Android 添加折线到地图错误

Question

我的应用程序从 URL 检索 JSON 并解析从用户位置到所选标记位置的方向。调试告诉我目的地和源是正确的，当我在地图中添加多段线时应用程序卡住了。这是代码：

for(int z = 0; z<list.size()-1;z++){
    LatLng src= list.get(z);
    LatLng dest= list.get(z+1);

    PolylineOptions line=  new PolylineOptions()
        .add(src, dest)
        .width(2)
        .color(Color.BLUE).geodesic(true);
        mMap.addPolyline(line);
}

这是编辑后的 logcat:

05-20 11:44:04.698 26190-27044/com.example.marco.progettoquinta E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #2
  Process: com.example.marco.progettoquinta, PID: 26190
  java.lang.RuntimeException: An error occurred while executing doInBackground()
      at android.os.AsyncTask.done(AsyncTask.java:309)
      at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
      at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
      at java.util.concurrent.FutureTask.run(FutureTask.java:242)
      at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
      at java.lang.Thread.run(Thread.java:818)
   Caused by: java.lang.IllegalStateException: Not on the main thread
      at maps.f.g.b(Unknown Source)
      at maps.z.D.a(Unknown Source)
      at maps.ag.t.a(Unknown Source)
      at uz.onTransact(:com.google.android.gms.DynamiteModulesB:137)
      at android.os.Binder.transact(Binder.java:387)
      at com.google.android.gms.maps.internal.IGoogleMapDelegate$zza$zza.addPolyline(Unknown Source)
      at com.google.android.gms.maps.GoogleMap.addPolyline(Unknown Source)
      at com.example.marco.progettoquinta.MapsActivity.drawPath(MapsActivity.java:210)
      at com.example.marco.progettoquinta.JSONParser.getJSONFromUrl(JSONParser.java:80)
      at com.example.marco.progettoquinta.JSONParser.doInBackground(JSONParser.java:35)
      at com.example.marco.progettoquinta.JSONParser.doInBackground(JSONParser.java:18)
      at android.os.AsyncTask.call(AsyncTask.java:295)
      at java.util.concurrent.FutureTask.run(FutureTask.java:237)
      at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234) 
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) 
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) 
      at java.lang.Thread.run(Thread.java:818)

说出处不详，其实是对的。当然这个方法是在AsyncTask.中实现的哪里出错了？

Answer 1

您的异常发生是因为您试图修改 UI 不是从主线程而是从异步任务的 doInBackground（这是您的请求所必需的）。尝试将您的代码封装成这样的东西

runOnUiThread(new Runnable() {

   @Override
   public void run()
   {
      //do your loop adding polyline
   }
});

或者获取从 doInBackground 返回的数据并处理它以在 OnPostExecute 中添加折线。

Android 添加折线到地图错误

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