本文介绍了在Android中如何prevent更新上notifyDataSetChanged现有项目（）的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我聊天应用
在自定义的阵列适配器。我设置随机颜色，以用户名与此code分别消息：
String []数组= context.getResources（）getStringArray（R.array.username_colors）。
randomColor =阵列[新的随机（）nextInt（array.length）];
nameTextView.setTextColor（Color.parseColor（randomColor））;
当新邮件到达我把它添加到列表视图，并调用adapter.notifyDataSetChanged（）;
这导致每次重新着色现有的用户名的消息。
我怎样才能prevent重新着色的列表视图中调用adapter.notifyDataSetChanged（）时，现有的项目;
修改1
@覆盖
公共查看getView（INT位置，查看convertView，父母的ViewGroup）{
ChatMessageElement EL = list.get（位置）;
ViewHolder支架=无效;
NewMessagesLabelHolder labelHolder = NULL; 如果（convertView == NULL）{
convertView = el.getView（吹气，父母）; 如果（el.isMessage（））{ 持有人=新ViewHolder（）;
holder.messageLayout =（RelativeLayout的）convertView.findViewById（R.id.message_container）;
holder.messageContent =（的LinearLayout）convertView.findViewById（R.id.message_content）;
holder.bottomIndicator =（的LinearLayout）convertView.findViewById（R.id.bottom_indicators）;
holder.dateTextView =（TextView中）convertView.findViewById（R.id.message_date）;
holder.timeAgo =（TextView中）convertView.findViewById（R.id.time_ago）;
holder.nameTextView =（TextView中）convertView.findViewById（R.id.user_name）;
holder.likesCountTextView =（TextView中）convertView.findViewById（R.id.likes_count）;
holder.likesLabelImageView =（ImageView的）convertView.findViewById（R.id.likes_label）;
holder.spamCountTextView =（TextView中）convertView.findViewById（R.id.spam_count）;
holder.spamLabelImageView =（ImageView的）convertView.findViewById（R.id.spam_label）;
holder.avatarImageView =（ImageView的）convertView.findViewById（R.id.avatar）;
holder.statusImageView =（ImageView的）convertView.findViewById（R.id.delivered_label）;
holder.progressBar =（进度）convertView.findViewById（R.id.progress_bar）;
holder.errorSign =（ImageView的）convertView.findViewById（R.id.error_sign）;
holder.spamSign =（ImageView的）convertView.findViewById（R.id.spam_sign）;
holder.bookmarkLabel =（ImageView的）convertView.findViewById（R.id.bookmark_label）;
holder.topIndicators =（的LinearLayout）convertView.findViewById（R.id.topIndicators）;
convertView.setTag（保持器）;
}
如果（el.isNewMessagesLabel（））{
convertView = inflater.inflate（R.layout.chat_new_messages_label_layout，父母，假）; labelHolder =新NewMessagesLabelHolder（）;
labelHolder.newMessagesLabel =（TextView中）convertView.findViewById（R.id.new_messages_label）;
convertView.setTag（labelHolder）;
}
}其他{
如果（el.isMessage（））{
支架=（ViewHolder）convertView.getTag（）;
}
如果（el.isNewMessagesLabel（））{
labelHolder =（NewMessagesLabelHolder）convertView.getTag（）;
}
} 如果（el.isMessage（））{
消息currentMessage =（消息）报;
drawMessage（保持，currentMessage，位）;
}
如果（el.isNewMessagesLabel（））{
NewMessagesLabel messagesLabel =（NewMessagesLabel）埃尔;
drawNewMessagesLabel（labelHolder，messagesLabel）;
} 返回convertView;
}私人无效drawMessage（ViewHolder架，留言信息，INT位置）{
字符串日期= message.getCreatedAt（）;
字符串formattedDate = DateHelper.getInstance（上下文）.formatDate（YYYY-MM-dd'T'HH：MM：ss.SSS'Z'，HH：MM，日期）; 字符串username = message.getUserName（）; holder.likesLabelImageView.setVisibility（View.GONE）;
holder.likesCountTextView.setVisibility（View.GONE）;
holder.spamCountTextView.setVisibility（View.GONE）;
holder.spamLabelImageView.setVisibility（View.GONE）;
holder.bookmarkLabel.setVisibility（View.GONE）;
holder.statusImageView.setVisibility（View.GONE）;
holder.progressBar.setVisibility（View.GONE）;
holder.statusImageView.setVisibility（View.GONE）;
holder.errorSign.setVisibility（View.GONE）;
holder.spamSign.setVisibility（View.GONE）;
holder.timeAgo.setVisibility（View.GONE）;
holder.timeAgo.setText（）;
holder.messageLayout.setAlpha（1F）;
holder.topIndicators.setVisibility（View.VISIBLE）; 如果（message.isNewDay（））{
holder.timeAgo.setVisibility（View.VISIBLE）;
字符串的DayDate = DateHelper.getInstance（上下文）.formatDate（YYYY-MM-dd'T'HH：MM：ss.SSS'Z'，MMMM D，YYYY，日期）;
//串的DayDate = getTimeAgo（mHelper.millisFromString（message.getCreatedAt（）），背景）;
holder.timeAgo.setText（的DayDate）;
}其他{
holder.timeAgo.setVisibility（View.GONE）;
} holder.avatarImageView.setImageResource（R.drawable.com_facebook_profile_default_icon）; 如果（GrouviDatabaseManager.getInstance（上下文）.getCurrentUser（）。的getId（）== message.getUserId（））{
的userName = USERNAME_ME;
如果（message.getStatus（）= NULL和放大器;！＆安培; message.getStatus（）等于（Message.MSG_STATUS_SEND））{
holder.statusImageView.setBackgroundResource（R.drawable.icon_chat_message_delivered）;
holder.statusImageView.setVisibility（View.VISIBLE）;
}
如果（message.getStatus（）= NULL和放大器;！＆安培; message.getStatus（）等于（Message.MSG_STATUS_SENDING））{
holder.progressBar.setVisibility（View.VISIBLE）;
}
如果（message.getStatus（）= NULL和放大器;！＆安培; message.getStatus（）等于（Message.MSG_STATUS_LOCAL））{
holder.statusImageView.setBackgroundResource（R.drawable.icon_chat_message_delivered）;
holder.statusImageView.setVisibility（View.VISIBLE）;
}
如果（message.getStatus（）== NULL || message.getStatus（）。等于（Message.MSG_STATUS_ERROR））{
holder.messageLayout.setAlpha（0.4f）;
holder.errorSign.setVisibility（View.VISIBLE）;
}
}
如果（message.getSpamCount（）大于0＆放大器;＆放大器; CURRENTMODE == MODE_NORMAL）{
holder.messageLayout.setAlpha（0.4f）;
holder.spamSign.setVisibility（View.VISIBLE）;
RelativeLayout.LayoutParams PARAMS =新RelativeLayout.LayoutParams（LayoutParams.MATCH_PARENT，LayoutParams.WRAP_CONTENT）;
holder.messageContent.setLayoutParams（PARAMS）; holder.spamCountTextView.setText（Integer.toString（message.getSpamCount（）））;
holder.spamCountTextView.setVisibility（View.VISIBLE）;
holder.spamLabelImageView.setVisibility（View.VISIBLE）;
}其他{
holder.messageLayout.setAlpha（1F）;
holder.spamSign.setVisibility（View.GONE）;
RelativeLayout.LayoutParams PARAMS =新RelativeLayout.LayoutParams（LayoutParams.MATCH_PARENT，LayoutParams.WRAP_CONTENT）;
holder.messageContent.setLayoutParams（PARAMS）;
} 如果（CURRENTMODE == MODE_REPORT）{
串TIMEAGO = getTimeAgo（mHelper.millisFromString（message.getCreatedAt（）））;
holder.timeAgo.setText（TIMEAGO）;
holder.timeAgo.setVisibility（View.VISIBLE）;
} 如果（message.getUserAvatar（）=空＆放大器;！＆放大器;！message.getUserAvatar（）的isEmpty（））{
尝试{
毕加索
。随着（上下文）
.load（message.getUserAvatar（））
.error（R.drawable.com_facebook_profile_default_icon）
.placeholder（R.drawable.com_facebook_profile_default_icon）
.into（holder.avatarImageView）;
}赶上（例外五）{
Log.e（主，e.getMessage（），E）;
}
}
colorUsername（持有人，信息，用户名）;
holder.nameTextView.setText（用户名）;
holder.dateTextView.setText（formattedDate）; 如果（message.getLikesCount（）大于0）{
holder.likesCountTextView.setText（Integer.toString（message.getLikesCount（）））;
holder.likesCountTextView.setVisibility（View.VISIBLE）;
holder.likesLabelImageView.setVisibility（View.VISIBLE）;
} 如果（message.isBookmarked（））{
holder.bookmarkLabel.setVisibility（View.VISIBLE）;
} 清单＆LT; MessageComponent＆GT; messageComponentList;
messageComponentList = message.getMessageComponents（）; drawMessageContent（架，messageComponentList，消息）; holder.nameTextView.setTag（位置）;
holder.avatarImageView.setTag（位置）;
holder.nameTextView.setOnClickListener（userClickListener）;
holder.avatarImageView.setOnClickListener（userClickListener）; //挂空onLingClickListener显示上下文菜单时
//长按一下整个邮件
holder.nameTextView.setOnLongClickListener（longClickListener）;
holder.avatarImageView.setOnLongClickListener（longClickListener）;
}私人无效colorUsername（ViewHolder架，留言消息，字符串username）{
字符串randomColor = prevColor;
如果（userName.equals（USERNAME_ME））{
randomColor =＃000000;
}否则如果（message.getUserId（）！= prevMsgUserID）{
做{
。String []数组= context.getResources（）getStringArray（R.array.username_colors）;
randomColor =阵列[新的随机（）nextInt（array.length）];
}而（prevColor.equals（randomColor））; }
holder.nameTextView.setTextColor（Color.parseColor（randomColor））;
prevColor = randomColor;
prevMsgUserID = message.getUserId（）;
}
解决方案
您应该保持颜色的数据类，例如在Message类，或保留在地图适配器，映射信息给颜色。然后随机创建颜色，当它不$在地图p $ psent。或者使用的颜色，如果美元在地图p $ psent。使用地图比保持在数据类中，当颜色不相关的信息，当它不是一个消息属性，所以在这种情况下，一个很好的解决方案是很好的解决方案一个保持它在适配器类，在地图，例如：
私人地图＆LT;消息，字符串＆GT; colorsMap =新的HashMap＆LT;消息，字符串＆GT;（）;私人无效colorUsername（ViewHolder架，留言消息，字符串username）{
串randomColor;
如果（colorsMap.contains（消息））{
randomColor = colorsMap.get（消息）;
}
其他{
如果（userName.equals（USERNAME_ME））{
randomColor =＃000000;
}否则如果（message.getUserId（）！= prevMsgUserID）{
做{
。String []数组= context.getResources（）getStringArray（R.array.username_colors）;
randomColor =阵列[新的随机（）nextInt（array.length）];
}而（prevColor.equals（randomColor））; }
colorsMap.put（消息，randomColor）;
}
holder.nameTextView.setTextColor（Color.parseColor（randomColor））;
}
I have chat appIn custom array adapter. I set random colors to usernames for each message with this code:
String[] array = context.getResources().getStringArray(R.array.username_colors);
randomColor = array[new Random().nextInt(array.length)];
nameTextView.setTextColor(Color.parseColor(randomColor));
When new message arrive I add it to listview, and call adapter.notifyDataSetChanged();This causes recoloring existing usernames in messages each time.How can I prevent recoloring existing items in listview when calling adapter.notifyDataSetChanged();
Edit 1
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ChatMessageElement el = list.get(position);
ViewHolder holder = null;
NewMessagesLabelHolder labelHolder = null;
if (convertView == null) {
convertView = el.getView(inflater, parent);
if (el.isMessage()) {
holder = new ViewHolder();
holder.messageLayout = (RelativeLayout) convertView.findViewById(R.id.message_container);
holder.messageContent = (LinearLayout) convertView.findViewById(R.id.message_content);
holder.bottomIndicator = (LinearLayout) convertView.findViewById(R.id.bottom_indicators);
holder.dateTextView = (TextView) convertView.findViewById(R.id.message_date);
holder.timeAgo = (TextView) convertView.findViewById(R.id.time_ago);
holder.nameTextView = (TextView) convertView.findViewById(R.id.user_name);
holder.likesCountTextView = (TextView) convertView.findViewById(R.id.likes_count);
holder.likesLabelImageView = (ImageView) convertView.findViewById(R.id.likes_label);
holder.spamCountTextView = (TextView) convertView.findViewById(R.id.spam_count);
holder.spamLabelImageView = (ImageView) convertView.findViewById(R.id.spam_label);
holder.avatarImageView = (ImageView) convertView.findViewById(R.id.avatar);
holder.statusImageView = (ImageView) convertView.findViewById(R.id.delivered_label);
holder.progressBar = (ProgressBar) convertView.findViewById(R.id.progress_bar);
holder.errorSign = (ImageView) convertView.findViewById(R.id.error_sign);
holder.spamSign = (ImageView) convertView.findViewById(R.id.spam_sign);
holder.bookmarkLabel = (ImageView) convertView.findViewById(R.id.bookmark_label);
holder.topIndicators = (LinearLayout) convertView.findViewById(R.id.topIndicators);
