android: ListView的简单用法详解

当你在android中看到一个  列表时, 它基本就是个ListView. 不过,还是需要通过源代码来获知的.

它需要3个元素: 

1. ListView   ( 定义在XML 或者activity 中)

2. Adapter    ( 定义在 activity 中, 与 ListView的实例一起使用)

3. 数据.  

下面是个例子:

public class ListActivity ... {

  public void onCreate(...){
    listView = new ListView(this);
    listView.setAdapter(new ArrayAdapter...,  getData());
  }

  // 在这里返回数据.
  private List getData(){

  }
}

自定义ListView

android提供的ListView在很多情况下满足不了我们的展现需求,这里我以一个图书列表为例,实现自定义的ListView

先看下要实现的效果,左侧显示图片,右边显示标题以及章节等信息,实现步骤如下:

20130509172934852.png

1. 创建一个用于控制每行显示效果的layout,名称为bookshelf

    android:layout_
    android:layout_ >

            android:layout_
        android:layout_ >

                    android:id="@+id/book_image"
            android:layout_
            android:layout_
            android:padding="5dip"
            android:paddingLeft="0dip" />

                    android:layout_
            android:layout_
            android:orientation="vertical" >

                            android:id="@+id/book_name"
                android:layout_
                android:layout_
                android:layout_marginBottom="10dip"
                android:layout_marginTop="2dip"
                android:textIsSelectable="true" />

                            android:layout_
                android:layout_
                android:orientation="horizontal"
                android:layout_marginBottom="5dip" >

                                    android:id="@+id/book_no_read_num"
                    android:layout_
                    android:layout_
                    android:textIsSelectable="true"
                    android:textSize="12sp" />

                                    android:id="@+id/book_has_update"
                    android:layout_
                    android:layout_
                    android:layout_marginLeft="5dip"
                    android:layout_marginTop="3dip"
                    android:visibility="gone"
                    android:contentDescription="@string/has_update"
                    android:src="@drawable/ic_new" />
           

                            android:id="@+id/book_lasttitle"
                android:layout_
                android:layout_
                android:ellipsize="end"
                android:paddingRight="5dip"
                android:singleLine="true"
                android:textIsSelectable="true"
                android:textSize="12sp" />
       
   

2. 创建一个新的ListViewAdapter,名称为bookshelfListViewAdapter
package com.brook.freenovelread.service;

import java.util.ArrayList;

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 com.brook.freenovelread.R;
import com.brook.freenovelread.object.BookData;
import com.brook.freenovelread.utility.HttpUtility;

public class bookshelfListViewAdapter extends BaseAdapter {

    private ArrayList bookshelfList = null;
    private Context             context       = null;

    /**
     * 构造函数,初始化Adapter,将数据传入
     * @param bookshelfList
     * @param context
     */
    public bookshelfListViewAdapter(ArrayList bookshelfList, Context context) {
        this.bookshelfList = bookshelfList;
        this.context = context;
    }

    @Override
    public int getCount() {
        return bookshelfList == null ? 0 : bookshelfList.size();
    }

    @Override
    public Object getItem(int position) {
        return bookshelfList == null ? null : bookshelfList.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //装载view
        LayoutInflater layoutInflater = LayoutInflater.from(this.context);
        View view = layoutInflater.inflate(R.layout.bookshelf, null);

        //获取控件
        ImageView bookImageView = (ImageView) view.findViewById(R.id.book_image);
        TextView bookNameTextView = (TextView) view.findViewById(R.id.book_name);
        TextView bookNoReadNumTextView = (TextView) view.findViewById(R.id.book_no_read_num);
        TextView bookLastTitleView = (TextView) view.findViewById(R.id.book_lasttitle);
        ImageView bookHasUpdateImageView = (ImageView) view.findViewById(R.id.book_has_update);
        //对控件赋值
        BookData bookData = (BookData) getItem(position);
        if (bookData != null) {
            bookImageView.setImageBitmap(HttpUtility.getHttpBitmap(bookData.getImageUrl()));
            bookNameTextView.setText(bookData.getName());
            Integer noReadNum = bookData.getTotalNum() - bookData.getCurrentNum();
            if (noReadNum > 0) {
                bookNoReadNumTextView.setText(noReadNum + "章节未读");
                //显示更新小图标
                bookHasUpdateImageView.setVisibility(View.VISIBLE);
            } else {
                bookNoReadNumTextView.setText("无未读章节");
                //隐藏更新小图标
                bookHasUpdateImageView.setVisibility(View.GONE);
            }
            bookLastTitleView.setText("更新至:" + bookData.getLastTitle());
        }

        return view;
    }
}

主要是对getView方法的重写,将数据插入到R.layout.bookshelf的各控件中,这里还用到了一个将网络图片下载的工具类HttpUtility,以下是工具类的代码
package com.brook.freenovelread.utility;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class HttpUtility {

   
    /**
     * 图片资源缓存
     */
    private static Map bitmapCache = new HashMap();
   
    /**
     * 获取网落图片资源
     * @param url
     * @return
     */
    public static Bitmap getHttpBitmap(String url) {
        //先从缓存里找
        Bitmap bitmap = bitmapCache.get(url);
        if (bitmap != null) {
            return bitmap;
        }
       
        //从网络上下载
        URL myFileURL;     
        try {
            myFileURL = new URL(url);
            //获得连接
            HttpURLConnection conn = (HttpURLConnection) myFileURL.openConnection();
            //设置超时时间为6000毫秒，conn.setConnectionTiem(0);表示没有时间限制
            conn.setConnectTimeout(6000);
            //连接设置获得数据流
            conn.setDoInput(true);
            //不使用缓存
            conn.setUseCaches(false);
            //这句可有可无，没有影响
            //conn.connect();
            //得到数据流
            InputStream is = conn.getInputStream();
            //解析得到图片
            bitmap = BitmapFactory.decodeStream(is);
            //关闭数据流
            is.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
       
        if (bitmap != null) {
            bitmapCache.put(url, bitmap);
        }

        return bitmap;

    }
}

3.在activity的layout文件中加上一个ListView控件
        android:id="@+id/listview_bookshelf"
        android:layout_
        android:layout_
        android:layout_weight="1" />

4.在activity中调用我们写的ListViewAdapter
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //设置主页面的标题栏
        requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
        setContentView(R.layout.activity_main);
        getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.title_bar);
       
        //更新标题栏中按钮的字体大小
        Button btnManage = (Button) findViewById(R.id.btn_manage);
        btnManage.setTextSize(10);
       
        //获取书架列表数据
        ArrayList bookshelf = new ArrayList();
        BookData bookData = new BookData();
        bookData.setAuthor("天蚕土豆");
        bookData.setCurrentNum(1);
        bookData.setDescription("修炼一途，乃窃阴阳，夺造化，转涅盘，握生死，掌轮回。武之极，破苍穹，动乾坤！");
        bookData.setId(1);
        bookData.setImageUrl("http://www.easou.org/files/article/image/0/308/308s.jpg");
        bookData.setLastTitle("第一千两百九十四章 魔皇之手");
        bookData.setName("武动乾坤");
        bookData.setTotalNum(1294);
       
        BookData bookData2 = new BookData();
        bookData2.setAuthor("忘语");
        bookData2.setCurrentNum(2343);
        bookData2.setDescription("一个普通的山村穷小子，偶然之下，进入到当地的江湖小门派，成了一名记名弟子。他以这样的身份，如何在门派中立足？又如何以平庸的资质，进入到修仙者的行列？和其他巨枭魔头，仙宗仙师并列于山海内外？希望书友们喜欢本书！");
        bookData2.setId(2342);
        bookData2.setImageUrl("http://www.easou.org/files/article/image/0/289/289s.jpg");
        bookData2.setLastTitle("第十一卷 真仙降世 第两千三百四十三章 九目血蟾");
        bookData2.setName("凡人修仙传");
        bookData2.setTotalNum(2343);
       
        bookshelf.add(bookData);
        bookshelf.add(bookData2);
        bookshelf.add(bookData);
        bookshelf.add(bookData2);
        bookshelf.add(bookData);
        bookshelf.add(bookData2);
       
        bookshelfListViewAdapter bookshelfListViewAdapter = new bookshelfListViewAdapter(bookshelf, this);
        ListView listView = (ListView) findViewById(R.id.listview_bookshelf);
        listView.setAdapter(bookshelfListViewAdapter);
    }

这样就ok了