android - 如何为 Spinner 实现 MatrixCursor？

Question

我有一个返回 Cursor 的 SQLite 查询。我想通过实现 MatrixCursor 向 Cursor 添加一些额外的行(以尝试在单击时避免自动选择第一项实际数据)。然后我想将它们映射到 SimpleCursorAdapter。我一直在阅读帖子(和代码)，但仍然不清楚如何将其编码为下面列出的现有代码。

    Cursor cursor = myDB.query(DATABASE_TABLE_NAME, resultColumns, whereClause,
            whereArgs, null, null, null, null);

    // Create Spinner View object from layout resource
    Spinner spinner = (Spinner) findViewById(R.id.spinner);

    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
            android.R.layout.simple_spinner_item, // Use a template
                                                  // that displays a
                                                  // text view
            cursor, // Give the cursor to the adapter
            new String[] {"ename"}, // Map the NAME column in the
                                                 // people database to...
            new int[] {android.R.id.text1}); 

    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);
    spinner.setOnItemSelectedListener(new MyOnItemSelectedListener());

Answer 1

如果您想从一个简单的 Cursor 构建一个 MatrixCursor，您必须解析整个初始 Cursor 并附加您需要的行想要:

//...
    MatrixCursor mc = new MatrixCursor(resultColumns);
    // add extra rows, this will probably not work if you want to insert them
    // between the initial cursor rows because of the _id column that need autoincrement values
    mc.addRow(new Object[] { new Long(-2), "Extra name1" }); 
    mc.addRow(new Object[] { new Long(-1), "Extra name2" });
    // I don't know what your cursor holds, I assumed you have the _id column(long value)
    // and a name(String value)
    int size = cursor.getCount();
    for (int i = 0; i < size; i++) {
        cursor.moveToPosition(i);
            mc.addRow(new Object[] {
            cursor.getLong(cursor.getColumnIndex(/*the _id column*/)),
            cursor.getString(cursor.getColumnIndex(/* the name column(ename?!?)*/)) });
    }
    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
            android.R.layout.simple_spinner_item, mc, new String[] {"ename"}, new int[] {android.R.id.text1}); 
//...

如果您这样做只是为了避免在显示 Spinner 时触发 OnItemSelectedListener，也许您可​​以采用另一种方法。例如在你的听众中:

    //boolean status = true; flag in MyOnItemSelectedListener

    @Override
    public void onItemSelected(AdapterView<?> parent, View view,
            int position, long id) {
        if (status) {
            status = false;// this is the first listener trigger so you probably want to ignore it
            return;
        }
        // do stuff here
    }

注意:我不知道上面的解决方案有多好。如果您查看这个 Spinner 相关问题，可能有更好的解决方案。