Question

我想使用此数据库代码将相机中的图像放入数据库中。保存按钮和预览按钮的代码应该是什么？

public class databases extends SQLiteOpenHelper {
        public static final String data = "student.db";
        public static final String TABLE_NAME = "Student_TABLE";
        public static final String COL_1 = "Fname";
        public static final String COL_2 = "password";
        public static final String COL_3 = "Fathers_name";
        public static final String COL_4 = "Roll";
        public static final String COL_5 = "Image";
        public databases(Context context) {
            super(context, data, null, 1);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL("create table " + TABLE_NAME + " (Fname TEXT,password TEXT,Fathers_name TEXT,Roll TEXT PRIMARY KEY,Image BLOB)");
        }

现在，这是包含相应按钮的活动代码。

public class home_page extends AppCompatActivity {
Button lout,homepage,showperson,picture;static final int REQUEST_IMAGE_CAPTURE = 1;
TextView showit;
String userid,pwrd,r2,r3,r4;
databases dbss;
    public void getterclass(String m)
    {
        userid=m;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_page);
        lout = (Button) findViewById(R.id.out);
        homepage = (Button) findViewById(R.id.home);
        showit=(TextView) findViewById(R.id.showtextdata);
        showperson=(Button)findViewById(R.id.showdata);
        picture=(Button)findViewById(R.id.images);
        dbss=new databases(home_page.this);
        getSupportActionBar().hide();
        homepage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent redirect=new Intent(home_page.this,home_page.class);
                startActivity(redirect);
            }
        });

        lout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent logout=new Intent(home_page.this,log_in.class);
                        startActivity(logout);
            }
        });
        showperson.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Cursor sh=dbss.givedata(userid);
                StringBuffer buf=new StringBuffer();
                buf.append("First name :" + sh.getString(0) + "\n");
                buf.append("password :" + sh.getString(1) + "\n");
                buf.append("Father's name :" + sh.getString(2) + "\n");
                buf.append("Roll :" + sh.getString(3) + "\n\n");
                showit.setText(buf.toString());
            }
        });
        picture.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
                    startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
                }
                databases help=new databases(home_page.this);
            }
        });

getterclass（）只不过是将用户的个人信息检索到其他活动中，但是当我尝试在同一活动中显示数据时，该方法就无法正常工作。

Answer 1

您将图像提取为一个字节[]，然后将其转换为字节，作为一个十六进制字符的字符串，然后将该字符串包含在 X' 中 your_hexadecimal_string < / em> '

例如可能是X'FFFEFDFCFBFA9........'

并使用该字符串作为通过本机SQL插入的值

例如INSERT INTO your_table (image_column) VALUES(X'FFFEFDFCFBFA9........')

或者您可以使用SQliteDatbase 插入便捷方法，该方法将Contentvalues对象作为第三个参数。您可以按照以下方式设置Contentvalues对象

ContentValues cv = new Contentvalues(); cv.put("Image",your_image_as_a_byte_array); db.insert("the_table_name",null,cv);

但是，存储图像可能会很麻烦，因此不建议存储图像，尤其是当图像的平均大小超过10万时。

如果图像接近或大于2M，您将无法使用标准的Android SQLite API检索该图像，因为CursorWindow的限制为2M。即使在1M时，您也可能在CursorWindow中获得1张图像。

推荐的方法是存储图像的路径或部分路径，并在需要时通过其路径检索图像。

示例

（上面）说，以下是一个应用程序，它将在图像小于100K（public static final int MAX_FILE_SIZE = 100 * 1024;）时将图像存储在数据库中，或者存储路径并通过该路径或数据库根据存储的内容。

该应用程序具有两个带有图像说明的ListView（最右边包括图像的路径）。单击任意一个中的项目都会显示图像。

例如

有很多图像超过100k，其中一个funny.png低于100k：-

对于此示例，图像已放置在Res文件夹的Raw文件夹中，然后将它们复制到data / data / files / images文件夹（其中代表应用程序包的名称）：-

