• 面试 -- ListView对其指定的子Item进行单独的刷新


    1,最近在面试题目的时候突然看到了问题“ListView对其指定的子Item进行单独的刷新”,当时感觉一脸懵逼,还是第一次听到这个问题,也就是不能使用adapter.notifyDataSetChanged(),一点思路都没有,下班吃饭之后,突然觉得还是敲代码来试试吧,说不定思路就出来了。

    2,首先添加我们在布局文件中添加ListView,布局文件如下:

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.qianmo.listviewupdatebyone.MainActivity">
    
        <ListView
            android:id="@+id/listview"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
    
        </ListView>
    
    </RelativeLayout>
    

      创建MyAdapter适配器,继承自BaseAdapter类,代码如下:

    package com.qianmo.listviewupdatebyone.adapter;
    
    import android.content.Context;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.BaseAdapter;
    import android.widget.TextView;
    
    import com.qianmo.listviewupdatebyone.R;
    
    import java.util.List;
    
    /**
     * Created by Administrator on 2017/3/22 0022.
     * E-Mail:543441727@qq.com
     */
    
    public class MyAdapter extends BaseAdapter {
        private Context mContext;
        private List<String> datas;
    
        public MyAdapter(Context context, List<String> datas) {
            this.mContext = context;
            this.datas = datas;
        }
    
        @Override
        public int getCount() {
            return datas == null ? 0 : datas.size();
        }
    
        @Override
        public Object getItem(int position) {
            return datas.get(position);
        }
    
        @Override
        public long getItemId(int position) {
            return position;
        }
    
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder = null;
            if (convertView == null) {
                convertView = LayoutInflater.from(mContext).inflate(R.layout.item_adapter, null);
                viewHolder = new ViewHolder();
                viewHolder.mTextView = (TextView) convertView.findViewById(R.id.textView);
                convertView.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            viewHolder.mTextView.setText(datas.get(position));
    
            return convertView;
        }
    
        class ViewHolder {
            private TextView mTextView;
        }
    }
    

      在activity中添加适配器,并添加点击监听

    package com.qianmo.listviewupdatebyone;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.ListView;
    import android.widget.TextView;
    
    import com.qianmo.listviewupdatebyone.adapter.MyAdapter;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class MainActivity extends AppCompatActivity {
        private ListView mListView;
        private List<String> datas;
        private MyAdapter myAdapter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            init();
        }
    
        private void init() {
            datas = new ArrayList<>();
            for (int i = 0; i < 20; i++) {
                datas.add(i + "");
            }
    
            mListView = (ListView) findViewById(R.id.listview);
            myAdapter = new MyAdapter(MainActivity.this, datas);
            mListView.setAdapter(myAdapter);
    
            //这里实现单个更新
            mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                   
                }
            });
        }
    }
    

      以上是最基本的ListView的创建,所以这里我们来看看我们能有几种方法来实现

    3,实现方法

      ①通过onItemClick()方法中的View就是我们的ViewHolder来更新数据

       所以我们的代码可以这样写

    mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    datas.set(position, "这是被更新的数据哦");
                    if (position != datas.size()-1){
                        datas.set(position+1, "这是被更新的数据哦,但是不展示");
                    }
    
                    //通过拿到TextView来更新数据
                    TextView testView = (TextView) view.findViewById(R.id.textView);
                    testView.setText(datas.get(position));
    
                
                }
            });

      看一下效果

      没问题 ,我们继续看下一种方法

      ②通过再次调用adapter的getView()方法来更新

      代码如下:

    mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    datas.set(position, "这是被更新的数据哦");
                    if (position != datas.size()-1){
                        datas.set(position+1, "这是被更新的数据哦,但是不展示");
                    }
    
                    //通过调用getview
    
                    myAdapter.getView(position, view, mListView);
    
                }
            });
    

      

      看一下效果,没问题

      暂且只试出来两种了,如果还有其他思路 ,欢迎共享·····

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  • 原文地址:https://www.cnblogs.com/wjtaigwh/p/6600769.html
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