安卓 数据库表

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".MainActivity">
<TextView
    android:id="@+id/tv1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="用户名："
    android:textSize="30dp"
    android:layout_marginTop="60dp"
    />
<EditText
    android:id="@+id/et1"
    android:layout_width="600dp"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@+id/tv1"
    android:layout_marginTop="50dp"
    android:textSize="30dp"
    />
<TextView
    android:id="@+id/tv2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="密码："
    android:textSize="30dp"
    android:layout_marginTop="50dp"
    android:layout_below="@+id/tv1"
    />
<EditText
    android:id="@+id/et2"
    android:layout_width="600dp"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@+id/tv2"
    android:layout_marginTop="30dp"
    android:textSize="30dp"
    android:layout_below="@+id/et1"
    />
    <Button
        android:layout_marginTop="80dp"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:text="注册"
        android:textSize="50dp"
        android:layout_below="@+id/et2"
        android:layout_centerHorizontal="true"
        android:onClick="click"
        />
</RelativeLayout>

　　

package com.example.aaa;
import android.content.ContentValues;
import android.os.Bundle;
import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
    private String username;
    private String password;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 }
    public void click(View view){
        username =((EditText) findViewById(R.id.et1)).getText().toString();
        password =((EditText) findViewById(R.id.et2)).getText().toString();
        StuOpenHelper helper = new StuOpenHelper(this);
        SQLiteDatabase db =helper.getReadableDatabase();
        ContentValues cv = new ContentValues();
        cv.put("username",username);
        cv.put("password",password);
        db.insert("stu",null,cv);
        db.close();
    }
}

　　

package com.example.aaa;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class StuOpenHelper extends SQLiteOpenHelper{
    public StuOpenHelper(Context context) {
        super(context, "stu.db", null, 5);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        System.out.println("第一次创建");
        String sql = "CREATE TABLE stu (_id integer PRIMARY KEY AUTOINCREMENT,USERNAME VARCHAR(20),PASSWORD  VARCHAR(20))";
        db.execSQL(sql);    
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            System.out.println("更新"+oldVersion+"  "+newVersion);
            if(oldVersion==5 && newVersion==6) {
                String sql = "CREATE TABLE bj (_id integer PRIMARY KEY AUTOINCREMENT,CLASSNAME VARCHAR(20))";
                db.execSQL(sql);
            }
    }
}