标签：android volley imageloader networkimageview
从前在学校用的最多的网络请求框架就是AsyncHttpClient，用久了发现这样一个问题，就是代码复用太难，基本上做不到，所以有一段时间又回归了HttpURLConnection和HttpClient，再后来又学习了OKHttp的使用，虽然这几种网络请求各有各的优势，但是原理基本上都是一样的，在android6.0中Google已经不提供HttpClient的API了，所以从长远的角度来考虑，推荐大家多用OKHttp，关于OKHttp的使用可以参见OKHttp的简单使用。除了上面说的这几种通信方式，Google在2013年(好早呀
)的I/O大会上还推出了一个网络请求框架Volley，这和AsyncHttpClient的使用非常像，之前一直没有总结过Volley的使用，周末有时间总结一下，与大家分享。
Volley适用于交互频繁但是数据量小的网络请求，比如我们在上一篇博客中介绍的新闻列表，这种情况下使用Volley就是非常合适的，但是对于一些数据量大的网络请求，比如下载，Volley就显得略有力不从心。
Volley是一个开源项目，我们可以在GitHub上获得它的源代码，地址https://github.com/mcxiaoke/android-volley，拿到之后我们可以将之打包成jar包使用，也可以直接将源码拷贝到我们的项目中使用，个人推荐第二种方式，这样发生错误的时候方便我们调试，同时也有利于我们修改源码，定制我们自己的Volley。如果要拷贝源码，我们只需要将“android-volley-master\android-volley-master\src\main\java”这个文件夹下的com包拷贝到我们的项目中即可。
RequestQueue mQueue = Volley.newRequestQueue(this);获得一个请求队列只需要一个参数，就是Context，这里因为在MainActivity发起请求，所以直接用this。字符型数据的请求，我们使用StringRequest：
StringRequest sr = new StringRequest("http://www.baidu.com",
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.i("lenve", response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});mQueue.add(sr);嗯，就是这么简单。那我们不禁有疑问了，刚才这个请求时get请求还是post请求？我们如何自己设置网络请求方式？我们看一下这个构造方法的源码：
/**
* Creates a new GET request.
*
* @param url URL to fetch the string at
* @param listener Listener to receive the String response
* @param errorListener Error listener, or null to ignore errors
*/
public StringRequest(String url, Listener<String> listener, ErrorListener errorListener) {
this(Method.GET, url, listener, errorListener);
} /**
* Creates a new request with the given method.
*
* @param method the request {@link Method} to use
* @param url URL to fetch the string at
* @param listener Listener to receive the String response
* @param errorListener Error listener, or null to ignore errors
*/
public StringRequest(int method, String url, Listener<String> listener,
ErrorListener errorListener) {
super(method, url, errorListener);
mListener = listener;
} /**
* Returns a Map of parameters to be used for a POST or PUT request. Can throw
* {@link AuthFailureError} as authentication may be required to provide these values.
*
* <p>Note that you can directly override {@link #getBody()} for custom data.</p>
*
* @throws AuthFailureError in the event of auth failure
*/
protected Map<String, String> getParams() throws AuthFailureError {
return null;
}看注释我们大概就明白这个方法是干什么的了，它将POST请求或者PUT请求需要的参数封装成一个Map对象，那么我们如果在POST请求中需要传参的话，直接重写这个方法就可以了，代码如下： StringRequest sr = new StringRequest("http://www.baidu.com",
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.i("lenve", response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
/**
* 重写getParams(),可以自己组装post要提交的参数
*/
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> map = new HashMap<String, String>();
map.put("params1", "value1");
map.put("params1", "value1");
return map;
}
};好了，请求字符数据就是这么简单。 JsonObjectRequest jsonReq = new JsonObjectRequest(HTTPURL,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
JSONObject jo = response.getJSONObject("paramz");
JSONArray ja = jo.getJSONArray("feeds");
for (int i = 0; i < ja.length(); i++) {
JSONObject jo1 = ja.getJSONObject(i)
.getJSONObject("data");
Log.i("lenve", jo1.getString("subject"));
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
mQueue.add(jsonReq);
ImageLoader il = new ImageLoader(mQueue, new BitmapCache()); ImageListener listener = ImageLoader.getImageListener(iv, R.drawable.ic_launcher, R.drawable.ic_launcher); il.get(IMAGEURL, listener);
public ImageContainer get(String requestUrl, ImageListener imageListener,
int maxWidth, int maxHeight, ScaleType scaleType) {
// only fulfill requests that were initiated from the main thread.
