BaseAdapter多种View适配，getItemViewType的作用

之前一直不知道有getItemViewType这个方法，多View适配一直多判断方法，如下：

ViewHolder viewHolder;if (convertView == null || convertView.getTag(R.drawable.ic_launcher + come) == null) {//自己发的if (come == ChatConstants.OUTGOING) {convertView = mInflater.inflate(R.layout.chat_item_right, parent, false);} else {//别人发 的convertView = mInflater.inflate(R.layout.chat_item_left, null);}viewHolder = buildHolder(convertView);convertView.setTag(R.drawable.ic_launcher + come, viewHolder);convertView.setTag(R.string.app_name, R.drawable.ic_launcher + come);} else {viewHolder = (ViewHolder) convertView.getTag(R.drawable.ic_launcher + come);}

因为要做聊天，后来了选择了第三方聊天环信。由于要自定义消息类型，所以要修改消息适配器。

环信官方demo就用到了getItemViewType来解决多View适配convertView重用的这个问题。请看下面代码：

由于官方demo代码比较多所以这里就粘贴一部分，如果想全面研究就下载附件吧

private static final int MESSAGE_TYPE_RECV_TXT = 0;private static final int MESSAGE_TYPE_SENT_TXT = 1;private static final int MESSAGE_TYPE_SENT_IMAGE = 2;private static final int MESSAGE_TYPE_SENT_LOCATION = 3;private static final int MESSAGE_TYPE_RECV_LOCATION = 4;private static final int MESSAGE_TYPE_RECV_IMAGE = 5;private static final int MESSAGE_TYPE_SENT_VOICE = 6;private static final int MESSAGE_TYPE_RECV_VOICE = 7;private static final int MESSAGE_TYPE_SENT_VIDEO = 8;private static final int MESSAGE_TYPE_RECV_VIDEO = 9;private static final int MESSAGE_TYPE_SENT_FILE = 10;private static final int MESSAGE_TYPE_RECV_FILE = 11;private static final int MESSAGE_TYPE_SENT_VOICE_CALL = 12;private static final int MESSAGE_TYPE_RECV_VOICE_CALL = 13;private static final int MESSAGE_TYPE_SENT_VIDEO_CALL = 14;private static final int MESSAGE_TYPE_RECV_VIDEO_CALL = 15;private static final int MESSAGE_TYPE_SENT_ROBOT_MENU = 16;private static final int MESSAGE_TYPE_RECV_ROBOT_MENU = 17;

/** * 获取item类型数 */public int getViewTypeCount() {        return 18;    }/** * 获取item类型 */public int getItemViewType(int position) {EMMessage message = getItem(position); if (message == null) {return -1;}if (message.getType() == EMMessage.Type.TXT) {if (message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VOICE_CALL, false))    return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_VOICE_CALL : MESSAGE_TYPE_SENT_VOICE_CALL;else if (message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VIDEO_CALL, false))    return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_VIDEO_CALL : MESSAGE_TYPE_SENT_VIDEO_CALL;else if(((DemoHXSDKHelper)HXSDKHelper.getInstance()).isRobotMenuMessage(message))return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_ROBOT_MENU : MESSAGE_TYPE_SENT_ROBOT_MENU;elsereturn message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_TXT : MESSAGE_TYPE_SENT_TXT;}if (message.getType() == EMMessage.Type.IMAGE) {return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_IMAGE : MESSAGE_TYPE_SENT_IMAGE;}if (message.getType() == EMMessage.Type.LOCATION) {return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_LOCATION : MESSAGE_TYPE_SENT_LOCATION;}if (message.getType() == EMMessage.Type.VOICE) {return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_VOICE : MESSAGE_TYPE_SENT_VOICE;}if (message.getType() == EMMessage.Type.VIDEO) {return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_VIDEO : MESSAGE_TYPE_SENT_VIDEO;}if (message.getType() == EMMessage.Type.FILE) {return message.direct == EMMessage.Direct.RECEIVE ? MESSAGE_TYPE_RECV_FILE : MESSAGE_TYPE_SENT_FILE;}return -1;// invalid}

@SuppressLint("NewApi")public View getView(final int position, View convertView, ViewGroup parent) {final EMMessage message = getItem(position);ChatType chatType = message.getChatType();final ViewHolder holder;if (convertView == null) {holder = new ViewHolder();convertView = createViewByMessage(message, position);if (message.getType() == EMMessage.Type.IMAGE) {try {holder.iv = ((ImageView) convertView.findViewById(R.id.iv_sendPicture));holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);holder.tv = (TextView) convertView.findViewById(R.id.percentage);holder.pb = (ProgressBar) convertView.findViewById(R.id.progressBar);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);} catch (Exception e) {}} else if (message.getType() == EMMessage.Type.TXT) {try {holder.pb = (ProgressBar) convertView.findViewById(R.id.pb_sending);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);// 这里是文字内容holder.tv = (TextView) convertView.findViewById(R.id.tv_chatcontent);holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);holder.tvTitle = (TextView) convertView.findViewById(R.id.tvTitle);holder.tvList = (LinearLayout) convertView.findViewById(R.id.ll_layout);} catch (Exception e) {}// 语音通话及视频通话if (message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VOICE_CALL, false)        || message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VIDEO_CALL, false)) {holder.iv = (ImageView) convertView.findViewById(R.id.iv_call_icon);holder.tv = (TextView) convertView.findViewById(R.id.tv_chatcontent);}} else if (message.getType() == EMMessage.Type.VOICE) {try {holder.iv = ((ImageView) convertView.findViewById(R.id.iv_voice));holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);holder.tv = (TextView) convertView.findViewById(R.id.tv_length);holder.pb = (ProgressBar) convertView.findViewById(R.id.pb_sending);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);holder.iv_read_status = (ImageView) convertView.findViewById(R.id.iv_unread_voice);} catch (Exception e) {}} else if (message.getType() == EMMessage.Type.LOCATION) {try {holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);holder.tv = (TextView) convertView.findViewById(R.id.tv_location);holder.pb = (ProgressBar) convertView.findViewById(R.id.pb_sending);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);} catch (Exception e) {}} else if (message.getType() == EMMessage.Type.VIDEO) {try {holder.iv = ((ImageView) convertView.findViewById(R.id.chatting_content_iv));holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);holder.tv = (TextView) convertView.findViewById(R.id.percentage);holder.pb = (ProgressBar) convertView.findViewById(R.id.progressBar);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.size = (TextView) convertView.findViewById(R.id.chatting_size_iv);holder.timeLength = (TextView) convertView.findViewById(R.id.chatting_length_iv);holder.playBtn = (ImageView) convertView.findViewById(R.id.chatting_status_btn);holder.container_status_btn = (LinearLayout) convertView.findViewById(R.id.container_status_btn);holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);} catch (Exception e) {}} else if (message.getType() == EMMessage.Type.FILE) {try {holder.iv_avatar = (ImageView) convertView.findViewById(R.id.iv_userhead);holder.tv_file_name = (TextView) convertView.findViewById(R.id.tv_file_name);holder.tv_file_size = (TextView) convertView.findViewById(R.id.tv_file_size);holder.pb = (ProgressBar) convertView.findViewById(R.id.pb_sending);holder.staus_iv = (ImageView) convertView.findViewById(R.id.msg_status);holder.tv_file_download_state = (TextView) convertView.findViewById(R.id.tv_file_state);holder.ll_container = (LinearLayout) convertView.findViewById(R.id.ll_file_container);// 这里是进度值holder.tv = (TextView) convertView.findViewById(R.id.percentage);} catch (Exception e) {}try {holder.tv_usernick = (TextView) convertView.findViewById(R.id.tv_userid);} catch (Exception e) {}}convertView.setTag(holder);} else {holder = (ViewHolder) convertView.getTag();}// 群聊时，显示接收的消息的发送人的名称if ((chatType == ChatType.GroupChat || chatType == chatType.ChatRoom) && message.direct == EMMessage.Direct.RECEIVE){    //demo里使用username代码nickholder.tv_usernick.setText(message.getFrom());}// 如果是发送的消息并且不是群聊消息，显示已读textviewif (!(chatType == ChatType.GroupChat || chatType == chatType.ChatRoom) && message.direct == EMMessage.Direct.SEND) {holder.tv_ack = (TextView) convertView.findViewById(R.id.tv_ack);holder.tv_delivered = (TextView) convertView.findViewById(R.id.tv_delivered);if (holder.tv_ack != null) {if (message.isAcked) {if (holder.tv_delivered != null) {holder.tv_delivered.setVisibility(View.INVISIBLE);}holder.tv_ack.setVisibility(View.VISIBLE);} else {holder.tv_ack.setVisibility(View.INVISIBLE);// check and display msg delivered ack statusif (holder.tv_delivered != null) {if (message.isDelivered) {holder.tv_delivered.setVisibility(View.VISIBLE);} else {holder.tv_delivered.setVisibility(View.INVISIBLE);}}}}} else {// 如果是文本或者地图消息并且不是group messgae,chatroom message，显示的时候给对方发送已读回执if ((message.getType() == Type.TXT || message.getType() == Type.LOCATION) && !message.isAcked && chatType != ChatType.GroupChat && chatType != ChatType.ChatRoom) {// 不是语音通话记录if (!message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VOICE_CALL, false)) {try {EMChatManager.getInstance().ackMessageRead(message.getFrom(), message.getMsgId());// 发送已读回执message.isAcked = true;} catch (Exception e) {e.printStackTrace();}}}}//设置用户头像setUserAvatar(message, holder.iv_avatar);switch (message.getType()) {// 根据消息type显示itemcase IMAGE: // 图片handleImageMessage(message, holder, position, convertView);break;case TXT: // 文本if (message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VOICE_CALL, false)        || message.getBooleanAttribute(Constant.MESSAGE_ATTR_IS_VIDEO_CALL, false))    // 音视频通话    handleCallMessage(message, holder, position);else if(((DemoHXSDKHelper)HXSDKHelper.getInstance()).isRobotMenuMessage(message))//含有列表的消息handleRobotMenuMessage(message, holder, position);else    handleTextMessage(message, holder, position);break;case LOCATION: // 位置handleLocationMessage(message, holder, position, convertView);break;case VOICE: // 语音handleVoiceMessage(message, holder, position, convertView);break;case VIDEO: // 视频handleVideoMessage(message, holder, position, convertView);break;case FILE: // 一般文件handleFileMessage(message, holder, position, convertView);break;default:// not supported}if (message.direct == EMMessage.Direct.SEND) {View statusView = convertView.findViewById(R.id.msg_status);// 重发按钮点击事件statusView.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// 显示重发消息的自定义alertdialogIntent intent = new Intent(activity, AlertDialog.class);intent.putExtra("msg", activity.getString(R.string.confirm_resend));intent.putExtra("title", activity.getString(R.string.resend));intent.putExtra("cancel", true);intent.putExtra("position", position);if (message.getType() == EMMessage.Type.TXT)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_TEXT);else if (message.getType() == EMMessage.Type.VOICE)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_VOICE);else if (message.getType() == EMMessage.Type.IMAGE)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_PICTURE);else if (message.getType() == EMMessage.Type.LOCATION)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_LOCATION);else if (message.getType() == EMMessage.Type.FILE)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_FILE);else if (message.getType() == EMMessage.Type.VIDEO)activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_VIDEO);}});} else {final String st = context.getResources().getString(R.string.Into_the_blacklist);if(!((ChatActivity)activity).isRobot && chatType != ChatType.ChatRoom){// 长按头像，移入黑名单holder.iv_avatar.setOnLongClickListener(new OnLongClickListener() {@Overridepublic boolean onLongClick(View v) {Intent intent = new Intent(activity, AlertDialog.class);intent.putExtra("msg", st);intent.putExtra("cancel", true);intent.putExtra("position", position);activity.startActivityForResult(intent, ChatActivity.REQUEST_CODE_ADD_TO_BLACKLIST);return true;}});}}TextView timestamp = (TextView) convertView.findViewById(R.id.timestamp);if (position == 0) {timestamp.setText(DateUtils.getTimestampString(new Date(message.getMsgTime())));timestamp.setVisibility(View.VISIBLE);} else {// 两条消息时间离得如果稍长，显示时间EMMessage prevMessage = getItem(position - 1);if (prevMessage != null && DateUtils.isCloseEnough(message.getMsgTime(), prevMessage.getMsgTime())) {timestamp.setVisibility(View.GONE);} else {timestamp.setText(DateUtils.getTimestampString(new Date(message.getMsgTime())));timestamp.setVisibility(View.VISIBLE);}}return convertView;}

demo点击下载