我正在尝试为我的应用设置登录页面，并希望为用户提供使用电子邮件/密码，Facebook和Google登录的选项。我能够成功登录和注销每种方法。我想用相同的电子邮件地址链接来自不同Auth提供程序的所有帐户。我正在浏览Firebase文档，并通过了linkwithcredential。如果我理解正确，Firebase会告诉您使用任何一种登录方法登录后使用linkwithcredential。在我的情况下，如果我先通过facebbok登录用户，则->用户注销->使用google登录->调用linkwithcredential（我的期望是Facebook在此被链接）。我的理解是否正确？否则，我如何在不要求用户采取任何措施的情况下，使用其他身份验证提供程序平稳地登录用户。请帮助
private void handleFacebookAccessToken(AccessToken token) {
Log.d(TAG, "handleFacebookAccessToken:" + token);
final AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
firebaseAuth.signInWithCredential(credential)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
linkCredential(credential);
// Sign in success, update UI with the signed-in user's information
Log.d(TAG, "signInWithCredential:success");
startActivity(new Intent(getApplicationContext(),ProfileActivity.class));
} else {
// If sign in fails, display a message to the user.
Log.d("***facebook fail", task.getException().toString());
Log.w(TAG, "signInWithCredential:failure", task.getException());
if(task.getException().toString().equals(getResources().getString(R.
string.fb_login_google))){
FirebaseUser mUser = firebaseAuth.getCurrentUser();
Toast.makeText(MainActivity.this,"User already signed in via google",
Toast.LENGTH_SHORT).show();
Log.d("***facebook failure ","failed");
}
else{
Toast.makeText(MainActivity.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
}
}
// ...
}
});
}
public void linkCredential(AuthCredential credential){
Log.d("shitttttt" + FirebaseAuth.getInstance().getCurrentUser(),credential.toString());
FirebaseAuth.getInstance().getCurrentUser().linkWithCredential(credential)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
Log.d(TAG, "linkWithCredential:success");
} else {
Log.w(TAG, "linkWithCredential:failure", task.getException());
Toast.makeText(MainActivity.this, "linkWithCredential:failure",
Toast.LENGTH_SHORT).show();
}
}
});
//final AuthCredential fbCredential = FacebookAuthProvider.getCredential(acct.getIdToken());
Log.d("fbcredential",credential.toString());
}