Android-SQLite使用总结
android中SQLiteDatabase的创建是通过SQLiteOpenHelper类的数据库获取方法完成的，其中包括getReadableDatabase()、getWritableDatabase()等。数据创建完成后，通过对数据库增、删、改、查等方法的重载，即可完成数据库操作的应用。
具体的SQLite使用的具体步骤如下：
1.新建一个继承自SQLiteOpenHelper的类DatabaseHelper；
2.通过DatabaseHelper的对象，调用其方法getReadableDatabase()，返回SQLiteDatabase数据库对象；
3.定义Button监听函数，再对应的监听函数中进行数据库增删改查操作。
下面以代码为主简单介绍起用法：
一、新建一个类DatabaseHelper，继承自SQLiteOpenHelper。类文件名DatabaseHelper.java，内容如下：
package com.example.sqlite.db;
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 = 1;
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){
this(context, name, VERSION);
}
public DatabaseHelper(Context context, String name, int version) {
// TODO Auto-generated constructor stub
this(context, name, null, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String sql = "create table user(id int, name varchar(20), score int)";
db.execSQL(sql);
System.out.println("create a database.");
}
@Override
public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {
// TODO Auto-generated method stub
System.out.println("update a database version.");
}
}
该类做了如下工作：1.重载了几个构造函数；2.重载了新建列表函数onCreate()。其中类的构造函数是为了传入数据库名称；列表创建函数重载是为了定义列表名称及结构。更多数据库的知识需另行学习。
二、主Activity文件
主Activity中主要定义了几个Button空间的监听函数，在对应的Button监听函数中完成数据库增删改查的操作。对数据库的操作一般有两种方式：1.通过SQLiteDatabase类的insert/delete/update/query等方法进行操作；2.通过SQLiteDatabase类的execSQL方法，使用数据库操作命令进行操作。
主Activity文件名MainActivity.java，具体内容如下：
package com.example.sqlite;
import android.R.integer;
import android.app.Activity;
import android.content.ContentValues;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import com.example.sqlite.db.DatabaseHelper;
public class MainActivity extends Activity {
//定义类的控件成员变量
private Button btn_ist = null;
private Button btn_dlt = null;
private Button btn_mdf = null;
private Button btn_qry = null;
private Button btn_crt = null;
private Button btn_upd = null;
private EditText edt_id = null;
private EditText edt_value = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//set background color
Resources res = getResources();
Drawable drawable = res.getDrawable(R.drawable.bkground);
this.getWindow().setBackgroundDrawable(drawable);
//通过id获取控件对象
btn_ist = (Button)findViewById(R.id.insert);
btn_dlt = (Button)findViewById(R.id.delete);
btn_mdf = (Button)findViewById(R.id.modify);
btn_qry = (Button)findViewById(R.id.query);
btn_crt = (Button)findViewById(R.id.createdb);
btn_upd = (Button)findViewById(R.id.updatedb);
edt_id = (EditText)findViewById(R.id.id);
edt_value=(EditText)findViewById(R.id.value);
//设置button的点击消息响应函数
//无名类定义的方式
btn_ist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
//获取edit text参数
String str = edt_id.getText().toString();
System.out.println("insert a data:"+str);
//if( str !="" )
{
int id_ist = Integer.parseInt(str);
String name_ist = edt_value.getText().toString();
//增加一条记录
ContentValues value = new ContentValues();
value.put("id", id_ist);
value.put("name", name_ist);
value.put("score", 100);
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx");
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.insert("user", null, value);
System.out.println("insert a data.");
}
//else
// System.out.println("Please input your record.");
}
});
//有名类定义的方式
btn_dlt.setOnClickListener(new deleteOnClickListener());
btn_mdf.setOnClickListener(new modifyOnClickListener());
btn_qry.setOnClickListener(new queryOnClickListener());
btn_crt.setOnClickListener(new createOnClickListener());
btn_upd.setOnClickListener(new updateOnClickListener());
//创建数据库助手类对象
}
class deleteOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
System.out.println("delete a data.");
String dlt_id = edt_id.getText().toString();
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx");
SQLiteDatabase db = dbHelper.getWritableDatabase();
//db.delete("user", "id=?", new String[]{dlt_id});
db.execSQL("delete from user where id="+dlt_id);//这句命令操作不能同时用多个条件限制
}
}
class modifyOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
System.out.println("modify a data.");
String mdf_id = edt_id.getText().toString();
String mdf_value = edt_value.getText().toString();
ContentValues value = new ContentValues();
value.put("score", mdf_value);
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx");
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.update("user", value, "id=?", new String[]{mdf_id});
}
}
class queryOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
System.out.println("query a data.");
//获取一条记录
String id_qry = edt_id.getText().toString();
//打开数据库
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx");
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("user", new String[]{"id","name","score"}, "id=?", new String[]{ id_qry }, null, null, null);
while (cursor.moveToNext())
{
String name = cursor.getString(cursor.getColumnIndex("name"));
String score = cursor.getString(cursor.getColumnIndex("score"));
System.out.println("query--->"+name+":"+score);
edt_value.setText(name+":"+score);
}
cursor.close();
}
}
class createOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//通过database helper创建数据库
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx");
SQLiteDatabase db = dbHelper.getReadableDatabase();
}
}
class updateOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//更新数据库版本号
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db_lx", 2);
SQLiteDatabase db = dbHelper.getReadableDatabase();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
注意：此处在每个Button监听函数中都重新new一个数据库Helper的类，并根据读写需求获取了相应的SQLiteDatabase对象。
三、其他文件内容
其他相关文件包括：布局文件activity_main.xml和strings.xml。内容分别如下：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#aaaaaa"
android:layout_weight="1"
android:gravity="left"
android:text="@string/id" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#aaaaaa"
android:layout_weight="1"
android:gravity="left"
android:text="@string/value"
/>
</LinearLayout>
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dip"
>
<EditText
android:id="@+id/id"
android:hint="@string/id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginRight="5dip"
android:background="#aaaaaa"
android:maxLines="1"
android:layout_weight="1" />
<EditText
android:id="@+id/value"
android:hint="@string/value"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginRight="5dip"
android:background="#aaaaaa"
android:maxLines="1"
android:layout_weight="1" />
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dip"
>
<Button
android:id="@+id/insert"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/insert"
android:clickable="true"
/>
<Button
android:id="@+id/delete"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/delete"
android:clickable="true"/>
<Button
android:id="@+id/modify"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/modify"
android:clickable="true"/>
<Button
android:id="@+id/query"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/query"
android:clickable="true"/>
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dip"
>
<Button
android:id="@+id/createdb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/createdb"
android:clickable="true"
/>
<Button
android:id="@+id/updatedb"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/updatedb"
android:clickable="true"/>
</LinearLayout>
</LinearLayout>
strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">sqlite</string>
<string name="action_settings">Settings</string>
<string name="hello_world">Hello world!</string>
<string name="id">id:</string>
<string name="value">value:</string>
<string name="operation">operation:</string>
<string name="insert">insert</string>
<string name="delete">delete</string>
<string name="modify">modifi</string>
<string name="query">query</string>
<string name="createdb">createdb</string>
<string name="updatedb">updatedb</string>
<drawable name="bkground">#000000</drawable>
</resources>