从 url 获取图片到数据库 SQLite Android答案

【问题标题】：Getting picture from url to database SQLite Android从 url 获取图片到数据库 SQLite Android
【发布时间】：2016-04-02 07:47:52
【问题描述】：

所以，我有一个从 url 下载图像并将其传输到 byte[] 的方法。然后，我将该字节 [] 放入我的数据库中。我在列中使用了 blob 类型，但它给了我一个错误。下面是从url下载图片的方法：

public static byte[] getByteFromUrl(URL src) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    InputStream is = null;
    try {
        is = src.openStream();
        byte[] byteChunk = new byte[4096]; // Or whatever size you want to read in at a time.
        int n;

        while ((n = is.read(byteChunk)) > 0) {
            baos.write(byteChunk, 0, n);
        }
        return baos.toByteArray();
    } catch (IOException e) {
        System.err.printf("Failed while reading bytes from %s: %s", src.toExternalForm(), e.getMessage());
        e.printStackTrace();
        // Perform any other exception handling that's appropriate.
    } finally {
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return null;
}

以及插入数据库的方法：

/**
 * Method for adding UserData into local database
 *
 * @param userData object that has all the user data information
 * @param id       id of the user
 */
public void addUserData(UserData userData, long id, byte[] picture) {
    SQLiteDatabase db = getWritableDatabase();
    ContentValues values = new ContentValues();

    values.put(USER_DATA_ID, id);
    values.put(USER_DATA_FIRST_NAME, userData.getFistName());
    values.put(USER_DATA_LAST_NAME, userData.getLastName());
    values.put(USER_DATA_NICK_NAME, userData.getNickname());
    values.put(USER_DATA_DISPLAY_NAME, userData.getHowPeopleSeeMe());
    values.put(USER_DATA_EMAIL, userData.getEmail());
    values.put(USER_DATA_PHONE_NUMBER, userData.getMobilePhoneNumber());
    values.put(USER_DATA_GENDER, userData.getGender());
    values.put(USER_DATA_RATING, userData.getReliabilityRating());
    values.put(USER_DATA_PASSWORD, userData.getPassword());
    values.put(USER_DATA_PICTURE, picture);

    db.insert(TABLE_USER_DATA, null, values);
}

现在，一切顺利，直到我想从数据库中获取所有内容：

/**
 * Method that fetches user data from local database
 *
 * @return UserData object is returned
 */
public UserData getUserData() {
    UserData userData = new UserData();
    SQLiteDatabase db = getReadableDatabase();
    String selectQuery = "SELECT * FROM " + TABLE_USER_DATA;
    Cursor c = db.rawQuery(selectQuery, null);
    if (c.moveToFirst()) {
        do {
            long id = c.getLong(0);
            userData.setFistName(c.getString(1));
            userData.setLastName(c.getString(2));
            userData.setNickname(c.getString(3));
            userData.setHowPeopleSeeMe(c.getString(4));
            userData.setEmail(c.getString(5));
            userData.setMobilePhoneNumber(c.getString(6));
            userData.setGender(c.getInt(7));
            userData.setPicture(c.getBlob(8) != null ? getImage(c.getBlob(8)) : null);
            userData.setReliabilityRating(c.getInt(9));
            userData.setPassword(c.getString(10));
            return userData;
        } while (c.moveToNext());

    }
    c.close();
    return null;
}

getImage 方法在哪里：

 /**
 * Method for converting bytes to bitmap
 *
 * @param image bytes[] that we are converting to bitmap
 * @return bitmap image
 */
public Bitmap getImage(byte[] image) {
    return BitmapFactory.decodeByteArray(image, 0, image.length);
}