convertView.setTag(holder);
}
if (el.isNewMessagesLabel()) {
convertView = inflater.inflate(R.layout.chat_new_messages_label_layout, parent, false);
labelHolder = new NewMessagesLabelHolder();
labelHolder.newMessagesLabel = (TextView) convertView.findViewById(R.id.new_messages_label);
convertView.setTag(labelHolder);
}
} else {
if (el.isMessage()) {
holder = (ViewHolder) convertView.getTag();
}
if (el.isNewMessagesLabel()) {
labelHolder = (NewMessagesLabelHolder) convertView.getTag();
}
}
if (el.isMessage()) {
Message currentMessage = (Message) el;
drawMessage(holder, currentMessage, position);
}
if (el.isNewMessagesLabel()) {
NewMessagesLabel messagesLabel = (NewMessagesLabel) el;
drawNewMessagesLabel(labelHolder, messagesLabel);
}
return convertView;
}
private void drawMessage(ViewHolder holder, Message message, int position) {
String date = message.getCreatedAt();
String formattedDate = DateHelper.getInstance(context).formatDate("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", "HH:mm", date);
String userName = message.getUserName();
holder.likesLabelImageView.setVisibility(View.GONE);
holder.likesCountTextView.setVisibility(View.GONE);
holder.spamCountTextView.setVisibility(View.GONE);
holder.spamLabelImageView.setVisibility(View.GONE);
holder.bookmarkLabel.setVisibility(View.GONE);
holder.statusImageView.setVisibility(View.GONE);
holder.progressBar.setVisibility(View.GONE);
holder.statusImageView.setVisibility(View.GONE);
holder.errorSign.setVisibility(View.GONE);
holder.spamSign.setVisibility(View.GONE);
holder.timeAgo.setVisibility(View.GONE);
holder.timeAgo.setText("");
holder.messageLayout.setAlpha(1f);
holder.topIndicators.setVisibility(View.VISIBLE);
if (message.isNewDay()) {
holder.timeAgo.setVisibility(View.VISIBLE);
String dayDate = DateHelper.getInstance(context).formatDate("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", "MMMM d, yyyy", date);
//String dayDate = getTimeAgo(mHelper.millisFromString(message.getCreatedAt()), context);
holder.timeAgo.setText(dayDate);
}else{
holder.timeAgo.setVisibility(View.GONE);
}
holder.avatarImageView.setImageResource(R.drawable.com_facebook_profile_default_icon);
if (GrouviDatabaseManager.getInstance(context).getCurrentUser().getId() == message.getUserId()) {
userName = USERNAME_ME;
if (message.getStatus() != null && message.getStatus().equals(Message.MSG_STATUS_SEND)) {
holder.statusImageView.setBackgroundResource(R.drawable.icon_chat_message_delivered);
holder.statusImageView.setVisibility(View.VISIBLE);
}
if (message.getStatus() != null && message.getStatus().equals(Message.MSG_STATUS_SENDING)) {
holder.progressBar.setVisibility(View.VISIBLE);
}
if (message.getStatus() != null && message.getStatus().equals(Message.MSG_STATUS_LOCAL)) {
holder.statusImageView.setBackgroundResource(R.drawable.icon_chat_message_delivered);
holder.statusImageView.setVisibility(View.VISIBLE);
}
if (message.getStatus() == null || message.getStatus().equals(Message.MSG_STATUS_ERROR)) {
holder.messageLayout.setAlpha(0.4f);
holder.errorSign.setVisibility(View.VISIBLE);
}
}
if (message.getSpamCount() > 0 && currentMode == MODE_NORMAL) {
holder.messageLayout.setAlpha(0.4f);
holder.spamSign.setVisibility(View.VISIBLE);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
holder.messageContent.setLayoutParams(params);
holder.spamCountTextView.setText(Integer.toString(message.getSpamCount()));
holder.spamCountTextView.setVisibility(View.VISIBLE);
holder.spamLabelImageView.setVisibility(View.VISIBLE);
} else {
holder.messageLayout.setAlpha(1f);
holder.spamSign.setVisibility(View.GONE);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
holder.messageContent.setLayoutParams(params);
}
if (currentMode == MODE_REPORT) {
String timeAgo = getTimeAgo(mHelper.millisFromString(message.getCreatedAt()));
holder.timeAgo.setText(timeAgo);
holder.timeAgo.setVisibility(View.VISIBLE);
}
if (message.getUserAvatar() != null && !message.getUserAvatar().isEmpty()) {
try {
Picasso
.with(context)
.load(message.getUserAvatar())
.error(R.drawable.com_facebook_profile_default_icon)
.placeholder(R.drawable.com_facebook_profile_default_icon)
.into(holder.avatarImageView);
} catch (Exception e) {
Log.e("Main", e.getMessage(), e);
}
}
colorUsername(holder, message, userName);
holder.nameTextView.setText(userName);
holder.dateTextView.setText(formattedDate);
if (message.getLikesCount()>0) {
holder.likesCountTextView.setText(Integer.toString(message.getLikesCount()));
holder.likesCountTextView.setVisibility(View.VISIBLE);
holder.likesLabelImageView.setVisibility(View.VISIBLE);
}
if (message.isBookmarked()) {
holder.bookmarkLabel.setVisibility(View.VISIBLE);
}
List<MessageComponent> messageComponentList;
messageComponentList = message.getMessageComponents();
drawMessageContent(holder, messageComponentList, message);
holder.nameTextView.setTag(position);
holder.avatarImageView.setTag(position);
holder.nameTextView.setOnClickListener(userClickListener);
holder.avatarImageView.setOnClickListener(userClickListener);
// hang empty onLingClickListener to display context menu when
// long click on whole message
holder.nameTextView.setOnLongClickListener(longClickListener);
holder.avatarImageView.setOnLongClickListener(longClickListener);
}
private void colorUsername(ViewHolder holder, Message message, String userName) {
String randomColor = prevColor;
if (userName.equals(USERNAME_ME)){
randomColor = "#000000";
}else if (message.getUserId()!=prevMsgUserID) {
do {
String[] array = context.getResources().getStringArray(R.array.username_colors);
randomColor = array[new Random().nextInt(array.length)];
}while (prevColor.equals(randomColor));
}
holder.nameTextView.setTextColor(Color.parseColor(randomColor));
prevColor = randomColor;
prevMsgUserID = message.getUserId();
}
解决方案
You should keep color in the data class, for example in the Message class, or keep Map in the adapter, that maps Message to Color. Then randomly create a color, when it doesn't present in the map. or use the color, if it present in the map. Using a map is good solution than keeping in the data class, when the color doesn't related to message, when it is not a message property, so in that case, a good solution is a keeping it in the adapter class, in the map, for example
private Map<Message, String> colorsMap = new HashMap<Message, String>();
private void colorUsername(ViewHolder holder, Message message, String userName) {
String randomColor;
if(colorsMap.contains(message)) {
randomColor = colorsMap.get(message);
}
else {
if (userName.equals(USERNAME_ME)){
randomColor = "#000000";
}else if (message.getUserId()!=prevMsgUserID) {
do {
String[] array = context.getResources().getStringArray(R.array.username_colors);
randomColor = array[new Random().nextInt(array.length)];
}while (prevColor.equals(randomColor));
}
colorsMap.put(message, randomColor);
}
holder.nameTextView.setTextColor(Color.parseColor(randomColor));
}
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