Question

我是android新手。我设法将JSON文件解析为我的应用程序。现在我想使用AsyncTask来获取Spinning progressBa，直到应用程序启动并加载数据。我尝试阅读很多内容，但他们只给出了如何获取onclick事件或下载事件的进度条。

这是我的代码......

我很困惑如何在启动应用程序时启动进度条以及以下代码的哪一部分转到asycTask类的哪个方法....

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 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;
    }
}

这里是xml文件... activity_main.xml中

<?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

这里是示例`

@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");
    }

` 我希望会有所帮助

Answer 2

尝试使用Async类，并在doInBackground（）方法中加载List视图。

这是如何调用异步类

new LoadListView(this).execute(listView);

这是你的异步类

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
}

加载listview时会自动隐藏进度条..

如何在应用程序启动时获得Spinning Progress Bar

2 个答案: