Question

所以我尝试使用自定义适配器重建我的ListView，这样我可以让它看起来更好一些，并为它添加更多功能。无论如何，这是我的适配器

HistoryAdapter.java

package com.this.app;

import android.content.Context;
import android.database.Cursor;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class HistoryAdapter extends BaseAdapter {

    private Context mContext;
    Cursor cursor;

    public HistoryAdapter(Context context, Cursor cur){
        super();
        mContext = context;
        cursor = cur;
    }

    public int getCount(){
        // return the number of records in cursor
        return cursor.getCount();
    }

    // getView method is called for each item of ListView
    public View getView(int position, View view, ViewGroup parent){

        // inflate the layout for each item of listView
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = inflater.inflate(R.layout.history_list_item, null);

        // move the cursor to required position
        cursor.moveToPosition(position);

        // fetch the information for each card
        String pricePerGallon = cursor.getString(cursor.getColumnIndex("pricePerGallon"));
        String gallons = cursor.getString(cursor.getColumnIndex("gallons"));
        String odometer = cursor.getString(cursor.getColumnIndex("odometer"));
        String date = cursor.getString(cursor.getColumnIndex("date"));
        String filledOrNot = cursor.getString(cursor.getColumnIndex("filledOrNot"));
        String comments = cursor.getString(cursor.getColumnIndex("comments"));
        //String milesPerGallon = cursor.getString(cursor.getColumnIndex("miledPerGallon"));
        String totalSpent = cursor.getString(cursor.getColumnIndex("totalSpent"));

        // get the reference of TextViews
        TextView textViewPricePerGallon = (TextView) view.findViewById(R.id.pricePerGallon);
        TextView textViewGallons = (TextView) view.findViewById(R.id.gallons);
        TextView textViewOdometer = (TextView) view.findViewById(R.id.odometer);
        TextView textViewDate = (TextView) view.findViewById(R.id.date);
        TextView textViewFilledOrNot = (TextView) view.findViewById(R.id.cardFilledOrNot);
        TextView textViewComments = (TextView) view.findViewById(R.id.comments);
        //TextView textViewMilesPerGallon = (TextView) view.findViewById(R.id.mpg);
        TextView textViewTotalSpent = (TextView) view.findViewById(R.id.totalSpentOnFillups);

        // Set the data to each TextView
        Log.d("HistoryAdapter", pricePerGallon);
        textViewPricePerGallon.setText(pricePerGallon);
        textViewGallons.setText(gallons);
        textViewOdometer.setText(odometer);
        textViewDate.setText(date);
        textViewFilledOrNot.setText(filledOrNot);
        textViewComments.setText(comments);
        //textViewMilesPerGallon.setText(milesPerGallon);
        textViewTotalSpent.setText(totalSpent);

        return view;
    }

    public Object getItem(int position){
        return position;
    }

    public long getItemId(int position){
        return position;
    }

}

我在第一个setText

处得到一个NullPointerException

textViewPricePerGallon.setText(pricePerGallon);

现在，如果我注释掉所有的setText，它会很好地加载列表（它只是不附加所有数据......而是显示XML中设置的所有默认值）

这是调试的副本

02-21 11:21:06.156: E/AndroidRuntime(30769): FATAL EXCEPTION: main
02-21 11:21:06.156: E/AndroidRuntime(30769): Process: com.this.app, PID: 30769
02-21 11:21:06.156: E/AndroidRuntime(30769): java.lang.NullPointerException
02-21 11:21:06.156: E/AndroidRuntime(30769):    at com.this.app.HistoryAdapter.getView(HistoryAdapter.java:60)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.AbsListView.obtainView(AbsListView.java:2263)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.ListView.makeAndAddView(ListView.java:1790)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.ListView.fillDown(ListView.java:691)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.ListView.fillFromTop(ListView.java:752)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.ListView.layoutChildren(ListView.java:1630)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.AbsListView.onLayout(AbsListView.java:2091)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.View.layout(View.java:14825)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewGroup.layout(ViewGroup.java:4641)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.View.layout(View.java:14825)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewGroup.layout(ViewGroup.java:4641)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.View.layout(View.java:14825)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewGroup.layout(ViewGroup.java:4641)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.View.layout(View.java:14825)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewGroup.layout(ViewGroup.java:4641)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.View.layout(View.java:14825)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewGroup.layout(ViewGroup.java:4641)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2016)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1773)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1022)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5708)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.Choreographer.doFrame(Choreographer.java:532)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.os.Handler.handleCallback(Handler.java:733)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.os.Handler.dispatchMessage(Handler.java:95)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.os.Looper.loop(Looper.java:137)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at android.app.ActivityThread.main(ActivityThread.java:5083)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at java.lang.reflect.Method.invokeNative(Native Method)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at java.lang.reflect.Method.invoke(Method.java:515)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
02-21 11:21:06.156: E/AndroidRuntime(30769):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

看起来是通话：view.findViewById(R.id.pricePerGallon)正在返回null。您确定pricePerGallon在项目中应该存在吗？

Answer 2

确保您拥有ID

R.id.pricePerGallon

XML中的

layout.history_list_item

如果您说该字符串不为null，则会离开TextView。

我的CustomAdapter中的NullPointerException

2 个答案: