Question

我必须通过在android中使用arrayadapter将项目添加到listview，这样就完成了编码，如果我运行项目，应用程序会强行关闭，甚至已经在清单中提到了这个活动，但仍然找不到崩溃的确切原因

public class Jobs extends ListActivity {
 private TextView selection;

private static final String[] items={"Computer Hardware", "Featured", "Information    Technology", "Software", "Technical"

 };
 @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.jobs);
    selection = (TextView)findViewById(R.id.selection);
    ListView list = (ListView)findViewById(android.R.id.list);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            R.layout.jobs, items);
        setListAdapter(adapter);    


  }
public void onListItemClick(ListView parent, View v, int position, long id)
{
    selection.setText(items[position]);
}
 }

的Manifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.rebuix.com"
 android:versionCode="1"
 android:versionName="1.0" >

<uses-sdk
android:minSdkVersion="9"
android:targetSdkVersion="15" />

<uses-permission android:name="android.permission.INTERNET" />

 <application
android:icon="@drawable/rebuix"
android:label="@string/app_name"
android:theme="@style/AppTheme" 
android:background="#3D0909">
<activity
    android:name=".LoadingScreen"
    android:label="@string/title_activity_loading_screen" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<activity
    android:name=".Rebuix"
    android:label="@string/title_activity_rebuix" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.rebuix.com.Rebuix" />
</activity>
<activity
    android:name=".com.rebuix.com.Jobs"
    android:label="@string/app_name" >

</activity>
<activity
    android:name=".Login"
    android:label="@string/title_activity_login" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.rebuix.com.Rebuix" />
</activity>
<activity
    android:name=".About"
    android:label="@string/title_activity_about" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="android.support.v4.app.FragmentActivity" />
</activity>
<activity
    android:name=".Home"
    android:label="@string/title_activity_home" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="android.support.v4.app.FragmentActivity" />
</activity>
<activity
    android:name=".Changepassword"
    android:label="@string/title_activity_changepassword" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="android.support.v4.app.FragmentActivity" />
</activity>

堆栈跟踪

01-31 12:31:53.133: I/Tutorial(531): Starting task with url: www.google.co.uk
 01-31 12:32:03.972: D/dalvikvm(531): GC_EXTERNAL_ALLOC freed 64K, 52% free  2595K/5379K, external 1645K/2137K, paused 52ms
  01-31 12:32:04.102: D/dalvikvm(531): GC_EXTERNAL_ALLOC freed 2K, 52% free 2594K/5379K, external 2687K/3355K, paused 45ms
  01-31 12:32:08.083: D/AndroidRuntime(531): Shutting down VM
   01-31 12:32:08.083: W/dalvikvm(531): threadid=1: thread exiting with uncaught exc eption (group=0x40015560)
   01-31 12:32:08.103: E/AndroidRuntime(531): FATAL EXCEPTION: main
  01-31 12:32:08.103: E/AndroidRuntime(531): android.content.ActivityNotFoundException: Unable to find explicit activity class {com.exm.com/com.exm.com.Jobs}; have you declared this activity in your AndroidManifest.xml?
  01-31 12:32:08.103: E/AndroidRuntime(531):  at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1405)
 01-31 12:32:08.103: E/AndroidRuntime(531):  at android.app.Instrumentation.execStartActivity(Instrumentation.java:1379)
 01-31 12:32:08.103: E/AndroidRuntime(531):  at android.app.Activity.startActivityForResult(Activity.java:2827)
  01-31 12:32:08.103: E/AndroidRuntime(531):  at android.app.Activity.startActivity(Activity.java:2933)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at com.rebuix.com.Rebuix$4.onClick(Rebuix.java:69)
  01-31 12:32:08.103: E/AndroidRuntime(531):  at android.view.View.performClick(View.java:2485)
  01-31 12:32:08.103: E/AndroidRuntime(531):  at android.view.View$PerformClick.run(View.java:9080)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at android.os.Handler.handleCallback(Handler.java:587)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at android.os.Handler.dispatchMessage(Handler.java:92)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at android.os.Looper.loop(Looper.java:123)
   01-31 12:32:08.103: E/AndroidRuntime(531):     at android.app.ActivityThread.main(ActivityThread.java:3683)
   01-31 12:32:08.103: E/AndroidRuntime(531):     at  java.lang.reflect.Method.invokeNative(Native Method)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at java.lang.reflect.Method.invoke(Method.java:507)
   01-31 12:32:08.103: E/AndroidRuntime(531):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    01-31 12:32:08.103: E/AndroidRuntime(531):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    01-31 12:32:08.103: E/AndroidRuntime(531):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

您必须在textview初始化onCreate()。

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.jobs);
ListView list = (ListView)findViewById(R.id.list);

selection = (TextView)findViewById(R.id.selection);

}

Answer 2

在ListActivity中，您不需要在您的Activity.It中自动从您的xml中获取ListView。您只需要为列表视图提供一个已定义的ID，即android：id =“@ android：id / list”，并且在适配器中也是如此你给了一个预定义的id。你可以写这样的程序：

jobs.xml

   <?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
  <ListView
    android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:clickable="true"
     />
   <TextView android:id="@+id/textSelected"
     android:layout_alignParentBottom="true"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
      />
    </RelativeLayout>

并在您的活动中：

  private TextView selection;

    private static final String[] items={"Computer Hardware", "Featured", "Information    Technology", "Software", "Technical"

     };
     @Override
     public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.jobs);
    selection=(TextView)findViewById(R.id.textSelected);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, items);
        setListAdapter(adapter);    


      }
     @Override
     public void onListItemClick(ListView parent, View v, int position, long                 id)
     {
    selection.setText(items[position]);
      }
  }

希望这会解决你的问题。

Answer 3

您现在没有初始化您正在使用的包含null的选择。所以你得到了NPE。

public void onListItemClick(ListView parent, View v, int position, long id)
{
    >>>>selection.setText(items[position]);
}

试试这个。

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.jobs);
    selection = (TextView)findViewById(R.id.selection);  //Write this
    //Rest of code
}

Answer 4

public class Jobs extends ListActivity {
 private TextView selection;

private static final String[] items={"Computer Hardware", "Featured", "Information    Technology", "Software", "Technical"

 };
 @Override
 public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.jobs);
ListView listView = getListView(); //use defailt listview of android
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
        android.R.layout.jobs, items);
    setListAdapter(adapter);    


  }
  public void onListItemClick(ListView parent, View v, int position, long id)
 {
selection.setText(items[position]);
  }
  }

使用列表活动时，您应该使用默认列表...而不是自定义列表名称

在向android中的listview添加项目时，应用程序崩溃

4 个答案: