[android] 练习使用ListView（二）详解手机开发

import com.nostra13.universalimageloader.core.ImageLoader; import com.nostra13.universalimageloader.core.ImageLoaderConfiguration; import com.nostra13.universalimageloader.core.assist.FailReason; import com.nostra13.universalimageloader.core.listener.ImageLoadingListener; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.drawable.BitmapDrawable; import android.os.AsyncTask; import android.os.Bundle; import android.support.v4.util.LruCache; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.ListAdapter; import android.widget.ListView; import android.widget.TextView; public class MainActivity extends Activity { private ListView lv_images; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv_images = (ListView) findViewById(R.id.lv_images); ImageLoaderConfiguration configuration=ImageLoaderConfiguration.createDefault(this); ImageLoader.getInstance().init(configuration); ListAdapter adapter = new ImageAdapter(); lv_images.setAdapter(adapter); /** * 适配器 * @author taoshihan class ImageAdapter extends BaseAdapter { private LruCache String, BitmapDrawable mImageCache; public ImageAdapter() { int maxSize=(int) (Runtime.getRuntime().maxMemory()/8); mImageCache=new LruCache String, BitmapDrawable (maxSize){ protected int sizeOf(String key, BitmapDrawable drawable) { return drawable.getBitmap().getByteCount(); @Override public View getView(int position, View convertView, ViewGroup parent) { String url=(String) getItem(position); View view; if(convertView!=null){ view=convertView; }else{ view=View.inflate(getApplicationContext(), R.layout.image_item, null); ImageView imageView=(ImageView) view.findViewById(R.id.tv_image); BitmapDrawable bitmapDrawable=getBitmapFromMemoryCache(url); if(bitmapDrawable!=null){ //读取缓存图片 imageView.setImageDrawable(bitmapDrawable); }else{ //读取网络图片 ImageWorkerTask task=new ImageWorkerTask(imageView); task.execute(url); return view; /** * 从缓存中读取图片 * @param key * @return public BitmapDrawable getBitmapFromMemoryCache(String key) { if(mImageCache.get(key)!=null){ return mImageCache.get(key); return null; public void addBitmapToMemoryCache(String key,BitmapDrawable drawable){ if(getBitmapFromMemoryCache(key)==null){ mImageCache.put(key, drawable); @Override public int getCount() { // TODO Auto-generated method stub return Images.IMAGE_URLS.length; @Override public Object getItem(int position) { return Images.IMAGE_URLS[position]; @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; /** * 异步任务 * @author taoshihan class ImageWorkerTask extends AsyncTask String, Void, BitmapDrawable { private ImageView imageView; public ImageWorkerTask(ImageView imageView) { this.imageView=imageView; @Override protected BitmapDrawable doInBackground(String... params) { String imageUrl=params[0]; Bitmap bitmap=downLoadBitmap(imageUrl); BitmapDrawable drawable=new BitmapDrawable(getApplicationContext().getResources(),bitmap); addBitmapToMemoryCache(imageUrl, drawable); return drawable; //下载图片 private Bitmap downLoadBitmap(String imageUrl) { Bitmap bitmap=null; try { URL url=new URL(imageUrl); HttpURLConnection conn=(HttpURLConnection) url.openConnection(); conn.setConnectTimeout(10000); InputStream is=conn.getInputStream(); bitmap=BitmapFactory.decodeStream(is); } catch (Exception e) { return bitmap; //下载完成的 @Override protected void onPostExecute(BitmapDrawable result) { if(imageView!=null result!=null){ imageView.setImageDrawable(result); static class Images{ public final static String[] IMAGE_URLS = new String[]{ "http://img.my.csdn.net/uploads/201508/05/1438760758_3497.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760758_6667.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760757_3588.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760756_3304.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760755_6715.jpeg", "http://img.my.csdn.net/uploads/201508/05/1438760726_5120.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760726_8364.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760725_4031.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760724_9463.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760724_2371.jpg", "http://img.my.csdn.net/uploads/201508/05/1438760707_4653.jpg" }

 

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app程序应用开发手机开发无线开发移动端开发