DatabaseHelper DBHelper.java 是：-

public class DBHelper extends SQLiteOpenHelper { public static final String DBNAME = "images.db"; public static final int DBVERSION = 1; // The maximum size of an image that should be stored 100K public static final int MAX_FILE_SIZE = 100 * 1024; public static final String TB_IMAGE = "image"; public static final String COL_IMAGE_ID = BaseColumns._ID; public static final String COL_IMAGE_PATH = "image_path"; public static final String COL_IMAGE_NAME = "image_name"; public static final String COl_IMAGE_DESCRIPTION = "image_description"; public static final String COL_IMAGE_SIZE = "image_size"; public static final String COL_IMAGE_IMAGE = "image"; SQLiteDatabase mDB; /** * Construct DBHelper, note that it will open the database and * thus create it if it doesn't exist * @param context a context from the invoking activity */ public DBHelper(Context context) { super(context, DBNAME, null, DBVERSION); mDB = this.getWritableDatabase(); } /** * Create the table(s) * @param db */ @Override public void onCreate(SQLiteDatabase db) { String crtsql = "CREATE TABLE IF NOT EXISTS " + TB_IMAGE + "(" + COL_IMAGE_ID + " INTEGER PRIMARY KEY, " + COL_IMAGE_PATH + " TEXT UNIQUE, " + COL_IMAGE_NAME + " TEXT, " + COl_IMAGE_DESCRIPTION + " TEXT, " + COL_IMAGE_SIZE + " INTEGER, " + COL_IMAGE_IMAGE + " BLOB DEFAULT x'00'" + ")"; db.execSQL(crtsql); } @Override public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) { } /** * Return a Cursor with all the rows from the image table * @return The Cursor */ public Cursor getImageList() { return mDB.query(TB_IMAGE,null,null,null,null,null,null); } /** * Store an image row in the image table, noting that is the image * size is small than the max size that the image will be stored as a blob * otherwise a blob of 1 byte is stored due to the default value. * @param path the path to the image * @param description a description for the image * @return the id (rowid) of the row */ public long addImageFromPath(String path, String description) { ContentValues cv = new ContentValues(); File f = new File(path); InputStream is; // If the file doesn't exist don't store a row if (!f.exists()) { return -1; } // Always store the name, description, path and size cv.put(COL_IMAGE_NAME,f.getName()); cv.put(COl_IMAGE_DESCRIPTION,description); cv.put(COL_IMAGE_SIZE,f.length()); cv.put(COL_IMAGE_PATH,f.getAbsolutePath()); // If the size is less than the max then get the filestream // and convert to a byte[]. // Note if larger then the max file size the default x'00' blob // will be applied if (f.length() < MAX_FILE_SIZE) { byte[] buffer = new byte[(int) f.length()]; try { is = new FileInputStream(f); is.read(buffer); } catch (IOException e) { e.printStackTrace(); return -1; } cv.put(COL_IMAGE_IMAGE,buffer); } // Do the insert return mDB.insert(TB_IMAGE,null,cv); } /** * get the image as a bitmap from the DB if stored, otherwise get it from * the file, according to the id. * @param id the id of the row in the image table * @return the bitmap to be returned (note may be empty bitmap) */ public Bitmap getImage(long id) { byte[] ba = new byte[0]; // If the image is stored in the DB then extract and return the bitmap if (isStoredAsImage(id)) { return getImageAsBitMap(id); } // If not then get the respective row from the DB Cursor csr = mDB.query( TB_IMAGE, null, COL_IMAGE_ID+"=?", new String[]{String.valueOf(id)}, null, null, null ); // Prepare to convert the path to a file String path = ""; //<<<< default to empty path File f = new File(path); //<<< default to empty file // If a valid row was found get the path and File from the row if (csr.moveToFirst()) { path = csr.getString(csr.getColumnIndex(COL_IMAGE_PATH)); f = new File(path); } // done with the cursor so close it csr.close(); // If the file exists then return the Bitmap if (f.exists()) { return BitmapFactory.decodeFile(f.getAbsolutePath()); } // return an empty bitmap return BitmapFactory.decodeByteArray(ba,0,ba.length); } /** * Check to see if an image is stored in the DB, * note assumes anything less than 8 bytes isn't an image * @param id the id of the row in the image table * @return true if like an image is stored, otherwise false */ private boolean isStoredAsImage(long id) { boolean rv = true; byte[] ba = new byte[0]; // Get the respective row from the image table Cursor csr = mDB.query( TB_IMAGE, null, COL_IMAGE_ID+"=?", new String[]{String.valueOf(id)}, null, null, null ); // If a row was found get the blob into byte array ba // if not then ready to return false if (csr.moveToFirst()) { ba = csr.getBlob(csr.getColumnIndex(COL_IMAGE_IMAGE)); } else { rv = false; } // If the byte array ba is less then 8 bytes then ready to return false if (ba == null || ba.length < 8) { rv = false; } // done with the Cursor so close it csr.close(); // return the result return rv; } /** * get the image (assumes isStoredAsImage is used prior to invocation) * @param id the id of the respective row * @return the bitmap (may be 0 length) */ private Bitmap getImageAsBitMap(long id) { byte[] ba = new byte[0]; Bitmap bmp; Cursor csr =mDB.query( TB_IMAGE, null, COL_IMAGE_ID+"=?", new String[]{String.valueOf(id)}, null, null, null ); if (csr.moveToFirst()) { ba = csr.getBlob(csr.getColumnIndex(COL_IMAGE_IMAGE)); } csr.close(); return BitmapFactory.decodeByteArray(ba,0,ba.length); } }

