加载列表时显示进度条

时间：2011-11-17 11:27:07

标签： android progress-bar android-listview

Ok现在我承认我是新手使用进度条我从不使用它但现在我需要使用它 我有一个活动（主要）和一个可以开始6个新活动的菜单。从这些活动中有一个活动，它在ListView中加载数据需要3-4秒才能加载。这个活动解析json并将数据传递给另一个活动。如果用户单击此活动的菜单选项，我将如何显示进度条，并在加载列表时将其消失。

这是活动

    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();
    }
}

先谢谢!!

5 个答案:

答案 0 :(得分：6)

使用AsyncTask在后​​台加载数据，同时显示加载指示符。在AsyncTask's doInBackground方法中，处理JSON或任何花费时间的事情。 

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 ( ) ;
        }
    }
}

在您的活动onCreate()执行AsyncTask

中 
new HeavyWorker().execute();

答案 1 :(得分：1)

对于此类操作，您应该使用AsyncTask，并在加载时显示进度对话框。

official tutorial非常有帮助。查看onPostExecute()方法，了解如何结束您可能拥有的任何类型的进度条。

希望有所帮助

答案 2 :(得分：1)

您应该使用AsyncTask并在onPreExecuteMethod中显示进度对话框并在onPostExecute上将其关闭：

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();
    }

}

答案 3 :(得分：1)

也许会有所帮助。我使用BroadcastReceiver在我的应用程序中更新ListView。

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

onPostExecute AsyncTask 

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

活动中的接收者

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));

答案 4 :(得分：0)

您可以为您的活动添加属性：

ProgressDialog dialog;

然后使用此代码显示您的对话框：

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

然后在要删除它时添加：

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

还要在onStop上添加这些行（以防万一用户存在活动）：

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