android - AsyncTask 和 listActivity

Question

我做了这个简单的应用程序，在这个应用程序中，当我点击开始按钮时，我想在 Listview 中查看数据，但它不起作用。你能帮帮我吗？

ma​​inActivity.java

public class MainActivity extends ListActivity {
public ArrayList<Map<String, String>> list= new ArrayList<Map<String, String>>();
public ListAdapter adapter;
public ProgressDialog progressDialog; 

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Button buttonAggiorna = (Button) findViewById(R.id.buttonStart);
    buttonAggiorna.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

        String[] from = { "name", "purpose" };
        int[] to = { android.R.id.text1, android.R.id.text2 };      
 adapter = new SimpleAdapter(MainActivity.this,     list,android.R.layout.simple_list_item_2, from, to);       

  progressDialog = ProgressDialog.show(MainActivity.this, "Getting data", "Loading...");
            taskBack t=new taskBack();
             t.execute();               
        }

    });// fine onClickListner


    Button buttonAllarm = (Button) findViewById(R.id.buttonAllarm);
    buttonAllarm.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {            
                AppLog.logString("list size:"+list.size()); 

        }
});


}

 private class taskBack 
 extends    AsyncTask<Void, Void, ArrayList<Map<String, String>>> {

    @Override
    protected ArrayList<Map<String, String>> doInBackground(Void... arg0) {
    ArrayList<Map<String, String>> l = new ArrayList<Map<String, String>>();
    l = startEla();
    return l;
    }

    protected void onPostExecute(ArrayList<Map<String, String>> result) {
        AppLog.logString("Parte onPostExecute");
        list=result;
        setListAdapter(adapter);    
        progressDialog.dismiss();

    }

    private ArrayList<Map<String, String>> startEla() {
    ArrayList<Map<String, String>> list = new ArrayList<Map<String, String>>();
        list.add(putData("android","mobile"));
        list.add(putData("Windows7", "Windows7"));
        list.add(putData("iPhone", "iPhone"));
        return list;

    }

    private Map<String, String> putData(String name, String purpose) {
        HashMap<String, String> item = new HashMap<String, String>();
        item.put("name", name);
        item.put("purpose", purpose);
        return item;

    }
}
}

在此链接中，您可以看到 xml 文件 enter link description here

最佳赛程 A.

Answer 1

将这两行移动到 ListActivity 的主体...

String[] from = { "name", "purpose" };
int[] to = { android.R.id.text1, android.R.id.text2 };      

从 onCreate(...)... 中的 onClick(...) 监听器中删除以下行

adapter = new SimpleAdapter(MainActivity.this, list, android.R.layout.simple_list_item_2, from, to);

...并把它放在AsyncTask的onPostExecute(...)方法中，如下...

protected void onPostExecute(ArrayList<Map<String, String>> result) {
    AppLog.logString("Parte onPostExecute");
    list=result;
    adapter = new SimpleAdapter(MainActivity.this, list, android.R.layout.simple_list_item_2, from, to);
    setListAdapter(adapter);    
    progressDialog.dismiss();
}