SQLite获取单个数据(*单个数据)(更新帖子)

Question

我是Android的初学者。请帮助我解决这个简单的问题：从SQLite中检索单个数据。

案例 1 ：

dbhelper.java
// Getting single part
    public lispar Look(int id) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor kr = db.query(TABLE_PART, new String[]{ID,
                        KODE, NAMA}, ID + "=?",
                new String[]{String.valueOf(id)}, null, null, null, null);
        if (kr != null)
            kr.moveToFirst();
        lispar contact = new lispar(Integer.parseInt(kr.getString(0)),
                kr.getString(1), kr.getString(2));
        // return contact
        kr.close();
        db.close();
        return contact;
    }
    
main.java
kodcari = (Button) findViewById(R.id.carikod);
        kodcari.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                ckodin = kodin.getText().toString(); //wrong string?
                parin.getText().toString();
                //what should i do?
            }
        });
        partnam = (EditText) findViewById(R.id.namepart);
        dbHandle = new DbHandle(this);

    }

案例2 ：

main.java ()
kodin = (EditText) findViewById(R.id.inkod);
        kodcari = (Button) findViewById(R.id.carikod);
        kodcari.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = mDbHelper.getReadableDatabase();
                String[] projection = {
                        FeedEntry._ID,
                        FeedEntry.KODE,
                        FeedEntry.NAMPART,
                        FeedEntry.BELANG
                };
                // Filter results WHERE "kode" = 'kode part'
                String selection = FeedEntry.KODE + " = ?";
                String[] selectionArgs = parin.getText().toString(), belangin.getText().toString();//{ "KODE_PART" }; //
                // How you want the results sorted in the resulting Cursor
                String sortOrder = FeedEntry.KODE + " DESC";
                Cursor kr = db.query(
                        FeedEntry.KODE,         // The table to query
                        projection,             // The columns to return
                        selection,              // The columns for the WHERE clause
                        selectionArgs,          // The values for the WHERE clause
                        null,                   // don't group the rows
                        null,                   // don't filter by row groups
                        sortOrder               // The sort order
                );
                if (kr != null)
                kr.moveToFirst();
                //String parin = kr.getString(
                //kr.getColumnIndexOrThrow(FeedEntry._ID)
                //);
            }
        });

主.xml

<TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Looking by Code"
        android:textSize="10pt"
        android:id="@+id/txkod"
        android:layout_marginTop="63dp"
        android:layout_centerHorizontal="true" />
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="insert code"
        android:textAlignment="center"
        android:layout_marginTop="25dp"
        android:id="@+id/inkod"
        android:layout_below="@+id/txkod"
        android:layout_alignLeft="@+id/txkod"
        android:layout_alignStart="@+id/txkod"
        android:layout_alignRight="@+id/txkod"
        android:layout_alignEnd="@+id/txkod" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Look"
        android:id="@+id/carikod"
        android:layout_below="@+id/inkod"
        android:layout_centerHorizontal="true" />
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/codepar"
        android:hint="code part"
        android:layout_below="@+id/namkod"/>
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/nampar"
        android:hint="name part"
        android:layout_below="@+id/nampar"/>
</LinearLayout>

插入数据成功，但读取数据不成功。（基准表示数据*）

在此处输入图像描述

Answer 1

我完全不确定以下内容是否会让您动起来。但似乎您没有获得视图 kodin 和 parin 的 ID。因此，也许可以尝试以下方法：-

 kodin = (EditText) findViewById(R.id.inkod);
 parin = (EditText) findViewById(R.id.nampar);

更详细的代码（未经测试和动态编写，因此可能有错误）

如果您使用的是Android Studio或具有调试功能的IDE，那么使用它可能会非常有帮助。

    kodcari = (Button) findViewById(R.id.carikod);
    // Adding the following lines may get the correct string
    kodin = (EditText) findViewById(R.id.inkod); //????
    parin = (EditText) findViewById(R.id.nampar); //????
    kodcari.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            ckodin = kodin.getText().toString(); //wrong string?
            parin.getText().toString();
            //what should i do? Perhaps the following :-
            lipsar myContact = Look(ckodin !!!!CONVERTED TO INT FROM STRING);
            // whatever else you need to do with the mycontact .....
        }
    });
    partnam = (EditText) findViewById(R.id.namepart);
    dbHandle = new DbHandle(this);

}