问题
i am new in android. I managed to parse JSON file to my application. Now i want to use AsyncTask to get Spinning progressBa untill application starts and load data. I tried to read many things, but they only give how to get progressbar on onclick events or for downloading events.
This is my code...
I just confused about how to start progressbar at starting of your application and which part of following code goes to which method of asycTask class....
package com.demojson;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import android.app.ListActivity;
public class MainActivity extends ListActivity {
private static String url = "http://timepasssms.com/webservices/ws.php?type=category";
private static final String TAG_DATA = "DATA";
private static final String TAG_0 = "0";
private static final String TAG_ID = "id";
private static final String TAG_1 = "1";
private static final String TAG_NAME = "name";
private static final String TAG_2 = "2";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_3 = "3";
private static final String TAG_NEW_NAME = "new_name";
private static final String TAG_4 = "4";
private static final String TAG_STATUS = "status";
JSONArray jArray = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<HashMap<String, String>> contents = new ArrayList<HashMap<String, String>>();
JSONMethod metObj = new JSONMethod();
JSONObject jOb = metObj.getUrl(url);
try {
jArray = jOb.getJSONArray(TAG_DATA);
for (int i = 0; i < jArray.length(); i++) {
JSONObject child = jArray.getJSONObject(i);
String tag_0 = child.getString(TAG_0);
String id = child.getString(TAG_ID);
String tag_1 = child.getString(TAG_1);
String name = child.getString(TAG_NAME);
String tag_2 = child.getString(TAG_2);
String description = child.getString(TAG_DESCRIPTION);
String tag_3 = child.getString(TAG_3);
String new_name = child.getString(TAG_NEW_NAME);
String tag_4 = child.getString(TAG_4);
String status = child.getString(TAG_STATUS);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_NAME , name);
contents.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
ListAdapter adapter = new SimpleAdapter(this, contents,
R.layout.list_items, new String[] { TAG_NAME },
new int[] { R.id.tvName });
setListAdapter(adapter);
// --To get listview set...--
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String item = ((TextView)view.findViewById(R.id.tvName)).getText().toString();
Toast toast = Toast.makeText(getApplicationContext(), item , Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER, 0, 0);
toast.show();
}
});
}
}
and JSONMethod Class...
package com.demojson;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONObject;
import android.util.Log;
public class JSONMethod {
InputStream is = null;
JSONObject jObj=null;
String json = "";
public JSONObject getUrl(String url){
try{
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpRespone = httpClient.execute(httpPost);
HttpEntity httpEntity = httpRespone.getEntity();
is = httpEntity.getContent();
}catch(UnsupportedEncodingException ue){
}catch(ClientProtocolException ce){
}catch(IOException ie){
}
try{
BufferedReader br = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line=null;
while((line=br.readLine())!= null){
sb.append(line + "/n");
}
is.close();
json = sb.toString();
}catch(Exception e){
Log.e("JSONMethod", "Error converting result" + e.toString());
}
try{
jObj = new JSONObject(json);
}catch(Exception e){
Log.e("JSONMethod", "Error parsing data" + e.toString());
}
return jObj;
}
}
here is xml files... activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ImageView
android:id="@+id/imageView1"
android:layout_width="fill_parent"
android:layout_height="60dp"
android:src="@drawable/timepasssms" />
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_gravity="center"
android:layout_height="wrap_content"/>
</LinearLayout>
and list_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/round_edge"
android:orientation="vertical" >
<TextView
android:id="@+id/tvName"
android:layout_width="fill_parent"
android:layout_height="45dp"
android:layout_marginLeft="10dp"
android:gravity="left"
android:padding="5dp"
android:textColor="#DF7401"
android:textSize="20dp" />
</LinearLayout>
回答1:
Try Using Async class and in doInBackground() method load your List view.
This is how to call Async Class
new LoadListView(this).execute(listView);
And here is your Async Class
public class LoadListView extends AsyncTask<ListView> {
private Context context;
public loadListView(Context context)
{
this.context = context;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressDialog.show();
}
@Override
protected String doInBackground(String... aurl) {
//Here you need to load your ListView
return null;
}
protected void onProgressUpdate(String... progress) {
//Show progress bar here
}
@Override
protected void onPostExecute(String unused) {
//Hide Progress Bar Here
}
It will automatically hide progress bar when listview is loaded..
回答2:
here is example `
@Override
protected void onPostExecute(Object table) {
// TODO Auto-generated method stub
super.onPostExecute(table);
dialog.dismiss();
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
dialog=ProgressDialog.show(Yourclass.this, "Loading Data.", "Please Wait");
}
` I hope would be helpful
来源：https://stackoverflow.com/questions/15153345/how-to-get-spinning-progress-bar-at-starting-of-application