调用活动 MainActivity.java 是：-

public class MainActivity extends AppCompatActivity { public static final String IMAGES_DIRECTORY = "images"; private static File images_file; ArrayAdapter<String> mAdapter; ListView mListView01, mListView02; ArrayList<String> mImages; CursorAdapter mCsrAdapter; Cursor mCsr; ImageView mImageView; DBHelper mDBHlpr; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // get the View/Viewgroup IDs mListView01 = this.findViewById(R.id.listview001); // File List mListView02 = this.findViewById(R.id.listview002); // DB List mImageView = this.findViewById(R.id.imageview001); // Image display // get an instance of the DBHelper mDBHlpr = new DBHelper(this); // Copy images from raw folder to data/data/<package>/Files/images // Also store all the images in the Database (or not depedning upon size) getImagesFile(this); if (getImagesCount() < 1) { loadRawImages(); storeImagesToDB(); } // Setup the two ListViews to display image name lists displayList(); displayListFromDB(); // setup the file list so that when an item is clicked the image is displayed mListView01.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) { String imagename = mListView01.getItemAtPosition(i).toString(); displayImage(imagename); } }); // setup the DB list so that when an item is clicked the image is displayed mListView02.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) { displayDBImage(l); } }); } /** * Store the images in the images folder to the DB giving then a calculated description * e.g. image1, image2 ..... */ private void storeImagesToDB() { File f = getImagesFile(this); File[] images = f.listFiles(); int imagecounter = 1; for (File img: images) { mDBHlpr.addImageFromPath(img.getPath(),"image" + String.valueOf(imagecounter++)); } } /** * return the directory/folder where the images are stored as a File * @param context a valid context * @return the number of images */ public static File getImagesFile(Context context) { if (images_file == null) { images_file = new File(context.getFilesDir().getPath() + File.separator + IMAGES_DIRECTORY); if (!images_file.exists()) { images_file.mkdirs(); } } return images_file; } /** * get the number of images * @return the number of images */ public static long getImagesCount() { File[] files = images_file.listFiles(new FileFilter() { @Override public boolean accept(File file) { return file.isFile(); } }); return (long) files.length; } /** * Setup/refresh the list of images according to the images folder * (left ListView) */ private void displayList() { if (mImages == null) { mImages = new ArrayList<>(); } else { mImages.clear(); } mImages.addAll(Arrays.asList(images_file.list())); if (mAdapter == null) { mAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, mImages); mListView01.setAdapter(mAdapter); } else { mAdapter.notifyDataSetChanged(); } } /** * Set the image view according to the file * @param imageName the name of the image (as per the ListView) */ private void displayImage(String imageName) { File img = new File(images_file.getPath() + File.separator + imageName); if (img.exists()) { Bitmap bmp = BitmapFactory.decodeFile(img.getAbsolutePath()); mImageView.setImageBitmap(bmp); } } /** * Set the image view according to the image stored/referred to by the DB * @param id the id of the respective row in the image table */ private void displayDBImage(long id) { mImageView.setImageBitmap(mDBHlpr.getImage(id)); } /** * Setup/refresh the list of images as obtained from the DB (right listview) */ private void