我得到的错误是下一个：

    12-28 13:41:32.348 8057-8057/share.advice.khalifa.adviceshare E/CursorWindow: Failed to read row 0, column 0 from a CursorWindow which has 0 rows, 11 columns.
12-28 13:41:32.349 8057-8057/share.advice.khalifa.adviceshare D/AndroidRuntime: Shutting down VM
12-28 13:41:32.349 8057-8057/share.advice.khalifa.adviceshare E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: share.advice.khalifa.adviceshare, PID: 8057
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{share.advice.khalifa.adviceshare/share.advice.khalifa.adviceshare.ui.activities.MainActivity}: java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                    at android.os.Looper.loop(Looper.java:148)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                                 Caused by: java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                                                                                    at android.database.CursorWindow.nativeGetLong(Native Method)
                                                                                    at android.database.CursorWindow.getLong(CursorWindow.java:511)
                                                                                    at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:75)
                                                                                    at share.advice.khalifa.adviceshare.io.SQLDatabase.getUserData(SQLDatabase.java:178)
                                                                                    at share.advice.khalifa.adviceshare.io.model.Model.setUpModel(Model.java:179)
                                                                                    at share.advice.khalifa.adviceshare.ui.activities.MainActivity.onCreate(MainActivity.java:115)
                                                                                    at android.app.Activity.performCreate(Activity.java:6251)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:148) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

【问题讨论】：

从有 0 行 11 列的 CursorWindow 中读取第 0 行第 0 列，这意味着您的数据库是创建的空表，但没有任何值
@DarshanKachhadiya 知道这意味着什么，如何防止它发生？
查看堆栈跟踪 android.database.CursorWindow.getLong(CursorWindow.java:511) 这似乎是原因。
您不应该将图像放入 SQLite DB，因为光标窗口的大小不能超过 1mb。参考这个答案：stackoverflow.com/a/5981771/906362
最好在 sdcard 中创建目录并通过其名称保存和访问图像。在 sqlite 中保存图像不是一个好习惯。

标签： java android sqlite bitmap blob

【解决方案1】：

我不是 Android 专家，但我有点担心c.getLong(0);。

Failed to read row 0, column 0 from a CursorWindow which has 0 rows, 11 columns

您的光标是否返回 0 行？

【讨论】：

是的，它似乎不接受字节[]，因为当我在没有图片的情况下执行此操作时，一切正常。
在Android中你把blob数据类型作为图像
如果游标返回零行，那么根据文档，moveToFirst() 将返回 false，所以我认为这不是问题。
@JonasCz 这就是我的想法。那么，有什么解决办法吗？
@MiljanVulovic，在您将数据插入数据库的方法中，我没有看到实际将图像数据放入数据库中。也许这就是问题所在？

【解决方案2】：

在您将数据插入数据库的updateUserData 方法中，我没有看到实际将图像数据添加到数据库中。也许这就是问题所在？

【讨论】：

【解决方案3】：

好的，所以，你想这样做：

在创建时检查您要放置图片的目录是否存在：

private boolean createDir() {
        File myDir = new File(getCacheDir(), "profile_picture");
        Log.d("CreateDir", myDir.mkdir() ? "Yes" : "No");
        return myDir.mkdir();
    }

现在，你想从 byte[] 中的 URL 下载图片：

 // DownloadImage AsyncTask
    private class DownloadImage extends AsyncTask<String, Void, byte[]> {

        UserData userData;

        public DownloadImage(UserData userData) {
            this.userData = userData;
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected byte[] doInBackground(String... URL) {
            try {
                return ViewUtils.getByteFromUrl(new URL(URL[0]));
            } catch (MalformedURLException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(byte[] result) {
            File photo = new File(getCacheDir() + "/profile_picture/", "photo.jpg");
            if (photo.exists()) {
                photo.delete();
            }
            try {
                BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(photo));
                bos.write(result);
                bos.flush();
                bos.close();
            } catch (java.io.IOException e) {
                Log.e("PictureDemo", "Exception in photoCallback", e);
            }

        }

    }

在哪里

ViewUtils.getByteFromUrl(new URL(URL[0]));

是

public static byte[] getByteFromUrl(URL src) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        InputStream is = null;
        try {
            is = src.openStream();
            byte[] byteChunk = new byte[4096]; // Or whatever size you want to read in at a time.
            int n;

            while ((n = is.read(byteChunk)) > 0) {
                baos.write(byteChunk, 0, n);
            }
            return baos.toByteArray();
        } catch (IOException e) {
            System.err.printf("Failed while reading bytes from %s: %s", src.toExternalForm(), e.getMessage());
            e.printStackTrace();
            // Perform any other exception handling that's appropriate.
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

现在您已成功将图像保存到本地存储。

【讨论】：

那么，不要将图像存储为 blob？
@MiljanVulovic 不，光标有限制，所以最好将图像存储在本地并作为字节[]。