如何在Android中将动态数据从一个活动发送到另一个活动

Question

我正在开发一个android应用程序，我从mysql数据库中获取数据并将其显示在Listview中。 我有数据“类别”，例如电信，银行，社交网站等。 从MySQL获得的此Category完美地显示在ListView中。 现在，当我单击其中任何一个时，这将移至下一个活动并根据该类别显示数据。 假设我单击“社交网站”，然后在下一个活动中，数据应该是Google Plus，Instagram，Twitter等，并且此列表将来自数据库并显示在列表视图中。 我对此一无所知.. !!! 请帮助我...这是我所做的代码。

Welcome.java

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

public class Welcome extends Activity 
{
    TextView text;
    //Button b1,b2,b3;
    String CompName,CompID;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);

        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

      //  b1=(Button)findViewById(R.id.dashboard_tab1);
      //  b1.setOnClickListener(this);

        connect();
    }

    public void connect() 
    {
        String data;
        List<String> r = new ArrayList<String>();
        ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);
        ListView list=(ListView)findViewById(R.id.list);
        try 
        {
                DefaultHttpClient client = new DefaultHttpClient();
                HttpGet request = new HttpGet("http://10.0.2.2/database/Retrive.php");
                HttpResponse response = client.execute(request);
                HttpEntity entity=response.getEntity();
                data=EntityUtils.toString(entity);
                Log.e("STRING", data);

                try 
                {
                   JSONArray json=new JSONArray(data);
                   for(int i=0;i<json.length(); i++)
                   {
                        JSONObject obj=json.getJSONObject(i);

                        CompName=obj.getString("fldCompName");
                        CompID=obj.getString("fldCompID");

                        Log.e("STRING", CompName);
                        Log.e("STRING",CompID);

                        r.add(CompName);
                        //r.add(CompID);
                        list.setAdapter(adapter);

                        list.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() 
                        {
                            @Override
                            public void onItemClick(AdapterView<?> parent,View view, int position, long id) 
                            {
                                Intent i1=new Intent(Welcome.this,Category1.class);
                                i1.putExtra("CompName", CompName);
                                startActivity(i1);
                            }
                        });
                   }
                } 
                catch (JSONException e) 
                {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            } catch (ClientProtocolException e) {
                Log.d("HTTPCLIENT", e.getLocalizedMessage());
            } catch (IOException e) {
                Log.d("HTTPCLIENT", e.getLocalizedMessage());
            }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.welcome, menu);
        return true;
    }
}

这是我的布局文件... !!!

activity_welcome.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

<ListView
    android:id="@+id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/bg" >
</ListView>

</LinearLayout>

Retrive.php

<?php

    $host='localhost';
    $uname='root';
    $pwd='';
    $db='database';

    $con=mysqli_connect($host,$uname,$pwd) or die("Connection Failed");
        mysqli_select_db($con,$db) or die("database selection failed");

    $sql=mysqli_query($con,"select fldCompName,fldCompID from tblCompanies where fldStatus='1'");
    while($row=mysqli_fetch_assoc($sql))
    $output[]=$row;
    $a=json_encode($output);
    print($a);
    mysqli_close();

?>

Answer 1

更换

 i1.putExtra("CompName", CompName);

通过

 i1.putExtra("CompName", r[position]);

然后在下一个活动中获取此数据，并根据传递的值从数据库中获取数据。

您必须传递用户选择的值。 因此，所有值都在适配器r ，您将了解按项目选定位置（ onItemClick第三个参数）选择了哪个用户。 所以应该是r[position] 。 最好在将适配器设置为ListView之前完全填充适配器。 因此，从JSON中获取所有数据，将其添加到适配器，然后将该适配器设置为ListView。

Answer 2

尝试使用AsyncTasks，这里是文档： http : //developer.android.com/reference/android/os/AsyncTask.html

Answer 3

试试这个，你必须在Intent中使用多余的东西，并将数据发送到其他活动，并在下一个活动中将其放在onCreate上

 listView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View view, int pos,
                long id) {
            SubCategoryModel scm = lstSubCategoryList.get(pos);
            Intent intent = new Intent(prestentactivity.this, nextactivity.class);
            intent.putExtra("ActivityKey", scm.getName());

            startActivity(intent);

        }


    });

下一个活动

Intent intent = getIntent();
 String Key= intent.getStringExtra("ActivityKey");

Answer 4

尝试这种方式，希望这将帮助您解决问题。

public class Welcome extends Activity
{

    private ListView list;
    private ArrayAdapter<String> adapter;
    private ArrayList<HashMap<String,String>> data;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);
        list=(ListView)findViewById(R.id.list);

        list.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener()
        {
            @Override
            public void onItemClick(AdapterView<?> parent,View view, int position, long id)
            {
                Intent i1=new Intent(Welcome.this,Category1.class);
                i1.putExtra("CompName",data.get(position).get("CompName"));
                i1.putExtra("fldCompID",data.get(position).get("fldCompID"));
                startActivity(i1);
            }
        });
        getDataFromServer(new CallListener() {
            @Override
            public void onComplete(ArrayList<HashMap<String, String>> response) {
                data = response;
                String[] listItemArray = new String[data.size()];
                for (int i = 0; i < data.size(); i++) {
                    listItemArray[i] = data.get(i).get("CompName");
                }
                adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, listItemArray);
                list.setAdapter(adapter);
            }
        });

    }

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

    public void getDataFromServer(final CallListener target){
        new AsyncTask<Void, Void, ArrayList<HashMap<String, String>>>() {
            ArrayList<HashMap<String,String>> data = new ArrayList<HashMap<String, String>>();
            @Override
            protected ArrayList<HashMap<String, String>> doInBackground(Void... params) {
                try {
                    DefaultHttpClient client = new DefaultHttpClient();
                    HttpGet request = new HttpGet("http://10.0.2.2/database/Retrive.php");
                    HttpResponse response = client.execute(request);
                    HttpEntity entity=response.getEntity();
                    Log.e("STRING", EntityUtils.toString(entity));


                    JSONArray json = new JSONArray(EntityUtils.toString(entity));

                    for (int i = 0; i < json.length(); i++) {
                        Log.e("STRING", json.getJSONObject(i).getString("fldCompName"));
                        Log.e("STRING", json.getJSONObject(i).getString("fldCompID"));

                        HashMap<String, String> row = new HashMap<String, String>();
                        row.put("CompName", json.getJSONObject(i).getString("fldCompName"));
                        row.put("fldCompID", json.getJSONObject(i).getString("fldCompID"));
                        data.add(row);
                    }
                }catch (Throwable e){
                    e.printStackTrace();
                }
                return data;
            }

            @Override
            protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
                super.onPostExecute(result);
                target.onComplete(result);

            }
        }.execute();
    }

    interface CallListener{
        public void onComplete(ArrayList<HashMap<String,String>> response);
    }
}