java - 从可绘制图像到数据库

Question

我搜索过很多不同的帖子和教程，但我似乎不知道如何将我的图像保存在数据库中。

似乎每次我尝试将图像放入数据库时​​，都会导致数据库无法创建，然后我会强制关闭。我希望得到一些帮助。

这是我的代码

 package com.ondrovic.boombozzpassport;

 import java.io.ByteArrayOutputStream;
 import java.io.IOException;

 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.BitmapFactory;
 import android.provider.BaseColumns;
 import android.util.Log;

 public class Database extends SQLiteOpenHelper implements BaseColumns {
     private final static String DB_NAME = "boombozz.db";
     private final static int DB_VERSION = 1;
     static final String TABLE_BEERS = "beers";
     static final String COL_NAME = "name";
     static final String COL_BREWER = "brewer";
     static final String COL_ABV = "abv";
     static final String COL_RATE = "rating";
     static final String COL_BDESC = "breifdescription";
     static final String COL_FDESC = "fulldescription";
     static final String COL_TYPE = "type";
     static final String COL_PIC = "picture";

     private Context mContext;
     private Bitmap picture = null;

 public Database(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE beers (" + "_id INTEGER PRIMARY KEY, "
            + "name TEXT, " + "brewer TEXT, " + "abv REAL, "
            + "rating REAL, " + "breifdescription TEXT, "
            + "fulldescription TEXT, " + "type TEXT, " + "picture BLOB);");

    addBeer(db, "NAME 1", "BREWER 1", "TYPE 1", "BDESC 1", "FDESC 1", 0, 0, R.drawable.beer1);

}

private void addBeer(SQLiteDatabase db, String name, String brewer,
        String type, String bdesc, String fdesc, int abv, int rate, int image) {
    final ContentValues cv = new ContentValues();
    cv.put(COL_NAME, name);
    cv.put(COL_BREWER, brewer);
    cv.put(COL_TYPE, type);
    cv.put(COL_BDESC, bdesc);
    cv.put(COL_FDESC, fdesc);
    cv.put(COL_ABV, abv);
    cv.put(COL_RATE, rate);


    final Bitmap bitmap = BitmapFactory.decodeResource(
            mContext.getResources(), image);
    writeBitmap(cv, COL_PIC, bitmap);

    db.insert(TABLE_BEERS, null, cv);
}

static void writeBitmap(ContentValues cv, String name, Bitmap image) {
    if (image != null) {
        try {
            int size = image.getWidth() * image.getHeight() * 2;
            ByteArrayOutputStream out = new ByteArrayOutputStream(size);

            image.compress(CompressFormat.PNG, 100, out);
            out.flush();
            out.close();

            cv.put(name, out.toByteArray());

        } catch (IOException e) {

        }
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    Log.w("onUpgrade", "Upgrading database from version: " + oldVersion
            + " to version: " + newVersion);
    db.execSQL("DROP TABLE IF EXISTS beers");
}
}

Answer 1

您正在下载这些图像吗？如果是，请按照 Venkata Krishna 的建议将其保存到 SDCard/手机内存中。将图像保存到磁盘中非常简单。

首先我们创建一个方法来检查是否可以读取和写入外部存储磁盘。

/**
 * @return true if the external storage is mounted or read only.
 */
public static boolean isExternalStorageReadable() {
    String state = Environment.getExternalStorageState();
    return Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state);
}

/**
 * @return true if the external storage is mounted and writable.
 */
public static boolean isExternalStorageWritable() {
    String state = Environment.getExternalStorageState();
    return Environment.MEDIA_MOUNTED.equals(state);
}

然后，另一种方法将检查外部存储磁盘中是否有足够的可用空间。

/**
 * @return the amount of free space on the external storage.
 */
public static long getAvailableExternalMemorySize() {
    File path = Environment.getExternalStorageDirectory();
    StatFs stat = new StatFs(path.getPath());
    long blockSize = stat.getBlockSize();
    long availableBlocks = stat.getAvailableBlocks();
    return availableBlocks * blockSize;
}

现在我们创建一个方法来告诉我们是否可以将文件存储在 SD 卡中。

/**
 * @return true if the external storage is available, writable, 
 * and contains enough free space.
 */
public static boolean isExternalStorageAvailable() {
    if (!isExternalStorageWritable()) return false;
    long availableSize = getAvailableExternalMemorySize();
    if (availableSize < REQUIRED_STORAGE_SPACE) {
        return false;
    }
    return true;
}

其中 REQUIRED_STORAGE_SPACE 是一个常量，表示您的应用将用于存储图像和其他内容的空间量。

现在我们将创建一个方法来存储图像。

/**
 * @return the File from the given filename.
 */
public static File getImageFile(String filename) {
    if (!isExternalStorageReadable()) return null;
    // The images folder path.
    String imagesFolder = Environment.getExternalStorageDirectory().getPath()
                          + "Android/data/your.app.package/images/";
    // Creating the file.
    File file = new File(imagesFolder + filename);        
    return file;
}

/**
 * Write the contents of the HTTP entity to the external 
 * storage if available and writable.
 */
public static boolean storeImage(HttpEntity entity, String filename) throws IOException     {
    if (isExternalStorageAvailable()) {
        File file = getImageFile(filename);
        if (file == null) return false;
        // Write to file output stream.
        FileOutputStream os = new FileOutputStream(file);
        entity.writeTo(os);
        os.close();
        return true;
    }
    return false;
}

将所有这些方法放入一个类中，例如 ImageHelper，检查 list 文件中是否有权限写入外部存储，然后就可以开始了。