throwIfNotOnMainThread();
final String cacheKey = getCacheKey(requestUrl, maxWidth, maxHeight, scaleType);
// Try to look up the request in the cache of remote images.
Bitmap cachedBitmap = mCache.getBitmap(cacheKey);
if (cachedBitmap != null) {
// Return the cached bitmap.
ImageContainer container = new ImageContainer(cachedBitmap, requestUrl, null, null);
imageListener.onResponse(container, true);
return container;
}
// The bitmap did not exist in the cache, fetch it!
ImageContainer imageContainer =
new ImageContainer(null, requestUrl, cacheKey, imageListener);
// Update the caller to let them know that they should use the default bitmap.
imageListener.onResponse(imageContainer, true);
// Check to see if a request is already in-flight.
BatchedImageRequest request = mInFlightRequests.get(cacheKey);
if (request != null) {
// If it is, add this request to the list of listeners.
request.addContainer(imageContainer);
return imageContainer;
}
// The request is not already in flight. Send the new request to the network and
// track it.
Request<Bitmap> newRequest = makeImageRequest(requestUrl, maxWidth, maxHeight, scaleType,
cacheKey);
mRequestQueue.add(newRequest);
mInFlightRequests.put(cacheKey,
new BatchedImageRequest(newRequest, imageContainer));
return imageContainer;
} <com.android.volley.toolbox.NetworkImageView
android:id="@+id/iv2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>NetworkImageView niv = (NetworkImageView) this.findViewById(R.id.iv2);
niv.setDefaultImageResId(R.drawable.ic_launcher); ImageLoader il = new ImageLoader(mQueue, new BitmapCache()); niv.setImageUrl(IMAGEURL, il);
public ImageContainer get(String requestUrl, ImageListener imageListener,
int maxWidth, int maxHeight, ScaleType scaleType) {
....
}没错，NetworkImageView和ImageLoader最终都会到达这个方法，所以说这两个东东其实非常像，那么在实际开发中究竟用哪个要视情况而定。 ImageRequest ir = new ImageRequest(IMAGEURL, new Listener<Bitmap>() {
@Override
public void onResponse(Bitmap response) {
iv3.setImageBitmap(response);
}
}, 200, 200, ScaleType.CENTER, Bitmap.Config.ARGB_8888,
new ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
mQueue.add(ir);public class JsonObjectRequest extends JsonRequest<JSONObject> {
/**
* Creates a new request.
* @param method the HTTP method to use
* @param url URL to fetch the JSON from
* @param requestBody A {@link String} to post with the request. Null is allowed and
* indicates no parameters will be posted along with request.
* @param listener Listener to receive the JSON response
* @param errorListener Error listener, or null to ignore errors.
*/
public JsonObjectRequest(int method, String url, String requestBody,
Listener<JSONObject> listener, ErrorListener errorListener) {
super(method, url, requestBody, listener,
errorListener);
}
/**
* Creates a new request.
* @param url URL to fetch the JSON from
* @param listener Listener to receive the JSON response
* @param errorListener Error listener, or null to ignore errors.
*/
public JsonObjectRequest(String url, Listener<JSONObject> listener, ErrorListener errorListener) {
super(Method.GET, url, null, listener, errorListener);
}
/**
* Creates a new request.
* @param method the HTTP method to use
* @param url URL to fetch the JSON from
* @param listener Listener to receive the JSON response
* @param errorListener Error listener, or null to ignore errors.
