13-4-1 Android中list和Adapter的使用
Android中list和Adapter的使用
java.util.List<E>
包含有：
AbstractList<E>, AbstractSequentialList<E>, ArrayList<E>, CopyOnWriteArrayList<E>, LinkedList<E>, Stack<E>, Vector<E>
private List<ChatMessage> messages = new ArrayList<ChatMessage>();
ChatMessage为数据列表
private ChattingAdapter chatHistoryAdapter;
chatHistoryAdapter为数据源也就是 listview 和 数据列表的 桥梁。
1、ChatMessage类定义
package cn.itcast.test.chat.adapter;
public class ChatMessage {
public static final int MESSAGE_FROM = 0;
public static final int MESSAGE_TO = 1;
private int direction;
private String content;
public ChatMessage(int direction, String content) {
super();
this.direction = direction;
this.content = content;
}
public int getDirection() {
return direction;
}
public void setDirection(int direction) {
this.direction = direction;
}
public void setContent(String content) {
this.content = content;
}
public CharSequence getContent() {
return content;
}
}
2. ChattingAdapter类定义
package cn.itcast.test.chat.adapter;
import java.util.List;
import cn.itcast.test.chat.R;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
public class ChattingAdapter extends BaseAdapter {
protected static final String TAG = "ChattingAdapter";
private Context context;
private List<ChatMessage> chatMessages;//关联数据
//析构函数
public ChattingAdapter(Context context, List<ChatMessage> messages) {
super();
this.context = context;
this.chatMessages = messages;
}
@Override
public int getCount() {//返回数据源中总的记录数目
return chatMessages.size();
}
@Override
public Object getItem(int position) {//获得选择的数据源中某个项目的数据
return chatMessages.get(position);
}
@Override
public long getItemId(int position) {//获取数据源中的索引值
return position;
}
@Override//获取要展示的项目View对象
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
ChatMessage message = chatMessages.get(position);
if (convertView == null || (holder = (ViewHolder) convertView.getTag()).flag != message.getDirection()) {
holder = new ViewHolder();
if (message.getDirection() == ChatMessage.MESSAGE_FROM) {
holder.flag = ChatMessage.MESSAGE_FROM;
convertView = LayoutInflater.from(context).inflate(R.layout.chatting_item_from, null);
} else {
holder.flag = ChatMessage.MESSAGE_TO;
convertView = LayoutInflater.from(context).inflate(R.layout.chatting_item_to, null);
}
holder.text = (TextView) convertView.findViewById(R.id.chatting_content_itv);
convertView.setTag(holder);
}
holder.text.setText(message.getContent());
return convertView;
}
//优化listview的Adapter
static class ViewHolder {
TextView text;
int flag;
}
}
3 主程序中的初始化调用
// 设置adapter
private void setAdapterForThis() {
initMessages();
chatHistoryAdapter = new ChattingAdapter(this, messages);
chatHistoryLv.setAdapter(chatHistoryAdapter);
}
// 为listView添加数据
private void initMessages() {
messages.add(new ChatMessage(ChatMessage.MESSAGE_FROM, "hello"));
messages.add(new ChatMessage(ChatMessage.MESSAGE_TO, "hello"));
messages.add(new ChatMessage(ChatMessage.MESSAGE_FROM, "welcome me blog:http://blog.csdn.net/feiyangxiaomi"));
}
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