實施SharedPreferences以保存用戶數據？

我正在開發一個將用戶數據保存在Firebase中的應用程序，但每次重新啓動應用程序時，用戶都必須再次登錄，因爲會話不會保持打開狀態，我已閱讀我可以實現SharedPreferences但我不知道如何在我的項目中做。實施SharedPreferences以保存用戶數據？

這裏是LoginActivity.java：

public class LoginActivity extends AppCompatActivity { 


private static final String TAG = "LoginActivity"; 
// La respuesta del JSON es 
private static final String username = "success"; 
private static final String TAG_MESSAGE = "message"; 

private Button btnLogin, btnLinkToSignUp; 
private ProgressBar progressBar; 
private FirebaseAuth auth; 
private EditText loginInputEmail, loginInputPassword; 
private TextInputLayout loginInputLayoutEmail, loginInputLayoutPassword; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_login); 
    auth = FirebaseAuth.getInstance(); 

    loginInputLayoutEmail = (TextInputLayout) findViewById(R.id.login_input_layout_email); 
    loginInputLayoutPassword = (TextInputLayout) findViewById(R.id.login_input_layout_password); 
    progressBar = (ProgressBar) findViewById(R.id.progressBar); 

    loginInputEmail = (EditText) findViewById(R.id.login_input_email); 
    loginInputPassword = (EditText) findViewById(R.id.login_input_password); 

    btnLogin = (Button) findViewById(R.id.btn_login); 
    btnLinkToSignUp = (Button) findViewById(R.id.btn_link_signup); 

    btnLogin.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      submitForm(); 
     } 
    }); 

    btnLinkToSignUp.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      Intent intent = new Intent(appz.seoallinone.LoginActivity.this, SignupActivity.class); 
      startActivity(intent); 
     } 
    }); 
} 

/** 
* Validating form 
*/ 
private void submitForm() { 
    String email = loginInputEmail.getText().toString().trim(); 
    String password = loginInputPassword.getText().toString().trim(); 

    if(!checkEmail()) { 
     return; 
    } 
    if(!checkPassword()) { 
     return; 
    } 
    loginInputLayoutEmail.setErrorEnabled(false); 
    loginInputLayoutPassword.setErrorEnabled(false); 

    progressBar.setVisibility(View.VISIBLE); 
    //authenticate user 
    auth.signInWithEmailAndPassword(email, password) 
      .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() { 
       @Override 
       public void onComplete(@NonNull Task<AuthResult> task) { 
        // If sign in fails, Log a message to the LogCat. If sign in succeeds 
        // the auth state listener will be notified and logic to handle the 
        // signed in user can be handled in the listener. 
        progressBar.setVisibility(View.GONE); 
        if (!task.isSuccessful()) { 
         // there was an error 
         Toast.makeText(LoginActivity.this, getString(R.string.auth_failed), Toast.LENGTH_LONG).show(); 

        } else { 
         Intent intent = new Intent(LoginActivity.this, MainActivity.class); 
         startActivity(intent); 
         finish(); 
        } 
       } 
      }); 
} 

private boolean checkEmail() { 
    String email = loginInputEmail.getText().toString().trim(); 
    if (email.isEmpty() || !isEmailValid(email)) { 

     loginInputLayoutEmail.setErrorEnabled(true); 
     loginInputLayoutEmail.setError(getString(R.string.err_msg_email)); 
     loginInputEmail.setError(getString(R.string.err_msg_required)); 
     requestFocus(loginInputEmail); 
     return false; 
    } 
    loginInputLayoutEmail.setErrorEnabled(false); 
    return true; 
} 

private boolean checkPassword() { 

    String password = loginInputPassword.getText().toString().trim(); 
    if (password.isEmpty() || !isPasswordValid(password)) { 

     loginInputLayoutPassword.setError(getString(R.string.err_msg_password)); 
     loginInputPassword.setError(getString(R.string.err_msg_required)); 
     requestFocus(loginInputPassword); 
     return false; 
    } 
    loginInputLayoutPassword.setErrorEnabled(false); 
    return true; 
} 

private static boolean isEmailValid(String email) { 
    return !TextUtils.isEmpty(email) && android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches(); 
} 

private static boolean isPasswordValid(String password){ 
    return (password.length() >= 6); 
} 

private void requestFocus(View view) { 
    if (view.requestFocus()) { 
     getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE); 
    } 
} 

@Override 
protected void onResume() { 
    super.onResume(); 
    progressBar.setVisibility(View.GONE); 
}

}

我怎樣才能在這個特定的項目實現它？謝謝！

來源

2017-01-12 Rodrigo Zid

[Android文檔]（https://developer.android.com/training/basics/data-storage/shared-preferences.html）是一個很好的開始。對於更直接的事情，你可以檢查[此鏈接]（http://androidexample.com/Android_SharedPreferences_Basics/index.php?view=article_discription&aid=126） – maxoumime

這個答案很容易在documentation和StackOverflow。

要回答你的問題，你可以使用下面的代碼來存儲和獲取的偏好：

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this); 
SharedPreferences.Editor editor = preferences.edit(); 
editor.putString("Car","Tesla"); 
editor.apply(); 


SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this); 
String name = preferences.getString("Car", "");

來源

2017-01-12 19:09:03 Orbit

的FirebaseAuth已經採取保持會話對你的照顧。

你只需要檢查，如果用戶在驗證實例存在在你登錄活動的onCreate：

if (FirebaseAuth.getInstance().getCurrentUser() != null) { 
    navigateToHomeScreen(); 
}

你應該實現navigateToHomeScreen啓動活動以顯示用戶是否登錄

這樣，您不需要在SharedPreferences中存儲任何內容。

來源

2017-01-12 19:16:23 BMacedo

實施SharedPreferences以保存用戶數據？

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