如何將圖像轉換為字符串以將其讀/寫到 SQLite 數據庫 - Android Studio (Java)

Question

我無法使用 Java 將圖像轉換為字符串以將其讀/寫到 Android Studio 上的 SQLite 數據庫。 我看了很多教程，似乎找不到我遺漏的東西。 任何幫助將不勝感激！

我的錯誤源於沒有從主活動中的 AddData 轉換它：

數據庫助手：

    public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "relove.db";
    public static final String TABLE_NAME = "PLGarments_Table";
    public static final String COL_ID = "ID";
    public static final String COL_TITLE = "TITLE";
    public static final String COL_DESCRIPTION = "DESCRIPTION";
    public static final String COL_OWNER = "OWNER";
    public static final String COL_IMAGE = "image";



    public DatabaseHelper(@Nullable Context context) {
        super(context, DATABASE_NAME , null, 1);


    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_NAME + "(ID INTEGER PRIMARY KEY AUTOINCREMENT, TITLE TEXT, DESCRIPTION TEXT, OWNER TEXT, IMAGE BLOB)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(" Drop table if exists " + TABLE_NAME );
        onCreate(db);
    }

    public void queryData(String sql){
        SQLiteDatabase database = getWritableDatabase();
        database.execSQL(sql);
    } //unnecessary?



    public boolean insertData(String TITLE, String DESCRIPTION, String OWNER, byte[] image){             //CREATE
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues contentValues = new ContentValues();
        contentValues.put(COL_TITLE,TITLE);
        contentValues.put(COL_DESCRIPTION,DESCRIPTION);
        contentValues.put(COL_OWNER,OWNER);
        contentValues.put(COL_IMAGE, image);


        long result = db.insert(TABLE_NAME, null,contentValues );
            if (result == -1)
                return false;
            else
                return true;
    }

    public Cursor getAllData(){                                                          //RETRIEVE
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("select * from " + TABLE_NAME, null);
        return res;
    }


    public boolean updateData(String ID,String TITLE, String DESCRIPTION, String OWNER, byte[] image ){  //UPDATE
        SQLiteDatabase db = this.getWritableDatabase(); //instance of database
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL_ID, ID);
        contentValues.put(COL_TITLE,TITLE);
        contentValues.put(COL_DESCRIPTION,DESCRIPTION);
        contentValues.put(COL_OWNER,OWNER);
        contentValues.put(COL_IMAGE, image);
        db.update(TABLE_NAME, contentValues, "ID = ?", new String[] {ID});
        return true;
    }

    public Integer deleteData (String ID){                                                  //DELETE
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_NAME, "ID = ?", new String[] {ID});
    }
}

主要活動：

public class MainActivity extends AppCompatActivity {

    DatabaseHelper myDb;
    EditText editTitle, editDescription, editOwner, editTextID;
    Button btnAddData, btnviewAll, btnviewUpdate, btnDelete, btnLogOut;
    ImageView mImageView;

    final int REQUEST_CODE_GALLERY = 999;

    //use lines 37 - 40 when starting a new activity
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myDb = new DatabaseHelper(this); /*calling constructor*/

        editTitle = (EditText)findViewById(R.id.editText_title);
        editDescription = (EditText)findViewById(R.id.editText_description);
        editOwner = (EditText)findViewById(R.id.editText_owner);
        editTextID = (EditText)findViewById(R.id.editText_id);
        btnAddData = (Button)findViewById(R.id.button_add);
        btnviewAll = (Button)findViewById(R.id.button_viewAll);
        btnviewUpdate = (Button)findViewById(R.id.button_update);
        btnDelete = (Button)findViewById(R.id.button_delete);
        btnLogOut = (Button)findViewById(R.id.button_logout);
        mImageView = (ImageView)findViewById(R.id.imageView);
        AddData();
        viewAll();
        UpdateGarment();
        DeleteGarment();

       btnLogOut.setOnClickListener( new View.OnClickListener(){
           @Override
           public void onClick(View view){
               launchLoginActivity();
           }
       }
       ); // Learn2Crack - Android Switching Between Activities

    mImageView.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
               //read external storage permissions to select image from gallery
                    // Runtime permission for devices Android 6.0 and above
                    ActivityCompat.requestPermissions(
                            MainActivity.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                    REQUEST_CODE_GALLERY
                    );
              }
            });
    }

    //back to login
    public void launchLoginActivity(){
        Intent intent = new Intent (this, LoginActivity.class);
        startActivity(intent);
    } // Learn2Crack - Android Switching Between Activities

