android Sqlite数据库的操作

苍天有泪

　　首先必须继承自：SQLiteOpenHelper，实现其onCreate，onUpgrade方法
　　构造方法：
　　

public DatabaseHelper(Context context, String name, CursorFactory factory, int version)

第一个参数：Context类型，上下文。

第二个参数：String类型，数据库名称

第三个参数：CursorFactory类型

第四个参数：int，数据库版本（>0）

　　DbHelper 继承自：SQLiteOpenHelper。。。。创建表:sqtb
　　package com.android.lp;


import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;


public class DbHelper extends SQLiteOpenHelper{


public DbHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}

//创建一个表sqtb,仅两个字段id,name
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
Log.v("dbhelperlog", "dbhelperlog");
db.execSQL("create table if not exists sqtb("
+"id int,"
+"name vachar)");
}


@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub

}
}

　　操作数据的类：
　　package com.android.lp;


import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;


public class TestSqliteActivity extends Activity {
/** Called when the activity is first created. */
private DbHelper dbHelper;
private TextView textVText;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//DbHelper(context, name, factory, version)
textVText= (TextView) findViewById(R.id.textview);
dbHelper = new DbHelper(this, "sqlite.db", null, 1);//此处是必须大于0，艹 12-22 19:10:22.759: E/AndroidRuntime(672): Caused by: java.lang.IllegalArgumentException: Version must be >= 1, was 0
　　
this.addData(dbHelper);
String rs = this.getData(dbHelper);
textVText.setText("id\t"+"name\n"+rs);

}
public void addData(DbHelper dbHelper){
SQLiteDatabase sqDb = dbHelper.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put("id", 28);
cv.put("name", "lp2");
sqDb.insert("sqtb", "id", cv);
}
public String getData(DbHelper dbHelper){
String rs = null;
　　//得到一个可写的db
SQLiteDatabase sqDb = dbHelper.getWritableDatabase();
Cursor c = sqDb.query("sqtb", null, null, null, null, null, null);
int idindex = c.getColumnIndex("id");
int nameindex = c.getColumnIndex("name");
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
rs = rs + c.getString(idindex)+"\t";
rs = rs + c.getString(nameindex)+"\n";
}
return rs;

}
}

　　main。xml中定义一个Textview用来显示数据
　　<TextView
android:id="@+id/textview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />

　　

　　运行，显示结果：