显示进度条在加载列表

问题描述：

现在好了，我承认我是新来使用进度条INFACT我从来没有使用它，但现在我需要使用它我有一个活动（主）和可同时启动6个新菜单活动。从这些活动中有其加载数据在ListView它需要3-4秒来加载。这活动解析JSON和数据传递到另一个活动的活动。我怎样才能尽快显示进度条用户点击菜单选项，这项活动消失它时，列表将被载入。显示进度条在加载列表

这里是activiy提前

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    final Intent intent=new Intent(this ,GetLatAndLng.class); 
    setContentView(R.layout.listplaceholder); 
    //ProgressBar pb=(ProgressBar)findViewById(R.id.progressbar); 
    LocationManager locationManager; 
    String context=Context.LOCATION_SERVICE; 
    locationManager=(LocationManager)getSystemService(context); 

    Criteria criteria = new Criteria(); 
    criteria.setAccuracy(Criteria.ACCURACY_FINE); 
    criteria.setAltitudeRequired(false); 
    criteria.setBearingRequired(false); 
    criteria.setCostAllowed(true); 
    criteria.setPowerRequirement(Criteria.POWER_LOW); 
    String provider = locationManager.getBestProvider(criteria, true); 
    Location location = locationManager.getLastKnownLocation(provider); 

    final LocationListener locationListener = new LocationListener() { 
     public void onLocationChanged(Location location) { 
     updateWithNewLocation(location); 
     } 
     public void onProviderDisabled(String provider){ 
     updateWithNewLocation(null); 
     } 
     public void onProviderEnabled(String provider){ } 
     public void onStatusChanged(String provider, int status, 
     Bundle extras){ } 
     }; 
    updateWithNewLocation(location); 
    locationManager.requestLocationUpdates(provider, 2000, 10, 
      locationListener); 
    double geoLat = location.getLatitute(); 
    double geoLng = location.getLongitude(); 
     Bundle b=new Bundle(); 
    //pb.setVisibility(View.VISIBLE); 
    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>(); 

    JSONObject json = JSONFunction.getJSONfromURL(getUrl()); 
    Log.v(TAG, "got the json"); 
    try{ 
     JSONArray JArray = json.getJSONArray("results"); 
      Log.v(TAG, "getting results"); 
     for(int i=0;i<JArray.length();i++){      
      HashMap<String, String> map = new HashMap<String, String>();  
      JSONObject e = JArray.getJSONObject(i); 
      JSONObject location1=e.getJSONObject("geometry").getJSONObject("location"); 
      latitude[i]=location1.getDouble("lat"); 
      longitude[i]=location1.getDouble("lng"); 
      reference[i]=e.getString("reference"); 
      Log.v(TAG, reference[i]); 
      distance[i]=GetLatAndLng.gps2m(geoLat, geoLng,latitude[i] ,longitude[i]); 
      map.put("id", String.valueOf(i)); 
      map.put("name", "" + e.getString("name")); 
      map.put("vicinity", "Address " + e.getString("vicinity")+" "+"Disance:"+distance[i]); 

      mylist.add(map);     
     }   
    }catch(JSONException e)  { 
     Log.e("log_tag", "Error parsing data "+e.toString()); 
    } 
// pb.setVisibility(View.GONE); 
    b.putStringArray("key", reference); 
    intent.putExtras(b); 
    Log.v(TAG, ""+reference); 
    ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.listview, 
        new String[] { "name", "vicinity", }, 
        new int[] { R.id.item_title, R.id.item_subtitle }); 

    setListAdapter(adapter); 
    final ListView lv = getListView(); 
    lv.setTextFilterEnabled(true); 
    lv.setOnItemClickListener(new OnItemClickListener() { 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) {   
      @SuppressWarnings("unchecked") 
      HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);     
      Toast.makeText(JsonExampleActivity.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show(); 
      intent.putExtra("clickedid",position); 
      startActivity(intent); 
     } 
    }); 
} 
public void updateWithNewLocation(Location location2) { 
    if(location2!=null) { 
      double geoLat = location2.getLatitude(); 
      double geoLng = location2.getLongitude(); 
    } 
}

谢谢！

答

使用AsyncTask在后台加载数据同时显示加载指示器。在AsyncTask'sdoInBackground方法处理JSON或任何其需要时间。

public class HeavyWorker extends AsyncTask < String , Context , Void > { 

    private ProgressDialog  progressDialog ; 
    private Context    targetCtx ; 

    public HeavyWorker (Context context) { 
     this.targetCtx = context ; 
     this.needToShow = true; 
     progressDialog = new ProgressDialog (targetCtx) ; 
     progressDialog.setCancelable (false) ; 
     progressDialog.setMessage ("Retrieving data...") ; 
     progressDialog.setTitle ("Please wait") ; 
     progressDialog.setIndeterminate (true) ; 
    } 

