Question

blist_activity.java

package com.hugelview.user.demo_architecture;

import android.app.ListActivity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;

import com.hugelview.demo_architecture.HttpManager.com.HttpManager;

import java.util.ArrayList;
import java.util.List;

import demo_architecture.adapter.bookingstatus;


public class blist extends ListActivity {

   ListView output;
   ProgressBar pb;
   List<blist> task;
   List<bookingstatus> status;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_blist);
        task = new ArrayList<>();
//        output = (ListView) findViewById(R.id.listView);
        pb = (ProgressBar) findViewById(R.id.progressBar);
        if (task.size() == 0) {
            pb.setVisibility(View.VISIBLE);
        }task.add(this);

//
//        listview_array listview = new listview_array(this, R.layout.item, status);
//        setListAdapter(listview);

        if (isonline()) {
            Requestdata("http://cita.co.in/androidapp/vehicle_info.php");
        } else {
            Toast.makeText(this, "CONNECT TO INTERNET", Toast.LENGTH_LONG).show();
        }




    }


    private void Requestdata(String uri) {
        mytask task = new mytask();
        task.execute(uri);
    }



    public boolean isonline(){
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netinfo = cm.getActiveNetworkInfo();
        if (netinfo != null && netinfo.isConnectedOrConnecting()) {
            return true;
        }
        else{
            return false;
        }
    }


    private class mytask extends AsyncTask<String, String, String>
    {
        @Override
        protected void onPreExecute() {
            task.remove(this);
            if (task.size() == 0) {
                pb.setVisibility(View.INVISIBLE);
            }
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(String... params) {
            String content = HttpManager.getdata(params[0]);
            return content;

        }

        @Override
        protected void onPostExecute(String result) {
            task.remove(this);
            if (task.size() == 0) {
                pb.setVisibility(View.INVISIBLE);
            }

            updatedisplay(result);

        }


    }

    private void updatedisplay(String result) {

        listview_array listview = new listview_array(this ,R.layout.item, status);
        setListAdapter(listview);

    }


//    @Override
//    public boolean onCreateOptionsMenu(Menu menu) {
//        // Inflate the menu; this adds items to the action bar if it is present.
//        getMenuInflater().inflate(R.menu.menu_blist, menu);
//        return true;
//    }
//
//    @Override
//    public boolean onOptionsItemSelected(MenuItem item) {
//        // Handle action bar item clicks here. The action bar will
//        // automatically handle clicks on the Home/Up button, so long
//        // as you specify a parent activity in AndroidManifest.xml.
//        int id = item.getItemId();
//
//        //noinspection SimplifiableIfStatement
//        if (id == R.id.action_settings) {
//            return true;
//        }
//
//        return super.onOptionsItemSelected(item);
//    }
}

bookingstatus.java

package demo_architecture.adapter;

/**
 * Created by user on 3/2/2015.
 */
public class bookingstatus {
    private int booking_id;
    private String pick_up;
    private String drop;
    private String time;
    private String date;

    public int getBooking_id() {
        return booking_id;
    }

    public void setBooking_id(int booking_id) {
        this.booking_id = booking_id;
    }

    public String getPick_up() {
        return pick_up;
    }

    public void setPick_up(String pick_up) {
        this.pick_up = pick_up;
    }

    public String getDrop() {
        return drop;
    }

    public void setDrop(String drop) {
        this.drop = drop;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getDriver_mobile() {
        return driver_mobile;
    }

    public void setDriver_mobile(String driver_mobile) {
        this.driver_mobile = driver_mobile;
    }

    public String getDriver_name() {
        return driver_name;
    }

    public void setDriver_name(String driver_name) {
        this.driver_name = driver_name;
    }

    public String getVehicle_number() {
        return vehicle_number;
    }

    public void setVehicle_number(String vehicle_number) {
        this.vehicle_number = vehicle_number;
    }

    private String driver_name;
    private String driver_mobile;
    private String vehicle_number;


}

Jsonlistparser.java

package com.hugelview.demo_architecture.parser;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;

import demo_architecture.adapter.bookingstatus;

/**
 * Created by user on 3/2/2015.
 */
public class Jsonlistparser {
    public static List<bookingstatus> parsefeed(String content){
        try {
            JSONArray jr = new JSONArray(content);
            List<bookingstatus> status =new ArrayList<>();

            for (int i=0; i < jr.length(); i++){

                JSONObject obj = jr.getJSONObject(i);
                bookingstatus bs = new bookingstatus();

                bs.setBooking_id(obj.getInt("booking id"));
                bs.setDate(obj.getString("date"));
                bs.setDriver_mobile(obj.getString("driver mobile"));
                bs.setDriver_name(obj.getString("driver name"));
                bs.setDrop(obj.getString("drop point"));
                bs.setDate(obj.getString("date"));
                bs.setPick_up(obj.getString("pick up"));
                bs.setTime(obj.getString("time"));
                bs.setVehicle_number(obj.getString("vehicle no:"));

                status.add(bs);


            }
            return status;
        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
    }
}

activity_blist.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.hugelview.user.demo_architecture.blist">

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@android:id/listView" />

    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/progressBar"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

item.xml

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:id="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="79dp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:layout_below="@+id/textView"
        android:id="@+id/textView1"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="79dp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:layout_below="@+id/textView1"
        android:id="@+id/textView2"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="79dp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:layout_below="@+id/textView2"
        android:id="@+id/textView3"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="79dp" />
</RelativeLayout>

listview_array

  package com.hugelview.user.demo_architecture;


    import android.app.Activity;
    import android.content.Context;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.TextView;

    import java.util.List;

    import demo_architecture.adapter.bookingstatus;

    /**
     * Created by user on 3/2/2015.
     */
    public class listview_array extends ArrayAdapter<bookingstatus> {
        private Context context;
        private List<bookingstatus> status;

        public listview_array(Context context, int resource , List<bookingstatus> objects)
        {
            super(context, resource, objects);
            this.context =context;
            this.status =objects;

        }

        @Override
        public View getView(int position, View convertview, ViewGroup parent){
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            View view = inflater.inflate(R.layout.item, parent, false);

            //display name in textview
            bookingstatus booking = status.get(position);
            TextView tv = (TextView) view.findViewById(R.id.textView);
            tv.setText(booking.getPick_up());

            return view;

        }

    }

当我在mainactivity.java的选项菜单中选择状态时，他们不应该进入列表视图，因为它应该是blist_activity.java，并且应该在开始活动时显示listview中的内容。不幸的是我收到了错误

java.lang.NullPointerException at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330) at android.widget.ListView.setAdapter(ListView.java:487) at android.app.ListActivity.setListAdapter(ListActivity.java:265) at com.hugelview.user.demo_architecture.blist.updatedisplay(blist.java:112) at com.hugelview.user.demo_architecture.blist.access$100(blist.java:22) at com.hugelview.user.demo_architecture.blist$mytask.onPostExecute(blist.java:102) at com.hugelview.user.demo_architecture.blist$mytask.onPostExecute(blist.java:77) at android.os.AsyncTask.finish(AsyncTask.java:632) at android.os.AsyncTask.access$600(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:5292) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640) at dalvik.system.NativeStart.main(Native Method)

请真正提出建议

Answer 1

ListView android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>

在xml文件中必须提到listView的ID。试试吧。

Answer 2

<强> chnage

android:id="@+id/listView"

以

android:id="@id/android:listView"

Answer 3

现在在您的xml中，

  <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/listView" /> /* <--------- */

必须如此，请尝试复制粘贴此内容并且您不太可能收到错误：

<ListView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@android:id/list" />

想要获取json api并在活动在android中打开时在列表视图中显示它

3 个答案: