首先要用一个类来继承SQLiteOpenHelper，并必须实现
代码语言：javascript复制 public DatabaseHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}具体类如下（关键地方我都加了注释）：
代码语言：javascript复制package com.example.sqllitedemo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
private static final int VERSION = 2;
// SQLiteOpenHelper子类必须有该构造函数
// 第一次参数Activity对象，第二个表名，第三个暂时空值，第四个数据库的版本号
public DatabaseHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
public DatabaseHelper(Context context, String name, int version) {
this(context, name, null, version);
}
public DatabaseHelper(Context context, String name) {
this(context, name, VERSION);
}
// 该函数第一次创建数据库的时候执行，实际上是在第一次得到SqliteDatabase对象的时候执行
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
System.out.println("create a database");
db.execSQL("create table user(id int,name verchar(20))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
System.out.println("update a database");
}
}调用代码如下：
代码语言：javascript复制package com.example.sqllitedemo;
import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.AutoCompleteTextView;
public class MainActivity extends Activity implements OnClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnCreate = (Button) findViewById(R.id.btnCreateDatabase);
btnCreate.setOnClickListener(this);
Button btnUpdatDatabase = (Button) findViewById(R.id.btnUpdateDatabase);
btnUpdatDatabase.setOnClickListener(this);
Button btnInsert = (Button) findViewById(R.id.btnInsert);
btnInsert.setOnClickListener(this);
Button btnUpdate = (Button) findViewById(R.id.btnUpdate);
btnUpdate.setOnClickListener(this);
Button btnQuery = (Button) findViewById(R.id.btnQuery);
btnQuery.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.btnCreateDatabase:
DatabaseHelper helper = new DatabaseHelper(this, "School_db");
SQLiteDatabase db = helper.getReadableDatabase();
break;
case R.id.btnUpdateDatabase:
DatabaseHelper helper1 = new DatabaseHelper(this, "School_db", 2);
SQLiteDatabase db1 = helper1.getReadableDatabase();
break;
case R.id.btnInsert:
// 用于存储数据的键值对，键为列名
ContentValues values = new ContentValues();
values.put("name", "张山");
values.put("id", 1);
DatabaseHelper helper2=new DatabaseHelper(this,"School_db");
SQLiteDatabase db2=helper2.getWritableDatabase();
db2.insert("user", null, values);
//方法二、直接使用ExecSQL
db2.execSQL("insert into user(id,name) values(?,?)", new Object[]{2,"李四"});
break;
case R.id.btnUpdate:
DatabaseHelper helper3=new DatabaseHelper(this,"School_db");
SQLiteDatabase db3=helper3.getWritableDatabase();
ContentValues values1=new ContentValues();
values1.put("name", "zhangshan");
db3.update("user", values1, "id=?" , new String[]{"1"});
break;
case R.id.btnQuery:
DatabaseHelper helper4=new DatabaseHelper(this,"School_db");
SQLiteDatabase db4=helper4.getReadableDatabase();
Cursor cursor=db4.query("user",new String[]{"id","name"},"id=?",new String[]{"1"},
"","","");
while(cursor.moveToNext())
{
String name=cursor.getString(cursor.getColumnIndex("name"));
System.out.println(name);
}
break;
default:
break;
}
}
}除了上述的crud的方法，还可以使用下面的方式
代码语言：javascript复制DatabaseHelper myDBHelper=new DatabaseHelper(this,"School_db");
//增加
public void addPerson(String name) {
SQLiteDatabase database = myDBHelper.getWritableDatabase();
//先判断数据库是否可用
if (database.isOpen()) {
database.execSQL("insert into user(name) values(?,?)", new Object[]{name});
database.close();
}
}
//查找
public boolean findPerson(String name) {
boolean result = false;
SQLiteDatabase database = myDBHelper.getReadableDatabase();
if (database.isOpen()) {
Cursor cursor = database.rawQuery("select * from user where name=?", new String[]{name});
if (cursor.moveToFirst()) {//游标是否移动到下一行,如果是,那说明有数据返回
Log.d(tag, "count:" cursor.getColumnCount());
int nameIndex = cursor.getColumnIndex("name");
Log.d(tag, "name:" cursor.getString(nameIndex));
cursor.close();
result = true;
} else {
result = false;
}
database.close();
}
return result;
}
//删除一条数据
public void deletePerson(String name) {
SQLiteDatabase database = myDBHelper.getWritableDatabase();
if (database.isOpen()) {
database.execSQL("delete from user where name=?", new Object[]{name});
}
database.close();
}
//更新一条数据
public void updatePerson( String newName,String name) {
SQLiteDatabase database = myDBHelper.getWritableDatabase();
if (database.isOpen()) {
database.execSQL("update user set name=? where name=?", new Object[]{newName, name});
}
database.close();
}
//查找所有person
public List<user> findAllPerson(){
List<user> userList = new ArrayList<user>();
SQLiteDatabase database = myDBHelper.getReadableDatabase();
if(database.isOpen()){
Cursor cursor = database.rawQuery("select * from user", null);
while(cursor.moveToNext()){
int nameIndex = cursor.getColumnIndex("name");
Person person = new Person(name);
personList.add(user);
}
}
database.close();
return uerList;
}
