如何在android SQLite数据库中存储和检索图像并将它们显示在gridview上
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how to store and retrieve images in android SQLite database and display them on a gridview
提问by user1427993
I am new to android. I created a table that has an itemName,Price and image. I am trying to retrieve the image and name fields and display them on a gridview
我是安卓新手。我创建了一个包含 itemName、Price 和 image 的表。我正在尝试检索图像和名称字段并将它们显示在网格视图上
Here is my create Database statement:
这是我的创建数据库语句：
DBAdapter class onCreate()
db.execSQL("CREATE TABLE "+ITEMS_TABLE+" ( "+ COLUMN_ITEM_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_ITEM_NAME +" TEXT, "+ COLUMN_ITEM_SPECS +" TEXT, " + COLUMN_ITEM_PRICE +
" NUMBER, " + COLUMN_ITEM_IMAGE + " BLOB, " + COLUMN_ITEM_QTY +" NUMBER)");
void AddItems(ItemsPojo itemsObj)
{
Log.i("in here", "item fields");
SQLiteDatabase db= DBHelper.getWritableDatabase();
if (db==null)
{
Log.i("nulll", "mnllllsg");
}
ContentValues cv=new ContentValues();
cv.put(COLUMN_ITEM_NAME, itemsObj.getItemName());
cv.put(COLUMN_ITEM_SPECS, itemsObj.getItemSpecs());
cv.put(COLUMN_ITEM_PRICE, itemsObj.getItemPrice());
cv.put(COLUMN_ITEM_QTY, itemsObj.getItemQty());
cv.put(COLUMN_ITEM_IMAGE, itemsObj.getItemImg());
long affectedColumnId = db.insert(ITEMS_TABLE, null, cv);
db.close();
}
public Bitmap getAllImages()
{
SQLiteDatabase db=DBHelper.getWritableDatabase();
//Cursor cur= db.rawQuery("Select "+colID+" as _id , "+colName+", "+colAge+" from "+employeeTable, new String [] {});
Cursor cur= db.rawQuery("SELECT * FROM "+ITEMS_TABLE,null);
//if(cur.getCount() > 0){
//Cursor c = mDb.query(" ... ");
cur.moveToFirst();
ByteArrayInputStream inputStream = new ByteArrayInputStream(cur.getBlob(cur.getColumnIndex(COLUMN_ITEM_IMAGE)));
Bitmap b = BitmapFactory.decodeStream(inputStream);
// }
return b;
}
In my Main Oncreate I populate my Database like this:
在我的 Main Oncreate 中，我像这样填充我的数据库：
Bitmap image = BitmapFactory.decodeResource(getResources(), R.drawable.red_bn);
ByteArrayOutputStream out = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.PNG, 100, out);
byte[] b = out.toByteArray();
String name;
name="QUEEN_BED1";
String specs = "blaBlaBla";
double price = 5420;
int qty = 10;
ItemsPojo itemsObj = new ItemsPojo(name,specs,price,b,qty);
db.AddItems(itemsObj);
I am now stuck, please can anyone help me to retrieve this picture and display it on a gridview?
我现在卡住了，请谁能帮我检索这张图片并将其显示在网格视图上？
回答by Jose L Ugia
The most efficient (and btw, most straight forward approach) is to save a bytearray of the image in your local database. For that you'll just need to use a TEXT datatype in your database. Like this:
最有效的（顺便说一句，最直接的方法）是将图像的字节数组保存在本地数据库中。为此，您只需要在数据库中使用 TEXT 数据类型。像这样：
CREATE TABLE IF NOT EXISTS Your_table ( id INTEGER PRIMARY KEY NOT NULL UNIQUE, someOtherField TEXT, pictureData TEXT);
There's one seamless way to avoid dealing with conversions: Just convert to Bitmap and back to bytearray in your setters and getters in such a way that you don't need to care about that in the whole dev cycle. Let's go for an example. Let's say you have an object user which is stored in your localDB for which you have an avatar.
有一种避免处理转换的无缝方法：只需在您的 setter 和 getter 中转换为 Bitmap 并返回到 bytearray，这样您就无需在整个开发周期中关心它。让我们举个例子。假设您有一个对象用户，该用户存储在您拥有头像的 localDB 中。
public class User {
private String email;
private String name;
private Drawable pictureDataDrawable;
public User() {}
public void setPictureData(byte[] pictureData) {
pictureDataDrawable = ImageUtils.byteToDrawable(pictureData);
}
public byte[] getPictureData(){
return ImageUtils.drawableToByteArray(pictureDataDrawable);
}
}
And wherever you retrieve your data from DB it'll be enough with adding something like that:
无论您从数据库中检索数据，添加以下内容就足够了：
user.setPictureData(cursor.getBlob(cursor.getColumnIndexOrThrow(DB_PICTURE_DATA_KEY)));
For the opposite way (writing the drawable to DB):
对于相反的方式（将 drawable 写入 DB）：
ContentValues c = new ContentValues();
c.put(DB_PICTURE_DATA_KEY, user.getPictureData());
...
Finally two easy methods in your ImageUtils to convert back and forth:
最后，您的 ImageUtils 中有两个简单的方法来回转换：
public static byte[] drawableToByteArray(Drawable d) {
if (d != null) {
Bitmap imageBitmap = ((BitmapDrawable) d).getBitmap();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
imageBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] byteData = baos.toByteArray();
return byteData;
} else
return null;
}
public static Drawable byteToDrawable(byte[] data) {
if (data == null)
return null;
else
return new BitmapDrawable(BitmapFactory.decodeByteArray(data, 0, data.length));
}
And you're good to go.
你很高兴去。
回答by B. TIger
It depends on how you want to store your Image, because you are storing as a byte array here is how to retrieve it
这取决于您想如何存储图像，因为您将存储为字节数组，这里是如何检索它
public Cursor fetchAll() {
return databaseHelper.query(ITEMS_TABLE, new String[] { COLUMN_ITEM_ID, COLUMN_ITEM_NAME, COLUMN_ITEM_SPECS,COLUMN_ITEM_PRICE, COLUMN_ITEM_IMAGE,COLUMN_ITEM_QTY},null, null, null, null, null);
}
/* this method will give you a cursor with all the records of your database table now you need to parse these records on to objects*/
private List<ItemsPojo> parse(Cursor cursor) {
List<ItemsPojo> toReturn = null;
toReturn = new ArrayList<SignImage>();
ItemsPojo obj;
if (cursor.moveToFirst()) {
while (cursor.isAfterLast() == false) {
obj = new ItemsPojo();
obj.setId(cursor.getInt(0));
obj.setItemName(cursor.getString(1));
obj.setItemSpecs(cursor.getString(2));
obj.setItemPrice(cursor.getDouble(3));
obj.setItemImg(cursor.getBlob(4));
obj.setItemQuantity(cursor.getInt(5));
toReturn.add(obj);
cursor.moveToNext();
}
}return toReturn;
}
now you have a List with all your records on your database, now what you need to do is create a ListActivity and show all your objects on it, If you dont know how to do this please post your comment here or if you have any doubt about the procedure above
现在您有一个包含数据库中所有记录的列表，现在您需要做的是创建一个 ListActivity 并在其上显示您的所有对象，如果您不知道如何执行此操作，请在此处发表您的评论，或者如果您有任何疑问关于上述程序
