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我正在创建一个应用程序，它以 JSON 格式从我的本地服务器中提取预订并以ListView.

我设法提取数据并以基本List格式显示，但决定创建一个更好看的List. 我一直在遵循ezzylearning的指南，该指南向ListView.

我检查了代码并四处搜索，但我仍然收到ListView某种形式的错误。不确定如何解决或调试此问题。

Ignition.java (mainActivity) ：

package com.systematix.sxConcept;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.ListView;


public class Ignition extends Activity {

    // url to make request
    private static String url = "http://10.0.0.103/android/data";

    public String company;
    public String course;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ignition);
        new ReadJSONFeedTask().execute(url);
    }

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

    public String readJSONFeed(String URL){
        StringBuilder stringBuilder = new StringBuilder();
        HttpClient client = new DefaultHttpClient();
        HttpGet httpget = new HttpGet(URL);
        try{
            HttpResponse response = client.execute(httpget);
            StatusLine statusLine = response.getStatusLine();
            int statusCode = statusLine.getStatusCode();
            if(statusCode == 200){
                HttpEntity entity = response.getEntity();
                InputStream content = entity.getContent();
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(content));
                String line;
                while ((line = reader.readLine()) != null){
                    stringBuilder.append(line);
                }
            }else{
                Log.e("JSON", "Failed to download list");
            }
        } catch (ClientProtocolException e){
            e.printStackTrace();
        } catch (IOException e){
            e.printStackTrace();
        }

        return stringBuilder.toString();
    }

    private class ReadJSONFeedTask extends AsyncTask<String, Void, String> {
        protected String doInBackground(String... urls){
            return readJSONFeed(urls[0]);
        }

        protected void onPostExecute(String result){
            try{
                JSONArray jsonArray = new JSONArray(result);
                Log.i("JSON", "Number of surveys in feed :" + jsonArray.length());
                ListView listView = (ListView) findViewById(R.id.listView1);

                /*String[] responseList;        
                responseList = new String[jsonArray.length()];*/

                Bookings[] booking_data;
                booking_data = new Bookings[jsonArray.length()];

                for (int i =0; i < jsonArray.length(); i++){
                    JSONObject jsonObject = jsonArray.getJSONObject(i);

                    booking_data[i] = new Bookings(jsonObject.getString("Company"),jsonObject.getString("CourseTitle"));

                    //responseList[i] = jsonObject.getString("bookdate") + " - " + jsonObject.getString("Company");
                }

                BookingsAdapter adapter = new BookingsAdapter(getBaseContext(),
                        R.layout.listview_item_row, booking_data); //export the data to a custom adapter

               /* View header = (View)getLayoutInflater().inflate(R.layout.listview_header_row, null);
                listView.addHeaderView(header);*/

                listView.setAdapter(adapter);

                /*ArrayAdapter<String> newAdapter = new ArrayAdapter<String>(getBaseContext(), android.R.layout.test_list_item, responseList);
                listView.setAdapter(newAdapter);*/

            } catch (Exception e){
                e.printStackTrace();
            }
        }
    }

}

BookingsAdapter.java：

package com.systematix.sxConcept;

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;

public class BookingsAdapter extends ArrayAdapter<Bookings>{

    Context context;
    int layoutResourceId;   
    Bookings data[] = null;

    public BookingsAdapter(Context context, int layoutResourceId, Bookings[] data) {
        super(context, layoutResourceId, data);
        this.layoutResourceId = layoutResourceId;
        this.context = context;
        this.data = data;
    }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View row = convertView;
            BookingHolder holder = null;

            if(row == null)
            {
                LayoutInflater inflater = ((Activity)context).getLayoutInflater();
                row = inflater.inflate(layoutResourceId, parent, false);

                holder = new BookingHolder();
                holder.company = (TextView)row.findViewById(R.id.rowCompany);
                holder.course = (TextView)row.findViewById(R.id.rowCourse);

                row.setTag(holder);
            }
            else
            {
                holder = (BookingHolder)row.getTag();
            }

            Bookings booking = data[position];
            holder.company.setText(booking.company);
            holder.course.setText(booking.course);

            return row;
        }

        static class BookingHolder
        {
            TextView company;
            TextView course;
        }
    }

预订.java： 

package com.systematix.sxConcept;

public class Bookings {
    public String company;
    public String course;
    public Bookings(){
        super();
    }

    public Bookings(String company, String course) {
        super();
        this.company = company;
        this.course = course;
    }
}

XML 布局文件是教程中 1 的副本，图标替换为Textview.

这些是错误：

07-24 12:36:10.154: E/AndroidRuntime(331): FATAL EXCEPTION: main
07-24 12:36:10.154: E/AndroidRuntime(331): java.lang.ClassCastException: android.app.ContextImpl
07-24 12:36:10.154: E/AndroidRuntime(331):  at com.systematix.sxConcept.BookingsAdapter.getView(BookingsAdapter.java:31)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.AbsListView.obtainView(AbsListView.java:1430)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.ListView.makeAndAddView(ListView.java:1745)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.ListView.fillDown(ListView.java:670)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.ListView.fillFromTop(ListView.java:727)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.ListView.layoutChildren(ListView.java:1598)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.AbsListView.onLayout(AbsListView.java:1260)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.View.layout(View.java:7175)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1047)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.View.layout(View.java:7175)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.View.layout(View.java:7175)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1047)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.View.layout(View.java:7175)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.View.layout(View.java:7175)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.os.Looper.loop(Looper.java:123)
07-24 12:36:10.154: E/AndroidRuntime(331):  at android.app.ActivityThread.main(ActivityThread.java:3683)
07-24 12:36:10.154: E/AndroidRuntime(331):  at java.lang.reflect.Method.invokeNative(Native Method)
07-24 12:36:10.154: E/AndroidRuntime(331):  at java.lang.reflect.Method.invoke(Method.java:507)
07-24 12:36:10.154: E/AndroidRuntime(331):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-24 12:36:10.154: E/AndroidRuntime(331):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-24 12:36:10.154: E/AndroidRuntime(331):  at dalvik.system.NativeStart.main(Native Method)
4

3 回答 3

0

线

LayoutInflater inflater = ((Activity)context).getLayoutInflater();

您正在将上下文投射到 Activity。Activity 继承自 Context 所以你不应该需要这个演员表。试试这个 

LayoutInflater inflater = LayoutInflater inflater = LayoutInflater inflater = 
                          context.getLayoutInflater();
于 2012-07-24T13:45:14.137 回答
0

尝试这个

BookingsAdapter adapter = new BookingsAdapter(Ignition.this,
                    R.layout.listview_item_row, booking_data);
于 2012-07-24T13:39:54.773 回答
0

尝试这样做：

LayoutInflater li = LayoutInflater.from(context);

或者

LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

我假设这是class cast exception发生的第 31 行。

于 2012-07-24T13:42:24.783 回答