，用户应用程序只能获得IMEI等不可重置的硬件标识符。

你需要在AndroidManifest.xml中设置以下权限:

<uses-permission android:name="android.permission.READ_PHONE_STATE" />

要获得IMEI(国际移动设备标识符)，如果它高于API级别26，那么我们将telephonyManager.getImei()作为null，因此，我们使用ANDROID_ID作为唯一标识符。

 public static String getIMEINumber(@NonNull final Context context)
            throws SecurityException, NullPointerException {
        TelephonyManager tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
        String imei;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            assert tm != null;
            imei = tm.getImei();
            //this change is for Android 10 as per security concern it will not provide the imei number.
            if (imei == null) {
                imei = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.ANDROID_ID);
            }
        } else {
            assert tm != null;
            if (tm.getDeviceId() != null && !tm.getDeviceId().equals("000000000000000")) {
                imei = tm.getDeviceId();
            } else {
                imei = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.ANDROID_ID);
            }
        }

        return imei;
    }

对不可重置设备标识符的限制

从Android 10开始，应用程序必须拥有READ_PRIVILEGED_PHONE_STATE特权权限才能访问设备的不可重置标识符，包括IMEI和序列号。

以下代码是为我工作。

val uid: String = Settings.Secure.getString(ctx.applicationContext.contentResolver, Settings.Secure.ANDROID_ID)
if (ContextCompat.checkSelfPermission(ctx, Manifest.permission.READ_PHONE_STATE) == PackageManager.PERMISSION_GRANTED) {
            imei = when {
                Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q -> {
                    uid
                }
                Build.VERSION.SDK_INT >= Build.VERSION_CODES.O -> {
                    telephonyManager.imei
                }
                else -> {
                    telephonyManager.deviceId
                }
            }
        }

你需要调用android.telephony.TelephonyManager.getDeviceId()。

这将返回唯一标识该设备的字符串(GSM上的IMEI, CDMA上的MEID)。

你需要在AndroidManifest.xml中设置以下权限:

< uses-permission android: name = " android.permission。READ_PHONE_STATE " / >

为了做到这一点。

话虽如此，做这件事要小心。用户不仅会想知道为什么您的应用程序要访问他们的电话堆栈，而且如果用户获得了新设备，可能很难迁移数据。

更新:正如下面评论中提到的，这不是一种安全的认证用户的方式，并引起了隐私问题。不建议使用。相反，如果您想实现一个无障碍的登录系统，请查看谷歌+ Login API。

如果你只是想在用户重置手机(或购买新设备)时以一种轻量级的方式持久化一束字符串，Android Backup API也是可用的。

对于Android 6.0+游戏已经改变，所以我建议你使用这个;

最好的方法是在运行时执行，否则会出现权限错误。

   /**
 * A loading screen after AppIntroActivity.
 */
public class LoadingActivity extends BaseActivity {
private static final int MY_PERMISSIONS_REQUEST_READ_PHONE_STATE = 0;
private TextView loading_tv2;

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

    //trigger 'loadIMEI'
    loadIMEI();
    /** Fading Transition Effect */
    overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
}

/**
 * Called when the 'loadIMEI' function is triggered.
 */
public void loadIMEI() {
    // Check if the READ_PHONE_STATE permission is already available.
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_PHONE_STATE)
            != PackageManager.PERMISSION_GRANTED) {
        // READ_PHONE_STATE permission has not been granted.
        requestReadPhoneStatePermission();
    } else {
        // READ_PHONE_STATE permission is already been granted.
        doPermissionGrantedStuffs();
    }
}



