当新数据插入 ListView 时Android自动刷新

Question

我一直在开发安卓应用程序。我有后端(Web 应用程序)和前端(Android 应用程序)。

在我的应用程序中，它有一个包含一堆项目列表的类别。当我选择一个类别时，它会调用一个任务来调用数据库中的所有数据。一旦任务完成调用所有数据，它将直接到 Activity 。 Activity 将在 ListView 中显示所有数据。

现在，例如，我从后端 ( Web ) 插入一个新数据。假设我在运动类别中插入了一个包含拳击的新行。所以，在 DB 中， table 上运动中会有拳击。

在我的 android 应用程序中，我目前处于运动类别中。因此，当将装箱插入新数据库时，它应该自动刷新并在列表中显示装箱。

但是当我单击类别列表中的类别时任务只运行一次，我该怎么做呢？我想比较数据库中的数据总数和 android 应用程序中显示的数据。当数据不一样时，它会再次调用任务。

这是我希望我的应用程序刷新的代码

ConnectivityManager connManager = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);

    if(mWifi.isConnected()) 
    {
        refresh = new Runnable() {
            public void run() {
                // Do something
                handler.postDelayed(refresh, 1000);
            }
        };
        handler.post(refresh);

        /*gridArray = new ArrayList<FlipItem>();
        adapter = new PackageListItemAdapter(this, this, gridArray);        
        adapter.notifyDataSetChanged();*/

    }
    else
    {
        refresh = new Runnable() {
            public void run() {
                // Do something
                handler.postDelayed(refresh, 60000);
            }
        };
        handler.post(refresh);
        /*gridArray = new ArrayList<FlipItem>();
        adapter = new PackageListItemAdapter(this, this, gridArray);        
        adapter.notifyDataSetChanged();*/
    }

我在那里评论的代码使我的列表只显示大约 9 个，而我在 DB 上有 15 个项目。这就是为什么我评论那行

Answer 1

调用notifyDataSetChanged()在您的适配器上。

关于如何/何时调用 notifyDataSetChanged() 的一些额外细节可以在 Google I/O video 中查看。 .

使用 Handler 及其 postDelayed 方法使列表的适配器无效，如下所示:

final Handler handler = new Handler()
handler.postDelayed( new Runnable() {

    @Override
    public void run() {
        adapter.notifyDataSetChanged();
        handler.postDelayed( this, 60 * 1000 );
    }
}, 60 * 1000 );

您只能在主 (UI) 线程中更新 UI。

通过在主线程中创建处理程序，您可以确保您发布到处理程序的所有内容也在主线程中运行。

try
                {
                    validat_user(receivedName);
                    final Handler handler = new Handler();
                    handler.postDelayed( new Runnable() {

                        @Override
                        public void run() {
                            todoItems.clear();
                            //alertDialog.cancel();
                            validat_user(receivedName);
                            handler.postDelayed( this, 60 * 1000 );
                        }
                    }, 60 * 1000 );


                }

                catch(Exception e)
                {
                    display("Network error.\nPlease check with your network settings.");
                }

第一个validate user是第一次加载数据，在使用处理程序后我可以每隔一分钟更新一次值

我的完整代码在下面

package com.example.employeeinduction;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;
import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.res.TypedArray;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.PopupMenu;
import android.widget.PopupMenu.OnMenuItemClickListener;
import android.widget.Toast;


public class pdf extends Activity
{

    ImageView iv;
    public boolean connect=false,logged=false;
    public String db_select;
    ListView l1;
    AlertDialog alertDialog;
    String mPwd,UName1="Success",UName,ret,receivedName;
    public Iterator<String> itr;
    //private String SERVICE_URL = "http://61.12.7.197:8080/pdf";
    //private String SERVICE_URL1 = "http://61.12.7.197:8080/url";
    //private final String SERVICE_URL = "http://10.54.3.208:8080/Employee/person/pdf";
    //private final String SERVICE_URL1 = "http://10.54.3.208:8080/Employee/person/url";
    private final String SERVICE_URL = Urlmanager.Address+"pdf";
    private final String SERVICE_URL1 = Urlmanager.Address+"url";
    private final String TAG = "Pdf";
    ArrayList<String> todoItems;
    Boolean isInternetPresent = false;
    ConnectionDetector cd;
    ArrayAdapter<String> aa;
    public List<String> list1=new ArrayList<String>();
    public DrawerLayout mDrawerLayout;
    public ListView mDrawerList;
    //public ActionBarDrawerToggle mDrawerToggle;

    // NavigationDrawer title "Nasdaq" in this example
    public CharSequence mDrawerTitle;

