如何使用异步任务定期保存位置更新？

Question

Currently I am trying to collect location updates periodically, say for every 10 samples. I am using an arraylist to collect them and clear off the arraylist in the main UI thread once I passed them to the server using async task. In the async task I am loading the arraylist with the one from main UI.

The problem is, it is clearing the arraylist in the async task even it is in separate variable. How can I keep the activity in sync. Do I need to sleep the main activity till the async task finishes. I am not sure about the variable. Can someone explain how to do this?

MainMapActivity(X){
  locationupdate for every 1 min{
  arraylist a;//this collects all location updates 10 samples each time
  call asynctask b;
  clear a;
}
asynctask b{
  arraylist c = getall from  a;
  db= insert(c);//save a into database;
}

Clearing a in main UI clears of variable c. How can I prevent that? The variable c should be only cleared after saving all the data in it.

Answer 1

If I'm getting what you are trying to say is,then yes, we have a way to fix your problem using handlers.

In your async task, do something like this -

   private mLocations;
 public MyTask(Handler mResponseHandler, List<Location> mLocations){
        super();
        this.mLocations = mLocations;
        this.mResponseHandler = mResponseHandler;
    }

in onPostExecute,

  onPostExecute(List<Location>){

 @Override
    protected void onPostExecute(Boolean result) {

        super.onPostExecute(result);

        Log.i(TAG, "result = "+result);
        if (mResponseHandler == null) return;

        MyLocationData<Location> resultData = new MyLocationData<Location>();
        if(result != null && result){
            resultData.requestSuccessful = true;
            resultData.responseErrorCode = 0;
        }else{
            resultData.requestSuccessful = false;
            resultData.responseErrorCode = errorCode;  //set this when result is null
        }

        android.os.Message m = android.os.Message.obtain();
        m.obj = resultData;
        mResponseHandler.sendMessage(m);
    }
}

Where MyLocationData is a model class in which I'm saving all relevant data. It can be a class like this -

 public class MyLocationData<Type> {

    public Type response;
    public int responseErrorCode;
    public boolean requestSuccessful;
}

Now, in your activity, you can get this data like,

private Handler mExportHandler = new Handler(){ 

        public void handleMessage(android.os.Message msg) {
                MyLocationData<Location> responseData = (MyLocationData<Location>) msg.obj;
                 // your logic for fetching new locations from responseData and using them in your activity   

        };
    };