从Asynctask更新MainActivity上的ListView

Question

I have a list view on the main Ui that I wish to update through an Asynctask which connects to a Mikrotik device to retrieve details.

I am passing the activity too, so that I can update the UI from a separate class file, however I keep getting the error "Class name expected here" for the activity (mActivity) in the ListAdapter constructor.

Here is the Asynctask code:

public class MikrotikReader extends AsyncTask<String, Void, ArrayList<String>> {

    //Default connection details for mikrotik
    private int mkPort = 8728;
    private int mkTimeout = 5000;
    private String userName;
    private String userPass;
    private String mkIpAddress;
    private String mkCommand;
    private ListView listView;
    private Activity mActivity;

    public MikrotikReader(String user, String pass, String ipaddress, String command, Activity activity) {
        this.userName = user;
        this.userPass = pass;
        this.mkIpAddress = ipaddress;
        this.mkCommand = command;
        this.mActivity = activity;
    }



    @Override
    protected ArrayList<String> doInBackground(String... params) {


        ArrayList<String> mylist = new ArrayList<String>();

        try {
            ApiConnection con = ApiConnection.connect(SocketFactory.getDefault(), mkIpAddress, mkPort, mkTimeout);
            con.login(userName, userPass); // log in to router
            if (con.isConnected()) {
                List<Map<String, String>> rs1 = con.execute(mkCommand);
                for (Map<String, String> results1 : rs1) {
                    getResults[0] = new String(results1.get("comment"));
                    mylist.add(getResults[0]);
                }
                con.close();
            }
        } catch (MikrotikApiException e) {
        } catch (Throwable e) {
            e.printStackTrace();
        }
        return mylist;
    }

@Override
    protected void onPostExecute(ArrayList<String> mylist) {

        System.out.println("This is the array content " + mylist.get(0));

        listView = (ListView) mActivity.this.findViewById(R.id.listView);
        listView.setAdapter(new ArrayAdapter<String>(mActivity.this,android.R.layout.simple_list_item_1,new ArrayList<String>())); }

This is how I call the Asynctask from the MainActivity class file, passing "this" as the activity:

new MikrotikReader(user_name, password, ipaddress,"/ip/firewall/filter/print where comment=Test", this).execute();

Here is the listview in the mainactivity.xml file:

<ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/gradient_bg" />

Answer 1

尝试在您的AsyncTask类中仅使用mActivity而不是mActivity.this

Answer 2

Don't do like this. Make interface like

    public interface ListPreparingListener {
void onListPrepared(ArrayList<String> mylist);
}

And implement it on your main activity like

@Override
onListPrepared(ArrayList<String> myList) {
 listView.setAdapter(new ArrayAdapter<String>(mActivity.this,android.R.layout.simple_list_item_1,new ArrayList<String>()));
}

Then, pass this interface to you reader's constructor and call this method on post execute

Upd: Actually it could produce memory leak, if you store a reference to your activity inside other objects. The most proper way is to make methods subscribeListener and unsubsucribeListener and subscribe when you need it from main activity, unsubscribe onStop . Also on your onPostExecute should be check if there are available listeners