在開始應用程序時如何獲取旋轉進度欄

Question

我是android新手。 我設法將JSON文件解析到我的應用程序中。 現在，我想使用AsyncTask獲取Spinning progressBa，直到應用程序啟動並加載數據。 我嘗試閱讀許多內容，但是它們只提供了如何在onclick事件或下載事件上獲得進度條。

這是我的代碼...

我只是對如何在應用程序啟動時啟動進度條以及以下代碼的哪一部分轉到asycTask類的哪種方法感到困惑。

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();
            }
        }); 
    }


}

和JSONMethod類...

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;
    }
}

這是xml文件... 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>

和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>

Answer 1

這是例子

@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");
    }

`我希望會有所幫助

Answer 2

嘗試使用Async類，並在doInBackground（）方法中加載列表視圖。

這是調用異步類的方法

new LoadListView(this).execute(listView);

這是您的異步​​類

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
}

加載列表視圖時，它將自動隱藏進度條。