Question

这是我的第一个Android应用程序，我遇到了一些问题。我想在teste_menu.xml中使用menu_item.xml作为Fragment，但我不知道我做错了什么。

E/AndroidRuntime: FATAL EXCEPTION: main
     Process: com.example.nunog.myapplication12, PID: 5342
     java.lang.NullPointerException
         at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:392)
         at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
         at android.widget.AbsListView.obtainView(AbsListView.java:2743)
         at android.widget.ListView.makeAndAddView(ListView.java:1811)
         at android.widget.ListView.fillDown(ListView.java:697)
         at android.widget.ListView.fillFromTop(ListView.java:763)
         at android.widget.ListView.layoutChildren(ListView.java:1641)
         at android.widget.AbsListView.onLayout(AbsListView.java:2564)
         at android.view.View.layout(View.java:15749)
         at android.view.ViewGroup.layout(ViewGroup.java:4880)
         at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
         at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
         at android.view.View.layout(View.java:15749)
         at android.view.ViewGroup.layout(ViewGroup.java:4880)
         at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1677)
         at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1531)
         at android.widget.LinearLayout.onLayout(LinearLayout.java:1440)
         at android.view.View.layout(View.java:15749)
         at android.view.ViewGroup.layout(ViewGroup.java:4880)
         at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
         at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
         at android.view.View.layout(View.java:15749)
         at android.view.ViewGroup.layout(ViewGroup.java:4880)
         at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2358)
         at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2071)
         at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1256)
         at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6635)
         at android.view.Choreographer$CallbackRecord.run(Choreographer.java:813)
         at android.view.Choreographer.doCallbacks(Choreographer.java:613)
         at android.view.Choreographer.doFrame(Choreographer.java:583)
         at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:799)
         at android.os.Handler.handleCallback(Handler.java:733)
         at android.os.Handler.dispatchMessage(Handler.java:95)
         at android.os.Looper.loop(Looper.java:146)
         at android.app.ActivityThread.main(ActivityThread.java:5593)
         at java.lang.reflect.Method.invokeNative(Native Method)
         at java.lang.reflect.Method.invoke(Method.java:515)
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
         at dalvik.system.NativeStart.main(Native Method)

Menu.class

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class Menu extends ListActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // storing string resources into Array
        String[] menu_entries = getResources().getStringArray(R.array.menu_options);

        // Binding resources Array to ListAdapter
        this.setListAdapter(new ArrayAdapter<String>(this, R.layout.teste_menu, R.id.label, menu_entries));

        ListView lv = getListView();

        // listening to single list item on click
        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {

                // selected item
                String product = ((TextView) view).getText().toString();

                // Launching new Activity on selecting single List Item
                Intent i = new Intent(getApplicationContext(), SingleListItem.class);
                // sending data to new activity
                i.putExtra("product", product);
                startActivity(i);

            }
        });
    }
}

MenuItemFragment.class

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MenuItemFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.menu_item, container, false);
        return view;
    }
}

teste_menu.XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    android:weightSum="1">

    <fragment
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:name="com.example.nunog.myapplication12.MenuItemFragment"
        android:id="@+id/fragment2"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        tools:layout="@layout/menu_item" />
</RelativeLayout>

menu_item.XML

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/label"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#670000"
    android:textColor="#ffffff"
    android:padding="25dip"
    android:textSize="30sp"
    android:textStyle="bold">
</TextView>

Answer 1

在Fragment使用的布局中使用ListView没有意义。

另外，当您查看正在使用的ArrayAdapter构造函数的文档时，第二个参数是要使用的布局文件的id，第三个参数是TextView内的teste_menu的id第二个参数中指定的相同布局文件。布局文件TextView没有label，标识为TextView。

由于您要使用的布局文件中只有this.setListAdapter(new ArrayAdapter<String>(this, R.layout.menu_item, menu_entries));，因此您可以使用不同的构造函数，如下所示，它将起作用：

left.png

我尝试在Android

1 个答案: