使用Android

Question

我在另一个文件中有一个带有listview和ArrayAdapter类的MainActivity Class文件。

在ArrayAdapter类中，我在listitem中有一个按钮，使用Volley来更新远程Rest服务器中的记录。

我已经阅读了关于Volley的取消请求：

@Override
protected void onStop () {
    super.onStop();
    if (mRequestQueue != null) {
        mRequestQueue.cancelAll(TAG);
    }
}

我的疑问是：在某些Android生命周期事件中我是否需要注意取消排球请求？ 如果是，我该如何进入arrayadapter类？

public class MainActivity extends Activity {
 ArrayList<ObjectQueue> lista = new ArrayList<ObjectQueue>();
 ListviewQueueAdapter lvA;
 ListView lv;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        Bundle args = new Bundle();
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.listmain);
        View v = (View) findViewById(R.id.emptymain);

        lv.setEmptyView(v);


        lvA = new ListviewQueueAdapter(MainActivity.this, lista);
        lv.setAdapter(lvA);
        lvA.setData(lista);

}

我的arrayadapter类是：

public class ListviewQueueAdapter extends ArrayAdapter<ObjectQueue>  implements Filterable {
    ArrayList<ObjectQueue> items; //working values
    ArrayList<ObjectQueue>  origitems; // data work
    private Activity context;

    RequestQueue reqQueue; //Volley request

    public ListviewQueueAdapter(Activity context, ArrayList<ObjectQueue> items) {
        super(context, R.layout.singlerowqueue, items);
        this.context = context;
        this.items=items;
    }

    public void add(ObjectQueue oq){
        this.items.add(oq);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ObjectQueue o = items.get(position);
        final ViewHolder holder;
        View vi = convertView;
        if (vi == null){
            LayoutInflater inflater = context.getLayoutInflater();
            vi = inflater.inflate(R.layout.singlerowqueue, null);// e' preciso fazer o inflate pois a view nao ainda nao esta em activity alguma
            holder = new ViewHolder();
            holder.mbut_stat = (Button) vi.findViewById(R.id.but_status);
            ....
            vi.setTag(holder);
        }
        else {
          holder = (ViewHolder) convertView.getTag();
        }


        holder.mbut_stat.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                  AlertDialog.Builder b = new AlertDialog.Builder(context);
                  b.setTitle("Mudar STATUS");
                  String[] types = {"Normal", "Urgente", "Pendente", "Atendido"};
                  b.setItems(types, new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        update_fila(o, which + 1);
                    }

                });
                b.show();
            }

        });
        ......
        ......
        return vi;
    }

    static class ViewHolder {
        Button mbut_stat;
    }

    private void update_fila(final ObjectQueue ob, final int st) {
        reqQueue = Volley.newRequestQueue(context);
        String url = Common.getServerURL() + "\"UpdateStatusFila\"";
        // constructs the POST body using the parameters
        JSONArray ja = new JSONArray();
        ...
        FillSomeArray(ja);  
        JSONObject jsonBody = new JSONObject();
        try {
            jsonBody.put("_parameters", ja);
        } catch (JSONException e) {
            e.printStackTrace();
        }

        JsonObjectRequest jr = new JsonObjectRequest(Request.Method.POST, url,
                jsonBody, new Response.Listener<JSONObject>() {

            @Override
            public void onResponse(JSONObject response) {
                // TODO Auto-generated method stub
                try {
                    dosomething()(; 
                    }
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                error.printStackTrace();
            }
        });
        jr.setRetryPolicy(new DefaultRetryPolicy(Common.DEFAULT_TIMEOUT_MS,
                Common.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));

        reqQueue.add(jr);
    }

Answer 1

您不需要在生命周期事件中取消请求。如果请求不再相关或有用，那么为用户节省带宽和电池寿命将是一个很好的礼仪。

你把它放在哪里是一个取决于你的特定需求的设计决定，但是你可以为你的适配器添加一个方法：

public void onStop () {
  mRequestQueue.cancelAll(TAG);
}

并从活动传播生命周期调用：

@Override
protected void onStop () {
  super.onStop();
  adapter.onStop();
}