阅读之前：我在这个程序中使用了可下载的GSON库。 http://webscripts.softpedia.com/script/Development-Scripts-js/Other-Libraries/Gson-71373.html
我一直在尝试解析JSON很长一段时间，但每次我尝试从URL中获取字符串时程序都“无法正常工作”。它不会失败或关闭或出错。它只是不解析。我的程序是从http://api.geonames.org/weatherIcaoJSON?ICAO=LSZH&username=demo解析并有一个更新按钮再次运行解析过程，以便它刷新信息。如果我使用硬编码的JSON字符串，该程序可以正常工作。我甚至放入了应该从URL中检索的字符串;但我似乎无法直接得到它。我正在使用GSON库。
在代码中，我提供了解释我思考过程的评论。请注意，我有2种不同的方法试图使用URL（我认为可能原来的一个是错的所以我试图使用另一个），这是我抓住稻草。请帮帮我。谢谢。
我的代码：
package com.android.testgson;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URI;
import java.net.URL;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.google.gson.Gson;
public class GSONTestActivity extends Activity {
/** Called when the activity is first created. */
//String test = "";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView tv = (TextView)findViewById(R.id.textViewInfo);
syncButtonClickListener();
runJSONParser(tv);
}
private void syncButtonClickListener()
{
Button syncButton = (Button)findViewById(R.id.buttonSync);
syncButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
TextView tv = (TextView)findViewById(R.id.textViewInfo);
runJSONParser(tv);
}
});
}
public InputStream getJSONData(String url){
// create DefaultHttpClient
HttpClient httpClient = new DefaultHttpClient();
URI uri; // for URL
InputStream data = null; // for URL's JSON
try {
uri = new URI(url);
HttpGet method = new HttpGet(uri); // Get URI
HttpResponse response = httpClient.execute(method); // Get response from method.
data = response.getEntity().getContent(); // Data = Content from the response URL.
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
public void runJSONParser(TextView tv){
try{
Gson gson = new Gson();
//Reader r = new InputStreamReader(getJSONData("http://api.geonames.org/weatherIcaoJSON?ICAO=LSZH&username=demo"));
/**I tried parsing the URL, but it didn't work. No error messages, just didn't parse.*/
//Reader r = new InputStreamReader(getJSONData("android.resource://"+ getPackageName() + "/" + R.raw.yourparsable));
/**I tried parsing from local JSON file. Didn't work. Again no errors. The program simply stalls. */
//String testString = "{\"weatherObservation\":{\"clouds\":\"few clouds\",\"weatherCondition\":\"n/a\",\"observation\":\"LSZH 041320Z 24008KT 210V270 9999 FEW022 SCT030 BKN045 05/01 Q1024 NOSIG\",\"windDirection\":\"240\",\"ICAO\":\"LSZH\",\"elevation\":\"432\",\"countryCode\":\"CH\",\"lng\":\"8.516666666666667\",\"temperature\":\"5\",\"dewPoint\":\"1\",\"windSpeed\":\"08\",\"humidity\":\"75\",\"stationName\":\"Zurich-Kloten\",\"datetime\":\"2012-01-04 13:20:00\",\"lat\":\"47.46666666666667\",\"hectoPascAltimeter\":\"1024\"}}";
/**If I parse this string. The parser works. It is the same exact string like in the URL.*/
//String failString = "{\"status\":{\"message\":\"the hourly limit of 2000 credits demo has been exceeded. Please throttle your requests or use the commercial service.\",\"value\":19}}";
/**Even if the url delivers this string (because the hourly limit would be reached), the string is still parsed correctly.*/
String json = readUrl("http://api.geonames.org/weatherIcaoJSON?ICAO=LSZH&username=demo");
/**At this point I tried a different means of accessing the URL but still I had the exact same problem*/
Observation obs = gson.fromJson(json, Observation.class);
// "json" can be replaced with r, testString, failString to see all my previous results.
if (obs.getWeatherObservation()!=null)
{
tv.setText("Clouds - " + obs.getWeatherObservation().getClouds()
+ "\nTemperature - " + obs.getWeatherObservation().getTemperature()
+ "\nWind Speed - " + obs.getWeatherObservation().getWindSpeed()
+ "\nHumidity - " + obs.getWeatherObservation().getHumidity());
}
else if (obs.getStatus()!=null)
{
tv.setText("Message - " + obs.getStatus().getMessage()
+ "\nValue - " + obs.getStatus().getValue());
}
}catch(Exception ex){
ex.printStackTrace();
}
}
public static String readUrl(String urlString) throws Exception {
BufferedReader reader = null;
try{
URL url = new URL(urlString);
reader = new BufferedReader(new InputStreamReader (url.openStream()));
StringBuffer buffer = new StringBuffer();
int read;
char[]chars = new char[1024];
while ((read = reader.read(chars)) != -1)
buffer.append(chars, 0, read);
return buffer.toString();
} finally {
if (reader != null)
reader.close();
}
}
}
答案 0 :(得分：2)
像谢尔盖一样，我发现Android上包含的json库org.json.*比GSON更容易使用。
例如，在您的场景中 - 您的JSON解析代码将如下所示。
String jsonData = readUrl("http://api.geonames.org/weatherIcaoJSON?ICAO=LSZH&username=demo");
JSONObject weatherJSONObject = new JSONObject( jsonData );
try {
// Not sure the format of your data, but you would want something like this
String clouds = weatherJSONObject.getString("clouds");
} catch (JSONException e) {
e.printStackTrace();
}
您还可以从AsyncTask或Thread中受益。您永远不希望在UI线程上运行长时间运行的操作，因为UI看起来没有响应和缓慢。
以下是有关如何使用AsyncTask实现目标的示例。详细了解here
private class FetchJSONDataTask extends AsyncTask<String, Void, JSONObject> {
// This gets executed on a background thread
protected JSONObject doInBackground(String... params) {
String urlString = params[0];
String jsonData = readUrl( urlString );
JSONObject weatherJSONObject = new JSONObject( jsonData );
return weatherJSONObject;
}
// This gets executed on the UI thread
protected void onPostExecute(JSONObject json) {
//Your function that takes a json object and populates views
setUpViews( json );
}
}
要执行您的任务，您应该在您的活动中运行此代码。
FetchJSONDataTask task = new FetchJSONDataTask();
task.execute( new String[] { "http://api.geonames.org/weatherIcaoJSON?ICAO=LSZH&username=demo" } );
注意：此代码未经测试，但这应该是一般的想法。
答案 1 :(得分：0)
我使用org.json完成了json解析。*
http://www.json.org/java/index.html Android 4中的文档。 http://developer.android.com/reference/org/json/package-summary.html（例如）
您可以从这里下载jar http://repo1.maven.org/maven2/org/json/json/20090211/json-20090211.jar
我还会考虑在不同的线程中运行您的http请求，然后重新绘制您的UI。为此目的也读了关于android.os.Handler的信息。
感谢
答案 2 :(得分：0)
JSON响应通常是gzip，请在getJSONData（）方法中尝试：
... ...
uri = new URI(url);
HttpGet method = new HttpGet(uri); // Get URI
HttpResponse response = httpClient.execute(method); // Get response from method.
InputStream in = response.getEntity().getContent();
GZIPInputStream gin = new GZIPInputStream(in);
BufferedReader reader = new BufferedReader(new InputStreamReader(gin));
String line = null;
while ((line = reader.readLine()) != null) {
jsonResponse.append(line);
}
reader.close();
... ...