Android ListView从网络获取图片及文字显示

如何从网络获取图片以及文本来显示。事实上,一般是先获取Josn或sml数据,然后解释显示。我们先从网上获取xml,然后对其进行解析,最后显示在ListView上。具体步骤:

  • 客户端发出请求,获取xml
  • 客户端异步解析xml
  • ListView将解析完的数据显示

一、Android客户端

(1)xml布局文件

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:divider="#b5b5b5"
android:dividerHeight="1dp"
android:listSelector="@drawable/list_selector" />
</LinearLayout>

ListView的每一行的布局,list_raw.xml,看一下结构图:

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<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@drawable/list_selector"
android:orientation="horizontal"
android:padding="5dip" >
<!-- ListView最左边的缩略图 -->
<LinearLayout android:id="@+id/thumbnail"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="3dip"
android:layout_alignParentLeft="true"
android:background="@drawable/image_bg"
android:layout_marginRight="5dip">
<ImageView
android:id="@+id/list_image"
android:layout_width="50dip"
android:layout_height="50dip"
android:src="@drawable/rihanna"/>
</LinearLayout>
<!-- 歌曲名-->
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/thumbnail"
android:layout_toRightOf="@+id/thumbnail"
android:text="Rihanna Love the way lie"
android:textColor="#040404"
android:typeface="sans"
android:textSize="15dip"
android:textStyle="bold"/>
<!-- 歌手名 -->
<TextView
android:id="@+id/artist"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@id/title"
android:textColor="#343434"
android:textSize="10dip"
android:layout_marginTop="1dip"
android:layout_toRightOf="@+id/thumbnail"
android:text="Just gona stand there and ..." />
<!-- 歌曲播放时间 -->
<TextView
android:id="@+id/duration"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignTop="@id/title"
android:gravity="right"
android:text="5:45"
android:layout_marginRight="5dip"
android:textSize="10dip"
android:textColor="#10bcc9"
android:textStyle="bold"/>
<!-- 进入播放 -->
<ImageView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/arrow"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"/>
</RelativeLayout>

另外我们打算使用几个特效,一个是当点击列表项目的时候,项目背景色改变,其实就是一个selector;另一个就是用shape美化视觉效果,具体看xml代码:

  1. list_selector.xml
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<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<!-- Selector style for listrow -->
<item
android:state_selected="false"
android:state_pressed="false"
android:drawable="@drawable/gradient_bg" />
<item android:state_pressed="true"
android:drawable="@drawable/gradient_bg_hover" />
<item android:state_selected="true"
android:state_pressed="false"
android:drawable="@drawable/gradient_bg_hover" />
</selector>

  1. gradient_bg.xml,是默认背景梯度风格
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<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<!-- Gradient Bg for listrow -->
<gradient
android:startColor="#f1f1f2"
android:centerColor="#e7e7e8"
android:endColor="#cfcfcf"
android:angle="270" />
</shape>
  1. gradient_bg_hover.xml 梯度风格在悬停状态
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<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
<!-- Gradient BgColor for listrow Selected -->
<gradient
android:startColor="#18d7e5"
android:centerColor="#16cedb"
android:endColor="#09adb9"
android:angle="270" />
</shape>

4.image_bg.xml在图片周围的白色边条

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<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item>
<shape
android:shape="rectangle">
<stroke android:width="1dp" android:color="#dbdbdc" />
<solid android:color="#FFFFFF" />
</shape>
</item>
</layer-list>

以上效果基本上都用到了shape,对此不了解的可以去查看相关资料。上面就是全部的xml布局文件,下面将开始写代码。

(2)主要代码

代码部分主要涉及到一下几个功能,重写ListView的适配器(BaseAdapter),从网络获取图片,图片缓存的处理,xml的解析。

①重写ListView的适配器,这部分可以参考上一篇文章,LazyAdapter.java

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  import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
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 LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader; //用来下载图片的类,后面有介绍
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}



public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.list_row, null);
TextView title = (TextView)vi.findViewById(R.id.title); // 标题
TextView artist = (TextView)vi.findViewById(R.id.artist); // 歌手名
TextView duration = (TextView)vi.findViewById(R.id.duration); // 时长
ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); // 缩略图
HashMap<String, String> song = new HashMap<String, String>();
song = data.get(position);
// 设置ListView的相关值
title.setText(song.get(CustomizedListView.KEY_TITLE));
artist.setText(song.get(CustomizedListView.KEY_ARTIST));
duration.setText(song.get(CustomizedListView.KEY_DURATION));
imageLoader.DisplayImage(song.get(CustomizedListView.KEY_THUMB_URL), thumb_image);
return vi;
}
}

