android - EditText afterTextChanged 不工作 : displays null

Question

我使用以下代码将 Uri 图像插入到 SQLite 中:

注册

private void insertData( String name,String pass, Uri image) throws SQLiteException {
        database = mdb.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(MyDatabaseHelper.KEY_NAME,    name);
        cv.put(MyDatabaseHelper.KEY_PASSWORD, pass);
        try {
            database = mdb.getWritableDatabase();
            InputStream iStream = getContentResolver().openInputStream(image);
            byte[] inputData = Utils.getBytes(iStream);
            cv.put(MyDatabaseHelper.KEY_IMAGE,inputData);
        }catch(IOException ioe)
        {
            Log.e(TAG, "<saveImageInDB> Error : " + ioe.getLocalizedMessage());
        }
        database.insert(MyDatabaseHelper.TABLE_USER, null, cv);
        Toast.makeText(getApplicationContext(),"Database Created",Toast.LENGTH_SHORT).show();
        database.close();
    }

当我看到 Database Created 时，我假设数据库已成功创建并且数据已插入。

在 Login 中，我希望根据用户名从 SQLite 检索图像。

name = (EditText) findViewById(R.id.name);

name.addTextChangedListener(new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

     @Override
    public void afterTextChanged(Editable editable) {
        String personName = name.getText().toString();
        database = mdb.getWritableDatabase();
        String selectQuery = " SELECT " + MyDatabaseHelper.KEY_IMAGE + " FROM " + MyDatabaseHelper.TABLE_USER + " WHERE " + MyDatabaseHelper.KEY_NAME + " = ' " + personName + " ' ";
        Cursor cursor = database.rawQuery(selectQuery, null);
        if (cursor.moveToFirst()) {
            byte[] blob = cursor.getBlob(cursor.getColumnIndex("Image"));
            Log.e("A", blob+"");
            cursor.close();
            mdb.close();
            imageView.setImageBitmap(getRoundedBitmap(Utils.getImage(blob)));
        }
        else
        {
            Toast.makeText(getApplication(),"NULL",Toast.LENGTH_SHORT).show();
        }
    }
});

    public Bitmap getRoundedBitmap(Bitmap bitmap){
    Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
    BitmapShader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
    Paint paint = new Paint();
    paint.setShader(shader);
    paint.setAntiAlias(true);
    Canvas c = new Canvas(circleBitmap);
    c.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2, bitmap.getWidth() / 2, paint);
    return circleBitmap;
   }

我的数据库助手

public class MyDatabaseHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION=1;
    public static final String DATABASE_NAME="mm.db";
    public static final String TABLE_USER="User";
    public static final String KEY_NAME="Name";
    public static final String KEY_PASSWORD="Password";
    public static final String KEY_IMAGE="Image";
    public static final String ID="id";

    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_USER + " ( " + ID + " INTEGER PRIMARY KEY ,Name TEXT,Password TEXT,Image BLOB )");
    }

    public void onUpgrade(SQLiteDatabase db, int oldVersion,int newVersion) {
        Log.w(MyDatabaseHelper.class.getName(), "Upgrading database from version" + oldVersion + "to" + newVersion + ",which will destroy all old data");
        db.execSQL("Drop TABLE IF EXISTS " + TABLE_USER);
        onCreate(db);
    }

    public MyDatabaseHelper(Context context)
    {
        super(context, DATABASE_NAME,null,1);
    }
}

工具

public class Utils {

    public static byte[] getImageBytes(Bitmap bitmap) {
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
        return stream.toByteArray();
    }

    public static Bitmap getImage(byte[] image) {
        return BitmapFactory.decodeByteArray(image, 0, image.length);
    }

    public static byte[] getBytes(InputStream inputStream) throws IOException {
        ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
        int bufferSize = 1024;
        byte[] buffer = new byte[bufferSize];

        int len = 0;
        while ((len = inputStream.read(buffer)) != -1) {
            byteBuffer.write(buffer, 0, len);
        }
        return byteBuffer.toByteArray();
    }
}

用户在 EditText 上输入他/她的名字后，名为 name 的图像没有检索，但向我显示 Null 消息!这里出了什么问题？

Answer 1

对于 EditText，每次 TextWatcher() 检测到文本更改时，afterTextChanged() 都会被调用，即在 EditText 中键入的每个字符都是一个textChange 事件。

因此，即使在键入整个用户名之前，afterTextChanged() 也会被多次调用，因此会出现空游标。但是，一旦用户名完全键入，光标就会提供正确的行，在您的情况下，是图像 blob。

正如您提到的，它是一个登录页面，因此必须有一个密码 editText 以及用户名 editText。

我建议的更好方法是使用 setOnFocusChangeListener() 检测用户名 EditText 的焦点变化。用户完成输入用户名后立即触发 Sql 查询，焦点现在位于密码 editText 上。

name = (EditText) findViewById(R.id.name);

name.setOnFocusChangeListener(new OnFocusChangeListener() {          
    public void onFocusChange(View v, boolean hasFocus) {
        if(!hasFocus) {               //Fire Query when focus is lost
            String personName = name.getText().toString();
            database = mdb.getWritableDatabase();
            String selectQuery = " SELECT " + MyDatabaseHelper.KEY_IMAGE + " FROM " + MyDatabaseHelper.TABLE_USER + " WHERE " + MyDatabaseHelper.KEY_NAME + " = ' " + personName + " ' ";
            Cursor cursor = database.rawQuery(selectQuery, null);
            if (cursor.moveToFirst()) {
                byte[] blob = cursor.getBlob(cursor.getColumnIndex("Image"));
                Log.e("A", blob+"");
                cursor.close();
                mdb.close();
                imageView.setImageBitmap(getRoundedBitmap(Utils.getImage(blob)));
            }
            else
            {
                Toast.makeText(getApplication(),"NULL",Toast.LENGTH_SHORT).show();
            }
        }
});

让我们知道这是否有效。