使用阵列适配器填充列表视图

Question

我正在尝试使用数组适配器填充列表。 我有3个类，Bike，CustomAdapter和UseCustomAdapter。 我有一个例子，我一直在通过比较它与我的例子，似乎无法弄清楚为什么它不运行！ 只是说，每次尝试加载它时，它都停止工作了。 这是代码：

Bike.java

package com.example.tasktwo;

public class Bike {

    private String title;
    private String imageName;


    //Constructor
    Bike (String title,  String imageName) {
        this.title= title;
        this.imageName = imageName;
    }

    public void setTitle(String title){
        this.title = title;
    }

    public void setImage(String imageName){
        this.imageName = imageName;
    }   

    public String getBikeTitle(){
        return title;
    }

    public String getBikeImageName(){
        return imageName;
    }
}

CustomerAdapter.java

public class CustomAdapter extends ArrayAdapter<Bike>  {
    private final Context context;
    //List of Walk Objects
    private ArrayList<Bike> bikes;

    //Receives the context and the list of walk objects
    public CustomAdapter  (Context context, ArrayList<Bike> bikes) {
        super(context, R.layout.bike_view, bikes);
        this.context = context; 
        this.bikes = bikes;
    }

    @SuppressLint("ViewHolder")
    public View getView(int position, View convertView, ViewGroup parent) {
        Bike bike = bikes.get(position);
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View rowView = inflater.inflate(R.layout.bike_view, parent, false);
        TextView textView = (TextView) rowView.findViewById(R.id.bike_names);
        textView.setText(bike.getBikeTitle());      
        ImageView imageView = (ImageView) rowView.findViewById(R.id.bike_image);
        Resources res = context.getResources();
        int imageId = res.getIdentifier(bike.getBikeImageName(), "drawable", "com.example.tasktwo");
        imageView.setImageResource(imageId);
        return rowView;
    }
}

UseCustomerAdapter.java

package com.example.tasktwo;

public class UseCustomAdapter extends ListActivity {

    ArrayList<Bike> bikes = new ArrayList<Bike>();

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); 
        bikes.add(new Bike("Honda", "honda"));
        bikes.add(new Bike("Suzuki", "suzuki"));
        bikes.add(new Bike("Kawasaki", "kawasaki"));
        bikes.add(new Bike("KTM", "ktm"));
        CustomAdapter adapter = new CustomAdapter(this, bikes);
        setListAdapter(adapter);
    }

    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Bike b = bikes.get(position);
        Toast.makeText(this,"You selected the " + b.getBikeTitle()
                        + "Motocross Bike",Toast.LENGTH_SHORT).show();
    }
}

logcat的：

03-10 14:34:53.240: E/AndroidRuntime(1009): FATAL EXCEPTION: main
03-10 14:34:53.240: E/AndroidRuntime(1009): Process: com.example.tasktwo, PID: 1009
03-10 14:34:53.240: E/AndroidRuntime(1009): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tasktwo/com.example.tasktwo.BikeList}: java.lang.NullPointerException
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.os.Handler.dispatchMessage(Handler.java:102)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.os.Looper.loop(Looper.java:136)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread.main(ActivityThread.java:5017)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at java.lang.reflect.Method.invokeNative(Native Method)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at java.lang.reflect.Method.invoke(Method.java:515)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at dalvik.system.NativeStart.main(Native Method)
03-10 14:34:53.240: E/AndroidRuntime(1009): Caused by: java.lang.NullPointerException
03-10 14:34:53.240: E/AndroidRuntime(1009):     at com.example.tasktwo.BikeList.onCreate(BikeList.java:20)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.Activity.performCreate(Activity.java:5231)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-10 14:34:53.240: E/AndroidRuntime(1009):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-10 14:34:53.240: E/AndroidRuntime(1009):     ... 11 more

AndroidManifest.xml中

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.tasktwo"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="19"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".BikeList"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

根据您的回答，我认为这是解决方案。

<activity android:name=".MainActivity" >
</activity>

请注意，名称为MainActivity ，这是默认名称。 此名称取决于您的主要Activity类的名称。 因此，将其设置为任何类名。 Android Studio或Eclipse的问题在于，当您开始更改项目名称时，所有引用均未正确更改。