android listview分页异步加载图片及图片缓存
来源：互联网 发布：cnzz 阿里云备案 编辑：程序博客网 时间：2024/04/26 19:14
引用
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
AsyncImageLoader.java
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
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
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ListViewLinearLayout listFooter = (LinearLayout) LayoutInflater.from(this).inflate(R.layout.main_foot, null);listView.addFooterView(listFooter);// 添加FooterViewbutton = (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UItry {Thread.sleep(5000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.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@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubsuper.handleMessage(msg);// 此处可以更新UIBundle b = msg.getData();String rmsg = b.getString("rmsg");if ("1".equals(rmsg)) {// do nothingbutton.setVisibility(View.GONE);layloading.setVisibility(View.VISIBLE);}else if ("2".equals(rmsg)) { try {Thread.sleep(3000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.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 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 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 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>
<?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>
转载自：http://yafei.iteye.com/blog/1160207
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