谷歌地方API返回java..lang.nullpointerexception

Question

我想實現Google Places API，但它一直髮送一個java.lang.nullpointerexception。我得到了這個網站的代碼：http://www.androidhive.info/2012/08/android-working-with-google-places-and-maps-tutorial/

從我可以收集我發送到一些谷歌服務器的網址，並得到一個迴應。該響應採用JSON格式，然後將其解析爲我的特定「位置」對象。我認爲在這個分析階段會發生一些事情。在網站中，他們使用了一些中間對象PlacesList，我認爲這是出錯的地方，因爲我不理解它。

PlacesList：

 public class PlacesList implements Serializable { 

    @Key 
    public String status; 

    @Key 
    public List<Locations> results; 

}

谷歌搜索：

 public PlacesList search(double latitude, double longitude, double radius) 
     throws Exception { 

    this._latitude = latitude; 
    this._longitude = longitude; 
    this._radius = radius; 

    try { 

     HttpRequestFactory httpRequestFactory = createRequestFactory(HTTP_TRANSPORT); 
     HttpRequest request = httpRequestFactory 
       .buildGetRequest(new GenericUrl(PLACES_SEARCH_URL)); 
     request.getUrl().put("key", API_KEY); 
     request.getUrl().put("location", _latitude + "," + _longitude); 
     request.getUrl().put("radius", _radius); // in meters 
     request.getUrl().put("sensor", "false"); 


     PlacesList list = request.execute().parseAs(PlacesList.class); 
     Log.i("placelist.class", list.toString()); 
     // Check log cat for places response status 
     // Log.i("Places Status", "" + list.status); 

     return list; 

    } catch (HttpResponseException e) { 
     Log.e("Error:", e.getMessage()); 
     return null; 
    } 

} 

主

從MainActivity System.err的（6447）：atcom.example.mapmapagain.MainActivity.onCreate（ MainActivity.java:86）==

   try { 
     PlacesList places = ps.search(curr_lat, curr_longitude, 100.0); 
    } catch (Exception e1) { 
     // TODO Auto-generated catch block 
     e1.printStackTrace(); 

這裏是logcat的：

   04-26 19:10:52.839: W/System.err(4156): android.os.NetworkOnMainThreadException 
       04-26 19:10:52.899: W/System.err(4156): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) 
       04-26 19:10:52.899: W/System.err(4156): at java.net.InetAddress.lookupHostByName(InetAddress.java:385) 
       04-26 19:10:52.899: W/System.err(4156): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 
       04-26 19:10:52.899: W/System.err(4156): at java.net.InetAddress.getAllByName(InetAddress.java:214) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316) 
       04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.makeSslConnection(HttpsURLConnectionImpl.java:461) 
      04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.connect(HttpsURLConnectionImpl.java:433) 
      04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290) 
      04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240) 
      04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:81) 
      04-26 19:10:52.899: W/System.err(4156): at libcore.net.http.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:165) 
      04-26 19:10:52.899: W/System.err(4156): at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:88) 
      04-26 19:10:52.899: W/System.err(4156): at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:814) 
      04-26 19:10:52.909: W/System.err(4156): at com.example.mapmapagain.PlaceSearch.search(PlaceSearch.java:64) 
      04-26 19:10:52.909: W/System.err(4156): at com.example.mapmapagain.MainActivity.onCreate(MainActivity.java:86) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.Activity.performCreate(Activity.java:5104) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
      04-26 19:10:52.909: W/System.err(4156): at android.os.Handler.dispatchMessage(Handler.java:99) 
      04-26 19:10:52.909: W/System.err(4156): at android.os.Looper.loop(Looper.java:137) 
      04-26 19:10:52.909: W/System.err(4156): at android.app.ActivityThread.main(ActivityThread.java:5039) 
      04-26 19:10:52.909: W/System.err(4156): at java.lang.reflect.Method.invokeNative(Native Method) 
      04-26 19:10:52.909: W/System.err(4156): at java.lang.reflect.Method.invoke(Method.java:511) 
      04-26 19:10:52.909: W/System.err(4156): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
      04-26 19:10:52.909: W/System.err(4156): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
      04-26 19:10:52.909: W/System.err(4156): at dalvik.system.NativeStart.main(Native Method) 

感謝您的幫助。

Answer 1

您正在主UI線程上進行網絡連接，現在被Android框架禁止，如您的android.os.NetworkOnMainThreadException例外所示。

這是被禁止的，因爲想象您的服務器無法訪問或者您的用戶的Internet連接速度非常慢。當程序啓動你的功能時，UI將被完全凍結，直到它返回，因爲UI線程將忙於嘗試聯繫該服務器。

將您的搜索功能放在AsyncTask中，或將其包裝在Runnable中，以便它在自己的線程中執行。看看這個問題的一個很好的例子AsyncTask Android example