**歡迎訪問我的個人博客轉(zhuǎn)發(fā)請注明出處：http://www.wensibo.top/2017/02/17/一口一口吃掉Volley（三）/ **
學(xué)習(xí)了一口一口吃掉Volley（二）之后，你應(yīng)該已經(jīng)學(xué)會了如何使用Volley自帶的Request，但是有的時候我們需要解析的數(shù)據(jù)多種多樣，例如XML又或者你想使用Google的gson，那么當(dāng)Volley不能直接提供給我們這些功能的時候就需要我們進(jìn)行自定義了，第一節(jié)我也向大家講過Volley面向接口編程，使得其很容易擴(kuò)展，那么這節(jié)課我們就一起來學(xué)習(xí)自定義的Request吧！
從StringRequest開始講講思路
先上最基本的StringRequest源碼
public class StringRequest extends Request<String>{
private final Response.Listener<String> mListener;
/** 根據(jù)給定的METHOD設(shè)置對應(yīng)的request. */
public StringRequest(int method, String url, Response.Listener<String> listener,
Response.ErrorListener errorListener) {
super(method, url, errorListener);
mListener = listener;
}
/** 默認(rèn)為GET請求的request. */
public StringRequest(String url, Response.Listener<String> listener,
Response.ErrorListener errorListener) {
this(Method.GET, url, listener, errorListener);
}
/** 將HTTP請求結(jié)果轉(zhuǎn)換為String. */
@Override
protected Response<String> parseNetworkResponse(NetworkResponse response) {
String parsed;
try {
parsed = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
} catch (UnsupportedEncodingException e) {
parsed = new String(response.data);
}
return Response.success(parsed, HttpHeaderParser.parseCacheHeaders(response));
}
/** 將解析的String結(jié)果傳遞給用戶的回調(diào)接口. */
@Override
protected void deliverResponse(String response) {
mListener.onResponse(response);
}
}
我們應(yīng)該可以提煉出如下幾點(diǎn)：
- StringRequest繼承自Request類，并制定其泛型為String，那么當(dāng)我們自定義XMLRequest時就應(yīng)該指定類型為XmlPullParser。
- 有兩個構(gòu)造函數(shù)，默認(rèn)使用的GET請求。
- 由于Request類中的deliverResponse()和parseNetworkResponse()是兩個抽象方法，因此自定義Request中需要對這兩個方法進(jìn)行實(shí)現(xiàn)。
- deliverResponse()方法中僅僅是調(diào)用了mListener中的onResponse()方法，并將response內(nèi)容傳入即可，這樣就可以將服務(wù)器響應(yīng)的數(shù)據(jù)進(jìn)行回調(diào)。
- parseNetworkResponse()方法中則是對服務(wù)器響應(yīng)的數(shù)據(jù)進(jìn)行解析，其中數(shù)據(jù)是以字節(jié)的形式存放在NetworkResponse的response變量中的，這里將數(shù)據(jù)取出然后組裝成一個String，并傳入Response的success()方法中即可。
既然知道內(nèi)部實(shí)現(xiàn)的邏輯，那就開始動手吧！
自定義XMLRequest
① 直接上代碼啦！
按照剛才我們解析StringRequest得到的幾點(diǎn)結(jié)論，我們應(yīng)該不難得到XMLRequest：
public class XMLRequest extends Request<XmlPullParser> {
private final Response.Listener<XmlPullParser> mListener;
public XMLRequest(int method, String url, Response.Listener<XmlPullParser> listener, Response.ErrorListener errorListener) {
super(method, url, errorListener);
mListener = listener;
}
public XMLRequest( String url, Response.Listener<XmlPullParser> listener, Response.ErrorListener errorListener) {
this(Method.GET, url, listener, errorListener);
}
@Override
protected Response<XmlPullParser> parseNetworkResponse(NetworkResponse response) {
try {
response.headers.put("HTTP.CONTENT_TYPE", "utf-8");
String xmlString = new String(response.data,"utf-8");
//加上這兩行可以解決亂碼的問題，尤其是對于中文的xml接口，由于每個xml的編碼格式不同，所以獲取原編碼格式之后再轉(zhuǎn)換為utf-8，即可。
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser xmlPullParser = factory.newPullParser();
xmlPullParser.setInput(new StringReader(xmlString));
Log.d("SUCCESS", "xmlString的內(nèi)容為" + xmlString);
return Response.success(xmlPullParser, HttpHeaderParser.parseCacheHeaders(response));
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
} catch (XmlPullParserException e) {
return Response.error(new ParseError(e));
}
}
@Override
protected void deliverResponse(XmlPullParser response) {
mListener.onResponse(response);
}
}
這里需要注意的一點(diǎn)我在上一篇文章中也已經(jīng)提到了，就是在解析數(shù)據(jù)的時候如果出現(xiàn)亂碼應(yīng)該轉(zhuǎn)換編碼為utf-8。
② 測試接口
作為測試，我使用的XML接口是：http://flash.weather.com.cn/wmaps/xml/guangdong.xml ，它返回的是廣東省各個城市的天氣預(yù)報(bào)，你也可以將guangdong改為你所在的省份就可以顯示其他數(shù)據(jù)了：
<guangdong dn="day">
<city cityX="137.7" cityY="385.95" cityname="湛江" centername="湛江" fontColor="FFFFFF" pyName="zhanjiang" state1="1" state2="1" stateDetailed="多云" tem1="23" tem2="16" temNow="24" windState="微風(fēng)" windDir="東南風(fēng)" windPower="2級" humidity="50%" time="15:30" url="101281001"/>
<city cityX="170.65" cityY="317.55" cityname="茂名" centername="茂名" fontColor="FFFFFF" pyName="maoming" state1="1" state2="1" stateDetailed="多云" tem1="26" tem2="14" temNow="26" windState="微風(fēng)" windDir="西南風(fēng)" windPower="1級" humidity="47%" time="15:30" url="101282001"/>
<city cityX="225" cityY="245" cityname="云浮" centername="云浮" fontColor="FFFFFF" pyName="yunfu" state1="1" state2="1" stateDetailed="多云" tem1="26" tem2="13" temNow="26" windState="微風(fēng)" windDir="東風(fēng)" windPower="2級" humidity="43%" time="15:30" url="101281401"/>
<city cityX="226.55" cityY="304.5" cityname="陽江" centername="陽江" fontColor="FFFFFF" pyName="yangjiang" state1="0" state2="1" stateDetailed="晴轉(zhuǎn)多云" tem1="24" tem2="15" temNow="23" windState="微風(fēng)" windDir="東南風(fēng)" windPower="3級" humidity="63%" time="15:30" url="101281801"/>
<city cityX="275.35" cityY="214.65" cityname="肇慶" centername="肇慶" fontColor="FFFFFF" pyName="zhaoqing" state1="1" state2="1" stateDetailed="多云" tem1="26" tem2="14" temNow="26" windState="微風(fēng)" windDir="西北風(fēng)" windPower="1級" humidity="43%" time="15:30" url="101280901"/>
<city cityX="291" cityY="285" cityname="江門" centername="江門" fontColor="FFFFFF" pyName="jiangmen" state1="0" state2="0" stateDetailed="晴" tem1="26" tem2="15" temNow="26" windState="微風(fēng)" windDir="東風(fēng)" windPower="2級" humidity="38%" time="15:30" url="101281101"/>
<city cityX="313.3" cityY="160.45" cityname="清遠(yuǎn)" centername="清遠(yuǎn)" fontColor="FFFFFF" pyName="qingyuan" state1="1" state2="1" stateDetailed="多云" tem1="25" tem2="15" temNow="26" windState="微風(fēng)" windDir="南風(fēng)" windPower="2級" humidity="44%" time="15:30" url="101281301"/>
<city cityX="308.7" cityY="225" cityname="佛山" centername="佛山" fontColor="FFFFFF" pyName="foshan" state1="0" state2="1" stateDetailed="晴轉(zhuǎn)多云" tem1="26" tem2="14" temNow="26" windState="微風(fēng)" windDir="北風(fēng)" windPower="1級" humidity="42%" time="15:30" url="101280800"/>
<city cityX="342.7" cityY="255" cityname="中山" centername="中山" fontColor="FFFFFF" pyName="zhongshan" state1="1" state2="1" stateDetailed="多云" tem1="25" tem2="14" temNow="26" windState="微風(fēng)" windDir="西北風(fēng)" windPower="2級" humidity="41%" time="15:30" url="101281701"/>
<city cityX="340.55" cityY="300" cityname="珠海" centername="珠海" fontColor="FFFFFF" pyName="zhuhai" state1="1" state2="1" stateDetailed="多云" tem1="23" tem2="17" temNow="23" windState="微風(fēng)" windDir="東風(fēng)" windPower="2級" humidity="48%" time="15:30" url="101280701"/>
<city cityX="352.6" cityY="80" cityname="韶關(guān)" centername="韶關(guān)" fontColor="FFFFFF" pyName="shaoguan" state1="1" state2="1" stateDetailed="多云" tem1="25" tem2="14" temNow="27" windState="微風(fēng)" windDir="西風(fēng)" windPower="1級" humidity="34%" time="15:30" url="101280201"/>
<city cityX="353" cityY="196" cityname="廣州" centername="廣州" fontColor="FFFF00" pyName="guangzhou" state1="0" state2="0" stateDetailed="晴" tem1="26" tem2="14" temNow="26" windState="微風(fēng)" windDir="南風(fēng)" windPower="1級" humidity="40%" time="15:20" url="101280101"/>
<city cityX="377" cityY="234" cityname="東莞" centername="東莞" fontColor="FFFFFF" pyName="dongguan" state1="0" state2="1" stateDetailed="晴轉(zhuǎn)多云" tem1="25" tem2="15" temNow="26" windState="微風(fēng)" windDir="北風(fēng)" windPower="1級" humidity="37%" time="15:30" url="101281601"/>
<city cityX="409" cityY="257" cityname="深圳" centername="深圳" fontColor="FFFFFF" pyName="shenzhen" state1="0" state2="0" stateDetailed="晴" tem1="24" tem2="15" temNow="24" windState="微風(fēng)" windDir="南風(fēng)" windPower="3級" humidity="49%" time="15:30" url="101280601"/>
<city cityX="423.85" cityY="214.65" cityname="惠州" centername="惠州" fontColor="FFFFFF" pyName="huizhou" state1="1" state2="0" stateDetailed="多云轉(zhuǎn)晴" tem1="26" tem2="13" temNow="26" windState="微風(fēng)" windDir="南風(fēng)" windPower="1級" humidity="38%" time="15:20" url="101280301"/>
<city cityX="442.55" cityY="141.6" cityname="河源" centername="河源" fontColor="FFFFFF" pyName="heyuan" state1="0" state2="1" stateDetailed="晴轉(zhuǎn)多云" tem1="25" tem2="15" temNow="27" windState="微風(fēng)" windDir="西南風(fēng)" windPower="1級" humidity="37%" time="15:30" url="101281201"/>
<city cityX="492" cityY="217" cityname="汕尾" centername="汕尾" fontColor="FFFFFF" pyName="shanwei" state1="1" state2="0" stateDetailed="多云轉(zhuǎn)晴" tem1="24" tem2="14" temNow="24" windState="東南風(fēng)3-4級轉(zhuǎn)微風(fēng)" windDir="東風(fēng)" windPower="2級" humidity="45%" time="15:30" url="101282101"/>
