Question

所以我的代码似乎运行得很好，直到它到达这一行

adapter.notifyDataSetChanged();

logcat中弹出的错误是CalledFromWrongThreadException。调试还显示正在后台线程中运行的处理程序。如何让处理程序绑定到主线程，而不是后台？我以为我只需要在主线程中创建处理程序，但我想我错了，很可能我是andriod的新手。我该如何解决这个问题？

//Imports are included
public class DirectoryActivity extends ListActivity {
    private ProgressDialog ProgressDialog = null;
    private ArrayList<DirectoryListing> listing = null;
    private DirectoryAdapter adapter;
    private Runnable viewOrders;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.directory);
    final Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {


            if (listing != null && listing.size() > 0) {
                adapter.notifyDataSetChanged();
                for (int i = 0; i < listing.size(); i++)
                    adapter.add(listing.get(i));
                Log.e("log_tag", "\nStill running\n");
            }
            ProgressDialog.dismiss();
            adapter.notifyDataSetChanged();

        }

    };
    listing = new ArrayList<DirectoryListing>();
    adapter = new DirectoryAdapter(this, R.layout.rows, listing);
    setListAdapter(adapter);
    ProgressDialog = ProgressDialog.show(DirectoryActivity.this, "Please wait...", "Retrieving data ...", true);
    viewOrders = new Runnable() {
        @Override
        public void run() {
            listing = PreparePage.getArrayList();
            handler.handleMessage(null);
        }
    };
    Thread thread = new Thread(null, viewOrders, "Background");
    thread.start();




}


private static class PreparePage {
    protected static ArrayList<DirectoryListing> getArrayList() {

        ArrayList<DirectoryListing> listings = new ArrayList<DirectoryListing>();
        JSONObject information = GetPageData.getJSONFromURL(url);
        Iterator key = information.keys();

        while (key.hasNext()) {
            String id = (String) key.next();
            JSONObject info = null;
            try {
                info = information.getJSONObject(id);
            } catch (JSONException e) {
                e.printStackTrace();
            }
            String name = "", title = "", photo = "";
            try {
                name = info.get("firstName") + " " + info.get("lastName");
                title = info.getJSONObject("position").getString("name");
                photo = info.optString("photoPath", "none");
            } catch (JSONException e) {
                e.printStackTrace();
            }
            listings.add(new DirectoryListing(name, title, photo));

        }
        return listings;
    }
}

}

Answer 1

根据我的经验，您应该创建自己的类，扩展AsyncTask类以在后台执行某些操作。这比使用线程+处理程序更简单，更有效。

Answer 2

尝试拨打handler.sendEmptyMessage(0);而不是handler.handleMessage(null);

我不知道为什么会导致你看到的错误，但是当我使用处理程序和线程而不是AsyncTask时，这就是我设置它的方式。而且我从未见过这样做错误。

@Nguyen是正确的，虽然AsyncTask是现在处理这些类型的事情的首选方式。它实际上使它更容易做到。

AsyncTask docs

AsyncTask Example

处理程序不会绑定到主线程

2 个答案: