Android----ListView的使用--->加载网络图片



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:

1. 创建一个用于控制每行显示效果的layout,名称为bookshelf

<?xml version="1.0" encoding="utf-8"?><TableLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <TableRow        android:layout_width="wrap_content"        android:layout_height="wrap_content" >        <ImageView            android:id="@+id/book_image"            android:layout_width="80dip"            android:layout_height="80dip"            android:padding="5dip"            android:paddingLeft="0dip" />        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:orientation="vertical" >            <TextView                android:id="@+id/book_name"                android:layout_width="match_parent"                android:layout_height="wrap_content"                android:layout_marginBottom="10dip"                android:layout_marginTop="2dip"                android:textIsSelectable="true" />            <LinearLayout                android:layout_width="match_parent"                android:layout_height="wrap_content"                android:orientation="horizontal"                android:layout_marginBottom="5dip" >                <TextView                    android:id="@+id/book_no_read_num"                    android:layout_width="wrap_content"                    android:layout_height="wrap_content"                    android:textIsSelectable="true"                    android:textSize="12sp" />                <ImageView                    android:id="@+id/book_has_update"                    android:layout_width="wrap_content"                    android:layout_height="wrap_content"                    android:layout_marginLeft="5dip"                    android:layout_marginTop="3dip"                    android:visibility="gone"                    android:contentDescription="@string/has_update"                    android:src="@drawable/ic_new" />            </LinearLayout>            <TextView                android:id="@+id/book_lasttitle"                android:layout_width="240dip"                android:layout_height="wrap_content"                android:ellipsize="end"                android:paddingRight="5dip"                android:singleLine="true"                android:textIsSelectable="true"                android:textSize="12sp" />        </LinearLayout>    </TableRow></TableLayout>

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<BookData> 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<BookData> 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<String, Bitmap> bitmapCache = new HashMap<String, Bitmap>();        /**     * 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

<ListView        android:id="@+id/listview_bookshelf"        android:layout_width="fill_parent"        android:layout_height="0dip"        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<BookData> bookshelf = new ArrayList<BookData>();        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

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看到加载网络图片的ListView就果断转了