android listview分页异步加载图片及图片缓存

我是开发android的新手，参考了很多大牛的资料，才完成这个demo的，分享出来和大家一同学习

如图：



AsyncImageLoader.java

Java代码


package cn.anycall.testlist;

import java.lang.ref.SoftReference;
import java.util.HashMap;

import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

public class AsyncImageLoader {

//SoftReference是软引用，是为了更好的为了系统回收变量
private static HashMap<String, SoftReference<Drawable>> imageCache;

static {
imageCache = new HashMap<String, SoftReference<Drawable>>();
}

public AsyncImageLoader() {

}
public Drawable loadDrawable(final String imageUrl,final ImageView imageView, final ImageCallback imageCallback){
if (imageCache.containsKey(imageUrl)) {
//从缓存中获取
SoftReference<Drawable> softReference = imageCache.get(imageUrl);
Drawable drawable = softReference.get();
System.out.println("111111111111111111111111111111");
if (drawable != null) {
System.out.println("11111111111122222222211111111111111111");
return drawable;
}
}
final Handler handler = new Handler() {
public void handleMessage(Message message) {
imageCallback.imageLoaded((Drawable) message.obj, imageView,imageUrl);
}
};
//建立新一个新的线程下载图片
new Thread() {
@Override
public void run() {
System.out.println("11111111111133333333333211111111111111111");
Drawable drawable = null;
try {
drawable = ImageUtil.geRoundDrawableFromUrl(imageUrl, 20);
} catch (Exception e) {
e.printStackTrace();
}
imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));
Message message = handler.obtainMessage(0, drawable);
handler.sendMessage(message);
}
}.start();
return null;
}
//回调接口
public interface ImageCallback {
public void imageLoaded(Drawable imageDrawable,ImageView imageView, String imageUrl);
}
}

ImageUtil.java

Java代码


package cn.anycall.testlist;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;

public class ImageUtil {

public static InputStream getRequest(String path) throws Exception {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
if (conn.getResponseCode() == 200){
return conn.getInputStream();
}
return null;
}

public static byte[] readInputStream(InputStream inStream) throws Exception {
ByteArrayOutputStream outSteam = new ByteArrayOutputStream();
byte[] buffer = new byte[4096];
int len = 0;
while ((len = inStream.read(buffer)) != -1) {
outSteam.write(buffer, 0, len);
}
outSteam.close();
inStream.close();
return outSteam.toByteArray();
}

public static Drawable loadImageFromUrl(String url){
URL m;
InputStream i = null;
try {
m = new URL(url);
i = (InputStream) m.getContent();
} catch (MalformedURLException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
Drawable d = Drawable.createFromStream(i, "src");
return d;
}

public static Drawable getDrawableFromUrl(String url) throws Exception{
return Drawable.createFromStream(getRequest(url),null);
}

public static Bitmap getBitmapFromUrl(String url) throws Exception{
byte[] bytes = getBytesFromUrl(url);
return byteToBitmap(bytes);
}

public static Bitmap getRoundBitmapFromUrl(String url,int pixels) throws Exception{
byte[] bytes = getBytesFromUrl(url);
Bitmap bitmap = byteToBitmap(bytes);
return toRoundCorner(bitmap, pixels);
}

public static Drawable geRoundDrawableFromUrl(String url,int pixels) throws Exception{
byte[] bytes = getBytesFromUrl(url);
BitmapDrawable bitmapDrawable = (BitmapDrawable)byteToDrawable(bytes);
return toRoundCorner(bitmapDrawable, pixels);
}

public static byte[] getBytesFromUrl(String url) throws Exception{
return readInputStream(getRequest(url));
}

public static Bitmap byteToBitmap(byte[] byteArray){
if(byteArray.length!=0){
return BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
}
else {
return null;
}
}

public static Drawable byteToDrawable(byte[] byteArray){
ByteArrayInputStream ins = new ByteArrayInputStream(byteArray);
return Drawable.createFromStream(ins, null);
}

public static byte[] Bitmap2Bytes(Bitmap bm){
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
return baos.toByteArray();
}

public static Bitmap drawableToBitmap(Drawable drawable) {

Bitmap bitmap = Bitmap
.createBitmap(
drawable.getIntrinsicWidth(),
drawable.getIntrinsicHeight(),
drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, drawable.getIntrinsicWidth(),
drawable.getIntrinsicHeight());
drawable.draw(canvas);
return bitmap;
}

/**
* 图片去色,返回灰度图片
* @param bmpOriginal 传入的图片
* @return 去色后的图片
*/
public static Bitmap toGrayscale(Bitmap bmpOriginal) {
int width, height;
height = bmpOriginal.getHeight();
width = bmpOriginal.getWidth();

Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
Canvas c = new Canvas(bmpGrayscale);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
paint.setColorFilter(f);
c.drawBitmap(bmpOriginal, 0, 0, paint);
return bmpGrayscale;
}

/**
* 去色同时加圆角
* @param bmpOriginal 原图
* @param pixels 圆角弧度
* @return 修改后的图片
*/
public static Bitmap toGrayscale(Bitmap bmpOriginal, int pixels) {
return toRoundCorner(toGrayscale(bmpOriginal), pixels);
}

/**
* 把图片变成圆角
* @param bitmap 需要修改的图片
* @param pixels 圆角的弧度
* @return 圆角图片
*/
public static Bitmap toRoundCorner(Bitmap bitmap, int pixels) {

Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);

final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final RectF rectF = new RectF(rect);
final float roundPx = pixels;

paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);

return output;
}

/**
* 使圆角功能支持BitampDrawable
* @param bitmapDrawable
* @param pixels
* @return
*/
public static BitmapDrawable toRoundCorner(BitmapDrawable bitmapDrawable, int pixels) {
Bitmap bitmap = bitmapDrawable.getBitmap();
bitmapDrawable = new BitmapDrawable(toRoundCorner(bitmap, pixels));
return bitmapDrawable;
}
}

TestListViewActivity.java

Java代码


package cn.anycall.testlist;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.ListActivity;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import cn.anycall.testlist.AsyncImageLoader.ImageCallback;

public class TestListViewActivity extends ListActivity {

private List<Map<String, Object>> mData = new ArrayList<Map<String, Object>>();
public final class ViewHolder {
public ImageView img;
public TextView title;
public TextView info;
}

public List<HashMap<String, String>> data = new ArrayList<HashMap<String, String>>();
public int a = 0;
public Button button;
public LinearLayout layloading;
public MyHandler myHandler;
public MyAdapter adapter ;
private AsyncImageLoader asyncImageLoader;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

myHandler = new MyHandler();

ListView listView = getListView();// 得到ListView
LinearLayout listFooter = (LinearLayout) LayoutInflater.from(this)
.inflate(R.layout.main_foot, null);
listView.addFooterView(listFooter);// 添加FooterView
button = (Button) findViewById(R.id.more);
layloading = (LinearLayout) findViewById(R.id.loading);
button.setVisibility(View.VISIBLE);
layloading.setVisibility(View.GONE);
adapter = new MyAdapter(this);
setListAdapter(adapter);
button.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
//起一个线程更新后台数据
MyThread m = new MyThread();
new Thread(m).start();

}
});
for(int i=0;i<20;i++){
a++;
Map<String, Object> map = new HashMap<String, Object>();
map.put("img", R.drawable.icon);
map.put("title", "G"+a);
map.put("info", "google"+a);
mData.add(map);
}
}
public class MyAdapter extends BaseAdapter {
private LayoutInflater mInflater;

public MyAdapter(Context context) {
this.mInflater = LayoutInflater.from(context);
}
public int getCount() {
return mData.size();
}
public Object getItem(int arg0) {
return null;
}
public long getItemId(int arg0) {
return 0;
}
public View getView(int position, View convertView, ViewGroup parent) {
asyncImageLoader = new AsyncImageLoader();
ViewHolder holder = null;
if (convertView == null) {
holder = new ViewHolder();
convertView = mInflater.inflate(R.layout.main_list, null);

holder.img = (ImageView)convertView.findViewById(R.id.img);
holder.title = (TextView) convertView
.findViewById(R.id.listtitle);
holder.info = (TextView) convertView
.findViewById(R.id.listtext);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}

//holder.img.setBackgroundResource((Integer)mData.get(position).get("img"));
holder.title.setText((String) mData.get(position).get("title"));
holder.info.setText((String) mData.get(position).get("info"));

//异步加载图片
Drawable cachedImage = asyncImageLoader.loadDrawable("http://www.1860.cn/tuangou/groupon/img/logo_v4.png",holder.img, new ImageCallback(){

public void imageLoaded(Drawable imageDrawable,ImageView imageView, String imageUrl) {
imageView.setImageDrawable(imageDrawable);
}
});
System.out.println(cachedImage);
if (cachedImage == null) {
holder.img.setImageResource(R.drawable.icon);
} else {
holder.img.setImageDrawable(cachedImage);
}

return convertView;

}

}

//更新后台数据
class MyThread implements Runnable {
public void run() {

String msglist = "1";
Message msg = new Message();
Bundle b = new Bundle();// 存放数据
b.putString("rmsg", msglist);
msg.setData(b);
TestListViewActivity.this.myHandler.sendMessage(msg); // 向Handler发送消息,更新UI

try {
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

msglist = "2";
msg = new Message();
b = new Bundle();// 存放数据
b.putString("rmsg", msglist);
msg.setData(b);
TestListViewActivity.this.myHandler.sendMessage(msg); // 向Handler发送消息,更新UI

}
}

class MyHandler extends Handler {
public MyHandler() {
}

public MyHandler(Looper L) {
super(L);
}

// 子类必须重写此方法,接受数据
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
// 此处可以更新UI
Bundle b = msg.getData();
String rmsg = b.getString("rmsg");
if ("1".equals(rmsg)) {
// do nothing
button.setVisibility(View.GONE);
layloading.setVisibility(View.VISIBLE);

}else if ("2".equals(rmsg)) {

try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
for(int i=0;i<20;i++){
a++;
Map<String, Object> map = new HashMap<String, Object>();
map.put("img", R.drawable.icon);
map.put("title", "G"+a);
map.put("info", "google"+a);
mData.add(map);
}
button.setVisibility(View.VISIBLE);
layloading.setVisibility(View.GONE);
adapter.notifyDataSetChanged();
}

}
}

}

布局文件：

main.xml

Xml代码


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content"

>

<ListView android:id="@id/android:list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:drawSelectorOnTop="false"
android:footerDividersEnabled="false"
android:scrollbars="vertical"
/>

</LinearLayout>

main_list.xml

Xml代码


<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
android:id="@+id/RelativeLayout01"
android:layout_width="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="wrap_content"
android:paddingBottom="4dip"
android:paddingLeft="12dip"
android:paddingRight="12dip"
android:background="#FFFFFF"
>
<ImageView
android:paddingTop="12dip"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_width="100dp"
android:layout_height="100dp"
android:id="@+id/img"
/>
<TextView
android:text="TextView01"
android:layout_height="wrap_content"
android:textSize="20dip"
android:layout_width="fill_parent"
android:id="@+id/listtitle"
android:layout_toRightOf="@id/img"
/>
<TextView
android:text="TextView02"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:id="@+id/listtext"
android:layout_toRightOf="@id/img"
android:layout_below="@id/listtitle"
/>
</RelativeLayout>

main_foot.xml

Xml代码


<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout android:layout_width="fill_parent"
android:layout_height="wrap_content" android:minHeight="?android:listPreferredItemHeight"
xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#FFFFFF"
>

<Button android:textSize="16.0sp" android:textColor="#ff545454"
android:gravity="center" android:id="@+id/more" android:layout_width="fill_parent"
android:layout_height="fill_parent" android:text="加载下20条" />

<LinearLayout android:gravity="center"
android:layout_gravity="center" android:orientation="horizontal"
android:id="@+id/loading" android:layout_width="fill_parent"
android:layout_height="fill_parent">

<ProgressBar android:layout_gravity="center_vertical"
android:id="@+id/footprogress" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:indeterminateBehavior="repeat"
style="?android:progressBarStyleSmallInverse" />

<TextView android:textColor="#ff000000" android:gravity="left|center"
android:padding="3.0px" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:text="加载中" />

</LinearLayout>

</LinearLayout>

AndroidManifest.xml

Xml代码


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="cn.anycall.testlist"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="4" />

<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".TestListViewActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<!-- 允许应用打开网络套接口 -->
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
</manifest> 源文件下载在附件中：

本文出自:http://yafei.iteye.com/blog/1160207