*/
public JsonObjectRequest(int method, String url, Listener<JSONObject> listener, ErrorListener errorListener) {
super(method, url, null, listener, errorListener);
}
/**
* Creates a new request.
* @param method the HTTP method to use
* @param url URL to fetch the JSON from
* @param jsonRequest A {@link JSONObject} to post with the request. Null is allowed and
* indicates no parameters will be posted along with request.
* @param listener Listener to receive the JSON response
* @param errorListener Error listener, or null to ignore errors.
*/
public JsonObjectRequest(int method, String url, JSONObject jsonRequest,
Listener<JSONObject> listener, ErrorListener errorListener) {
super(method, url, (jsonRequest == null) ? null : jsonRequest.toString(), listener,
errorListener);
}
/**
* Constructor which defaults to <code>GET</code> if <code>jsonRequest</code> is
* <code>null</code>, <code>POST</code> otherwise.
*
* @see #JsonObjectRequest(int, String, JSONObject, Listener, ErrorListener)
*/
public JsonObjectRequest(String url, JSONObject jsonRequest, Listener<JSONObject> listener,
ErrorListener errorListener) {
this(jsonRequest == null ? Method.GET : Method.POST, url, jsonRequest,
listener, errorListener);
}
@Override
protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
try {
String jsonString = new String(response.data,
HttpHeaderParser.parseCharset(response.headers, PROTOCOL_CHARSET));
return Response.success(new JSONObject(jsonString),
HttpHeaderParser.parseCacheHeaders(response));
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
} catch (JSONException je) {
return Response.error(new ParseError(je));
}
}
}哈，原来这么简单，光是构造方法就有五个，不过构造方法都很简单，我们就不多说，核心的功能在parseNetworkResponse方法中，这里调用成功的时候返回一个Response泛型，泛型里边的东西是一个JSONObject，其实也很简单，我们如果要处理XML，那么直接在重写parseNetworkResponse方法，在调用成功的时候直接返回一个Response泛型，这个泛型中是一个XmlPullParser对象，哈哈，很简单吧，同时，结合StringRequest的实现方式，我们实现了XMLRequest的代码：public class XMLRequest extends Request<XmlPullParser> {
private Listener<XmlPullParser> mListener;
public XMLRequest(String url, Listener<XmlPullParser> mListener,
ErrorListener listener) {
this(Method.GET, url, mListener, listener);
}
public XMLRequest(int method, String url,
Listener<XmlPullParser> mListener, ErrorListener listener) {
super(method, url, listener);
this.mListener = mListener;
}
@Override
protected Response<XmlPullParser> parseNetworkResponse(
NetworkResponse response) {
String parsed;
try {
parsed = new String(response.data,
HttpHeaderParser.parseCharset(response.headers));
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser parser = factory.newPullParser();
parser.setInput(new StringReader(parsed));
return Response.success(parser,
HttpHeaderParser.parseCacheHeaders(response));
} catch (UnsupportedEncodingException e) {
parsed = new String(response.data);
} catch (XmlPullParserException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void deliverResponse(XmlPullParser response) {
if (mListener != null) {
mListener.onResponse(response);
}
}
@Override
protected void onFinish() {
super.onFinish();
mListener = null;
}
} XMLRequest xr = new XMLRequest(XMLURL,
new Response.Listener<XmlPullParser>() {
@Override
public void onResponse(XmlPullParser parser) {
try {
int eventType = parser.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
switch (eventType) {
case XmlPullParser.START_DOCUMENT:
break;
case XmlPullParser.START_TAG:
String tagName = parser.getName();
if ("city".equals(tagName)) {
Log.i("lenve",
new String(parser.nextText()));
}
break;
case XmlPullParser.END_TAG:
break;
}
eventType = parser.next();
}
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
mQueue.add(xr);版权声明：本文为博主原创文章，未经博主允许不得转载。若有错误地方，还望批评指正，不胜感激。
标签：android volley imageloader networkimageview
原文地址：http://blog.csdn.net/u012702547/article/details/49718955
