Android共享首选项声明默认值

Question

So I'm having a small issue with declaring the default value "ipAddress" in my onCreate function. ipAddress is declared in the bottom void but not for checking whether the ip exists. This is the code that I'm working with:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(LoginActivity.this);
    if (sharedPreferences.contains("ip")) {
        performLogin(etUsername, etPassword, sharedPreferences.getString("ip", ipAddress));
    }

    // declaring variebles
    etUsername = (EditText)findViewById(R.id.etUsername);
    etPassword = (EditText) findViewById(R.id.etPassword);
    btnLogin = (Button) findViewById(R.id.btnLogin);
    etIpAddress = (EditText) findViewById(R.id.etIpAddress);

    // setting up things for login button
    btnLogin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String ipAddress = etIpAddress.getText().toString();

            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(LoginActivity.this);

            sharedPreferences.edit()
                    .putString("ip", ipAddress)
                    .apply();

            String username = etUsername.getText().toString().trim();
            String password = etPassword.getText().toString().trim();

            performLogin(username, password, ipAddress);
        }

    });
}

Answer 1

make this change in your code

..
setContentView(R.layout.activity_login);

SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(LoginActivity.this);

String ip=sharedPreferences.getString("ip",null);
if(ip!=null){
  performLogin(etUsername, etPassword, ip);
}