一点小小的贡献。在我的例子中，代码启动了一个错误异常。我需要把一个注释，为代码运行和修复这个问题。这里我让这段代码。

public static String getLineNumberPhone(Context scenario) {
    TelephonyManager tMgr = (TelephonyManager) scenario.getSystemService(Context.TELEPHONY_SERVICE);
    @SuppressLint("MissingPermission") String mPhoneNumber = tMgr.getLine1Number();
    return mPhoneNumber;
}

这是一个更简单的答案:

public String getMyPhoneNumber()
{
    return ((TelephonyManager) getSystemService(TELEPHONY_SERVICE))
            .getLine1Number();
}

不建议使用TelephonyManager，因为它要求应用程序在运行时需要READ_PHONE_STATE权限。

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

应该使用谷歌的播放服务进行身份验证，它将能够允许用户选择使用哪个phoneNumber，并处理多个SIM卡，而不是我们试图猜测哪一个是主SIM卡。

implementation "com.google.android.gms:play-services-auth:$play_service_auth_version"

fun main() {
    val googleApiClient = GoogleApiClient.Builder(context)
        .addApi(Auth.CREDENTIALS_API).build()

    val hintRequest = HintRequest.Builder()
        .setPhoneNumberIdentifierSupported(true)
        .build()

    val hintPickerIntent = Auth.CredentialsApi.getHintPickerIntent(
        googleApiClient, hintRequest
    )

    startIntentSenderForResult(
        hintPickerIntent.intentSender, REQUEST_PHONE_NUMBER, null, 0, 0, 0
    )
}

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    when (requestCode) {
        REQUEST_PHONE_NUMBER -> {
            if (requestCode == Activity.RESULT_OK) {
                val credential = data?.getParcelableExtra<Credential>(Credential.EXTRA_KEY)
                val selectedPhoneNumber = credential?.id
            }
        }
    }
}

while working on a security app which needed to get the phone number of who so ever my phone might get into their hands, I had to do this; 1. receive Boot completed and then try getting Line1_Number from telephonyManager which returns a string result. 2. compare the String result with my own phone number and if they don't match or string returns null then, 3. secretly send an SMS containing the string result plus a special sign to my office number. 4. if message sending fails, start a service and keep trying after each hour until sent SMS pending intent returns successful. With this steps I could get the number of the person using my lost phone. it doesn't matter if the person is charged.

我注意到有几个回复都发了同样的东西。首先，从2021年开始，onActivityResult已弃用。下面是不弃用的解决方案。

private fun requestHint() {

    val hintRequest = HintRequest.Builder()
        .setPhoneNumberIdentifierSupported(true)
        .build()

    val intent = Credentials.getClient(this).getHintPickerIntent(hintRequest)
    val intentSender = IntentSenderRequest.Builder(intent.intentSender).build()

    val resultLauncher = registerForActivityResult(
        ActivityResultContracts.StartIntentSenderForResult()
    ) { result ->
        if (result.resultCode == Activity.RESULT_OK) {
            val credential: Credential? = result.data?.getParcelableExtra(Credential.EXTRA_KEY)
            // Phone number with country code
            Log.i("mTag", "Selected phone No: ${credential?.id}")
        }
    }
    resultLauncher.launch(intentSender)
}

注意:虽然很多人认为这可以让你检索用户的手机号码。通常情况并非如此。谷歌播放服务缓存了几个电话号码，有时对话框显示电话号码，其中不属于用户。

一个重要的导入。com.google.android.gms.auth.api.credentials.Credential

参考文档提供了详细信息，但代码有些不推荐。

只是想在以上回答中对以上解释做一点补充。这也会为其他人节省时间。

在我的情况下，这个方法没有返回任何手机号码，返回一个空字符串。这是由于我把我的号码移植到新的sim卡上的情况。所以如果我进入设置>关于电话>状态>我的电话号码，它显示我“未知”。