我有一个ListView是复杂的,因为有可能的情况下,4个视图类型,例如{book,movie,music cd,concert}
目前,要确定什么对象膨胀等,我得到与列表行相关的项目.然后我将在对象的type字段上做一个switch().
这给我留下了很多代码,并且在getView()中很重.
我正确地说,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这种方法的ListAdapter的例子？注意：这是为了平滑我现在看起来相当迟钝的ListView.
谢谢
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;
}
}
解决方法
***更新提示****
您没有正确实现getViewTypeCount()和getItemViewType().
您没有正确实现getViewTypeCount()和getItemViewType().
阅读我在下面的链接中提供的教程.我不想重新解释他们,因为我会做更糟糕的工作.但是请先阅读下面的内容,因为您并不真的需要,因为您只有1个视图类型.
选项1：使用正确的资源映像创建16个不同的行.然后在getView()方法内调用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).这样你就不用继续调用“setImageResource”调用,这是昂贵的.
选项2：根据您的视图持有者,您似乎只有1个视图,您只需更改3个文本字段和2个位图.但是每个位图调用很重,您需要创建一个HashMap来缓存这些图标.对于每个调用,引用哈希映射,如果该项不存在,创建它,添加它并继续.这很重要,因为每次调用setImageResource()都在进行位图解码,并且需要时间.那就是你真正的错误在下面看到伪代码.
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,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,false);
break;
default:
// default to sortable
mRow = li.inflate(R.layout.row_offline,false);
break;
}
item = new ViewHolder(mRow);
mRow.setTag(item);
} else {
item = (ViewHolder) mRow.getTag();
}
item.icon.setImageBitmap(BitmapCache.get(object.key));
return mRow;
}
*教程老回答*
StackOverflow上有几个帖子已经是我昨天刚刚经历的与此相关的帖子. (见下面的链接).
>是的,使用getItemViewType()来检索正确的视图类型.据了解,这里的真正好处是在getView()调用期间进行优化.实现getItemViewType()允许getView()类型返回正确的缓存视图.
>在充气视图中使用静态视图支架图案进行文字和图像视图.
你不应该每次充气,你应该重用由getView()调用提供的convertView.
确保实现getViewTypeCount()
这是一个教程,深入解释如何执行自定义列表视图,包括优化.
http://www.vogella.com/articles/AndroidListView/article.html
这里有两个stackoverflow帖子,它们也讨论你想要做的事情：
Android Programming tutorials – Tutorial 5
Restaurant Program Tutorial
