在android中用NetworkImageView读取网络图片并通过ListView显示出来

注：Volley库的NetworkImageView怎么用，网上有很多资料，这里只是记述我在项目中使用NetworkImageView读取网络图片然后通过ListView显示出来的做法和步骤（由于是截取删减项目代码，可能会有遗漏的地方），以备我以后查用（能帮助其他人将是我的荣幸），因为我也是在同学的帮助以及查询网络下完成的。

0、引用Volley库

1、布局文件

主页面布局xml中的ListView控件

<ListView      android:id="@+id/lv_typelist"      android:layout_width="match_parent"      android:layout_height="match_parent"      android:divider="@null"      android:scrollbars="none"/>

显示图片加文字的模板xml文件

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="horizontal">    <LinearLayout        android:layout_width="80dp"        android:layout_height="100dp">        <com.android.volley.toolbox.NetworkImageView            android:id="@+id/imageview_typeImg"            android:layout_width="match_parent"            android:layout_height="80dp"            android:scaleType="centerCrop"            android:layout_gravity="center"            android:gravity="center">        </com.android.volley.toolbox.NetworkImageView>        <TextView            android:id="@+id/textview_typeName"            android:layout_width="match_parent"            android:layout_height="20dp"            android:layout_gravity="center"            android:gravity="center"/>    </LinearLayout></LinearLayout>

用NetworkImageView替代安卓自身的ImageView控件。

2、创建自定义的Application，用来获取Volley的队列对象

public class MyApplication extends Application {    public static RequestQueue queue;    @Override    public void onCreate() {        super.onCreate();        queue = Volley.newRequestQueue(getApplicationContext());    }    public static RequestQueue getHttpQueue() {        return queue;    }}

修改AndroidManifest.xml文件

android:name=".MyApplication

如下：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.user.myfirstapp">    <uses-permission android:name="android.permission.INTERNET"/>    <application        android:name=".MyApplication"        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppBaseTheme">        <activity android:name=".MainActivity">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>

3、创建自定义ImageCache类

import android.graphics.Bitmap;import android.support.v4.util.LruCache;import com.android.volley.toolbox.ImageLoader;public class BitmapCache implements ImageLoader.ImageCache {    //内存缓存    private static LruCache<String, Bitmap> mMemoryCache;    //单例    private static BitmapCache lruImageCache;    private BitmapCache(){        // Get the Max available memory        int maxMemory = (int) Runtime.getRuntime().maxMemory();        int cacheSize = maxMemory/10;        mMemoryCache = new LruCache<String, Bitmap>(cacheSize){            @Override            protected int sizeOf(String key, Bitmap bitmap){                return bitmap.getRowBytes() * bitmap.getHeight();            }        };    }    //获取单例实例    public static BitmapCache instance(){        if(lruImageCache == null){            lruImageCache = new BitmapCache();        }        return lruImageCache;    }    //从内存获取图片    @Override    public Bitmap getBitmap(String url){        return mMemoryCache.get(url);    }    //图片放入到内存    @Override    public void putBitmap(String url, Bitmap bitmap){        if(getBitmap(url) == null){            mMemoryCache.put(url, bitmap);        }    }}

4、Activity或Fragment中代码(我这里是在Fragment中)

    private View view;    private ListView lv_type;    private TextView typename;    private ImageView right_top_img;    private Gson gson;    private List<GoodsType> list;    private ArrayList<HashMap<String, Object>> listItem;    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        view =inflater.inflate(R.layout.flg_type,container,false);        lv_type=(ListView)view.findViewById(R.id.lv_typelist);        ....此处省略一些代码....        showImageList();        ....此处省略一些代码....        return view;    }    private void showImageList(){        if(list!=null&&list.size()>0) {            NetworkImageViewAdapter adapter = new NetworkImageViewAdapter(getActivity());            lv_type.setAdapter(adapter);            //点击事件            lv_type.setOnItemClickListener(new AdapterView.OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {                if(id==-1)                    return;                int realPosition=(int)id;                ListView lv = (ListView)ListView;                Object object=lv.getItemAtPosition(realPosition);                //转对应的自定义的实体类型                GoodsType gt = (GoodsType)object;                //分类id                int typeId = gt.getId();                .........            }        }    }    public class NetworkImageViewAdapter extends BaseAdapter {        private LayoutInflater layoutInflater = null;        class ViewHolder {            TextView name;            NetworkImageView image;        }        public NetworkImageViewAdapter(Context context)        {            layoutInflater = LayoutInflater.from(context);        }        @Override        public int getCount() {            return list == null ? 0 : list.size();        }        @Override        public Object getItem(int position) {            return list == null ? null : list.get(position);        }        @Override        public long getItemId(int position) {            return position;        }        public View getView(int position, View convertView, ViewGroup parent) {            ViewHolder viewHolder = null;            if (convertView == null) {                viewHolder = new ViewHolder();                convertView = layoutInflater.inflate(R.layout.twoleveltypelist_item, null);                viewHolder.name = (TextView) convertView.findViewById(R.id.textview_typeName);                viewHolder.image = (NetworkImageView) convertView.findViewById(R.id.imageview_typeImg);                convertView.setTag(viewHolder);            } else {                viewHolder = (ViewHolder) convertView.getTag();            }            GoodsType gt = list.get(position);            viewHolder.name.setText(gt.getTypeName());    ImageLoader imageLoader = new ImageLoader(MyApplication.getHttpQueue(), BitmapCache.instance());    viewHolder.image.setTag("url");            viewHolder.image.setImageUrl(gt.getTypeImg(), imageLoader);            return convertView;        }    }

上面代码中的list是通过volley获取服务器的json对象发序列化得到的集合，GoodsType是一个实体对象，list就是GoodsType实体的集合，gt.getTypeName()获取的商品类型的名称，gt.getTypeImg()获取的商品类型的图片url。

5、效果图如下：