java - 在android java中从XML填充ListView

Question

public class MainActivity extends Activity {

ArrayList <String> cars;
ListView list;
ArrayAdapter <String> adapter;

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

    populateListView();

}

private void populateListView() {
    if(!checkForCars()){

    } else{
    list = (ListView) findViewById(R.id.listView1);
    adapter = new ArrayAdapter <String>(this, R.layout.carprofileview, cars);
    list.setAdapter(adapter);

    }
}

private boolean checkForCars() {

    if(getNodeValue().size() > 0){
        return true;
    }
    return false;

}

private ArrayList getNodeValue(){

    try {
     DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = domFactory.newDocumentBuilder();
        Document dDoc = builder.parse("raw/cars.xml");

        XPath xPath = XPathFactory.newInstance().newXPath();

        NodeList make = (NodeList) xPath.evaluate("//carMake//text()", dDoc, XPathConstants.NODE);
        NodeList model = (NodeList) xPath.evaluate("//carModel//text()", dDoc, XPathConstants.NODE);

        String car;

        for(int i=0; i< make.getLength(); i++){
         for(int j=0; j< model.getLength(); j++){
             car = make.item(i).getNodeValue() + " " + model.item(j).getNodeValue();
             cars.add(car);
            } 
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return cars;
    }
}

这是我的java类(class)。以下 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="Choose a profile"
    android:textSize="25dp" />

<Button
    android:id="@+id/bCreateCar"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/textView1"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="46dp"
    android:text="Create a new car profile" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/bCreateCar"
    android:layout_below="@+id/bCreateCar"
    android:layout_marginTop="25dp"
    android:text="Choose car profile"
    android:textSize="15dp"/>

<ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/textView2"
    android:layout_below="@+id/textView2"
    android:layout_marginTop="32dp" >
</ListView>

我正在尝试解析 XML 文档和放入 ArrayList 中的值，然后在 ListView 中预览 ArrayList 项目，但出现很多错误。有人可以告诉我我做错了什么吗？

R.layout.carproileview

    <?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="schemas.android.com/apk/res/android"; android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" android:gravity="center"> 
<TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Large Text" android:textAppearance="?android:attr/textAppearanceLarge" /> 
</LinearLayout>    

Answer 1

您尚未初始化 ArrayList ArrayList <String> cars;

如下所示

cars = new ArrayList<String>();