ListView实战技巧-优快云博客

本文链接：https://blog.youkuaiyun.com/qw1026967001/article/details/51172656

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));
    }
}