我有一个类GetWeather.java，可以从API提取天气数据。我的应用程序的主要活动会定期通过一个单独的线程调用它。该线程命中GetWeather类，并将返回的数据发布到TextView。
无论哪种情况，从GetWeather类内部返回的数据的System.out.println都表明确实在返回数据。
以下是GetWeather.java：
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.net.Uri;
import android.util.Log;
public class GetWeather {
InputStream is = null;
JSONArray jArray = null;
JSONObject json_data = new JSONObject();
String result = "";
String strTemp = "";
String strWindSpeed = "";
String strWindDir = "";
String strVisibility = "";
String strPosition = "";
public static final Uri KEY_121 = Uri.parse("http://api.worldweatheronline.com/free/v1/weather.ashx");
String strWeatherApiKey = "REMOVED";
public GetWeather(String Location) {
strPosition = Location;
}
public void returnWeather() {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_121 + "?key="
+ strWeatherApiKey + "&q=" + strPosition + "&format=json");
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
// convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
// parse json data
try {
JSONObject object = new JSONObject(result);
JSONObject weather = object.getJSONObject("data");
JSONArray current_conditions = weather
.getJSONArray("current_condition");
for (int i = 0; i < current_conditions.length(); i++) {
JSONObject object1 = (JSONObject) current_conditions.get(i);
strTemp = object1.getString("temp_C");
strWindSpeed = object1.getString("windspeedMiles");
strWindDir = object1.getString("winddir16Point");
strVisibility = object1.getString("visibility");
// Testing output
System.out.println(strTemp);
System.out.println(strWindSpeed);
System.out.println(strWindDir);
System.out.println(strVisibility);
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
}
}
这是主要活动中的相关代码：
Runnable updateConsoleRunnable = new Runnable() {
public void run() {
tvConsole.setMovementMethod(new ScrollingMovementMethod());
tvConsole.setSelected(true);
handler.postDelayed(this, TIME_DELAY);
// Only display weather data while service is enabled
if (isServiceRunning()) {
GetWeather weather = new GetWeather(strPosition);
weather.returnWeather();
// Weather package
tvConsole
.append("Weather Update\n-------------------\n\nCurrent Temp (C): "
+ weather.strTemp
+ "C\n"
+ "Wind is out of the "
+ weather.strWindDir
+ " at "
+ weather.strWindSpeed
+ " MPH\n"
+ "Visibility is "
+ weather.strVisibility
+ " miles\n\n");
// Auto-scroll textview
// Does not function on Android 4.0+
final Layout layout = tvConsole.getLayout();
if (layout != null) {
int scrollDelta = layout.getLineBottom(tvConsole
.getLineCount() - 1)
- tvConsole.getScrollY()
- tvConsole.getHeight();
if (scrollDelta > 0)
tvConsole.scrollBy(0, scrollDelta);
}
}
}
};
正如我之前提到的，这在Gingerbread和
FroYo中可以正常工作，但是ICS和JellyBean操作系统看不到GetWeather设置的变量。我想，我在某处读到这与需要AsyncTask有关，但我无法弄清它的正面还是反面。预先感谢
最佳答案
尝试使用这样的异步任务，
在您的主要活动中
public class GetWeather extends AsyncTask<Void, Integer, Void> {
public GetWeather(Activity activity) {
this.activity = activity;
context = activity;
dialog = new ProgressDialog(context);
}
/** progress dialog to show user that the backup is processing. */
private ProgressDialog dialog;
/** application context. */
private Activity activity;
private Context context;
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
@Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
GetWeather weather = new GetWeather(strPosition);
weather.returnWeather();
return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
tvConsole
.append("Weather Update\n-------------------\n\nCurrent Temp (C): "
+ weather.strTemp
+ "C\n"
+ "Wind is out of the "
+ weather.strWindDir
+ " at "
+ weather.strWindSpeed
+ " MPH\n"
+ "Visibility is "
+ weather.strVisibility
+ " miles\n\n");
// Auto-scroll textview
// Does not function on Android 4.0+
final Layout layout = tvConsole.getLayout();
if (layout != null) {
int scrollDelta = layout.getLineBottom(tvConsole
.getLineCount() - 1)
- tvConsole.getScrollY()
- tvConsole.getHeight();
if (scrollDelta > 0)
tvConsole.scrollBy(0, scrollDelta);
}
}
}
并这样称呼它，
new GetWeather(Mainactivity.this).execute();