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：

<?xml version="1.0" encoding="utf-8"?>

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：

<?xml version="1.0" encoding="utf-8"?>

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