    //  App title "Navigation Drawer" in this example 
    public CharSequence mTitle;

    // slider menu items details 
    public String[] navMenuTitles=null;
    public TypedArray navMenuIcons;

    public ArrayList<NavDrawerItem> navDrawerItems;
    public NavDrawerListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sliding_project);
         iv = (ImageView)findViewById(R.id.imageView2);
        l1 = (ListView)findViewById(R.id.list);


        mTitle = mDrawerTitle = getTitle();

        // getting items of slider from array
        navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

        // getting Navigation drawer icons from res 
        navMenuIcons = getResources()
                .obtainTypedArray(R.array.nav_drawer_icons);

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

        navDrawerItems = new ArrayList<NavDrawerItem>();


        // list item in slider at 1 Home Nasdaq details
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
        // list item in slider at 2 Facebook details
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
        // list item in slider at 3 Google details
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
        // list item in slider at 4 Apple details


        // Recycle array
        navMenuIcons.recycle();

        mDrawerList.setOnItemClickListener(new SlideMenuClickListener());

        // setting list adapter for Navigation Drawer
        adapter = new NavDrawerListAdapter(getApplicationContext(),
                navDrawerItems);
        mDrawerList.setAdapter(adapter);

        if (savedInstanceState == null) {
              displayView(0);
        }

          iv.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {


                    PopupMenu popup = new PopupMenu(getBaseContext(), v);

                    /** Adding menu items to the popumenu */
                    popup.getMenuInflater().inflate(R.menu.main, popup.getMenu());

                    popup.setOnMenuItemClickListener(new OnMenuItemClickListener() {

                        @Override
                        public boolean onMenuItemClick(MenuItem item) {

                            switch (item.getItemId()){
                            case R.id.Home:
                                Intent a = new Intent(pdf.this,Design_Activity.class);
                                startActivity(a);
                                //Projects_Accel.this.finish();
                            //  return true;
                                break;
                            case R.id.Logout:
                                /*Intent z = new Intent(this,MainActivity.class);
                                z.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                                startActivity(z);
                                this.finish();*/
                                Intent z = new Intent(pdf.this,MainActivity.class);
                                z.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | 
                                        Intent.FLAG_ACTIVITY_CLEAR_TASK |
                                        Intent.FLAG_ACTIVITY_NEW_TASK);
                                startActivity(z);
                                pdf.this.finish();
                            //  return true;
                                break;
                            }

                            return true;
                        }
                    });
                        popup.show();
                }
            });

             todoItems = new ArrayList<String>();
                aa = new ArrayAdapter<String>(this,R.layout.list_row,R.id.title,todoItems);
                l1.setAdapter(aa);
                todoItems.clear();
                Intent intent = getIntent();
                receivedName = (String) intent.getSerializableExtra("PROJECT");
                cd = new ConnectionDetector(getApplicationContext());
                isInternetPresent = cd.isConnectingToInternet();
                if(isInternetPresent)
                {
                try
                {
                    validat_user(receivedName);
                    final Handler handler = new Handler();
                    handler.postDelayed( new Runnable() {

                        @Override
                        public void run() {
                            todoItems.clear();
                            //alertDialog.cancel();
                            validat_user(receivedName);
                            handler.postDelayed( this, 60 * 1000 );
                        }
                    }, 60 * 1000 );


                }

                catch(Exception e)
                {
                    display("Network error.\nPlease check with your network settings.");
                }
                }
                else
                {
                    display("No Internet Connection..");
                }

                l1.setOnItemClickListener(new OnItemClickListener() {
                    public void onItemClick(AdapterView<?> parent, View view,
                        int position, long id) {

                     String name=(String)parent.getItemAtPosition(position);

                     /*Toast.makeText(getBaseContext(), name, Toast.LENGTH_LONG).show();
                      Intent i = new Intent(getBaseContext(),Webview.class);
                      i.putExtra("USERNAME", name);
                      startActivity(i);*/
                     cd = new ConnectionDetector(getApplicationContext());
                        isInternetPresent = cd.isConnectingToInternet();
                     if(isInternetPresent)
                        {
                     try
                        {
                            validat_user1(receivedName,name);

                        }
                        catch(Exception e)
                        {
                            display("Network error.\nPlease check with your network settings.");

                        }

                        }
                     else
                        {
                            display("No Internet Connection..");
                        }
                    }
                });

             }      
    private class SlideMenuClickListener implements
    ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
        long id) {
    // display view for selected item
    displayView(position);
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
//setMenuBackground();
return true;
}


/*@Override
public boolean onOptionsItemSelected(MenuItem item) {
//  title/icon
if (mDrawerToggle.onOptionsItemSelected(item)) {
    return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
    return true;
default:
    return super.onOptionsItemSelected(item);
}
}*/

//called when invalidateOptionsMenu() invoke 

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if Navigation drawer is opened, hide the action items
//boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
//menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}

private void displayView(int position) {
// update the main content with called Fragment
switch (position) {

case 1:
    //fragment = new Fragment2Profile();
    Intent i = new Intent(pdf.this,Design_Activity.class);
    startActivity(i);
    pdf.this.finish();
    break;
case 2:
    //fragment = new Fragment3Logout();
    Intent z = new Intent(pdf.this,MainActivity.class);
    z.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | 
             Intent.FLAG_ACTIVITY_CLEAR_TASK |
             Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(z);
        pdf.this.finish();
    break;

default:
    break;
}



}




        public void display(String msg) 
        {
            Toast.makeText(pdf.this, msg, Toast.LENGTH_LONG).show();
        }
        private void validat_user(String st)
        {

            WebServiceTask wst = new WebServiceTask(WebServiceTask.POST_TASK, this, "");

           wst.addNameValuePair1("TABLE_NAME", st);
           // wst.addNameValuePair("Emp_PWD", stg2);
           // db_select=stg1;
            //display("I am");
            wst.execute(new String[] { SERVICE_URL });
            //display(SERVICE_URL);

        }
        private void validat_user1(String stg1,String stg2)
        {
            db_select=stg1;
            WebServiceTask wst = new WebServiceTask(WebServiceTask.POST_TASK, this, "Loading...");

            wst.addNameValuePair1("PDF_NAME", stg1);
            wst.addNameValuePair1("TABLE_NAME1", stg2);
            wst.execute(new String[] { SERVICE_URL1 });

        }
        @SuppressWarnings("deprecation")
        public void no_net()
        {
            display( "No Network Connection");
            final AlertDialog alertDialog = new AlertDialog.Builder(pdf.this).create();
            alertDialog.setTitle("No Internet Connection");
            alertDialog.setMessage("You don't have internet connection.\nElse please check the Internet Connection Settings.");
            //alertDialog.setIcon(R.drawable.error_info);
            alertDialog.setCancelable(false);
            alertDialog.setButton("Close", new DialogInterface.OnClickListener() 
            {
                public void onClick(DialogInterface dialog, int which)
                {   
                    alertDialog.cancel();
                    pdf.this.finish();
                    System.exit(0);
                }
            });
            alertDialog.setButton2("Use Local DataBase", new DialogInterface.OnClickListener() 
            {
                public void onClick(DialogInterface dialog, int which)
                {
                    display( "Accessing local DataBase.....");
                    alertDialog.cancel();
                }
            });
            alertDialog.show();
        }

        private class WebServiceTask extends AsyncTask<String, Integer, String> {

            public static final int POST_TASK = 1;

            private static final String TAG = "WebServiceTask";

            // connection timeout, in milliseconds (waiting to connect)
            private static final int CONN_TIMEOUT = 12000;

            // socket timeout, in milliseconds (waiting for data)
            private static final int SOCKET_TIMEOUT = 12000;

            private int taskType = POST_TASK;
            private Context mContext = null;
            private String processMessage = "Processing...";

            private ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();

            private ProgressDialog pDlg = null;

            public WebServiceTask(int taskType, Context mContext, String processMessage) {

                this.taskType = taskType;
                this.mContext = mContext;
                this.processMessage = processMessage;
            }

            public void addNameValuePair1(String name, String value) {

                params.add(new BasicNameValuePair(name, value));
            }
            @SuppressWarnings("deprecation")
            private void showProgressDialog() {

                pDlg = new ProgressDialog(mContext);
                pDlg.setMessage(processMessage);
                pDlg.setProgressDrawable(mContext.getWallpaper());
                pDlg.setProgressStyle(ProgressDialog.STYLE_SPINNER);
                pDlg.setCancelable(false);
                pDlg.show();

            }

            @Override
            protected void onPreExecute() {

                showProgressDialog();

            }

            protected String doInBackground(String... urls) {

                String url = urls[0];
                String result = "";

                HttpResponse response = doResponse(url);

                if (response == null) {
                    return result;
                } else {

                    try {

                        result = inputStreamToString(response.getEntity().getContent());

                    } catch (IllegalStateException e) {
                        Log.e(TAG, e.getLocalizedMessage(), e);

                    } catch (IOException e) {
                        Log.e(TAG, e.getLocalizedMessage(), e);
                    }

