如何將圖片轉換存入到數據庫中，並從數據庫中取出轉換成圖片

有時候咱們想把圖片存入到數據庫中，儘管這不是一種明智的選擇，但有時候仍是不得以會用到，下面說說將圖片轉換成byte[]數組存入到數據庫中去，並從數據庫中取出來轉換成圖像顯示出來。

　　首先，咱們要把圖片存入到數據庫中，首先要建立一個數據庫， 以下所示：

 

package com.android.test;

import java.io.ByteArrayOutputStream;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.provider.BaseColumns;

public class PictureDatabase extends SQLiteOpenHelper {
    
    //數據庫的字段
    public static class PictureColumns implements BaseColumns {
        public static final String PICTURE = "picture";
    }
    
    private Context mContext;
    
    //數據庫名
    private static final String DATABASE_NAME = "picture.db";
    //數據庫版本號
    private static final int DATABASE_Version = 1;
    //表名
    private static final String TABLE_NAME = "picture";
    
    //建立數據庫
    public PictureDatabase (Context context) {
        super(context, DATABASE_NAME, null, DATABASE_Version);
        this.mContext = context;
    }

    //建立表並初始化表
    @Override
    public void onCreate (SQLiteDatabase db) {
        String sql = "Create table " + TABLE_NAME + "(" + BaseColumns._ID
        + " integer primary key autoincrement," + PictureColumns.PICTURE
        + " blob not null);";
        db.execSQL(sql);
        
        //初始化
        initDataBase(db,mContext);
    }
    
    //將轉換後的圖片存入到數據庫中
    private void initDataBase (SQLiteDatabase db, Context context) {
        Drawable drawable = context.getResources().getDrawable(R.drawable.test_icon_resizer);
        ContentValues cv = new ContentValues();
        cv.put(PictureColumns.PICTURE, getPicture(drawable));
        db.insert(TABLE_NAME, null, cv);
    }

    //將drawable轉換成能夠用來存儲的byte[]類型
    private byte[] getPicture(Drawable drawable) {
        if(drawable == null) {
            return null;
        }
        BitmapDrawable bd = (BitmapDrawable) drawable;
        Bitmap bitmap = bd.getBitmap();
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        bitmap.compress(CompressFormat.PNG, 100, os);
        return os.toByteArray();
    }
    
    //更新數據庫
    @Override
    public void onUpgrade (SQLiteDatabase db, int oldVersion, int newVersion) {
        String sql = " DROP TABLE IF EXISTS " + TABLE_NAME;
        db.execSQL(sql);
        onCreate(db);
    } 
}