Android列表组件ListView使用详解之数据为空提示信息

在使用ListView显示数据时，有时候可能显示的数据为空，此时界面可能需要给出友好的提示，使用ListView类的方法：

/**
     * Sets the view to show if the adapter is empty
     */
    @android.view.RemotableViewMethod
    public void setEmptyView(View emptyView) {
        mEmptyView = emptyView;

        // If not explicitly specified this view is important for accessibility.
        if (emptyView != null
                && emptyView.getImportantForAccessibility() == IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
            emptyView.setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
        }

        final T adapter = getAdapter();
        final boolean empty = ((adapter == null) || adapter.isEmpty());
        updateEmptyStatus(empty);
    }

给出一个提示信息的View即可，关键代码如下：

testLv.setEmptyView(findViewById(R.id.empty_tv));

效果图：

当前界面显示的代码：

package net.oschina.git.zhaikun.androiddeveloped.activitys;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;

import net.oschina.git.zhaikun.androiddeveloped.R;
import net.oschina.git.zhaikun.androiddeveloped.adapter.ListViewDemoAdapter;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by zhaikun68 on 2018/3/5.
 * 

 * ListView演示Demo
 */
public class ListViewDemoActivity extends AppCompatActivity implements View.OnClickListener {

    private ListView testLv;//ListView组件
    private Button updateDataBtn;//动态加载数据组件

    private List dataList = new ArrayList<>();//存储数据
    private ListViewDemoAdapter listViewDemoAdapter;//ListView的数据适配器

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_listview_demo);

        initView();//初始化组件
        initData();//初始化数据
    }

    /**
     * 初始化组件
     */
    private void initView() {
        testLv = (ListView) findViewById(R.id.test_lv);
        updateDataBtn = (Button) findViewById(R.id.update_data_btn);

        updateDataBtn.setOnClickListener(this);
    }

    /**
     * 初始化数据
     */
    private void initData() {
        //初始化10项数据
        /*for (int i = 1; i <= 20; i++) {
            dataList.add("显示内容" + i);
        }*/

        //设置ListView的适配器
        listViewDemoAdapter = new ListViewDemoAdapter(this, dataList);
        testLv.setAdapter(listViewDemoAdapter);
        testLv.setSelection(4);
        //数据为空时显示的提示信息
        testLv.setEmptyView(findViewById(R.id.empty_tv));
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.update_data_btn://动态加载列表数据
                dataList.add("动态加载的数据项");
                //通知ListView更改数据源
                if (listViewDemoAdapter != null) {
                    listViewDemoAdapter.notifyDataSetChanged();
                    testLv.setSelection(dataList.size() - 1);//设置显示列表的最后一项
                } else {
                    listViewDemoAdapter = new ListViewDemoAdapter(this, dataList);
                    testLv.setAdapter(listViewDemoAdapter);
                    testLv.setSelection(dataList.size() - 1);
                }
                break;
        }
    }
}

界面对应的布局文件：

数据适配器代码：

package net.oschina.git.zhaikun.androiddeveloped.adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import net.oschina.git.zhaikun.androiddeveloped.R;

import java.util.List;

/**
 * Created by zhaikun68 on 2018/3/5.
 * 

 * ListView演示Demo中的数据适配器
 */
public class ListViewDemoAdapter extends BaseAdapter {

    private Context context;//上下文对象
    private List dataList;//ListView显示的数据

    /**
     * 构造器
     *
     * @param context  上下文对象
     * @param dataList 数据
     */
    public ListViewDemoAdapter(Context context, List dataList) {
        this.context = context;
        this.dataList = dataList;
    }

    @Override
    public int getCount() {
        return dataList == null ? 0 : dataList.size();
    }

    @Override
    public Object getItem(int position) {
        return dataList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        //判断是否有缓存
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.item_listview_demo, null);
            viewHolder = new ViewHolder(convertView);
            convertView.setTag(viewHolder);
        } else {
            //得到缓存的布局
            viewHolder = (ViewHolder) convertView.getTag();
        }

        //设置图片
        viewHolder.pictureImg.setImageResource(R.mipmap.ic_launcher);
        //设置内容
        viewHolder.contentTv.setText(dataList.get(position));

        return convertView;
    }

    /**
     * ViewHolder类
     */
    private final class ViewHolder {

        ImageView pictureImg;//图片
        TextView contentTv;//内容

        /**
         * 构造器
         *
         * @param view 视图组件（ListView的子项视图）
         */
        ViewHolder(View view) {
            pictureImg = (ImageView) view.findViewById(R.id.picture_img);
            contentTv = (TextView) view.findViewById(R.id.content_tv);
        }
    }
}

列表子项的布局文件：