Android Studio 无法识别输入字段“从未使用过字段”

Question

so I'm trying to learn Android Studio and this is the first time I've done anything. I'm trying to make a simple login app and I just added two EditText fields but they are not being recognized.

I get this error;

Cannot resolve symbol EditText

Although I made sure I have an EditText field in my application.

This is the Java code:

package localhost.testloginphpapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

EditText usernameField, passwordField;

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

And the XML code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="localhost.testloginphpapp.MainActivity"
tools:layout_editor_absoluteY="81dp"
tools:layout_editor_absoluteX="0dp">

<EditText
    android:id="@+id/usernameField"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="textPersonName"
    android:text="Username"
    tools:layout_editor_absoluteX="85dp"
    tools:layout_editor_absoluteY="133dp" />

<EditText
    android:id="@+id/passwordField"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="textPassword"
    tools:layout_editor_absoluteX="85dp"
    tools:layout_editor_absoluteY="190dp" />

<Button
    android:id="@+id/loginButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Login"
    tools:layout_editor_absoluteX="148dp"
    tools:layout_editor_absoluteY="245dp" />

</android.support.constraint.ConstraintLayout>

Thanks a lot.

Answer 1

您必须在包下但在类之前编写以下代码：

import android.widget.EditText;

Answer 2

EditText is a widget. You can use it in XML. But in Java, You have to import its class by adding

android.widget.EditText

on top of the file before class declaration.