displayListFromDB() { mCsr = mDBHlpr.getImageList(); if (mCsrAdapter == null) { mCsrAdapter = new SimpleCursorAdapter( this, android.R.layout.simple_list_item_2, mCsr, new String[]{DBHelper.COL_IMAGE_NAME,DBHelper.COL_IMAGE_PATH}, new int[]{android.R.id.text1,android.R.id.text2}, 0 ); mListView02.setAdapter(mCsrAdapter); } else { mCsrAdapter.swapCursor(mCsr); } } /** * Load (copy from raw folder to images folder) all images */ private void loadRawImages() { Field[] fields = R.raw.class.getFields(); int resourceID = 0; String resourceName; for (Field fld: fields) { resourceName = fld.getName(); try { resourceID = fld.getInt(fld); } catch (IllegalAccessException e) { e.printStackTrace(); } Log.d("RAW FLDINFO","name=" + fld.getName() + " ID=" + String.valueOf(resourceID)); copyResourceImageToImages(resourceID,resourceName, true); } } /** * Copy an image from the raw directory (app/src/main/res/raw directory) to * the Apps data/data/files/images folder * @param resourceID ID of the resource * @param resourceName name of the resource (file name less extension) * @param throw_exception true if an exception should be thrown */ private void copyResourceImageToImages(int resourceID, String resourceName, boolean throw_exception) { String tag = "CPYRSRCTOIMAGES"; InputStream is = getResources().openRawResource(resourceID); File of = new File(images_file.getPath() + File.separator + resourceName + ".jpg"); Log.d(tag,"Initiating Copy of File " + of.getName()); int buffer_size = 1024 * 4; int bytesread = 0; long bytescopied = 0; OutputStream os; byte[] buffer = new byte[buffer_size]; if (!of.exists()) { try { of.createNewFile(); } catch (IOException e) { Log.d(tag,"Error Creating File " + of.getName()); e.printStackTrace(); if (throw_exception) { throw new RuntimeException("Error Creating Output File" + of.getName()); } return; } } try { os = new FileOutputStream(of); } catch (IOException e) { Log.d(tag,"Error Creating OutputStream for File " + of.getName()); e.printStackTrace(); if (throw_exception) { throw new RuntimeException("Error Creating OutputStream for File " + of.getName()); } return; } if (os == null) { throw new RuntimeException("OutputStream not initialised."); } try { while ((bytesread = is.read(buffer)) > 0 ){ try { os.write(buffer, 0, bytesread); } catch (IOException e) { String msg = "Error Writing to Output File " + of.getName() + " Bytes Copied = " + bytescopied; Log.d(tag, msg); e.printStackTrace(); if (throw_exception) { os.close(); of.delete(); throw new RuntimeException(msg); } is.close(); os.close(); of.delete(); return; } bytescopied = bytescopied + bytesread; } }catch (IOException e) { String msg = "Error reading Input File " + resourceName + " Bytes Copied = " + bytescopied; Log.d(tag,"Error Reading Input File " + resourceName); e.printStackTrace(); if (throw_exception) { throw new RuntimeException(msg); } try { is.close(); os.close(); of.delete(); } catch (IOException e2) { e2.printStackTrace(); } } Log.d(tag,"File " + of.getName() +" Copied - Bytes Successfully Copied = " + bytescopied); try { os.flush(); } catch (IOException e) { e.printStackTrace(); } try { os.close(); } catch (IOException e) { e.printStackTrace(); } try { is.close(); } catch (IOException e) { e.printStackTrace(); } } }

Answer 2

通常，我们不将图像存储在sqlite数据库中，因为这会花费很多时间并且不鼓励使用，而是将图像存储在应用程序的内部私有存储中，并将图像的名称存储在我们的sqlite数据库，并相应地获取它们。数据库不是用于存储图像的，而是仅用于文本的（如果您尝试存储图像的话），这将导致大量的读写时间开销。您可以按照以下说明将图像存储在内部存储中 https://developer.android.com/training/data-storage/files

如何在sqlite数据库中插入图像

2 个答案:

示例