Question

我的ListView很复杂，因为有4种视图类型的可能情况，例如{ book, movie, music cd, concert }

目前，为了决定要膨胀的对象等，我得到了与列表行相关的项目。然后，我将在对象的类型字段上执行switch()。

这给我留下了很多代码和繁重的getView()。

我是否正确地说getItemViewType()用于返回当前项目的正确视图类型？

我在哪里可以找到使用此方法的ListAdapter示例？注意：这是为了平滑我现在非常迟缓的ListView。

由于

编辑：我的适配器

public class MyListAdapter extends BaseAdapter implements ListAdapter {

    private Context ctx;
    private int layoutResourceId;
    private ArrayList<ItemType> items;

    public MyListAdapter(Context context, ArrayList<ItemType> data) {

        this.layoutResourceId = R.layout.timeline_item_row;
        this.ctx = context;
        this.setitems(data);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View row = convertView;
        TimelineHolder holder = null;
        ItemType transaction = getitems().get(position);

        if (row == null) {

            LayoutInflater inflater = ((Activity) ctx).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);

            holder = new TimelineHolder();
            holder.imgActivityIcon = (ImageView)row.findViewById(R.id.imgActivityImageIcon);
            holder.imgActivityLabel = (ImageView)row.findViewById(R.id.imgActivityImageLabel);
            holder.lblMerchantName = (TextView)row.findViewById(R.id.lblMerchantName);
            holder.lblLocation = (TextView)row.findViewById(R.id.lblLocation);
            holder.lblActivityType = (TextView)row.findViewById(R.id.lblActivityType);
            holder.lblActivityLabelUpper = (TextView)row.findViewById(R.id.lblActivityTypeLabel);
            holder.lblTimeSinceActivity = (TextView)row.findViewById(R.id.lblTimeSinceActivity);
            holder.lblActivityAmount = (TextView)row.findViewById(R.id.lblActivityAmount);

            row.setTag(holder);

        }
        else {

            holder = (TimelineHolder) row.getTag();
        }

        // Get/Populate common values here

        String address = "";

        Date hostTime = Helper.parse8601UTC(transaction.getCurrentHostTime());
        Date transactionTime = Helper.parse8601UTC(transaction.getHostTransactionTime());
        String merchantName = transaction.getMerchant().getName();

        holder.lblMerchantName.setText(merchantName);
        holder.lblLocation.setText(address);
        holder.lblTimeSinceActivity.setText(Helper.timeSince(transactionTime, hostTime));
        holder.lblActivityAmount.setText(Helper.doubleToCurrency(transaction.getAmount(), transaction.getCurrency()));

        switch (transaction.getTransactionTypeId()) {

        case TYPE_ONE:

            holder.imgActivityIcon.setImageResource(R.drawable.redemmedicon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Loyalty_Earned);
            holder.lblActivityLabelUpper.setText(R.string.EARNED);
            holder.lblActivityAmount.setText(transaction.getResponsePoints() + " pts");

            break;

        case TYPE_TWO:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Prepay_Redeem_Refund);
            holder.lblActivityLabelUpper.setText(R.string.REDEEMED);

            break;

        case TYPE_THREE:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityLabelUpper.setText(R.string.REFUND);
            holder.lblActivityType.setText(R.string.Prepay_Purchase_Refund);

            break;
        case TYPE_FOUR:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityLabelUpper.setText(R.string.REFUND);
            holder.lblActivityType.setText(R.string.Prepay_Deposit_Refund);

            break;

        case TYPE_FIVE:

            holder.imgActivityIcon.setImageResource(R.drawable.reward_earned_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Reward_Redeemed);
            holder.lblActivityLabelUpper.setText(R.string.REDEEMED);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_SIX:

            holder.imgActivityIcon
                    .setImageResource(R.drawable.reward_earned_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.redeemed_flag);
            holder.lblActivityType.setText(R.string.Points_Redeemed);
            holder.lblActivityLabelUpper.setText(R.string.REDEEMED);
            holder.lblActivityAmount.setText(transaction.getResponsePoints()
                    + " pts");

            break;

        case TYPE_SEVEN:

            holder.imgActivityIcon.setImageResource(R.drawable.stamp_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.redeemed_flag);
            holder.lblActivityType.setText(R.string.Checked_In);
            holder.lblActivityLabelUpper.setText(R.string.CHECK_IN);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_EIGHT:

            holder.imgActivityIcon.setImageResource(R.drawable.shared_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.redeemed_flag);
            holder.lblActivityType.setText(R.string.Shared_Coupon);
            holder.lblActivityLabelUpper.setText(R.string.SHARED);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_NINE:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Prepay_Deposit);
            holder.lblActivityLabelUpper.setText(R.string.DEPOSIT);

            break;

        case TYPE_TEN:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.redeemed_flag);
            holder.lblActivityType.setText(R.string.Prepay_Purchase);
            holder.lblActivityLabelUpper.setText(R.string.PURCHASE);

            break;

        case TYPE_ELEVEN:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Prepay_Redeemed);
            holder.lblActivityLabelUpper.setText(R.string.REDEEMED);

            break;

        case TYPE_TWELVE:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Refund);
            holder.lblActivityLabelUpper.setText(R.string.REFUND);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_THIRTEEN:

