简单的读取数据库 SQLiteOpenHelper

DBAdapter.java

 

package com.android.db;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DBAdapter
{
public static final String KEY_ROWID = "_id";
public static final String KEY_ISBN = "isbn";
public static final String KEY_TITLE = "title";
public static final String KEY_PUBLISHER = "publisher";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "books";
private static final String DATABASE_TABLE = "titles";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table titles (_id integer primary key autoincrement, "
+ "isbn text not null, title text not null, "
+ "publisher text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS titles");
onCreate(db);
}
}
//---打开数据库---

public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---关闭数据库---

public void close()
{
DBHelper.close();
}
//---向数据库中插入一个标题---

public long insertTitle(String isbn, String title, String publisher)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_ISBN, isbn);
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_PUBLISHER, publisher);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---删除一个指定标题---

public boolean deleteTitle(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID +
"=" + rowId, null) > 0;
}
//---检索所有标题---

public Cursor getAllTitles()
{
return db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_ISBN,
KEY_TITLE,
KEY_PUBLISHER},
null,
null,
null,
null,
null);
}
//---检索一个指定标题---

public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_ISBN,
KEY_TITLE,
KEY_PUBLISHER
},
KEY_ROWID + "=" + rowId,
null,
null,
null,
null,
null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---更新一个标题---

public boolean updateTitle(long rowId, String isbn,
String title, String publisher)
{
ContentValues args = new ContentValues();
args.put(KEY_ISBN, isbn);
args.put(KEY_TITLE, title);
args.put(KEY_PUBLISHER, publisher);
return db.update(DATABASE_TABLE, args,
KEY_ROWID + "=" + rowId, null) > 0;
}
}

 

firstDB.java

 

package com.android.db;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class firstDB extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    DBAdapter db = new DBAdapter(this);
    db.open();
    long id;
    id = db.insertTitle(
    "0470285818",
    "C# 2008 Programmer's Reference",
    "Wrox");
    id = db.insertTitle(
    "047017661X",
    "Professional Windows Vista Gadgets Programming",
    "Wrox");
    db.close();
   
String ss="";
    db.open();
    Cursor c = db.getAllTitles();
    if (c.moveToFirst())
    {
    do {
//   
    ss=ss+    DisplayTitle(c);
    } while (c.moveToNext());
    }
    db.close();
    TextView tv=(TextView)findViewById(R.id.tv);
    tv.setText(ss);
    }
    public String DisplayTitle(Cursor c)
    {
    /*
        Toast.makeText(this,
    "id: " + c.getString(0) + "/n" +
    "ISBN: " + c.getString(1) + "/n" +
    "TITLE: " + c.getString(2) + "/n" +
    "PUBLISHER: " + c.getString(3),
    Toast.LENGTH_LONG).show();
    */
    return "id: " + c.getString(0) + "/n" +
    "ISBN: " + c.getString(1) + "/n" +
    "TITLE: " + c.getString(2) + "/n" +
    "PUBLISHER: " + c.getString(3);
    }
    }