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我对android编程和java编程完全陌生。我有一个现有的网络应用程序，其坐标存储在 mysql 数据库中。通过遵循一些关于 Google Map API 和 JSON 的在线教程，我编写了代码以显示存储数据库的点的地图标记。

我的 php 脚本在运行时返回以下输出

[{"RowID":"15","LatLng":"(27.70171145916157, 85.30419380111698)","Type":"hospital"},{"RowID":"16","LatLng":"(27.704200193429045, 85.32494337005619)","Type":"hospital"}]

我创建了一个类来解析 JSON 数据

    public class ImportMarkers {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public ImportMarkers() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        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();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

最后为了在我创建的地图视图中显示标记，我使用了以下代码

    //url to make request
private static String url = "http://10.0.2.2/jsonsenddata.php";

//JSON Node names
private static final String id = "RowID";
private static final String latlng = "LatLng";
private static final String type = "Type";

JSONArray markers = null;

     // Creating JSON Parser instance
        ImportMarkers marker = new ImportMarkers();

        // getting JSON string from URL
        JSONObject json = marker.getJSONFromUrl(url);

        try {
            // Getting AJSONObjectrray 
            markers = json.getJSONArray(null);

            // looping through All rows
            for(int i = 0; i < markers.length(); i++){
                JSONObject c = markers.getJSONObject(i);

                // Storing each json item in variable
                String RowID = c.getString(id);
                String LatLng = c.getString(latlng);
                String Type = c.getString(type);
                String[] parts = LatLng.split(",");
                String lat = parts[0]; 
                String lon = parts[1]; 
                float latInt = Float.valueOf(lat).floatValue(); 
                float longInt = Float.valueOf(lon).floatValue(); 
                GeoPoint X = new GeoPoint((int) (latInt*1E6),(int) (longInt*1E6) ); 
                if (Type == "hospital"){
                    OverlayItem overlayItem = new OverlayItem (X , "Hospital", "ADDITION");
                    AddLocation hospital = new AddLocation (hos, MainActivity.this);
                    hospital.addLocation(overlayItem);
                    overlayList.add(hospital);
                }
                else {
                    OverlayItem overlayItem = new OverlayItem (X , "Airport", "ADDITION");
                    AddLocation airport = new AddLocation (air, MainActivity.this);
                    airport.addLocation(overlayItem);
                    overlayList.add(airport);
                }


            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

我不知道我的代码有什么问题，如果有人提供一些帮助，我将不胜感激。

这是我的 logcat 日志

12-02 13:45:41.348: D/dalvikvm(448): GC_CONCURRENT freed 174K, 4% free 6623K/6855K, paused 6ms+4ms
12-02 13:45:41.628: D/dalvikvm(448): GC_CONCURRENT freed 356K, 6% free 6823K/7239K, paused 4ms+4ms
12-02 13:45:42.028: D/dalvikvm(448): GC_CONCURRENT freed 699K, 11% free 6616K/7431K, paused 4ms+5ms
12-02 13:45:42.028: W/CursorWrapperInner(448): Cursor finalized without prior close()
12-02 13:45:42.038: W/CursorWrapperInner(448): Cursor finalized without prior close()
12-02 13:45:42.438: D/dalvikvm(448): GC_CONCURRENT freed 198K, 7% free 6929K/7431K, paused 4ms+7ms
12-02 13:45:42.789: D/dalvikvm(448): GC_CONCURRENT freed 311K, 5% free 7189K/7559K, paused 8ms+16ms
12-02 13:45:43.258: D/dalvikvm(448): GC_CONCURRENT freed 519K, 8% free 7234K/7815K, paused 5ms+7ms
12-02 13:45:43.580: D/dalvikvm(448): GC_CONCURRENT freed 267K, 6% free 7385K/7815K, paused 5ms+4ms
12-02 13:45:44.048: D/dalvikvm(448): GC_CONCURRENT freed 675K, 10% free 7259K/8007K, paused 5ms+4ms
12-02 13:45:44.148: D/AndroidRuntime(448): Shutting down VM
12-02 13:45:44.148: W/dalvikvm(448): threadid=1: thread exiting with uncaught exception (group=0x40014760)
12-02 13:45:44.168: E/AndroidRuntime(448): FATAL EXCEPTION: main
12-02 13:45:44.168: E/AndroidRuntime(448): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.finalyear.quakereact/com.finalyear.quakereact.MainActivity}: android.os.NetworkOnMainThreadException
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1815)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1831)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread.access$500(ActivityThread.java:122)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1024)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.os.Looper.loop(Looper.java:132)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread.main(ActivityThread.java:4123)
12-02 13:45:44.168: E/AndroidRuntime(448):  at java.lang.reflect.Method.invokeNative(Native Method)
12-02 13:45:44.168: E/AndroidRuntime(448):  at java.lang.reflect.Method.invoke(Method.java:491)
12-02 13:45:44.168: E/AndroidRuntime(448):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
12-02 13:45:44.168: E/AndroidRuntime(448):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
12-02 13:45:44.168: E/AndroidRuntime(448):  at dalvik.system.NativeStart.main(Native Method)
12-02 13:45:44.168: E/AndroidRuntime(448): Caused by: android.os.NetworkOnMainThreadException
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1077)
12-02 13:45:44.168: E/AndroidRuntime(448):  at dalvik.system.BlockGuard$WrappedNetworkSystem.connect(BlockGuard.java:368)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:208)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:431)
12-02 13:45:44.168: E/AndroidRuntime(448):  at java.net.Socket.connect(Socket.java:901)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:143)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
12-02 13:45:44.168: E/AndroidRuntime(448):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
12-02 13:45:44.168: E/AndroidRuntime(448):  at com.finalyear.quakereact.ImportMarkers.getJSONFromUrl(ImportMarkers.java:38)
12-02 13:45:44.168: E/AndroidRuntime(448):  at com.finalyear.quakereact.MainActivity.onCreate(MainActivity.java:80)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.Activity.performCreate(Activity.java:4397)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
12-02 13:45:44.168: E/AndroidRuntime(448):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1779)
12-02 13:45:44.168: E/AndroidRuntime(448):  ... 11 more
12-02 13:46:42.368: I/Process(448): Sending signal. PID: 448 SIG: 9

先感谢您。

4

1 回答 1

1

例外是NetworkOnMainThreadException

当应用程序尝试在其主线程上执行网络操作时引发的异常。

这仅针对面向 Honeycomb SDK 或更高版本的应用程序抛出。允许以早期 SDK 版本为目标的应用程序在其主事件循环线程上进行网络连接，但非常不鼓励这样做。

因此，在单独的线程上获取。AsyncTask也许？（如果您需要更新 UI）

于 2012-12-02T14:03:23.763 回答