<city cityX="522.55" cityY="110.45" cityname="梅州" centername="梅州" fontColor="FFFFFF" pyName="meizhou" state1="1" state2="0" stateDetailed="多云轉(zhuǎn)晴" tem1="27" tem2="12" temNow="26" windState="微風(fēng)" windDir="東風(fēng)" windPower="1級" humidity="36%" time="15:30" url="101280401"/>
<city cityX="526.8" cityY="182" cityname="揭陽" centername="揭陽" fontColor="FFFFFF" pyName="jieyang" state1="0" state2="0" stateDetailed="晴" tem1="26" tem2="13" temNow="26" windState="微風(fēng)" windDir="東風(fēng)" windPower="2級" humidity="34%" time="15:30" url="101281901"/>
<city cityX="579" cityY="137.45" cityname="潮州" centername="潮州" fontColor="FFFFFF" pyName="chaozhou" state1="0" state2="0" stateDetailed="晴" tem1="25" tem2="12" temNow="26" windState="微風(fēng)" windDir="東南風(fēng)" windPower="2級" humidity="38%" time="15:30" url="101281501"/>
<city cityX="566.45" cityY="179.25" cityname="汕頭" centername="汕頭" fontColor="FFFFFF" pyName="shantou" state1="0" state2="1" stateDetailed="晴轉(zhuǎn)多云" tem1="24" tem2="13" temNow="24" windState="東北風(fēng)轉(zhuǎn)東風(fēng)小于3級" windDir="東風(fēng)" windPower="2級" humidity="54%" time="15:30" url="101280501"/>
</guangdong>
③ 調(diào)用XMLRequest，并加入RequestQueue
代碼中我將解析XML數(shù)據(jù)的城市展示在List View中：
XMLRequest xmlRequest = new XMLRequest(
"http://flash.weather.com.cn/wmaps/xml/guangdong.xml",
new Response.Listener<XmlPullParser>() {
@Override
public void onResponse(XmlPullParser response) {
try {
int eventType = response.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
switch (eventType) {
case XmlPullParser.START_TAG:
String nodeName = response.getName();
if ("city".equals(nodeName)) {
String pname = response.getAttributeValue(2);
Log.d("CITY", "PName is" + pname);
citys.add(pname);
}
break;
}
eventType = response.next();
}
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(XMLRequestActivity.this, android.R.layout.simple_list_item_1, citys);
lv_xml_request.setAdapter(arrayAdapter);
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
lv_xml_request.setVisibility(View.GONE);
mTextView.setVisibility(View.VISIBLE);
Log.d("ERROR", "返回XMLRequest失敗");
}
}
);
mQueue.add(xmlRequest);
}
人品爆發(fā)，看截圖
XMLRequest
自定義GsonRequest
雖然Volley提供了JsonRequest為我們解析Json，但是使用JSONObject還是太麻煩了，還有很多方法可以讓JSON數(shù)據(jù)解析變得更加簡單，比如說GSON，所以何不如自定義一個GsonRequest呢？思路也是大同小異！
① 直接上代碼啦！
public class GsonRequest<T> extends Request<T> {
private final Response.Listener<T> mListener;
private Gson mGson;
private Class<T> mClazz;
public GsonRequest(int method, String url, Class<T> clazz, Response.Listener<T> listener, Response.ErrorListener errorListener) {
super(method, url, errorListener);
mGson = new Gson();
mClazz = clazz;
mListener = listener;
}
public GsonRequest(String url, Class<T> clazz, Response.Listener<T> listener, Response.ErrorListener errorListener) {
this(Method.GET, url, clazz, listener, errorListener);
}
@Override
protected Response<T> parseNetworkResponse(NetworkResponse response) {
try {
response.headers.put("HTTP.CONTENT_TYPE", "utf-8");
String jsonString = new String(response.data,"utf-8");
//加上這兩行可以解決亂碼的問題，尤其是對于中文的json接口，由于每個網(wǎng)頁的編碼格式不同，所以獲取原編碼格式之后再轉(zhuǎn)換為utf-8，即可。
return Response.success(mGson.fromJson(jsonString, mClazz),
HttpHeaderParser.parseCacheHeaders(response)
);
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
}
}
@Override
protected void deliverResponse(T response) {
mListener.onResponse(response);
}
}
同樣需要注意編碼的問題。在parseNetworkResponse()方法中，先是將服務(wù)器響應(yīng)的數(shù)據(jù)解析出來，然后通過調(diào)用Gson的fromJson方法將數(shù)據(jù)組裝成對象。在deliverResponse方法中仍然是將最終的數(shù)據(jù)進(jìn)行回調(diào)。
- 記得為工程加入gson庫
compile 'com.google.code.gson:gson:2.8.0'
② json接口
使用之前使用的json接口：http://www.weather.com.cn/data/sk/101010100.html ，它返回的數(shù)據(jù)是一個叫做weatherinfo的jsonObject：
{"weatherinfo":{"city":"北京","cityid":"101010100","temp":"19","WD":"南風(fēng)","WS":"2級","SD":"43%","WSE":"2","time":"19:45","isRadar":"1","Radar":"JC_RADAR_AZ9010_JB"}}
③ 新建bean類
由于返回的jsonObject名字叫做weatherinfo，所以我們新建一個WeatherInfo類，定義了幾個最基本的屬性就行了：
public class WeatherInfo{
private String city;
private String temp;
private String time;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getTemp() {
return temp;
}
public void setTemp(String temp) {
this.temp = temp;
}
public String gettime() {
return time;
}
public void settime(String time) {
this.time = time;
}
}
另外還需要再定義一個Weather類，來獲取WeatherInfo對象：
public class Weather {
//此處的weatherinfo不可以修改為weatherInfo，因?yàn)閺膉son獲取的數(shù)據(jù)格式為
// {"weatherinfo":{"city":"北京","cityid":"101010100","temp":"19","WD":"南風(fēng)","WS":"2級","SD":"43%","WSE":"2","time":"19:45","isRadar":"1","Radar":"JC_RADAR_AZ9010_JB"}}
private WeatherInfo weatherinfo;
public WeatherInfo getWeatherInfo() {
return weatherinfo;
}
public void setWeatherInfo(WeatherInfo weatherinfo) {
this.weatherinfo = weatherinfo;
}
}
此處的weatherinfo不可以修改為weatherInfo
④調(diào)用GsonRequest
我們將獲取的數(shù)據(jù)顯示在Text View上就行了。
GsonRequest<Weather> gsonRequest=new GsonRequest<Weather>("http://www.weather.com.cn/data/sk/101010100.html"
, Weather.class,
new Response.Listener<Weather>() {
@Override
public void onResponse(Weather weather) {
WeatherInfo weatherInfo = weather.getWeatherInfo();
if (weatherInfo != null) {
StringBuffer str = new StringBuffer();
str.append("城市：" + weatherInfo.getCity() + "\n");
str.append("溫度：" + weatherInfo.getTemp() + "\n");
str.append("時間：" + weatherInfo.gettime());
tv_gson_request.setText(str);
Log.d("SUCCESS", "成功返回GsonRequest " + str.toString());
} else {
Log.d("ERROR", "weatherinfo對象為空");
}
}
}
, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.d("ERROR", "返回GsonRequest失敗");
tv_gson_request.setText(getResources().getString(R.string.error_message));
}
}
);
mQueue.add(gsonRequest);
看截圖啦！
GsonRequest
這一節(jié)只是向大家介紹了如何自定義Request，其實(shí)都是大同小異的，例如你覺得Gson不能滿足你，那你也可以改為FastJson或者其他的功能，但是請一定要注意編碼問題！最后一節(jié)我們將一起通過閱讀源碼來分析Volley的工作流程！
