Question

我的代码有些麻烦，我一定错过了什么。这是我的代码。我正在尝试使用一个listview窗口为用户构建一个简单的片段应用程序。而我似乎无法做到这一点。

public class MainActivity extends Activity {

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

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

activity_main.xml中

<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="com.example.shoppinglist.MainActivity" >
<fragment
android:name="com.example.shoppinglist.CartList"
android:id="@+id/fragment1"
android:layout_width="0px"
android:layout_height="match_parent" />

</RelativeLayout>

购物清单代码

public class CartList extends ListFragment{
MyArray ma;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    /*
    // Create the adapter to convert the array to views


    User newUser = new User("Nathan", "San Diego");
    adapter.add(newUser);*/
    ArrayList<User> arrayOfUsers = new ArrayList<User>();
    UsersAdapter adapter = new UsersAdapter(getActivity(), arrayOfUsers);
        ListView listView = (ListView)         getView().findViewById(R.id.CartListView);
    listView.setAdapter(adapter);
 }

cartlist.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ListView
    android:id="@+id/CartListView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
</ListView>

UsersAdapter代码

public class UsersAdapter extends ArrayAdapter<User> {
// View lookup cache
private static class ViewHolder {
    TextView name;
    TextView home;
}

public UsersAdapter(Context context, ArrayList<User> users) {
   super(context, R.layout.item_user, users);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
   // Get the data item for this position
   User user = getItem(position);    
   // Check if an existing view is being reused, otherwise inflate the view
   ViewHolder viewHolder; // view lookup cache stored in tag
   if (convertView == null) {
      viewHolder = new ViewHolder();
      LayoutInflater inflater = LayoutInflater.from(getContext());
      convertView = inflater.inflate(R.layout.item_user, parent, false);
      viewHolder.name = (TextView) convertView.findViewById(R.id.tvName);
      viewHolder.home = (TextView) convertView.findViewById(R.id.tvHome);
      convertView.setTag(viewHolder);
   } else {
       viewHolder = (ViewHolder) convertView.getTag();
   }
   // Populate the data into the template view using the data object
   viewHolder.name.setText(user.name);
   viewHolder.home.setText(user.hometown);
   // Return the completed view to render on screen
   return convertView;


public class User {
public String name;
public String hometown;

public User(String name, String hometown) {
   this.name = name;
   this.hometown = hometown;
}

我得到了这个致命的例外

FATAL EXCEPTION: main
 02-25 00:39:00.237: E/AndroidRuntime(1912): Process:   com.example.shoppinglist, PID: 1912
 02-25 00:39:00.237: E/AndroidRuntime(1912): java.lang.RuntimeException: Unable  to start activity     ComponentInfo{com.example.shoppinglist/com.example.shoppinglist.MainActivity}: android.view.InflateException: Binary XML file line #10: Error inflating class fragment
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread.access$800(ActivityThread.java:144)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.os.Handler.dispatchMessage(Handler.java:102)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.os.Looper.loop(Looper.java:135)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread.main(ActivityThread.java:5221)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at java.lang.reflect.Method.invoke(Native Method)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at java.lang.reflect.Method.invoke(Method.java:372)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 02-25 00:39:00.237: E/AndroidRuntime(1912): Caused by: android.view.InflateException: Binary XML file line #10: Error inflating class fragment
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at    android.view.LayoutInflater.inflate(LayoutInflater.java:414)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.Activity.setContentView(Activity.java:2144)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at com.example.shoppinglist.MainActivity.onCreate(MainActivity.java:13)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.Activity.performCreate(Activity.java:5933)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    ... 10 more
 02-25 00:39:00.237: E/AndroidRuntime(1912): Caused by:   java.lang.NullPointerException: Attempt to invoke virtual method '    android.view.View android.view.View.findViewById(int)' on a null object reference
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at com.example.shoppinglist.CartList.onCreate(CartList.java:25)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.Fragment.performCreate(Fragment.java:2031)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:863)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1045)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1147)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2116)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at android.app.Activity.onCreateView(Activity.java:5282)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    at       android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
 02-25 00:39:00.237: E/AndroidRuntime(1912):    ... 20 more`

Answer 1

更改

android:name="com.example.shoppinglist.CartList"

要

class="com.example.shoppinglist.CartList"

确保您的活动正在扩展FragmentActivity而不是Activity

还要确保您的arraylist不为空。以这种方式添加项目

ArrayList<User> arrayOfUsers = new ArrayList<User>();
User newUser = new User("Nathan", "San Diego");
arrayOfUsers.add(newUser);

加载我的Listfragment Android时出现致命异常

1 个答案: