java - Android 正确的变量声明

Question

由于某种原因，我的用户名和密码变量是红色的。当我将它们定义为字符串时，我收到错误，指出它们无法从编辑文本中转换......有什么方法可以真正解决这个问题吗？这很令人恼火，因为我正在逐字逐句地学习教程，而他们似乎没有这些问题。我已经尝试过做各种事情，例如将密码和用户名转换为字符串。它只是无法正常工作。

这是我到目前为止所尝试过的。我只希望这个简单的登录/注册代码能够工作。 (代码已更新)

package myapplication.example.com.cis490_project;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.parse.LogInCallback;
import com.parse.Parse;
import com.parse.ParseObject;
import com.parse.ParseUser;
import com.parse.SignUpCallback;

public class loginactivity extends AppCompatActivity {

    Button loginButton;
   Button signUpButton;
   EditText usernameField;
    EditText passwordField;

    String username;
    String password;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_loginactivity);

        loginButton = (Button) findViewById(R.id.btlogin);
        signUpButton = (Button) findViewById(R.id.btsignup);
        usernameField = (EditText) findViewById(R.id.tusername);
        passwordField = (EditText) findViewById(R.id.tpassword);


        // Enable Local Datastore.
        Parse.enableLocalDatastore(this);

        Parse.initialize(this, "SECRET_KEY", "SECRET_KEY");

        ParseObject testObject = new ParseObject("Testing");
        testObject.put("foo", "badr");
        testObject.saveInBackground();


        loginButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                username = usernameField.getText().toString();
                password = passwordField.getText().toString();
                ParseUser.logInInBackground(username, password, new LogInCallback() {
                    public void done(ParseUser user, com.parse.ParseException e) {
                        if (user != null) {
                            //start next activity
                            //start sinch service
                        } else {
                        Toast.makeText(getApplicationContext(),
                                "There was an error logging in.",
                                Toast.LENGTH_LONG).show();
                    }
                }
                });
            }
        });
        signUpButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
               username = usernameField.getText().toString();
                  password = passwordField.getText().toString();
                ParseUser user = new ParseUser();
                user.setUsername(username);
                user.setPassword(password);
                user.signUpInBackground(new SignUpCallback() {
                    public void done(com.parse.ParseException e) {
                        if (e == null) {
                            //start next activity
                            //start sinch service
                        } else {
                            Toast.makeText(getApplicationContext(),
                                    "There was an error signing up."
                                    , Toast.LENGTH_LONG).show();
                        }
                    }
                });
            }
        });
    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_loginactivity, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}


XML:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="myapplication.example.com.cis490_project.loginactivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Login"
        android:id="@+id/btlogin"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:text="Password"
        android:id="@+id/tpassword"
        android:layout_above="@+id/btlogin"
        android:layout_centerHorizontal="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:text="Username"
        android:id="@+id/tName"
        android:layout_above="@+id/tpassword"
        android:layout_alignLeft="@+id/tpassword"
        android:layout_alignStart="@+id/tusername"
        android:layout_marginBottom="40dp" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/iprofile"
        android:src="@drawable/com_facebook_profile_picture_blank_square"
        android:layout_above="@+id/tName"
        android:layout_alignRight="@+id/btlogin"
        android:layout_alignEnd="@+id/btlogin"
        android:layout_marginBottom="56dp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Signup"
        android:id="@+id/btsignup"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

</RelativeLayout>

Answer 1

在onCreate内的setContentView之后定义所有小部件。并将用户名和密码定义为字符串变量。因为您没有在代码中的任何位置定义用户名和密码。

    public class loginactivity extends AppCompatActivity {

    Button loginButton;
    Button signUpButton;
    EditText usernameField;
    EditText passwordField;

    String username;
    String password;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_loginactivity);

        loginButton = (Button) findViewById(R.id.btlogin);
        signUpButton = (Button) findViewById(R.id.btsignup);
        usernameField = (EditText) findViewById(R.id.tusername);
        passwordField = (EditText) findViewById(R.id.tpassword);

        //rest of your code
        ..............
        }