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·····

 

posted @ 2017-03-22 16:48  阿呆哥哥  阅读(3839)  评论(0编辑  收藏  举报