java - Android 4.0 中的类没有响应 - 适用于 2.3 及更低版本

Question

我有一个类 GetWeather.java，它从 API 获取天气数据。它是通过一个单独的线程定期从我的应用程序的主要 Activity 中调用的。该线程调用 GetWeather 类并将返回的数据发布到 TextView。

无论哪种情况，GetWeather 类中返回的数据的 System.out.println 都显示数据确实正在返回。

下面是 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());
        }
    }
}

以下是主要 Activity 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 中按预期工作，但是 ICS 和 JellyBean 操作系统无法看到由获取天气。我想，我在某处读到这与需要 AsyncTask 有关，但我无法弄清楚它的头部或尾部。

提前致谢

Answer 1

您无法从后台线程触摸 ui 线程中的任何内容，为此，请使用处理程序，初始化您的后台线程，并向其传递一个处理程序对象。当数据到达时，使用处理程序向用户界面发送消息。在ui中，当后台线程的消息到来时，只需更新 View 即可。