[英]How to update listview from AsyncTask
首先很抱歉,如果它是重復的,因為我在問它,因為無法從其他問題中理解任何東西,或者我可以說我無法在我的情況下執行它。 實際上,我堅持要用AsyncTask
網絡更新一個ListView
來更新我的ListView
的情況,但是現在如何實現它,不知道我嘗試了幾件事但無法使其工作。 請任何人詳細解釋我如何做,這是我的活動和異步類代碼
package app.balaji.sid.listapp;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import it.sauronsoftware.ftp4j.FTPClient;
import it.sauronsoftware.ftp4j.FTPFile;
public class ListActivity extends ActionBarActivity {
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list);
lv=(ListView)findViewById(R.id.listView);
String[] values = new String[] { "Item 1",
"Item 2",
"Item 3 ",
"Item 4",
"Item 5",
"Item 6",
"Item 7",
"Item 8"
};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, android.R.id.text1, values);
lv.setAdapter(adapter);
new ListFetcher().execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.list, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
protected class ListFetcher extends AsyncTask<String,String,String>{
String sid;
@Override
protected String doInBackground(String... params) {
String user = "user";
String pass="password";
String host="204.236.238.164";
FTPClient client = new FTPClient();
try {
client.connect(host,21);
client.login(user, pass);
client.setType(FTPClient.TYPE_BINARY);
client.changeDirectory("/");
FTPFile[] files = client.list();
String[] fileNames = new String[files.length];
for (int i = 0; i < files.length; i++)
{
fileNames[i] = files[i].getName();
String logVariable=fileNames[i];
Log.v(sid, logVariable); // Here i am able to see list in log
}
}catch (Exception e)
{
Log.v(sid,e.toString());
}
return sid;
}
protected void onPostExecute()
{
//i think list should be updated from here but don't know how to do it correctly
// i just know i can update my listview by creating a new adapter and assign it to listview but don't know how
// also i am not able to get the fileNames array here
}
}
}
如果您發布了您嘗試過的欺騙對象的鏈接並解釋了您不了解的內容,則答案會更容易回答。 發生/未發生的事情也將有所幫助。 但是,據我onPostExecute()
,您只需要將新的String
傳遞給onPostExecute()
並在那里更新列表和Adapter
。
protected void onPostExecute(String result) // get the String you are passing
{
//i think list should be updated from here but don't know how to do it correctly
// I agree. Let's try this
if(result != null) // let's make sure you got something
{
values.add(result); // add the new String to your list
adapter.notifyDataSetChanged(); // Hey, Adapter, we've got some new data
}
您需要將Array
更改為ArrayList
以便長度可以是動態的。 您還需要使用它和Adapter
成員變量,以便內部類可以看到它們。
public class ListActivity extends ActionBarActivity {
ListView lv;
// Declare them here
ArrayAdapter<String> adapter;
ArrayList<String> values = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list);
lv=(ListView)findViewById(R.id.listView);
values.add("Item 1");
values.add("Items 2");
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,
android.R.id.text1, values);
lv.setAdapter(adapter);
new ListFetcher().execute();
您沒有向任務傳遞任何內容,但想返回一個數組
@Override
protected String[] doInBackground(Void... params) {
protected void onPostExecute(String[] result)
如果您要為適配器返回一組全新的值,則可以使用新值對其進行更新。 如果您只是添加一些值,則可以遍歷它們並將它們添加到ArrayList
並像上面顯示的那樣調用notifyDataSetChanged()
。
我只是解決了我的問題,所以以為我需要分享它,這樣其他面臨相同問題的人就可以輕松解決。
因此,首先在我的問題中,我只是用字符串參數聲明了AsyncTask類,但實際上我需要從此處填充ListView。
所以我做了什么:
protected class ListFetcher extends AsyncTask<ArrayList,ArrayList,ArrayList>{
String sid;
ArrayList list;
@Override
protected ArrayList doInBackground(ArrayList... params) {
FTPClient client = new FTPClient();
try {
client.connect(host,21);
client.login(user, pass);
client.setType(FTPClient.TYPE_BINARY);
client.changeDirectory("/");
FTPFile[] files = client.list();
String[] fileNames = new String[files.length];
for (int i = 0; i < files.length; i++)
{
fileNames[i] = files[i].getName();
String logVariable=fileNames[i];
Log.v(sid, logVariable);
values.add(fileNames[i]);
}
}catch (Exception e)
{
Log.v(sid,e.toString());
}
return list;
}
protected void onPostExecute(final ArrayList result)//received result but didn't use it because in my case i don't need it instead of it i just updated my arraylist in doInbackground and updated my ui from here
{
adapter = new ArrayAdapter<String>(ListActivity.this, android.R.layout.simple_list_item_1, android.R.id.text1, values);
ListView listView =(ListView)findViewById(R.id.listView);
listView.setAdapter(adapter);
}
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