数据库sql的简单操作

[YXTS122]

DatabaseHelper.java

package com.selfteaching.learningdatabases;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper{
	public DatabaseHelper(Context context)
	{
		super(context,"myfirst.db",null,2);
	}
	
	public void onCreate(SQLiteDatabase db)
	{
		String DATABASE_CREATE="create table books(_id integer primary key autoincrement,name text,authors text);";
		db.execSQL(DATABASE_CREATE);
	}
	
	public void onUpgrade(SQLiteDatabase db,int arg1,int arg2)
	{
		String sql="DROP TABLE IF EXISTS books";
		db.execSQL(sql);
		this.onCreate(db);
	}
	
}
  

DBAdapter.java

package com.selfteaching.learningdatabases;

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

public class DBAdapter {
	Context context;
	DatabaseHelper DBHelper;
	SQLiteDatabase db;
	public DBAdapter(Context ctx)
	{
		this.context=ctx;
		DBHelper=new DatabaseHelper(context);
	}
	public DBAdapter open() throws SQLException
	{
		db=DBHelper.getWritableDatabase();
		return this;
	}
	public void close()
	{
		DBHelper.close();
	}
	public long insertBook(String name,String authors)
	{
		ContentValues initialValues=new ContentValues();
		initialValues.put("name", name);
		initialValues.put("authors", authors);
		return db.insert("books", null, initialValues);
	}
	public boolean deleteBook(long rowId)
	{
		return db.delete("books", "_id="+rowId, null)>0;
	}
	public Cursor getAllBooks()
	{
		return db.query("books", new String[]{"_id","name","authors"}, null, null, null, null, null);
	}
    public Cursor getBook(long rowId) throws SQLException
    {
    	Cursor mCursor=db.query(true, "books", new String[]{"_id","name","authors"}, "_id="+rowId, null, null, null, null, null);
    	if (mCursor!=null)
    	{
    		mCursor.moveToFirst();
    	}
    	return mCursor;
    }
    public boolean updateBook(long rowId,String name,String authors)
	{
		ContentValues args=new ContentValues();
		args.put("name", name);
		args.put("authors", authors);
		return db.update("books", args, "_id="+rowId, null)>0;
	}
}
  

LearningDatabasesActivity.java

package com.selfteaching.learningdatabases;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class LearningDatabasesActivity extends Activity {
    DBAdapter db;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_learning_databases);
		db=new DBAdapter(this);
		
		db.open();
		long id=db.insertBook("Learning Android", "Jim");
		id=db.insertBook("Learning Python", "Tom");
		db.close();
		
		db.open();
		Cursor c=db.getAllBooks();
		if (c.moveToFirst())
		{
			do
			{
				DisplayBook(c);
			}
			while (c.moveToNext());
		}
		db.close();
		
		db.open();
		c=db.getBook(2);
		if (c.moveToFirst())
		{
			DisplayBook(c);
		}
		else
		{
			Toast.makeText(this, "没找到书!", Toast.LENGTH_LONG).show();
		}
		db.close();
		
		db.open();
		if (db.updateBook(1, "Learning Android 2", "Smith"))
		{
			Toast.makeText(this, "更新成功!", Toast.LENGTH_LONG).show();
		}
		else
		{
			Toast.makeText(this, "更新失败!", Toast.LENGTH_LONG).show();
		}
		db.close();
		
		db.open();
		if (db.deleteBook(1))
		{
			Toast.makeText(this, "删除成功!", Toast.LENGTH_LONG).show();
		}
		else
		{
			Toast.makeText(this, "删除失败!", Toast.LENGTH_LONG).show();
		}
		db.close();
	}
	
	public void DisplayBook(Cursor c)
	{
		Toast.makeText(this, "id:"+c.getString(0)+"\n Name:"+c.getString(1)+"\n Authors:"+c.getString(2), Toast.LENGTH_LONG).show();
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.learning_databases, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}
  

[chinahbbt]