            holder.imgActivityIcon.setImageResource(R.drawable.prepay_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.reversal);
            holder.lblActivityLabelUpper.setText(R.string.REVERSAL);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_FOURTEEN:

            holder.imgActivityIcon.setImageResource(R.drawable.unlocked_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Check_In_Reward_Unlocked);
            holder.lblActivityLabelUpper.setText(R.string.UNLOCKED);
            holder.lblActivityAmount.setText("");

            break;

        case TYPE_FIFTEEN:

            holder.imgActivityIcon.setImageResource(R.drawable.reward_earned_icon_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText(R.string.Coupon_Received);
            holder.lblActivityLabelUpper.setText(R.string.RECEIVED);
            holder.lblActivityAmount.setText("");

            break;

        default:

            holder.imgActivityIcon.setImageResource(R.drawable.stamp_2x);
            holder.imgActivityLabel.setImageResource(R.drawable.earned_flag);
            holder.lblActivityType.setText("");
            holder.lblActivityLabelUpper.setText("");
            holder.lblActivityAmount.setText("");

            break;
        }

        return row;
    }

    @Override
    public int getCount() {

        return getitems() == null ? 0 : getitems().size();
    }

    @Override
    public Object getItem(int position) {

        return getitems() == null ? null : getitems().get(
                position);
    }

    @Override
    public long getItemId(int position) {

        return layoutResourceId;
    }

    public void addItem(ItemType item, boolean addFirst) {

        if (addFirst) {

            getitems().add(0, item);
        } else {

            getitems().add(item);
        }

        notifyDataSetChanged();
    }

    public ArrayList<ItemType> getitems() {
        return items;
    }

    public void setitems(ArrayList<ItemType> items) {
        this.items = items;
    }

    public int getFirstTransactionId() {

        int result = 0;

        if (items != null && !items.isEmpty()) {

            ItemType txn = items.get(0);
            result = txn.getId();
        }

        return result;
    }

    public int getLastTransactionId() {

        int result = 0;

        if (items != null && !items.isEmpty()) {

            ItemType txn = items.get(items.size() - 1);
            result = txn.getId();
        }

        return result;
    }

    @Override
    public int getViewTypeCount() {

        return 1;
    }

    @Override
    public int getItemViewType(int position) {

        return 0;
    }
}

Answer 1

***更新提示****
您没有正确实现getViewTypeCount（）和getItemViewType（）。

阅读我在下面链接中提供的教程。我不想重新解释它们，因为我会做得更糟糕。但请先阅读下面的内容，因为您实际上并不需要，因为您只有1种视图类型。

选项1 ：使用正确的资源图像创建16个不同的行。然后在getView（）方法中调用getItemViewType（position）。对其进行切换，并根据返回的视图类型对正确的行进行充气。（教程将解释这一点）。这样你就不必继续调用“setImageResource”调用，这很昂贵。

选项2 ：根据您的视图持有者，您似乎只有1个视图，而您只需更改3个文本字段和2个位图。但是每个位图调用都很繁重，您需要创建一个HashMap来缓存这些图标。每次调用时，引用哈希映射，如果该项不存在，则创建它，添加它，然后继续。这很重要，因为每次调用setImageResource（）都会进行位图解码并需要时间。 这是您真正的错误 请参阅下面的伪代码。

private static HashMap<Integer, Bitmap> cache;
static class BitmapCache {
    public static Bitmap get(Integer id) {
        if (cache.containsKey(id)) {
            return cache.get(id);
        } else {
            Bitmap t = BitmapFactory.decodeResource(getContext(), id);
            cache.put(key, t);
            return t;
        }
    }
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder item = null;
    Object o = getItem(position);

    View mRow = convertView;
    if (mRow == null) {
        LayoutInflater li = LayoutInflater.from(getContext());
        switch (getItemViewType(position)) {
        case VIEW_ONLINE:
            mRow = li.inflate(R.layout.row_online, parent, false);
            break;
        default:
            // default to sortable
            mRow = li.inflate(R.layout.row_offline, parent, false);
            break;
        }

        item = new ViewHolder(mRow);
        mRow.setTag(item);
    } else {
        item = (ViewHolder) mRow.getTag();
    }


    item.icon.setImageBitmap(BitmapCache.get(object.key));

    return mRow;
}

*旧答案与教程*
StackOverflow上已有几篇帖子，我昨天刚刚与之相关。（见下面的链接）。

是的，使用getItemViewType（）来检索正确的视图类型。据我了解，这里的真正好处是在getView（）调用期间的视图优化中。实现getItemViewType（）允许getView（）类型返回正确的缓存视图。
在充气视图中的文本和图像视图中使用静态视图保持器模式。你不应该每次都膨胀视图，你应该重用getView（）调用提供的convertView。
请务必实施getViewTypeCount（）

这是一个深入解释如何执行自定义列表视图（包括优化）的教程。 http://www.vogella.com/articles/AndroidListView/article.html

这里有两个stackoverflow帖子，它们也讨论了你要做的事情：
1. Android Programming tutorials - Tutorial 5
2. Restaurant Program Tutorial

ListView getItemViewType（）的复杂示例

1 个答案: