← Android ListView Checkbox 混乱 Android ListView 删除数据 →

Android ListView 添加插入数据

前面几章节，我们给 ListView 的数据都是预先定义好的，实际开发中这样的情况少之又少

要么要动态增加数据，要么要删除一些数据，要么要更改一些数据，这时候，我们的 ListView 就要同步更改才对

本节我们就来学习如何动态的更改 ListView 中的数据

基本的 demo

我们先来写一个基本的列表

又一次练写代码速度的时候到了

  1. 创建一个 空的 Android 项目 cn.twle.android.ListViewCRUD

  2. 下载 /static/i/android/golf.png 并拖到 res/drawable 目录

  3. 修改 activity_main.xml 添加一个 ListView

    <?xml version="1.0" encoding="utf-8" ?>
<LinearLayout 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"
    android:padding="8dp" 
    android:orientation="vertical" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

  4. 在 res/layout 目录下新建一个列表项的布局 listview_item.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="8dp"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/avatar"
        android:layout_weight="1" 
        android:layout_width="32dp"
        android:layout_height="32dp"/>

    <TextView
        android:id="@+id/say"
        android:layout_weight="7" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_vertical"
        android:textSize="18sp" />

</LinearLayout>

  5. 在 MainActivity.java 同一目录下新建一个 Bean 类 TalkBean.java

    package cn.twle.android.listviewcrud;

public class TalkBean {
    private int avatar_id;
    private String say;

    public TalkBean() {}

    public TalkBean(int avatar_id, String say) {
        this.avatar_id = avatar_id;
        this.say = say;
    }

    public int getAvatarId() {
        return avatar_id;
    }

    public String getSay() {
        return say;
    }

    public void setAvatarId(int avatarId) {
        this.avatar_id = avatarId;
    }

    public void setSay(String say) {
        this.say = say;
    }
}

  6. 在 MainActivity.java 目录下新建一个 Adapter 文件 TalkAdapter.java

    package cn.twle.android.listviewcrud;

import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import android.content.Context;

import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;

import java.util.LinkedList;

public class TalkAdapter extends BaseAdapter {

    private Context mContext;
    private LinkedList<TalkBean> mData;

    public TalkAdapter() {}

    public TalkAdapter(LinkedList<TalkBean> mData, Context mContext) {
        this.mData = mData;
        this.mContext = mContext;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;

        if(convertView == null){

            convertView = LayoutInflater.from(mContext).inflate(R.layout.listview_item,parent,false);

            holder = new ViewHolder();

            holder.avatar = (ImageView) convertView.findViewById(R.id.avatar);
            holder.say = (TextView) convertView.findViewById(R.id.say);
            convertView.setTag(holder);
        }else{
            holder = (ViewHolder) convertView.getTag();
        }

        holder.avatar.setImageResource(mData.get(position).getAvatarId());
        holder.say.setText(mData.get(position).getSay());
        return convertView;
    }

    private class ViewHolder{
        ImageView avatar;
        TextView  say;
    }

}

  7. 修改 MainActivity.java

    package cn.twle.android.listviewcrud;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.widget.SimpleAdapter;
import android.widget.ListView;
import android.widget.Toast;
import android.widget.AdapterView;

import android.view.View;

import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listview;
    private TalkAdapter talkAdapter = null;
    private List<TalkBean> mData = null;
    private int flag = 0;

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

        listview = (ListView) findViewById(R.id.listview);

        mData = new LinkedList<TalkBean>();
        talkAdapter = new TalkAdapter((LinkedList<TalkBean>) mData,MainActivity.this);

        listview.setAdapter(talkAdapter);
    }
}

运行后发现我们的页面并没有任何的数据，白茫茫的一片，这样的用户体验并不好

数据为空时提示用户没数据

可以调用 ListView 的一个 setEmptyView(View) 的方法，当 ListView 数据为空的时候， 显示一个对应的 View

  1. 复用上面的 demo

  2. 在 res/layout 目录下新建一个 listview_empty.xml 

    <?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
              android:orientation="vertical"  
              android:layout_width="match_parent"  
              android:layout_height="match_parent">

    <TextView  
        android:gravity="center"  
        android:textSize="18sp"  
        android:textColor="#333333"  
        android:text="没有可显示的数据"  
        android:layout_width="match_parent"  
        android:layout_height="match_parent"/>

</LinearLayout>

  3. 修改 activity_main.xml 包含 listview_empty.xml

    <?xml version="1.0" encoding="utf-8" ?>
<LinearLayout 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"
    android:padding="8dp" 
    android:orientation="vertical" >

    <include  
            android:id="@+id/talk_empty"  
            layout="@layout/listview_empty"/>

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

  4. 然后修改 MainActivity.java 调用 setEmptyView(View)

    package cn.twle.android.listviewcrud;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.widget.ListView;
import android.widget.Toast;
import android.widget.AdapterView;

import android.view.View;

import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listview;
    private TalkAdapter talkAdapter = null;
    private List<TalkBean> mData = null;
    private int flag = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        listview = (ListView) findViewById(R.id.listview);

        View listview_empty = findViewById(R.id.talk_empty);  
        listview.setEmptyView(listview_empty);

        mData = new LinkedList<TalkBean>();
        talkAdapter = new TalkAdapter((LinkedList<TalkBean>) mData,MainActivity.this);

        listview.setAdapter(talkAdapter);
    }
}

运行效果如下

添加记录

我们在顶部添加一个按钮，每次点击添加一条记录


  1. 复用上面的 demo

  2. 修改 TalkAdapter.java 添加一个 add() 添加数据的方法

    public void add(TalkBean data) {
    if (mData == null) {
        mData = new LinkedList<>();
    }
    mData.add(data);
    notifyDataSetChanged();
}

  3. 然后修改 activity_main.xml 添加一个按钮

    <?xml version="1.0" encoding="utf-8" ?>
<LinearLayout 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"
    android:padding="8dp" 
    android:orientation="vertical" >

    <Button
        android:id="@+id/btn_add"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content" 
        android:text = "添加数据" />

    <include  
            android:id="@+id/talk_empty"  
            layout="@layout/listview_empty"/>

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

  4. 修改 MainActivity.java 添加按钮的点击事件

    package cn.twle.android.listviewcrud;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.widget.ListView;
import android.widget.Button;
import android.widget.Toast;
import android.widget.AdapterView;

import android.view.View;

import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listview;
    private TalkAdapter talkAdapter = null;
    private List<TalkBean> mData = null;
    private int flag = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        listview = (ListView) findViewById(R.id.listview);

        View listview_empty = findViewById(R.id.talk_empty);  
        listview.setEmptyView(listview_empty);

        mData = new LinkedList<TalkBean>();
        talkAdapter = new TalkAdapter((LinkedList<TalkBean>) mData,MainActivity.this);

        listview.setAdapter(talkAdapter);

        Button btn_add = findViewById(R.id.btn_add);

        btn_add.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                switch (v.getId()){
                    case R.id.btn_add:
                        talkAdapter.add(new TalkBean(R.drawable.golf,"你好 " + flag));
                        flag++;
                        break;
                }
            }
        });
    }
}

TalkBean。add() 方法中的 notifyDataSetChanged() 调用很重要，它用于通知 ListView 数据已经更改，你要重新加载数据

在指定位置插入数据


如果想在特定位置插入数据，只要传递位置即可

  1. 复用上面的 demo

  2. 修改 TalkAdapter.java 添加一个方法 insert()

    // 往特定位置，添加一个元素
public void insert(TalkBean data, int position){
    if (mData == null) {
        mData = new LinkedList<>();
    }

    int len = mData.size();

    if ( 0 > position )
    {
        position = 0;
    }

    if ( position > len )
    {
        position = len;
    }

    mData.add(position,data);
    notifyDataSetChanged();
}

  3. 然后修改布局添加一个 插入数据按钮

    <?xml version="1.0" encoding="utf-8" ?>
<LinearLayout 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"
    android:padding="8dp" 
    android:orientation="vertical" >

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="8dp" 
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn_add"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content" 
            android:text = "添加" />

        <Button
            android:id="@+id/btn_insert"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content" 
            android:text = "插入数据到位置 3 " />

    </LinearLayout>

    <include  
            android:id="@+id/talk_empty"  
            layout="@layout/listview_empty"/>

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

  4. 修改 MainActivity.java 添加按钮的点击事件

    package cn.twle.android.listviewcrud;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.widget.ListView;
import android.widget.Button;
import android.widget.Toast;
import android.widget.AdapterView;

import android.view.View;

import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private ListView listview;
    private TalkAdapter talkAdapter = null;
    private List<TalkBean> mData = null;
    private int flag = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        listview = (ListView) findViewById(R.id.listview);

        View listview_empty = findViewById(R.id.talk_empty);  
        listview.setEmptyView(listview_empty);

        mData = new LinkedList<TalkBean>();
        talkAdapter = new TalkAdapter((LinkedList<TalkBean>) mData,MainActivity.this);

        listview.setAdapter(talkAdapter);

        Button btn_add = findViewById(R.id.btn_add);
        Button btn_insert = findViewById(R.id.btn_insert);

        btn_add.setOnClickListener(this);
        btn_insert.setOnClickListener(this);
    }

    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_add:
                talkAdapter.add(new TalkBean(R.drawable.golf,"你好 " + flag));
                flag++;
                break;

            case R.id.btn_insert:
                // position 从 0 开始算的
                talkAdapter.insert(new TalkBean(R.drawable.golf,"你好 " + flag),2);
                flag++;
                break;
        }
    }
}
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