②网络获取图片的类,ImageLoader.java:

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import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;

public class ImageLoader {

MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;

public ImageLoader(Context context){
fileCache=new FileCache(context);
executorService=Executors.newFixedThreadPool(5);
}

final int stub_id = R.drawable.no_image;
public void DisplayImage(String url, ImageView imageView)
{
imageViews.put(imageView, url);
Bitmap bitmap=memoryCache.get(url);
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
{
queuePhoto(url, imageView);
imageView.setImageResource(stub_id);
}
}

private void queuePhoto(String url, ImageView imageView)
{
PhotoToLoad p=new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}

private Bitmap getBitmap(String url)
{
File f=fileCache.getFile(url);

//从sd卡
Bitmap b = decodeFile(f);
if(b!=null)
return b;

//从网络
try {
Bitmap bitmap=null;
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
conn.setConnectTimeout(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is=conn.getInputStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
return null;
}
}

//解码图像用来减少内存消耗
private Bitmap decodeFile(File f){
try {
//解码图像大小
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);

//找到正确的刻度值,它应该是2的幂。
final int REQUIRED_SIZE=70;
int width_tmp=o.outWidth, height_tmp=o.outHeight;
int scale=1;
while(true){
if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
break;
width_tmp/=2;
height_tmp/=2;
scale*=2;
}

BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
return null;
}

/任务队列
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}

class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad){
this.photoToLoad=photoToLoad;
}

@Override
public void run() {
if(imageViewReused(photoToLoad))
return;
Bitmap bmp=getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if(imageViewReused(photoToLoad))
return;
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}

boolean imageViewReused(PhotoToLoad photoToLoad){
String tag=imageViews.get(photoToLoad.imageView);
if(tag==null || !tag.equals(photoToLoad.url))
return true;
return false;
}

//用于显示位图在UI线程
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
public void run()
{
if(imageViewReused(photoToLoad))
return;
if(bitmap!=null)
photoToLoad.imageView.setImageBitmap(bitmap);
else
photoToLoad.imageView.setImageResource(stub_id);
}
}

public void clearCache() {
memoryCache.clear();
fileCache.clear();
}

}

⑤还有一个读取流的工具类,

Utils.java:

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import java.io.InputStream;
import java.io.OutputStream;
public class Utils {
public static void CopyStream(InputStream is, OutputStream os)
{
final int buffer_size=1024;
try
{
byte[] bytes=new byte[buffer_size];
for(;;)
{
int count=is.read(bytes, 0, buffer_size);
if(count==-1)
break;
os.write(bytes, 0, count);
is.close();
os.close();
}
}
catch(Exception ex){}
}
}

还可以像下面这样表达,方法是一样的,就是表达形式上不同:

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public static byte[] readStream(InputStream inStream) throws Exception{
ByteArrayOutputStream outSteam = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
while( (len=inStream.read(buffer)) != -1){
outSteam.write(buffer, 0, len);
}
outSteam.close();
inStream.close();
return outSteam.toByteArray();
}

最后就是主Activity的代码了,

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package com.example.androidhive;
import java.util.ArrayList;
import java.util.HashMap;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
public class CustomizedListView extends Activity {
// 所有的静态变量
static final String URL = "http://api.androidhive.info/music/music.xml";//xml目的地址,打开地址看一下
// XML 节点
static final String KEY_SONG = "song"; // parent node
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_ARTIST = "artist";
static final String KEY_DURATION = "duration";
static final String KEY_THUMB_URL = "thumb_url";

ListView list;
LazyAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // 从网络获取xml
Document doc = parser.getDomElement(xml); // 获取 DOM 节点

NodeList nl = doc.getElementsByTagName(KEY_SONG);
// 循环遍历所有的歌节点 <song>
for (int i = 0; i < nl.getLength(); i++) {
// 新建一个 HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
//每个子节点添加到HashMap关键= >值
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
map.put(KEY_DURATION, parser.getValue(e, KEY_DURATION));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
// HashList添加到数组列表
songsList.add(map);
}

list=(ListView)findViewById(R.id.list);
adapter=new LazyAdapter(this, songsList);
list.setAdapter(adapter);

//为单一列表行添加单击事件
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {

//这里可以自由发挥,比如播放一首歌曲等等
}
});
}
}
}

最后看一下效果:

请输入图片描述

reference: 请输入链接描述

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