-Android数据库SQLiteDatabase的使用

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。
第三种是数据库SQLiteDatabase存储。

文件存储我就不多说了，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。详细可以参见本系列《Android高手进阶教程》7.Android Preferences的使用

今天我们将讲一下Android 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。

为了让大家更好的掌握，我们手把手完成该节的Demo。

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这个类要继承于android.database.sqlite.SQLiteOpenHelper抽象类，我们要实现其中两个方法：onCreate(),onUpdate。具体代码如下：

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

}
}

第五步:运行程序效果如下：

第六步：查看我们所建的数据库。有两种方法：第一种用命令查看：adb shell ls data/data/com.android.tutor/databases。

另一种方法是用DDMS查看，在data/data下面对应的应用程序的包名 下会有如下数据库，如图所示：