package com.example.sjk;import android.content.Context;
import android.database.sqlite.SQLiteCursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;public class SqlText extends SQLiteOpenHelper{private static final String DB_NAME = "mydata.db"; //数据库名称private static final int version =2; // 当前数据库版本号是升级到2了public SqlText(Context context) {super(context, DB_NAME, null, version);}@Overridepublic void onCreate(SQLiteDatabase db) { //新安装的软件从这里开始String sql_message = "create table t_message (id int  primary key,name varchar(50),age varchar(50),sex varchar(10))";//升级的时候增加了一个列sex，所以为了和版本2升级的一样这里也要对应db.execSQL(sql_message);Log.i("onCreate", "你是新用户，我们在帮你创建表--->成功");String sql_up1 = "insert into t_message values(1,'小白','18','男')";db.execSQL(sql_up1);Log.i("onCreate", "你是新用户,我们帮你插入一条数据-->成功");}@Override//在原来的软件上更新会从这里开始，不卸载在线更新public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {   //本文讨论这个方法if(oldVersion == 1){//如果版本是1.0的，升级下面的内容或修改String sql_upgrade = "alter table t_message add sex varchar(10)";//增加一个列sex
             db.execSQL(sql_upgrade);String sql_up2 ="insert into t_message values(3,'小红','18','男')";db.execSQL(sql_up2);Log.i("onUpgrade","你在没有卸载的情况下，在线更新了版本2.0,同时列表增加了一个列sex"); }}}

package com.example.sjk;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;public class MainActivity extends Activity {private SqlText st; //得到SqlText这个类的contextprivate TextView tv;   @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);tv = (TextView) findViewById(R.id.TextView);//找到这个TextView组件st = new SqlText(MainActivity.this);String text = query();//调用查询这个方法tv.setText("id \t"+"name\t"+"age\t"+"sex\n"+text+"\n");//显示}public String query(){//查询数据库的数据String result = "";//获取数据库对象SQLiteDatabase db = st.getReadableDatabase();//只读:ReadableDatabase;读写:WritableDatabase//查询数据库中的数据Cursor cursor = db.query("t_message", null, null, null, null, null, null);//结果集for(int i=0;i<cursor.getCount();i++) {cursor.moveToNext();result +=  cursor.getInt(cursor.getColumnIndex("id"));result +=  cursor.getString(cursor.getColumnIndex("name"));result +=  cursor.getString(cursor.getColumnIndex("age"));   result +=  cursor.getString(cursor.getColumnIndex("sex"));  }cursor.close();//关闭结果集db.close();//关闭数据库对象return result;}}