Android学习笔记-SQLite的使用
界面文件activity_main.xml
<Button android:id="@+id/createButton" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/hello_world" android:text="create database"/> <Button android:id="@+id/updateButton" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/createButton" android:text="update database"/> <Button android:id="@+id/insertButton" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/updateButton" android:text="insert database"/> <Button android:id="@+id/updateRecordButton" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/insertButton" android:text="update record"/> <Button android:id="@+id/queryRecordButton" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/updateRecordButton" android:text="Query record"/>
DatabaseHelper.java
package com.example.sqlite_01;
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);
}
public DatabaseHelper(Context context, String name, int version) {
this(context, name, null, version);
}
public DatabaseHelper(Context context, String name) {
this(context, name, VERSION);
}
//第一次创建数据库的时候执行，实际上是在第一次得到SQLiteDatabase对象的时候调用
@Override
public void onCreate(SQLiteDatabase db) {
System.out.println("Create a database");
db.execSQL("create table user(id int, name varchar(20))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println("Update a database");
}
/*
* abd shell进入当前App的目录下的databases目录下就可以看到创建的数据库
* 打开数据库sqlite3 test_db
* 查看当前数据库里的表以及创建表的语句 .schema
*/
}
MainActivity.java
package com.example.sqlite_01;
import android.support.v7.app.ActionBarActivity;
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.Button;
public class MainActivity extends ActionBarActivity {
private Button createButton = null;
private Button updateButton = null;
private Button insertButton = null;
private Button updateRecordButton = null;
private Button queryRecordButton = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
createButton = (Button) findViewById(R.id.createButton);
updateButton = (Button) findViewById(R.id.updateButton);
insertButton = (Button) findViewById(R.id.insertButton);
updateRecordButton = (Button) findViewById(R.id.updateRecordButton);
queryRecordButton = (Button) findViewById(R.id.queryRecordButton);
createButton.setOnClickListener(new CreateListener());
updateButton.setOnClickListener(new UpdateListener());
insertButton.setOnClickListener(new InsertListener());
updateRecordButton.setOnClickListener(new UpdateRecordListener());
queryRecordButton.setOnClickListener(new QueryListener());
}
class CreateListener implements OnClickListener{
@Override
public void onClick(View v) {
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db");
SQLiteDatabase db = dbHelper.getReadableDatabase();//执行了这一句才会创建数据库
}
}
class UpdateListener implements OnClickListener{
@Override
public void onClick(View v) {
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db", 2);
SQLiteDatabase db = dbHelper.getReadableDatabase();//执行了这一句才会创建数据库
}
}
class InsertListener implements OnClickListener{
@Override
public void onClick(View v) {
ContentValues contentValues = new ContentValues();
contentValues.put("id", 1);
contentValues.put("name", "umgsai");
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db", 2);
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.insert("user", null, contentValues);
}
}
class UpdateRecordListener implements OnClickListener{
@Override
public void onClick(View v) {
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db", 2);
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "admin");
db.update("user", values, "id = ?", new String[]{"1"});
}
}
class QueryListener implements OnClickListener{
@Override
public void onClick(View v) {
DatabaseHelper dbHelper = new DatabaseHelper(MainActivity.this, "test_db", 2);
SQLiteDatabase db = dbHelper.getReadableDatabase();
//db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy)
Cursor cursor = db.query("user", new String[]{"id", "name"}, "id = ?", new String[]{"1"}, null, null, "id");
while (cursor.moveToNext()) {
String name = cursor.getString(cursor.getColumnIndex("name"));
System.out.println("name>>>" + name);
}
}
}
}
可以通过adb shell命令来查看数据库
>abd shell
>ls -l (查看当前目录下的文件及文件夹)
>cd data (进入data目录)
>ls -l (查看当前目录下的文件及文件夹)
>cd data (进入data目录)
>ls -l (查看当前目录下的文件及文件夹)
>cd com.example.sqlite_01 (进入当前项目目录)
>ls -l (查看当前目录下的文件及文件夹)
>cd databases (进入databases目录)
>ls -l (此时就可以看到数据库文件test_db)
>sqlite3 test_db (使用sqlite打开test_db数据库)
>.schema (查看当前数据库中的表以及建表的语句)
>select * from user; (从user表中查询数据)