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：

复制代码 代码如下:

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。

复制代码 代码如下:

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。

复制代码 代码如下:

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：

复制代码 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：

复制代码 代码如下:

Bitmap bitmap = BitmapFactory.decodeByteArray(b, 0, b.length, null);

BitmapDrawable bitmapDrawable = new BitmapDrawable(bitmap);

Drawable drawable = bitmapDrawable;

运行效果如下：