Android 继承SQLiteOpenHelper自定义DBHelper存取数据与图像

 

Android 继承SQLiteOpenHelper自定义DBHelper存取数据与图像如下：

package com.test;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class DBHelper extends SQLiteOpenHelper {

	private static final String DB_NAME = "test.db";
	private static final int DB_VERSION = 1;
	private static final String TABLE_NAME = "info";
	private static final String CREATE_INFO = "create table if not exists info("
			+ "id integer primary key autoincrement,name varchar(20),"
			+ "time varchar(20),img BLOB)";
	private SQLiteDatabase db;

	DBHelper(Context c) {
		//
		super(c, DB_NAME, null, DB_VERSION);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		this.db = db;
		db.execSQL(CREATE_INFO);
	}

	public void insert(ContentValues values, String tableName) {
		db = getWritableDatabase();
		db.insert(tableName, null, values);
		db.close();
	}

	// Return cursor with all columns by tableName
	public Cursor query(String tableName) {
		db = getWritableDatabase();
		Cursor c = db.query(tableName, null, null, null, null, null, null);
		return c;
	}

	// Return cursor by SQL string
	public Cursor rawQuery(String sql, String[] args) {
		db = getWritableDatabase();
		Cursor c = db.rawQuery(sql, args);
		return c;
	}

	// Execute a single SQL statement(as insert,create,delete)instead of a query
	public void execSQL(String sql) {
		db = getWritableDatabase();
		db.execSQL(sql);
	}

	// Delete by id
	public void del(int id) {
		if (db == null)
			db = getWritableDatabase();
		db.delete(TABLE_NAME, "id=?", new String[] { String.valueOf(id) });
	}

	public void close() {
		if (db != null)
			db.close();
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
	}

	// Bitmap to byte[]
	public byte[] bmpToByteArray(Bitmap bmp) {
		// Default size is 32 bytes
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		try {
			bmp.compress(Bitmap.CompressFormat.JPEG, 100, bos);
			bos.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return bos.toByteArray();
	}

	// Cursor to bitmap
	Bitmap cursorToBmp(Cursor c, int columnIndex) {

		byte[] data = c.getBlob(columnIndex);
		try {
			return BitmapFactory.decodeByteArray(data, 0, data.length);
		} catch (Exception e) {
			return null;
		}
	}

}

DBhelper调用方法：

//定义helper
private static DBHelper helper;
//创建helper
 helper = new DBHelper(this);
//插入数据与图像
ContentValues values = new ContentValues();
values.put("name", "test");
values.put("img", helper.bmpToByteArray(bmp));
helper.insert(values, "info");
//访问数据与图像
Cursor c = helper.rawQuery("select * from info", null);
c.moveToLast();
String name = c.getString(c.getColumnIndex("name"));
Bitmap bmp = cursorToBmp(c, c.getColumnIndex("img"));