ViewHolder模式在自定义CursorAdapter中正确实现了吗？

Question

这是我的自定义CursorAdapter：

public class TasksAdapter extends CursorAdapter implements Filterable {

    private final Context context;

    public TasksAdapter(Context context, Cursor c) {
        super(context, c);
        this.context = context;
    }

    /**
     * @see android.widget.CursorAdapter#newView(android.content.Context, android.database.Cursor, android.view.ViewGroup)
     */
    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(android.R.layout.simple_list_item_checked, parent, false);

        ViewHolder holder = new ViewHolder();
        holder.textview = (CheckedTextView)v.findViewById(android.R.id.text1);
        v.setTag(holder);

        return v;
    }

    /**  
     * @see android.widget.CursorAdapter#bindView(android.view.View, android.content.Context, android.database.Cursor)
     */
    @Override
    public void bindView(View view, Context context, Cursor cursor) {

        ViewHolder holder = (ViewHolder)view.getTag();
        int titleCol = cursor.getColumnIndexOrThrow(Tasks.TITLE);
        int completedCol = cursor.getColumnIndexOrThrow(Tasks.COMPLETED);

        String title = cursor.getString(titleCol);
        boolean completed = Util.intToBool(cursor.getInt(completedCol));

        holder.textview.setText(title);
        holder.textview.setChecked(completed);
    }

    /**
     * @see android.widget.CursorAdapter#runQueryOnBackgroundThread(java.lang.CharSequence)
     */
    @Override
    public Cursor runQueryOnBackgroundThread(CharSequence constraint) {

        StringBuffer buffer = null;
        String[] args = null;

        if (constraint != null) {
            buffer = new StringBuffer();
            buffer.append("UPPER (");
            buffer.append(Tasks.TITLE);
            buffer.append(") GLOB ?");
            args = new String[] { "*" + constraint.toString().toUpperCase() + "*" };
        }

        Cursor c = context.getContentResolver().query(Tasks.CONTENT_URI,
            null, (buffer == null ? null : buffer.toString()), args,
            Tasks.DEFAULT_SORT_ORDER);

        c.moveToFirst();
        return c;
    }

    /**
     * @see android.widget.CursorAdapter#convertToString(android.database.Cursor)
     */
    @Override
    public CharSequence convertToString(Cursor cursor) {
        final int titleCol = cursor.getColumnIndexOrThrow(Tasks.TITLE);
        String title = cursor.getString(titleCol);
        return title;
    }

    static class ViewHolder {
        CheckedTextView textview;
    }

}

这是否属于ViewHolder模式的约束？我不确定，因为这是CursorAdapter，那里没有getView。如果有任何问题或建议，请指出。

Answer 1

CursorAdapter``newView每次需要新行时都不会调用；如果它已经有一个View，它将调用bindView，因此创建的视图实际上已被重用。

就是说，正如 约瑟夫 在评论中指出的那样，您仍然可以使用ViewHolder以避免findViewById重复调用。

如果您仍然担心效率，那么请看一下SimpleCursorAdapter使用的实现WeakHashMap（的映射WeakReferences）：

WeakHashMap<View, View[]> mHolders = new WeakHashMap<View, View[]>();