Introducing: Volley Library

Posted Mar 2, 2014

By Shen Lin 6 min read

What is Volley?

Volley is a library that makes networking for Android apps easier and most importantly, faster.

在 Google I/O 2013, Google 介绍了这个高大上的玩意儿。作为 Apache 的 HttpClient 解决方案的又一选择， Volley 具有如下优点：

Volley 会自动对齐所有的网络请求。
Volley 提供了完全透明化的磁盘和内存缓存。
Volley 提供了一套强大的“取消请求”的 API，可以轻松取消请求池中的请求。
Volley提供了强大的个性化功能、debug 和跟踪工具。

然后呢，咳咳。。。嗯嗯，技术文章要严肃！据说介个呢，就是 Volley 一词灵感的由来了。话说乍一看这一个个的真的好像那啥啊有木有！！！真是羞羞～(｡•ˇ‸ˇ•｡)

Where to get it?

Volley 并没有像其它库一样提供现成的 jar 包给我们，而是非常可爱地提供了整个项目的源代码供我们下载，自行编译。

1.Clone Volley 的源码：

git clone https://android.googlesource.com/platform/frameworks/volley

2.安装 Ant

  
sudo apt-get install ant1.7
sudo apt-get install ant-optional

3.准备配置环境变量

vim ~/.bashrc

4.配置 ANDROID_HOME 环境变量，提供我的配置供参考

  
export JAVA_HOME=/opt/java
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools
export ANDROID_HOME=/opt/adt/sdk

5.进入 Volley 目录，编译 jar 包

cd volley
ant jar

6.从 /volley/bin 中获得新成就——volley.jar

Sample Project

在接下来的项目中，我用了三个按钮，分别用来:

获得一串Json对象
获取一张图片并设置到imageView
获取一张图片并设置到 Volley 提供的 NetworkImageView (Recommended)

在测试前，请确保已将之前获得的 Volley.jar 放入项目的 /libs 并 add to buildpath。另外，项目中有网络请求，所以请确保在 AndroidManifest.xml 中请求完全的网络访问权限。

activity_main.xml

  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btn_json"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Get Json" />

    <TextView
        android:id="@+id/tv_json"
        android:layout_width="match_parent"
        android:hint="This request returns your Json-formatted ip address as reponse."
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btn_imageview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Set ImageView" />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btn_networkimageview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Set NetworkImageView" />

    <com.android.volley.toolbox.NetworkImageView
        android:id="@+id/iv_net"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

MainActivity.java

  
public class MainActivity extends Activity {

	private Button mButtonJson;
	private Button mButtonImageView;
	private Button mButtonNetImageView;
	private TextView mTextViewJson;
	private ImageView mImageView;
	private NetworkImageView mNetworkImageView;

	private final String JSON_URL = "http://ip.jsontest.com/";
	private final String AVATAR_URL = "http://www.gravatar.com/avatar/2395dcaf9490cb28a21bf1e75af6f352?s=160";
	private static final String TAG = MainActivity.class.getSimpleName();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		findViewById();
		setJsonListener();
		setImageViewListener();
		setNetworkImageViewListener();
	}

	/**
	 * This is damned easy!!!
	 */
	private void setNetworkImageViewListener() {
		mButtonNetImageView.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				RequestQueue requestQueue = Volley
						.newRequestQueue(getApplicationContext());
				final LruCache<String, Bitmap> lru = new LruCache<String, Bitmap>(
						50);
				ImageCache cache = new ImageCache() {

					@Override
					public void putBitmap(String key, Bitmap value) {
						// TODO Auto-generated method stub
						lru.put(key, value);
					}

					@Override
					public Bitmap getBitmap(String key) {
						// TODO Auto-generated method stub
						Bitmap bitmap = lru.get(key);
						return bitmap;
					}
				};
				ImageLoader loader = new ImageLoader(requestQueue, cache);
				mNetworkImageView.setImageUrl(AVATAR_URL, loader);
			}
		});
	}

	/**
	 * The getImageListener's calling will need 3 parameters. Here are the
	 * official comments in volley's source code.
	 * 
	 * @param imageView
	 *            The imageView that the listener is associated with.
	 * @param defaultImageResId
	 *            Default image resource ID to use, or 0 if it doesn't exist.
	 * @param errorImageResId
	 *            Error image resource ID to use, or 0 if it doesn't exist.
	 */
	private void setImageViewListener() {
		mButtonImageView.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				RequestQueue requestQueue = Volley
						.newRequestQueue(getApplicationContext());
				final LruCache<String, Bitmap> lru = new LruCache<String, Bitmap>(
						50); // 50 is the cache size
				ImageCache cache = new ImageCache() {

					@Override
					public void putBitmap(String key, Bitmap value) {
						lru.put(key, value);
					}

					@Override
					public Bitmap getBitmap(String key) {
						Bitmap bitmap = lru.get(key);
						return bitmap;
					}
				};
				ImageLoader loader = new ImageLoader(requestQueue, cache);
				// Here I use "android.R.drawable.ic_delete" simply because
				// it looks like a cross which means error.
				ImageListener listener = ImageLoader.getImageListener(
						mImageView, 0, android.R.drawable.ic_delete);
				loader.get(AVATAR_URL, listener);
			}
		});
	}

	private void setJsonListener() {
		mButtonJson.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View arg0) {
				// Any of your requests should be added to the RequestQueue
				// instance. Use Volley's static method instead of retriving new
				// instance manually.
				RequestQueue requestQueue = Volley
						.newRequestQueue(getApplicationContext());
				// Build up the request
				JsonObjectRequest request = new JsonObjectRequest(
						Request.Method.GET, JSON_URL, null,
						new Listener<JSONObject>() {

							@Override
							public void onResponse(JSONObject response) {
								// TODO Auto-generated method stub
								mTextViewJson.setText(response.toString());
							}
						}, new Response.ErrorListener() {

							@Override
							public void onErrorResponse(VolleyError arg0) {
								// TODO Auto-generated method stub
								Log.i(TAG, "---->onErrorResponse");
							}
						});
				// Add the request to the request queue
				requestQueue.add(request);
			}
		});
	}

	private void findViewById() {
		mButtonJson = (Button) findViewById(R.id.btn_json);
		mButtonImageView = (Button) findViewById(R.id.btn_imageview);
		mButtonNetImageView = (Button) findViewById(R.id.btn_networkimageview);
		mTextViewJson = (TextView) findViewById(R.id.tv_json);
		mImageView = (ImageView) findViewById(R.id.iv);
		mNetworkImageView = (NetworkImageView) findViewById(R.id.iv_net);
	}
}

References

《Google I/O 2013 - Volley: Easy, Fast Networking for Android》

《Android 网络通信框架 Volley 简介》

《快速构建Android REST客户端系列》

Android

This post is licensed under CC BY 4.0 by the author.

What is Volley?

Where to get it?

Sample Project

References

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