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在以下代码中，错误是：Can not resolve the symbol 'firstname','lastname' and 'email'。我还交叉验证了.xml文件中的相同变量，但它仍然向我显示该错误。

import android.R;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Color;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.TableLayout.*;

public class MainActivity extends Activity
{
    String fname, lname, email;

    SQLiteDatabase db;

    TableRow tableRow;

    String firstname, lastname;

    TextView textView, textView1, textView2, textView3, textView4, textView5;

    EditText editText1, editText2, editText3;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_item);
        db = openOrCreateDatabase("MyDB1", MODE_PRIVATE, null);
        db.execSQL("CREATE TABLE IF NOT EXIST Student(fname VARCHAR,lname VARCHAR,email VARCHAR);");
    }

    public void Adddata(View view)
    {
        editText1 = (EditText) finViewById(R.id.firstname);
        editText2 = (EditText) finViewById(R.id.lastname);
        editText3 = (EditText) finViewById(R.id.email);
        fname = editText1.getText().toString();
        fname = editText2.getText().toString();
        fname = editText3.getText().toString();
        db.execSQL("INSERT INTO Studnet VALUES('" + fname + "','" + lname + "','" + email + "');");
    }

    private void Showdata(View view)
    {
        Cursor c = db.rawQuery("SELECT * from Student", null);
        int count = c.getCount();
        c.moveToFirst();
        TableLayout tableLayout = new TableLayout(getApplicationContext());
        tableLayout.setVerticalScrollBarEnabled(true);
        tableRow = new TableRow(getApplicationContext());

        textView = new TextView(getApplicationContext());
        textView.setText("Firstname");
        textView.setTextColor(Color.RED);
        textView.setTypeface(null, Typeface.BOLD);
        textView.setPadding(20, 20, 20, 20);
        tableRow.addView(textView);

        textView4 = new TextView(getApplicationContext());
        textView4.setText("Lastname");
        textView4.setTextColor(Color.RED);
        textView4.setTypeface(null, Typeface.BOLD);
        textView4.setPadding(20, 20, 20, 20);
        tableRow.addView(textView4);

        textView5 = new TextView(getApplicationContext());
        textView5.setText("Email");
        textView5.setTextColor(Color.RED);
        textView5.setTypeface(null, Typeface.BOLD);
        textView5.setPadding(20, 20, 20, 20);
        tableRow.addView(textView5);

        tableLayout.addView(tableRow);
        for (Integer j = 0; j <= count; j++)
        {
            tableRow = new TableRow(getApplicationContext());
            textView1 = new TextView(getApplicationContext());
            textView1.setText(c.getString(c.getColumnIndex("fname")));
            textView2 = new TextView(getApplicationContext());
            textView2.setText(c.getString(c.getColumnIndex("lname")));
            textView3 = new TextView(getApplicationContext());
            textView3.setText(c.getString(c.getColumnIndex("email")));

            textView1.setPadding(20, 20, 20, 20);
            textView2.setPadding(20, 20, 20, 20);
            textView3.setPadding(20, 20, 20, 20);

            tableRow.addView(textView1);
            tableRow.addView(textView2);
            tableRow.addView(textView3);
            tableLayout.addView(tableLayout);
            db.close();
        }
    }

    public void close(View view)
    {
        System.exit(0);
    }
}

XML 代码是：

<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:background="@style/AppBaseTheme"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="22dp"
        android:layout_marginTop="34dp"
        android:text="FirstName" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="43dp"
        android:text="LastName" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView2"
        android:layout_alignRight="@+id/textView1"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="49dp"
        android:text="E-mail" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView3"
        android:layout_centerVertical="true"
        android:onClick="Adddata"
        android:text="create" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/button1"
        android:layout_marginTop="32dp"
        android:onClick="Showdata"
        android:text="Show Table" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/button3"
        android:layout_toRightOf="@+id/button3"
        android:onClick="close"
        android:text="close" />

    <EditText
        android:id="@+id/firstname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView1"
        android:layout_alignBottom="@+id/textView1"
        android:layout_toRightOf="@+id/button3"
        android:ems="10"
        android:inputType="textPersonName" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/lastname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView2"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignLeft="@+id/editText1"
        android:ems="10"
        android:inputType="textPersonName" />

    <EditText
        android:id="@+id/email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView3"
        android:layout_alignLeft="@+id/editText2"
        android:ems="10"
        android:inputType="textEmailAddress" />

</RelativeLayout>

清单文件是：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.studentdatabase"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.studentdatabase.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>
4

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