写在开头

google官方介绍
如果在没有读写短信权限的情况下获取用户的短信验证码呢？google为我们提供了SMSRetrieverAPI这个Api。解决了我们在用户收到短信后自动回填界面的需求。但是google为了安全性，短信格式需要时固定的，那么我们先来看下短信的固定格式！

短信格式

短信固定格式（#号可以不要，sha256一定需要）
<#> Your ExampleApp code is: 123ABC78
FA+9qCX9VSu

google要求我们的短信：

• 不能超过140个字节
• 包含一个11个字符的哈希字符串来标识您的应用（也就是上文的sha256）

sha256如何生成

网上通用的生成方式，总结了一个工具类AppSignatureHashHelper

	public class AppSignatureHashHelper extends ContextWrapper {public static final String TAG = AppSignatureHashHelper.class.getSimpleName();private static final String HASH_TYPE = "SHA-256";public static final int NUM_HASHED_BYTES = 9;public static final int NUM_BASE64_CHAR = 11;public AppSignatureHashHelper(Context context) {super(context);}public ArrayList<String> getAppSignatures() {ArrayList<String> appSignaturesHashs = new ArrayList<>();try {String packageName = getPackageName();PackageManager packageManager = getPackageManager();Signature[] signatures = packageManager.getPackageInfo(packageName,PackageManager.GET_SIGNATURES).signatures;for (Signature signature : signatures) {String hash = hash(packageName, signature.toCharsString());if (hash != null) {appSignaturesHashs.add(String.format("%s", hash));}}} catch (Exception e) {Log.e(TAG, "Package not found", e);}return appSignaturesHashs;}@TargetApi(19)private static String hash(String packageName, String signature) {String appInfo = packageName + " " + signature;try {MessageDigest messageDigest = MessageDigest.getInstance(HASH_TYPE);messageDigest.update(appInfo.getBytes(StandardCharsets.UTF_8));byte[] hashSignature = messageDigest.digest();hashSignature = Arrays.copyOfRange(hashSignature, 0, NUM_HASHED_BYTES);String base64Hash = Base64.encodeToString(hashSignature, Base64.NO_PADDING | Base64.NO_WRAP);base64Hash = base64Hash.substring(0, NUM_BASE64_CHAR);return base64Hash;} catch (NoSuchAlgorithmException e) {Log.e(TAG, "No Such Algorithm Exception", e);}return null;}
}

接下来我们要开始集成SMSRetrieverAPI了

首先我们要依赖google的两个库才能使用这个功能

dependencies {implementation 'com.google.android.gms:play-services-auth:19.2.0'implementation 'com.google.android.gms:play-services-auth-api-phone:17.5.1'
}

然后要通过google的系统广播的action–SmsRetriever.SMS_RETRIEVED_ACTION和SmsRetriever实现监听的需求

接下来第一步
先创建SMSReceiver这个BroadcastReceiver接收系统给我推送的SMS广播，并创建OTPReceiveListener接口来实现监听结果的返回，代码如下：

	public class SMSReceiver extends BroadcastReceiver {private OTPReceiveListener otpListener;public void setOTPListener(OTPReceiveListener otpListener) {this.otpListener = otpListener;}@Overridepublic void onReceive(Context context, Intent intent) {if (SmsRetriever.SMS_RETRIEVED_ACTION.equals(intent.getAction())) {Bundle extras = intent.getExtras();Status status = (Status) extras.get(SmsRetriever.EXTRA_STATUS);switch (status.getStatusCode()) {case CommonStatusCodes.SUCCESS:String message = (String) extras.get(SmsRetriever.EXTRA_SMS_MESSAGE);if (otpListener != null) {otpListener.onOTPReceived(message);}break;case CommonStatusCodes.TIMEOUT:if (otpListener != null) {otpListener.onOTPTimeOut();}break;case CommonStatusCodes.API_NOT_CONNECTED:if (otpListener != null) {otpListener.onOTPReceivedError("API NOT CONNECTED");}break;case CommonStatusCodes.NETWORK_ERROR:if (otpListener != null) {otpListener.onOTPReceivedError("NETWORK ERROR");}break;case CommonStatusCodes.ERROR:if (otpListener != null) {otpListener.onOTPReceivedError("SOME THING WENT WRONG");}break;}}}public interface SMSReceiveListener {void onSMSReceived(String otp);void onSMSTimeOut();void onSMSReceivedError(String error);}
}

第二步的话我们要主动开启这个监听：

private void startSMSListener() {try {smsReceiver = new SMSReceiver();smsReceiver.setOTPListener(this);//this指的是要在这个activity实现这个接口IntentFilter intentFilter = new IntentFilter();intentFilter.addAction(SmsRetriever.SMS_RETRIEVED_ACTION);this.registerReceiver(smsReceiver, intentFilter);SmsRetrieverClient client = SmsRetriever.getClient(this);Task<Void> task = client.startSmsRetriever();task.addOnSuccessListener(new OnSuccessListener<Void>() {@Overridepublic void onSuccess(Void aVoid) {//代表监听成功开始了}});task.addOnFailureListener(new OnFailureListener() {@Overridepublic void onFailure(@NonNull Exception e) {//代表监听失败了，后续也不会收到系统推送的SMS通知}});} catch (Exception e) {e.printStackTrace();}}

实现接口的方法获取结果：

	@Overridepublic void onSMSReceived(String otp) {//成功接收到结果}@Overridepublic void onSMSTimeOut() {//接收结果超时}@Overridepublic void onSMSReceivedError(String error) {//接收结果报错}

写在最后

这种方式不是一定会成功的，google告诉我们可以检测广播意图是使用短信API通过添加com.google.android.gms.auth.api.phone.permission.SEND允许你的接收SMS。此权限设置在 Google Play 服务 19.8.31 或更高版本中可用。也就是低于Google Play 服务 19.8.31 的手机是不能使用的，不过作为辅助功能，也可以了。。