Android数据库SQList的使用示例

Android 提供了三种数据存储方式，第一种是文件存储;第二种是SharedPreferences存储;第三种就是数据库SQLiteDatabase存储。文件存储我就不用多说了，而SharedPreferences可以存取简单的数据(int,double,float.etc)，它经常用于数据缓存，因为它读取存储简单。今天我们将讲一下SQLiteDatabase的使用。而掌握SqliteDatabase，将会我们接下来掌握ContentProvider打下良好的基石。

第一步：新建一个Android工程，命名为SQLiteDatabaseDemo.

第二步:创建一个新的类BooksDB.java这个类要继承

package com.android.tutor;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class BooksDB extends SQLiteOpenHelper {
private final static String DATABASE_NAME = "BOOKS.db";
private final static int DATABASE_VERSION = 1;
private final static String TABLE_NAME = "books_table";
public final static String BOOK_ID = "book_id";
public final static String BOOK_NAME = "book_name";
public final static String BOOK_AUTHOR = "book_author"; 

public BooksDB(Context context) {
// TODO Auto-generated constructor stub
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//创建table
@Override
public void onCreate(SQLiteDatabase db) {
String sql = "CREATE TABLE " + TABLE_NAME + " (" + BOOK_ID
+ " INTEGER primary key autoincrement, " + BOOK_NAME + " text, "+ BOOK_AUTHOR +" text);";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;
db.execSQL(sql);
onCreate(db);
} 

public Cursor select() {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db
.query(TABLE_NAME, null, null, null, null, null, null);
return cursor;
}
//增加操作
public long insert(String bookname,String author)
{
SQLiteDatabase db = this.getWritableDatabase();
/* ContentValues */
ContentValues cv = new ContentValues();
cv.put(BOOK_NAME, bookname);
cv.put(BOOK_AUTHOR, author);
long row = db.insert(TABLE_NAME, null, cv);
return row;
}
//删除操作
public void delete(int id)
{
SQLiteDatabase db = this.getWritableDatabase();
String where = BOOK_ID + " = ?";
String[] whereValue ={ Integer.toString(id) };
db.delete(TABLE_NAME, where, whereValue);
}
//修改操作
public void update(int id, String bookname,String author)
{
SQLiteDatabase db = this.getWritableDatabase();
String where = BOOK_ID + " = ?";
String[] whereValue = { Integer.toString(id) }; 

ContentValues cv = new ContentValues();
cv.put(BOOK_NAME, bookname);
cv.put(BOOK_AUTHOR, author);
db.update(TABLE_NAME, cv, where, whereValue);
}
}第三步:修改main.xml布局如下，由两个EditText和一个ListView组成，代码如下:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 

android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<EditText
android:id="@+id/bookname"
android:layout_width="fill_parent"
android:layout_height="wrap_content" 

>
</EditText>
<EditText
android:id="@+id/author"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
</EditText>
<ListView
android:id="@+id/bookslist" 

android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
</ListView>
</LinearLayout> 第四步:修改SQLiteDatabaseDemo.java代码如下:

package com.android.tutor;
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class SQLiteDatabaseDemo extends Activity implements AdapterView.OnItemClickListener {
private BooksDB mBooksDB;
private Cursor mCursor;
private EditText BookName;
private EditText BookAuthor;
private ListView BooksList; 

private int BOOK_ID = 0;
protected final static int MENU_ADD = Menu.FIRST;
protected final static int MENU_DELETE = Menu.FIRST + 1;
protected final static int MENU_UPDATE = Menu.FIRST + 2; 

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setUpViews();
} 

public void setUpViews(){
mBooksDB = new BooksDB(this);
mCursor = mBooksDB.select(); 

BookName = (EditText)findViewById(R.id.bookname);
BookAuthor = (EditText)findViewById(R.id.author);
BooksList = (ListView)findViewById(R.id.bookslist); 

BooksList.setAdapter(new BooksListAdapter(this, mCursor));
BooksList.setOnItemClickListener(this);
} 

@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu); 

menu.add(Menu.NONE, MENU_ADD, 0, "ADD");
menu.add(Menu.NONE, MENU_DELETE, 0, "DELETE");
menu.add(Menu.NONE, MENU_DELETE, 0, "UPDATE");
return true;
} 

public boolean onOptionsItemSelected(MenuItem item)
{
super.onOptionsItemSelected(item);
switch (item.getItemId())
{
case MENU_ADD:
add();
break;
case MENU_DELETE:
delete();
break;
case MENU_UPDATE:
update();
break;
}
return true;
} 

public void add(){
String bookname = BookName.getText().toString();
String author = BookAuthor.getText().toString();
//书名和作者都不能为空，或者退出
if (bookname.equals("") || author.equals("")){
return;
}
mBooksDB.insert(bookname, author);
mCursor.requery();
BooksList.invalidateViews();
BookName.setText("");
BookAuthor.setText("");
Toast.makeText(this, "Add Successed!", Toast.LENGTH_SHORT).show();
} 

public void delete(){
if (BOOK_ID == 0) {
return;
}
mBooksDB.delete(BOOK_ID);
mCursor.requery();
BooksList.invalidateViews();
BookName.setText("");
BookAuthor.setText("");
Toast.makeText(this, "Delete Successed!", Toast.LENGTH_SHORT).show();
} 

public void update(){
String bookname = BookName.getText().toString();
String author = BookAuthor.getText().toString();
//书名和作者都不能为空，或者退出
if (bookname.equals("") || author.equals("")){
return;
}
mBooksDB.update(BOOK_ID, bookname, author);
mCursor.requery();
BooksList.invalidateViews();
BookName.setText("");
BookAuthor.setText("");
Toast.makeText(this, "Update Successed!", Toast.LENGTH_SHORT).show();
} 

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 

mCursor.moveToPosition(position);
BOOK_ID = mCursor.getInt(0);
BookName.setText(mCursor.getString(1));
BookAuthor.setText(mCursor.getString(2)); 

} 

public class BooksListAdapter extends BaseAdapter{
private Context mContext;
private Cursor mCursor;
public BooksListAdapter(Context context,Cursor cursor) { 

mContext = context;
mCursor = cursor;
}
@Override
public int getCount() {
return mCursor.getCount();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
TextView mTextView = new TextView(mContext);
mCursor.moveToPosition(position);
mTextView.setText(mCursor.getString(1) + "___" + mCursor.getString(2));
return mTextView;
} 

}
}