Android(安卓)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);}@Overridepublic 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 tableNamepublic Cursor query(String tableName) {db = getWritableDatabase();Cursor c = db.query(tableName, null, null, null, null, null, null);return c;}// Return cursor by SQL stringpublic 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 querypublic void execSQL(String sql) {db = getWritableDatabase();db.execSQL(sql);}// Delete by idpublic 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();}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}// Bitmap to byte[]public byte[] bmpToByteArray(Bitmap bmp) {// Default size is 32 bytesByteArrayOutputStream bos = new ByteArrayOutputStream();try {bmp.compress(Bitmap.CompressFormat.JPEG, 100, bos);bos.close();} catch (IOException e) {e.printStackTrace();}return bos.toByteArray();}// Cursor to bitmapBitmap 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helperprivate 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"));

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