                }

                return result;
            }

            @Override
            protected void onPostExecute(String response) {

                handleResponse(response);
                pDlg.dismiss();

            }


            // Establish connection and socket (data retrieval) timeouts
            private HttpParams getHttpParams() {

                HttpParams htpp = new BasicHttpParams();

                HttpConnectionParams.setConnectionTimeout(htpp, CONN_TIMEOUT);
                HttpConnectionParams.setSoTimeout(htpp, SOCKET_TIMEOUT);

                return htpp;
            }

            private HttpResponse doResponse(String url) {

                // Use our connection and data timeouts as parameters for our
                // DefaultHttpClient
                HttpClient httpclient = new DefaultHttpClient(getHttpParams());

                HttpResponse response = null;

                try {
                    switch (taskType) {

                    case POST_TASK:
                        HttpPost httppost = new HttpPost(url);
                        // Add parameters
                        httppost.setEntity(new UrlEncodedFormEntity(params));

                        response = httpclient.execute(httppost);
                        break;
                    }
                } catch (Exception e) {
                    display("Remote DataBase can not be connected.\nPlease check network connection.");

                    Log.e(TAG, e.getLocalizedMessage(), e);
                    return null;

                }

                return response;
            }

            private String inputStreamToString(InputStream is) {

                String line = "";
                StringBuilder total = new StringBuilder();

                // Wrap a BufferedReader around the InputStream
                BufferedReader rd = new BufferedReader(new InputStreamReader(is));

                try {
                    // Read response until the end
                    while ((line = rd.readLine()) != null) {
                        total.append(line);
                    }
                } catch (IOException e) {
                    Log.e(TAG, e.getLocalizedMessage(), e);
                }

                // Return full string
                return total.toString();
            }

        }
        public void handleResponse(String response) 
        {    //display("JSON responce is : "+response);
            if(!response.equals(""))
            {
           try {

                JSONObject jso = new JSONObject(response);


                      int UName = jso.getInt("status1");

                      if(UName==1)
                      {
                            String status = jso.getString("reps1");
                            ret=status.substring(12,status.length()-2);
                            todoItems.add(0, ret);
                            aa.notifyDataSetChanged();
                      }
                      else if(UName==-1)
                      {
                          String status = jso.getString("status");
                          //ret=status.substring(12,status.length()-2);
                          //display(status);
                            Intent intObj=new Intent(pdf.this,Webview.class);
                             intObj.putExtra("USERNAME",status);
                            startActivity(intObj);
                      }
                      else if(UName>1)
                      {
//                       int count=Integer.parseInt(UName);
//                       display("Number of Projects have been handling in AFL right now: "+count);
                        list1=new ArrayList<String>();

                        JSONArray array=jso.getJSONArray("reps1");
                        for(int i=0;i<array.length();i++)
                        {
                            list1.add(array.getJSONObject(i).getString("pdfName"));

                        }Collections.sort(list1);
                        Collections.reverse(list1);
                        itr=list1.iterator();
                        while(itr.hasNext())
                        {
                             //str1=itr.next()+"\n";
                            todoItems.add(0, itr.next().toString());
                            aa.notifyDataSetChanged();
                        }

                        //tv1.setText(str1);


                      }  
                      else
                      {
                          final Context context = this;
                            AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                                context);

                            // set title
                            alertDialogBuilder.setTitle("");

                            // set dialog message
                            alertDialogBuilder
                                .setMessage("Records unavailable for this project!")
                                .setCancelable(false)
                                .setPositiveButton("Exit",new DialogInterface.OnClickListener() {
                                    public void onClick(DialogInterface dialog,int id) {
                                        // if this button is clicked, close
                                        // current activity
                                        pdf.this.finish();
                                    }
                                  });

                                // create alert dialog
                                alertDialog = alertDialogBuilder.create();

                                // show it
                                alertDialog.show();
                      }
            } catch (Exception e) {
                Log.e(TAG, e.getLocalizedMessage(), e);
                return;
            }
            }
            else
            {
                display("unable to reach the server");
            }


        }



        /**
         * Slider menu item click listener
         * */
        /*private class SlideMenuClickListener implements
                ListView.OnItemClickListener {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position,
                    long id) {
                // display view for selected item
                displayView(position);
            }
        }


        private void displayView(int position) {
            // update the main content with called Fragment
        //  Fragment fragment = null;
            switch (position) {
            case 0:
            //  fragment = new Fragment1User();
                break;
            case 1:
            //  fragment = new Fragment2Profile();
                break;
            case 2:
            //  fragment = new Fragment3Logout();
                break;

            default:
                break;
            }
        }*/


}