/**
 * Requests the READ_PHONE_STATE permission.
 * If the permission has been denied previously, a dialog will prompt the user to grant the
 * permission, otherwise it is requested directly.
 */
private void requestReadPhoneStatePermission() {
    if (ActivityCompat.shouldShowRequestPermissionRationale(this,
            Manifest.permission.READ_PHONE_STATE)) {
        // Provide an additional rationale to the user if the permission was not granted
        // and the user would benefit from additional context for the use of the permission.
        // For example if the user has previously denied the permission.
        new AlertDialog.Builder(LoadingActivity.this)
                .setTitle("Permission Request")
                .setMessage(getString(R.string.permission_read_phone_state_rationale))
                .setCancelable(false)
                .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        //re-request
                        ActivityCompat.requestPermissions(LoadingActivity.this,
                                new String[]{Manifest.permission.READ_PHONE_STATE},
                                MY_PERMISSIONS_REQUEST_READ_PHONE_STATE);
                    }
                })
                .setIcon(R.drawable.onlinlinew_warning_sign)
                .show();
    } else {
        // READ_PHONE_STATE permission has not been granted yet. Request it directly.
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_PHONE_STATE},
                MY_PERMISSIONS_REQUEST_READ_PHONE_STATE);
    }
}

/**
 * Callback received when a permissions request has been completed.
 */
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                       @NonNull int[] grantResults) {

    if (requestCode == MY_PERMISSIONS_REQUEST_READ_PHONE_STATE) {
        // Received permission result for READ_PHONE_STATE permission.est.");
        // Check if the only required permission has been granted
        if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // READ_PHONE_STATE permission has been granted, proceed with displaying IMEI Number
            //alertAlert(getString(R.string.permision_available_read_phone_state));
            doPermissionGrantedStuffs();
        } else {
            alertAlert(getString(R.string.permissions_not_granted_read_phone_state));
          }
    }
}

private void alertAlert(String msg) {
    new AlertDialog.Builder(LoadingActivity.this)
            .setTitle("Permission Request")
            .setMessage(msg)
            .setCancelable(false)
            .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    // do somthing here
                }
            })
            .setIcon(R.drawable.onlinlinew_warning_sign)
            .show();
}


public void doPermissionGrantedStuffs() {
    //Have an  object of TelephonyManager
    TelephonyManager tm =(TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
    //Get IMEI Number of Phone  //////////////// for this example i only need the IMEI
    String IMEINumber=tm.getDeviceId();

    /************************************************
     * **********************************************
     * This is just an icing on the cake
     * the following are other children of TELEPHONY_SERVICE
     *
     //Get Subscriber ID
     String subscriberID=tm.getDeviceId();

     //Get SIM Serial Number
     String SIMSerialNumber=tm.getSimSerialNumber();

     //Get Network Country ISO Code
     String networkCountryISO=tm.getNetworkCountryIso();

     //Get SIM Country ISO Code
     String SIMCountryISO=tm.getSimCountryIso();

     //Get the device software version
     String softwareVersion=tm.getDeviceSoftwareVersion()

     //Get the Voice mail number
     String voiceMailNumber=tm.getVoiceMailNumber();


     //Get the Phone Type CDMA/GSM/NONE
     int phoneType=tm.getPhoneType();

     switch (phoneType)
     {
     case (TelephonyManager.PHONE_TYPE_CDMA):
     // your code
     break;
     case (TelephonyManager.PHONE_TYPE_GSM)
     // your code
     break;
     case (TelephonyManager.PHONE_TYPE_NONE):
     // your code
     break;
     }

     //Find whether the Phone is in Roaming, returns true if in roaming
     boolean isRoaming=tm.isNetworkRoaming();
     if(isRoaming)
     phoneDetails+="\nIs In Roaming : "+"YES";
     else
     phoneDetails+="\nIs In Roaming : "+"NO";


     //Get the SIM state
     int SIMState=tm.getSimState();
     switch(SIMState)
     {
     case TelephonyManager.SIM_STATE_ABSENT :
     // your code
     break;
     case TelephonyManager.SIM_STATE_NETWORK_LOCKED :
     // your code
     break;
     case TelephonyManager.SIM_STATE_PIN_REQUIRED :
     // your code
     break;
     case TelephonyManager.SIM_STATE_PUK_REQUIRED :
     // your code
     break;
     case TelephonyManager.SIM_STATE_READY :
     // your code
     break;
     case TelephonyManager.SIM_STATE_UNKNOWN :
     // your code
     break;

     }
     */
    // Now read the desired content to a textview.
    loading_tv2 = (TextView) findViewById(R.id.loading_tv2);
    loading_tv2.setText(IMEINumber);
}
}

希望这能帮助到你或其他人。