    //Create
    public void AddData(){
        btnAddData.setOnClickListener(
            new View.OnClickListener(){
                @Override
                public void onClick(View v){
                    boolean isInserted = myDb.insertData(editTitle.getText().toString(), editDescription.getText().toString(),
                            editOwner.getText().toString(), *mImageView.*);
                    if (isInserted == true)
                        Toast.makeText(MainActivity.this, "Garment Inserted", Toast.LENGTH_LONG).show();
                    else
                        Toast.makeText(MainActivity.this, "Garment Not Inserted", Toast.LENGTH_LONG).show(); }
            });
    } /*end of add button*/


    //Retrieve
    public void viewAll(){
        btnviewAll.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) { /*the actual action goes in here */
                        Cursor res = myDb.getAllData();
                        if (res.getCount() == 0){
                            //show message
                            showMessage("Error", "No Garments Found");
                            return;
                        }
                        StringBuffer buffer = new StringBuffer();
                        while ( res.moveToNext()){
                            buffer.append("ID :" + res.getString(0)+ "\n");
                            buffer.append("TITLE :" + res.getString(1)+ "\n");
                            buffer.append("DESCRIPTION :" + res.getString(2)+ "\n");
                            buffer.append("OWNER :" + res.getString(3)+ "\n\n");
                        }
                        //show all data
                        showMessage("Garments", buffer.toString());
                    }
                }
        );
    }

    //Update
    public void UpdateGarment(){
        btnviewUpdate.setOnClickListener(
                new View.OnClickListener(){
                    @Override
                    public void onClick(View v){
                        boolean isUpdate = myDb.updateData(editTextID.getText().toString(), editTitle.getText().toString(),
                                editDescription.getText().toString(), editOwner.getText().toString() );
                        if (isUpdate == true)
                            Toast.makeText(MainActivity.this, "Garment Updated", Toast.LENGTH_LONG).show();
                        else
                            Toast.makeText(MainActivity.this, "Garment Not Updated", Toast.LENGTH_LONG).show();
                    }
                }
        );
    }

    //Delete
    public void DeleteGarment(){
        btnDelete.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Integer deletedRows = myDb.deleteData(editTextID.getText().toString());
                        if (deletedRows > 0)
                            Toast.makeText(MainActivity.this, "Garment Deleted", Toast.LENGTH_LONG).show();
                        else
                            Toast.makeText(MainActivity.this, "Garment Not Deleted", Toast.LENGTH_LONG).show();
                    }
                }
        );
    }


    public void showMessage(String title, String message){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }

    //Gallary permission
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
       if (requestCode == REQUEST_CODE_GALLERY){
           if (grantResults.length>0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
              //gallery intent
               Intent galleryIntent = new Intent(Intent.ACTION_GET_CONTENT);
               galleryIntent.setType("image/*");
               startActivityForResult(galleryIntent, REQUEST_CODE_GALLERY);
           }
           else {
               Toast.makeText(this, "Don't have permission to access file location", Toast.LENGTH_SHORT).show();
           }
           return;
       }
       super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
       if(requestCode == REQUEST_CODE_GALLERY && resultCode == RESULT_OK) {
           Uri imageUri = data.getData();
          CropImage.activity(imageUri)
                  .setGuidelines(CropImageView.Guidelines.ON)
                  .setAspectRatio(1,1)
                  .start(this);

       }
       if (requestCode == CropImage.CROP_IMAGE_ACTIVITY_REQUEST_CODE){
           CropImage.ActivityResult result = CropImage.getActivityResult(data);
           if (resultCode == RESULT_OK){
               Uri resultUri = result.getUri();
               //set image chosen from gallery to image view
               mImageView.setImageURI(resultUri);
           }
           else if (resultCode == CropImage.CROP_IMAGE_ACTIVITY_RESULT_ERROR_CODE){
               Exception error = result.getError();
           }
       }
       super.onActivityResult(requestCode, resultCode, data);
    }


}

Answer 1

您需要轉換mImageView。 到一個字節[]（位圖）。

所以

BitmapDrawable d = (BitmapDrawable) mImageView.getDrawable();
Bitmap b = d.getBitmap();
boolean isInserted = myDb.insertData(editTitle.getText().toString(), editDescription.getText().toString(),
                    editOwner.getText().toString(), b);

如果位圖大於 2Mb，則無法從 Cursor 獲取。 不建議將位圖存儲在數據庫中，而是將位圖存儲為文件並將路徑存儲在數據庫中。