    @ Override 
    protected void onPreExecute () { 
     progressDialog.show () ; 
    } 

    @ Override 
    protected Void doInBackground (String ... params) { 
     // Do Your WORK here 

     return null ; 
    } 

    @ Override 
    protected void onPostExecute (Void result) { 
     if(progressDialog != null && progressDialog.isShowing()){ 
      progressDialog.dismiss () ; 
     } 
    } 
}

在你活动的onCreate()执行AsyncTask

new HeavyWorker().execute();

这会导致'progress.getialArgumentException：View未附加到'progressDialog.dismiss（） '当屏幕方向改变时显示对话框。 – AndreKR

答

你可以做到这一点添加一个属性到你的活动：

ProgressDialog dialog;

然后，只需使用此代码来显示您的对话框：

dialog = ProgressDialog.show(this, "Title", "Loading", true);

然后当你想删除它补充一点：

if(dialog!= null && dialog.isShowing()) 
    dialog.dismiss();

还添加到您的onStop这些行（以防万一用户存在活动）：

public void onStop() 
{ 
    if(dialog!= null && dialog.isShowing()) 
     dialog.dismiss(); 
    super.onStop(); 
}

答

对于这种类型的操作，你应该使用AsyncTask与您可以显示进度对话框，而它加载。

的official tutorial是非常有益的。查看onPostExecute()方法，了解如何结束您可能拥有的任何类型的进度栏。

希望它可以帮助

好的我承认我需要asynkTask，但我可以将数据从asynkTask类传递到另一个活动？当我通过上面。 –

是的，你可以，在onPostExecute方法中，你可以工作UI操作并且可以将数据传递给其他活动。 – Udaykiran

答

你应该用的AsyncTask做到这一点，并显示在onPreExecuteMethod进度对话框，并关闭它在onPostExecute：

class MyAsyncTask extends AsyncTask<String,Void,Object> { 
    ProgressDialog pd; 
    Context context; 
    public MyAsyncTask(Context c) { 
     context = c; 
    } 
    @Override 
    protected void onPreExecute() { 
     pd = ProgressDialog.show(context, "Loading", "Wait", true, true); 
     pd.setOnCancelListener(new OnCancelListener() { 

      @Override 
      public void onCancel(DialogInterface dialog) { 
       finish(); 
      } 
     }); 
    } 
    @Override 
    protected Object doInBackground(String... params) { 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Object result) { 
     if(pd.isShowing()) 
      pd.dismiss(); 
    } 

}

答

也许会有所帮助。我用广播接收器在我的应用程序更新的ListView。

public static final String UPDATE_HISTORY_LIST = "com.myapp.update_history_list";

onPostExecute的AsyncTask

@Override 
    protected void onPostExecute(JSONObject par) { 
     Intent intent = new Intent(AppSettings.UPDATE_HISTORY_LIST); 
     LocalBroadcastManager.getInstance(mContext).sendBroadcast(intent); 
    }

接收机在活动

private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() { 
      @Override 
      public void onReceive(Context context, Intent intent) { 
       Log.i(TAG, "Action: " + intent.getAction()); 
       if (AppSettings.UPDATE_HISTORY_LIST.equals(intent.getAction())) { 
        OrderHistoryFragment history = (OrderHistoryFragment)getFragmentManager().findFragmentByTag("history"); 
        if(history != null && history.isVisible()){ 
         history.refresh(); 
        } 
       } 
      } 
    }; 
    @Override 
    protected void onPause() { 
     Log.i(TAG, "onPause"); 
     LocalBroadcastManager.getInstance(this).unregisterReceiver(mMessageReceiver); 
     super.onPause(); 
    } 

    @Override 
    protected void onResume() { 
     Log.i(TAG, "onResume"); 
     super.onResume(); 
     LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(this); 
     IntentFilter filter = new IntentFilter(); 
     filter.addAction(AppSettings.UPDATE_HISTORY_LIST); 
     lbm.registerReceiver(mMessageReceiver, filter); 
    }

布局

<ListView 
     android:id="@+id/listView1" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 
</ListView> 
<ProgressBar 
     android:id="@android:id/progress" 
     style="?android:attr/progressBarStyleLarge" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:indeterminate="true" />

活动

mList = (ListView)rootView.findViewById(R.id.listView1); 
mList.setEmptyView(rootView.findViewById(android.R.id.progress));

显示进度条在加载列表

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