listView学习记录

listView常用属性值:
xml文件属性：
android:divider="@null", 取消（设置）分割线
android:dividerHeight="10dp" ，分割线高度
android:scrollbars=”none” 隐藏listView滚动条
android:listSelector=”@android:color/transparent” 设置透明色以取消item点击效果

代码中设置
listView.setSelection(15); 指定显示第15个item
listView.getFirstVisiblePosition();获取当前可视区域第一个item的id（包含不完整的item）
listView.getLastVisiblePosition();获取当前可视区域最后一个item的id（包含不完整的item）
listView.setEmptyView(tv);listView设置空数据（空数据时显示，有数据则不显示）
示例布局

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.learn.listviewtest.MainActivity">    <TextView        android:id="@+id/tv1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="ListView is empty"        android:textSize="24sp"        android:layout_gravity="center"/>    <ListView        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/listView"        android:divider="@color/colorAccent"        android:dividerHeight="5dp"        android:scrollbars="none"        android:listSelector="@android:color/transparent"        ></ListView></FrameLayout>

代码中使用 ：
tv = (TextView) findViewById(R.id.tv1);
listView.setEmptyView(tv);

1.使用ViewHolder提高效率

简单示例

public class MyAdapter extends BaseAdapter{    private List<String> data;//数据源    private Context context;    private LayoutInflater inflater;    public MyAdapter(Context context, List<String> data) {        this.context = context;        this.data = data;        inflater = LayoutInflater.from(context);    }    @Override    public int getCount() {        return data.size();    }    @Override    public Object getItem(int position) {        return data.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder holder = null;        if (convertView==null){            holder = new ViewHolder();//实例化ViewHolder            //通过LayoutInflater实例化布局            convertView = inflater.inflate(R.layout.item_list1,null);            holder.im = (ImageView) convertView.findViewById(R.id.imageView);            holder.tv = (TextView) convertView.findViewById(R.id.tv);            convertView.setTag(holder);//设置Tag将两者联系起来        }else {            //通过Tag找到缓存的布局            holder = (ViewHolder) convertView.getTag();        }        holder.im.setImageResource(R.mipmap.ic_launcher);        holder.tv.setText("hello:"+data.get(position));        return convertView;    }    private class ViewHolder{        TextView tv;        ImageView im;    }}

2.listView实现简单聊天界面

chat_item_me.XML

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/tv_time_me"        android:layout_alignParentTop="true"        android:text="10:28"        android:layout_marginBottom="10dp"        android:layout_centerHorizontal="true"/>    <ImageView        android:layout_width="60dp"        android:layout_height="60dp"        android:id="@+id/iv_me"        android:layout_below="@id/tv_time_me"        android:layout_alignParentRight="true"        android:src="@mipmap/ic_launcher"/>    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/tv_me"        android:layout_below="@id/tv_time_me"        android:text=""        android:gravity="center"        android:maxWidth="550px"        android:layout_toLeftOf="@id/iv_me"        android:background="@drawable/chatitem_out_bg"/></RelativeLayout>

chat_item_other.XML

public class ChatAdapter extends BaseAdapter {    private List<ChatBean> data;    private LayoutInflater inflater;    public ChatAdapter(Context context, List<ChatBean> data) {        this.data = data;        inflater = LayoutInflater.from(context);    }    @Override    public int getCount() {        return data.size();    }    @Override    public Object getItem(int position) {        return data.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder holder;        if (convertView==null){            if (getItemViewType(position)==0){                holder = new ViewHolder();                convertView = inflater.inflate(R.layout.chat_item_me,null);                holder.iv = (ImageView) convertView.findViewById(R.id.iv_me);                holder.tv = (TextView) convertView.findViewById(R.id.tv_me);                holder.time = (TextView) convertView.findViewById(R.id.tv_time_me);            }else {                holder = new ViewHolder();                convertView = inflater.inflate(R.layout.chat_item_other,null);                holder.iv = (ImageView) convertView.findViewById(R.id.iv_other);                holder.tv = (TextView) convertView.findViewById(R.id.tv_other);                holder.time = (TextView) convertView.findViewById(R.id.tv_time_other);            }            convertView.setTag(holder);        }else {            holder = (ViewHolder) convertView.getTag();        }        holder.iv.setImageBitmap(data.get(position).getIcon());        holder.tv.setText(data.get(position).getText());        holder.time.setText(data.get(position).getTime());        return convertView;    }    @Override//返回第position个item是何类型    public int getItemViewType(int position) {        ChatBean bean = data.get(position);        return bean.getType();    }    @Override//返回不同布局的总数    public int getViewTypeCount() {        return 2;    }    class ViewHolder{        public ImageView iv;        public TextView tv;        public TextView time;    }}

bean类

/** * Created by Administrator on 2016/4/17. */public class ChatBean {    private int type;//信息来源类型    private String text;//聊天信息    private String time;//聊天时间    private Bitmap icon;//聊天头像    public int getType() {        return type;    }    public void setType(int type) {        this.type = type;    }    public String getText() {        return text;    }    public void setText(String text) {        this.text = text;    }    public String getTime() {        return time;    }    public void setTime(String time) {        this.time = time;    }    public Bitmap getIcon() {        return icon;    }    public void setIcon(Bitmap icon) {        this.icon = icon;    }}

Activity

public class ChatViewActivity extends AppCompatActivity {    private ListView listView;    private List<ChatBean> list = new ArrayList<>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_chat_view);        listView = (ListView) findViewById(R.id.listView);        ChatBean bean1 = new ChatBean();        bean1.setType(0);        bean1.setText("你好啊");        bean1.setTime("10:50");        bean1.setIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher));        list.add(bean1);        ChatBean bean2 = new ChatBean();        bean2.setType(1);        bean2.setText("你好");        bean2.setTime("10:50");        bean2.setIcon(BitmapFactory.decodeResource(getResources(),R.drawable.in_icon));        list.add(bean2);        ChatBean bean3 = new ChatBean();        bean3.setType(0);        bean3.setText("Hello,it's nice to meet you");        bean3.setTime("10:50");        bean3.setIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher));        list.add(bean3);        ChatBean bean4 = new ChatBean();        bean4.setType(1);        bean4.setText("It's nice to meet you too!");        bean4.setTime("10:50");        bean4.setIcon(BitmapFactory.decodeResource(getResources(),R.drawable.in_icon));        list.add(bean4);        ChatBean bean5 = new ChatBean();        bean5.setType(1);        bean5.setText("How old are you?");        bean5.setTime("10:50");        bean5.setIcon(BitmapFactory.decodeResource(getResources(),R.drawable.in_icon));        list.add(bean5);        ChatBean bean6 = new ChatBean();        bean6.setType(0);        bean6.setText("I am 22 years old");        bean6.setTime("10:50");        bean6.setIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher));        list.add(bean6);        listView.setAdapter(new ChatAdapter(this,list));    }}