android将图片转换存到数据库再从数据库读取转换成图片实现代码

首先，我们要把图片存入到数据库中，首先要创建一个数据库， 如下所示：

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 {

    //数据库的字段
    public static class picturecolumns implements basecolumns {
        public static final string picture = "picture";
    }

    private context mcontext;

    //数据库名
    private static final string database_name = "picture.db";
    //数据库版本号
    private static final int database_version = 1;
    //表名
    private static final string table_name = "picture";

    //创建数据库
    public picturedatabase (context context) {
        super(context, database_name, null, database_version);
        this.mcontext = context;
    }

    //创建表并初始化表
    @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);
    }

    //将转换后的图片存入到数据库中
    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);
    }

    //将drawable转换成可以用来存储的byte[]类型
    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();
    }

    //更新数据库
    @override
    public void onupgrade (sqlitedatabase db, int oldversion, int newversion) {
        string sql = " drop table if exists " + table_name;
        db.execsql(sql);
        oncreate(db);
    }
}

代码注释的比较详细.

这里重点要说的是初始化数据库的时候，将drawable转变成byte[]的时候，先讲drawable转换成bitmap，然后将bitmap存入字节数据输出流，从输出流里获取byte[]数组。

bytearrayoutputstream os = new bytearrayoutputstream();
bitmap.compress(compressformat.png, 100, os);
return os.tobytearray();

之后将字符数组存入到类型为blob的数据库中去。

contentvalues cv = new contentvalues();
cv.put(picturecolumns.picture, getpicture(drawable));
db.insert(table_name, null, cv);

之后在代码中从数据库中取出byte[]，然后转换成drawable，设置图片即可。

代码如下：

package com.android.test;

import java.util.arraylist;

import android.app.activity;
import android.database.cursor;
import android.database.sqlite.sqlitedatabase;
import android.graphics.bitmap;
import android.graphics.bitmapfactory;
import android.graphics.drawable.bitmapdrawable;
import android.graphics.drawable.drawable;
import android.os.bundle;
import android.widget.imageview;

public class testpicture extends activity {

    @override
    protected void oncreate (bundle savedinstancestate) {
        super.oncreate(savedinstancestate);
        imageview iv = new imageview(this);
        if(getdrawable().size() != 0) {
            iv.setimagedrawable(getdrawable().get(0));
        }
        setcontentview(iv);
    }

   
    private arraylist<drawable> getdrawable() {
        picturedatabase pd = new picturedatabase(this);
        sqlitedatabase sd = pd.getwritabledatabase();

        arraylist<drawable> drawables = new arraylist<drawable>();

        //查询数据库
        cursor c = sd.query("picture", null, null, null, null, null, null);

        //遍历数据
        if(c != null && c.getcount() != 0) {
            while(c.movetonext()) {
                //获取数据
                byte[] b = c.getblob(c.getcolumnindexorthrow(picturedatabase.picturecolumns.picture));
                //将获取的数据转换成drawable
                bitmap bitmap = bitmapfactory.decodebytearray(b, 0, b.length, null);
                bitmapdrawable bitmapdrawable = new bitmapdrawable(bitmap);
                drawable drawable = bitmapdrawable;
                drawables.add(drawable);
            }
        }
        return drawables;
    }
}

重点注意如何将数据库中取出的byte[]转换成drawable：

bitmap bitmap = bitmapfactory.decodebytearray(b, 0, b.length, null);
bitmapdrawable bitmapdrawable = new bitmapdrawable(bitmap);
drawable drawable = bitmapdrawable;

 

运行效果如下：