Question

我有一个跟随jsonarray，我想解析它，但我得到空指针异常。网址在浏览器中工作，数据如下

{"showDriver":
               [{"IDDriver":"1","Driverlogtit":"24.614095","Driverlatite":"46.509689"},
                 {"IDDriver":"2","Driverlogtit":"24.639199","Driverlatite":"46.557047"},
                   {"IDDriver":"3","Driverlogtit":"24.651724","Driverlatite":"46.559131"},
                    {"IDDriver":"4","Driverlogtit":"24.625951","Driverlatite":"46.569466"},
                     {"IDDriver":"8","Driverlogtit":"24.626692","Driverlatite":"46.544095"}]}

在android中调用json时得到我的错误

java.lang.NullPointerException
at com.project.ytubasi.speedtaxi.MapsActivity.WhereDriver(MapsActivity.java:329)
at com.project.ytubasi.speedtaxi.MapsActivity$3.onCameraIdle(MapsActivity.java:166)
at com.google.android.gms.maps.GoogleMap$22.onCameraIdle(Unknown Source)
at com.google.android.gms.maps.internal.zzf$zza.onTransact(Unknown Source)
at android.os.Binder.transact(Binder.java:361)
at ys.a(:com.google.android.gms.DynamiteModulesB:79)
at maps.ad.j.b(Unknown Source)
at maps.ad.j.a(Unknown Source)
at maps.ad.j$2.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5293)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:855)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:671)
at dalvik.system.NativeStart.main(Native Method)

我班上有任何不妥之处

这里打电话

  mGoogleMap.setOnCameraIdleListener(new GoogleMap.OnCameraIdleListener() {
        @Override
        public void onCameraIdle() {


            CameraLat = googleMap.getCameraPosition().target.latitude;
            CameraLong = googleMap.getCameraPosition().target.longitude;


            markerlocationtext.setText(getCompleteAddressString(CameraLat, CameraLong));


                WhereDriver(String.valueOf(CameraLong), String.valueOf(CameraLat));

                String lat = DriverList.get(0).Driverlatite;
                Toast.makeText(getApplicationContext(),""+lat,Toast.LENGTH_LONG).show();



        }
    });


}

我的数据类

 AQuery aq;
public void WhereDriver(String longt ,String lati) {


    String url=muUrl+"WhereDriver?logt=24.632652&lat=46.558625";//+longt+"&lat="+lati; i used stable Number to see data
    aq.ajax(url, JSONObject.class, this, "jsonCallback");
}


public void  jsonCallback(String url, JSONObject json, AjaxStatus status) throws JSONException {

    if(json != null){

        try {
            JSONArray DriverArray = json.getJSONArray("showDriver");

            for (int z = 0; z < DriverArray.length(); z++) {

                JSONObject jsDriverArray = DriverArray.getJSONObject(z);
                DriverList.add(new AllDriverLocation(jsDriverArray.getString("IDDriver"),
                        jsDriverArray.getString("Driverlogtit"),
                        jsDriverArray.getString("Driverlatite")));
            }
        }catch (Exception ex)
        {

        }



    }else{
    }

}

我将我的列表定义为

public ArrayList <AllDriverLocation>  DriverList = new ArrayList<>();

和AllDriverLocation类

public class AllDriverLocation {
String  IDDriver;
String  Driverlogtit;
String  Driverlatite;


public AllDriverLocation(String IDDriver, String driverlogtit, String driverlatite) {
    this.IDDriver = IDDriver;
    Driverlogtit = driverlogtit;
    Driverlatite = driverlatite;
}
}

Answer 1

这个问题似乎就在这一行 -

   SELECT T1.S.no FROM Your_tableName T1 WHERE T1.SampleNo = (
   SELECT MAX(T2.SampleNo) FROM Your_tableName T2 WHERE T2.SampleNo BETWEEN @val1 AND @val2 );

请检查变量CameraLong和CameraLat是否为空

Answer 2

试试这个：

JSONArray driverArray = response.getJSONArray("showDriver");
                    String IDDriver = "",Driverlogtit="",Driverlogtit="";
                    for (int z = 0; z < driverArray.length(); z++) {
                        try {
                            JSONObject jsDriverArray = driverArray.getJSONObject(z);
                            if(jsDriverArray.has("IDDriver")){
                                IDDriver = jsDriverArray.getString("IDDriver");
                            } if(jsDriverArray.has("Driverlogtit")){
                                Driverlogtit = jsDriverArray.getString("Driverlogtit");
                            } if(jsDriverArray.has("Driverlatite")){
                                Driverlogtit = jsDriverArray.getString("Driverlatite");
                            }

                            DriverList.add(new AllDriverLocation(IDDriver,Driverlogtit,Driverlogtit));
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }

JSONObject类有一个名为＆＃34;的方法有＆＃34;：

http://developer.android.com/reference/org/json/JSONObject.html#has(java.lang.String)

如果此对象具有name的映射，则返回true。映射可能为NULL。

Answer 3

为了避免应用程序崩溃，您可以添加条件来检查驱动程序数组是否为空？试试这个

JSONArray DriverArray = !data.isNull(getString("showDriver"))?data.getJSONArray(getString("showDriver")) : new JSONArray();

如何在android中读取JSONArray中的数据？

3 个答案: