关于listview的自定义适配器

listview是什么？

listview是展示列表的view

listview的作用？

展示列表

适配器的作用是什么？

适配器是将数据显示在listview上的中介

数据是什么？

具体的将被映射的字符串，图片，或者基本组件。

listview自定义适配器的步骤？

第一步：创建listview xml文件 并找到id；

第二步：创建一个装数据的容器 此处我用的是arraylist；

ArrayList<HashMap<String, String>> data=new ArrayList<HashMap<String, String>>

第三步：将数据放入容器中：

hash = new HashMap<String, String>();
hash.put("ctime", ctime);
hash.put("title", title);
hash.put("description", description);
hash.put("picUrl", picUrl);
hash.put("url", url);
data.add(hash);

第四步：创建自定义适配器

创建适配器步骤：

第一步：继承baseadapter

第二步：填写一些方法：

@Override
    public int getCount() {
        
        return data.size();//得到数据的长度
    }

    @Override
    public Object getItem(int arg0) {
    
        return arg0;//返回一个位置
    }

    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;//返回一个id
    }

@Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {//此处有些许的复杂
        myHolder myholder;//缓冲机制
        if (arg1==null) {判断view是否为空
            myholder=new myHolder();
              //得到小布局中的控件
            arg1=LayoutInflater.from(news).inflate(R.layout.list_item,null);
            myholder.img=(ImageView) arg1.findViewById(R.id.img);
            myholder.content=(TextView) arg1.findViewById(R.id.content);
            myholder.title=(TextView) arg1.findViewById(R.id.title);
            myholder.time=(TextView) arg1.findViewById(R.id.time);
            //利用setTag把查找的view缓存起来方便多次重用
            arg1.setTag(myholder);
        }else{
             //取出setTag中缓存的view
            myholder=(myHolder) arg1.getTag();
            
        }
            //将数据存入hashmap中
        HashMap<String, String> hashmap=data.get(arg0);
            //17 18 19 20 21是json解析的内容 紧接上一篇博客
        myholder.title.setText(hashmap.get("title"));
        myholder.time.setText(hashmap.get("ctime"));
        myholder.content.setText(hashmap.get("description"));
        
        String img1=hashmap.get("picUrl");
        Picasso.with(news).load(img1).into(myholder.img);
        
        
        return arg1;
    }
    
 class myHolder{
     TextView title;
     TextView content;
     ImageView img;
     TextView time;
 }

 //adapter部分

 

package com.example.adapter;

import java.util.ArrayList;
import java.util.HashMap;

import com.example.z01.NewsActivity;
import com.example.z01.R;
import com.squareup.picasso.Picasso;

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;

public class ListAdapter extends BaseAdapter {

    ArrayList<HashMap<String, String>> data;
    Context news;

    public ListAdapter(ArrayList<HashMap<String, String>> data,Context news) {
        this.data=data;
        this.news=news;
    }
    @Override
    public int getCount() {
        
        return data.size();
    }

    @Override
    public Object getItem(int arg0) {
    
        return arg0;
    }

    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;
    }

    @Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {
        myHolder myholder;
        if (arg1==null) {
            myholder=new myHolder();
            arg1=LayoutInflater.from(news).inflate(R.layout.list_item,null);
            myholder.img=(ImageView) arg1.findViewById(R.id.img);
            myholder.content=(TextView) arg1.findViewById(R.id.content);
            myholder.title=(TextView) arg1.findViewById(R.id.title);
            myholder.time=(TextView) arg1.findViewById(R.id.time);
            arg1.setTag(myholder);
        }else{
            myholder=(myHolder) arg1.getTag();
            
        }
        HashMap<String, String> hashmap=data.get(arg0);
        myholder.title.setText(hashmap.get("title"));
        myholder.time.setText(hashmap.get("ctime"));
        myholder.content.setText(hashmap.get("description"));
        
        String img1=hashmap.get("picUrl");
        Picasso.with(news).load(img1).into(myholder.img);
        
        
        return arg1;
    }
    
 class myHolder{
     TextView title;
     TextView content;
     ImageView img;
     TextView time;
 }
}

json解析以及listview 接送解析紧跟上一篇博客

 

public class NewsActivity extends Activity {
    @ViewInject(value = R.id.news_list)
    private ListView list;
    private ArrayList<HashMap<String, String>> data;
    HashMap<String, String> hash;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.news);
        ViewUtils.inject(NewsActivity.this);
        data = new ArrayList<HashMap<String, String>>();
        myList();
        Log.e("aa","a1");

        list.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                    long arg3) {

                HashMap<String, String> map1 = data.get(arg2);
                String name = map1.get("url");
                Intent intent = new Intent(NewsActivity.this, UrlActivity.class);
                intent.putExtra("zwn", name);
                startActivity(intent);
                Log.e("aa","a2");

            }
        });
        ListAdapter adapter = new ListAdapter(data, NewsActivity.this);
        list.setAdapter(adapter);
        Log.e("aa","a3");

    }

    private void myList() {
        
        // 打开文件将文件转化为字符流
        InputStream input = getResources().openRawResource(R.raw.u12);
        Log.e("aa","a4");
        byte[] inputdata;

        try {
            // input.available()得到流的可利用长度 以字节的方式存储
            inputdata = new byte[input.available()];

            // 将流读入字节数组里
            // output.write(inputdata) 将字节数组里面缓存的数据写到output所指向的那个文件中去。
            input.read(inputdata);
            // 关闭流
            input.close();
            // 将byte字节数组转化为字符串
            String bytedata = new String(inputdata,"GBK");
            try {
                JSONObject objec = new JSONObject(bytedata);
                String aa = objec.getString("code");
                String bb = objec.getString("msg");
                
                JSONArray jsonarray=objec.getJSONArray("newslist");
                for (int i = 0; i < inputdata.length; i++) {
                    
                    JSONObject objec1 = jsonarray.getJSONObject(i);
                    String ctime = objec1.getString("ctime");
                    String title = objec1.getString("title");
                    String description = objec1.getString("description");
                    String picUrl = objec1.getString("picUrl");
                    String url = objec1.getString("url");
                    hash = new HashMap<String, String>();
                    hash.put("ctime", ctime);
                    hash.put("title", title);
                    hash.put("description", description);
                    hash.put("picUrl", picUrl);
                    hash.put("url", url);
                    data.add(hash);

                }

            } catch (JSONException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }


        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}