[android] 練習使用ListView（二）

標籤：

主要練習非同步任務和LrcCache緩衝

package com.android.test;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;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);    }    /**     * 適配器     * @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){                //讀取緩衝圖片                imageView.setImageDrawable(bitmapDrawable);            }else{                //讀取網狀圖片                ImageWorkerTask task=new ImageWorkerTask(imageView);                task.execute(url);            }            return view;        }        /**         * 從緩衝中讀取圖片         * @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;        }        /**         * 非同步任務         * @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;            }            //下載圖片            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;            }            //下載完成的            @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"        };    }}

 

[android] 練習使用ListView（二）