Question

我似乎已经使用我的自定义ArrayAdapter撞墙了。我开始访问特定的R元素，具体取决于传入的类类型，但从那以后BOOM！（以下NPE）。麻烦的是，它没有列出我的任何代码，而且我有点失明。我知道这是我的代码，因为注释掉setListAdapter（以及其他位），运行正常。我只是不知道我做了什么。

我现在只测试ArrayAdapter，因此for循环创建对象。但至少我知道那些不是空的，因为我尽可能地完成了代码。

非常感谢任何帮助。我很确定我做了一些愚蠢的事情，但现在已经过了一个小时，而且我已经失去了密码！

非常感谢。

PS。我已经检查了其他问题，但大多数问题似乎是关于发送的空对象，或者没有正确创建布局或实例化的人。我看起来完全不同，因为LogCat没有显示任何指向我代码的链接：（

logcat的：

11-19 13:12:44.968: E/AndroidRuntime(7406): FATAL EXCEPTION: main
11-19 13:12:44.968: E/AndroidRuntime(7406): java.lang.NullPointerException
11-19 13:12:44.968: E/AndroidRuntime(7406):     at  android.widget.AbsListView.obtainView(AbsListView.java:1454)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.ListView.makeAndAddView(ListView.java:1745)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.ListView.fillDown(ListView.java:670)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.ListView.fillFromTop(ListView.java:727)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.ListView.layoutChildren(ListView.java:1598)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.AbsListView.onLayout(AbsListView.java:1282)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.view.View.layout(View.java:7175)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.view.View.layout(View.java:7175)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.view.View.layout(View.java:7175)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.os.Looper.loop(Looper.java:130)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at android.app.ActivityThread.main(ActivityThread.java:3683)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at java.lang.reflect.Method.invokeNative(Native Method)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at java.lang.reflect.Method.invoke(Method.java:507)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-19 13:12:44.968: E/AndroidRuntime(7406):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
11-19 13:12:44.968: E/AndroidRuntime(7406):     at dalvik.system.NativeStart.main(Native Method)

ListActivity：

package com.goosesys.dta_pta_test;

import com.goosesys.gooselib.Views.GooseArrayAdapter;
import com.goosesys.gooselib.Views.GooseDeliveryItem;
import com.goosesys.gooselib.Interfaces.*;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.ListView;
import android.widget.Toast;

public class DeliveryList extends ListActivity implements OnTaskFinished {
public String response = "";

static String[] vals;
static String[] vals2;

@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE); 

    populate();
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id){
    String selectedValue = (String)getListAdapter().getItem(position);
    Toast.makeText(this, selectedValue, Toast.LENGTH_LONG).show();
}

private void populate(){
    //new GetFromNetTask(this).execute(AppSettings.DELIV_LIST_URL);
    GooseDeliveryItem[] deliveries = new GooseDeliveryItem[50];

    for(int i=0; i<50; i++){
        GooseDeliveryItem gdi = new GooseDeliveryItem(i, "Some Customer " + String.valueOf(i));
        deliveries[i] = gdi;
    }

    setListAdapter(new GooseArrayAdapter<Object>(this, R.layout.goose_delivery_item, deliveries));
    ListView listView = getListView();
    listView.setTextFilterEnabled(true);

    // on click stuff here

}

@Override
public void onTaskFinished(String result) {
}
}

ArrayAdapter：

package com.goosesys.gooselib.Views;

import com.goosesys.gooselib.R;

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

public class GooseArrayAdapter<T> extends ArrayAdapter<T> {
private Context context;
private int layoutResId;
T data[] = null;

public GooseArrayAdapter(Context context, int layoutResId, T[] data){
    super(context, layoutResId, data);

    this.layoutResId = layoutResId;
    this.context = context;
    this.data = data;
}

@Override
public View getView(int position, View convertView, ViewGroup parent){
    LayoutInflater inflater = (LayoutInflater)this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View rowView = inflater.inflate(this.layoutResId, parent, false);           

    T obj = data[position];

    //if(obj instanceof GooseDeliveryItem){
        //TextView tv = (TextView)rowView.findViewById(R.id.customerName);
        //tv.setText(((GooseDeliveryItem)obj).customerText);
    //}

    return convertView;
}   
}

我如何从主要活动中调用Intent：

    GooseMenuItem gmi2 = (GooseMenuItem)findViewById(R.id.gmiDelivery);
    gmi2.setHeaderText("DELIVERIES");
    gmi2.setDescriptionText("Out and about");
    gmi2.setButtonImageSrc(getResources().getDrawable(R.drawable.truck));
    gmi2.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(Main.this, DeliveryList.class);
            startActivity(i);
        }
    });

可怕的goose_delivery_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/mainContainer"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/White"
android:orientation="horizontal" >

<TableLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true" >

    <TableRow
        android:id="@+id/tableRow1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <ImageView
            android:id="@+id/listImage"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:maxHeight="40dp"
            android:maxWidth="40dp"
            android:padding="2dp"
            android:scaleType="fitCenter"
            android:src="@drawable/truck" />

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="match_parent" >

            <TextView
                android:id="@+id/customerName"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:text="CUSTOMER NAME/ADDRESS"
                android:textAppearance="?android:attr/textAppearanceSmall"
                android:textColor="@color/black" />

        </LinearLayout>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="left"
            android:orientation="vertical" >

            <ImageView
                android:id="@+id/mapPointImage"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="3dp"
                android:scaleType="centerInside"
                android:src="@drawable/mappoint" />

        </LinearLayout>

    </TableRow>
</TableLayout>

</RelativeLayout>

Answer 1

尝试将getView更改为：

@Override
public View getView(int position, View convertView, ViewGroup parent){
LayoutInflater inflater = (LayoutInflater)this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(this.layoutResId, parent, false);           

T obj = data[position];

//if(obj instanceof GooseDeliveryItem){
    //TextView tv = (TextView)rowView.findViewById(R.id.customerName);
    //tv.setText(((GooseDeliveryItem)obj).customerText);
//}

return rowView ;
}

返回rowView而不是convertView，因为永远不会分配convertView

Answer 2

您的getView函数返回null，因为除了传递的参数之外，您永远不会返回任何内容。最初convertView将为null，您需要初始化它。之后，如果它不为null，您可以简单地重复使用它。

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ...
    if (convertView == null) {
        convertView = ... // Create you view here
    }

    return convertView;
}

调用setListAdapter（）时自定义ArrayAdapter NullPointerException

2 个答案: