尝试在 android 中添加两个 setContentView 时出现空指针异常

我正在创建一个自定义列表视图，其中我的列表视图 xml 是关键字列表 .我也正在使用教程 http://mtmurdockblog.com/2011/10/17/navigation-bar-for-android/以编程方式创建自定义导航栏。因为有两个setContentView()一个用于 ListView xml，另一个用于导航栏.我得到异常，你们能帮我一下吗下面是代码。

public class KeywordListView extends Activity{
public LinkedList<String> mListItems;
KeyWordAdapter keywordAdapter;
ProgressDialog  progressDialog=null;
Runnable updateRunnable;    
public static String email;
Button btnSettings;
Button btnAddKeyWord;
static ListView lv;
public final Handler myHandler = new Handler();
static ArrayAdapter<String> arrayAdapter;
public static List<KeyWordDetails>responseArray;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.keywordlist);
LinearLayout ll = new LinearLayout(this);
NavigationBar nb = new NavigationBar(this);
nb.setLeftBarButton("Back");
nb.setRightBarButton("Menu");
nb.setBarTitle("The Bar Title");
NavigationBar.NavigationBarListener nbl = new NavigationBar.NavigationBarListener() {
    @Override
    public void OnNavigationButtonClick(int which) {
        // TODO Auto-generated method stub  
    }
};
nb.setNavigationBarListener(nbl);
ll.addView(nb);
setContentView(ll);

错误日志：-

12-04 13:17:49.780: E/AndroidRuntime(1533): FATAL EXCEPTION: main
   12-04 13:17:49.780: E/AndroidRuntime(1533): java.lang.RuntimeException: Unable to start  
   activity ComponentInfo{com.example.shortcode/com.example.shortcode.KeywordListView}:   java.lang.NullPointerException
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.os.Looper.loop(Looper.java:123)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread.main(ActivityThread.java:3683)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at java.lang.reflect.Method.invokeNative(Native Method)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at java.lang.reflect.Method.invoke(Method.java:507)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at dalvik.system.NativeStart.main(Native Method)
12-04 13:17:49.780: E/AndroidRuntime(1533): Caused by: java.lang.NullPointerException
12-04 13:17:49.780: E/AndroidRuntime(1533):     at com.example.shortcode.KeywordListView.onCreate(KeywordListView.java:111)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-04 13:17:49.780: E/AndroidRuntime(1533):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)

我说避免调用setContentView两次。如果这样做，第一个将被覆盖。这可能是您收到异常的原因。尝试创建一个 xml 布局文件，并在其中定义所需的所有视图。

再次检查教程，他只使用过一次setContentView。ll.addView（nb）;setContentView（ll）;您应该在列表视图中加载关键字，然后在列表视图中添加导航栏li.addView（navigationBar）;

或

您可以使用 XML 进行导航，然后可以在该 naviation 栏下方添加一个列表视图。之后，以编程方式在列表视图中加载关键字。我已经做了这样的观点，检查这个

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:weightSum="100" >
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="9"
                    android:background="@drawable/header" >
        <ImageView
            android:id="@+id/imageViewHome"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_gravity="center"
            android:layout_marginBottom="5dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="5dp"
            android:scaleType="fitCenter"
            android:src="@drawable/home" />
        <TextView
            android:id="@+id/textViewTitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:layout_gravity="center_vertical|center_horizontal"
            android:text="Groups"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:textColor="@android:color/white"
            android:textStyle="bold" />
        <ImageView
            android:id="@+id/imageViewCreate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_marginRight="5dp"
            android:layout_toLeftOf="@+id/imageViewDelete"
            android:src="@drawable/add" />
        <ImageView
            android:id="@+id/imageViewDelete"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            android:layout_gravity="center_vertical"
            android:layout_marginRight="5dp"
            android:scaleType="fitXY"
            android:src="@drawable/delete" />
    </RelativeLayout>
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="9"
        android:background="@drawable/bg_gradient_grey" >
        <EditText
            android:id="@+id/editTextSearch"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_marginBottom="5dp"
            android:layout_marginLeft="15dp"
            android:layout_marginRight="15dp"
            android:layout_marginTop="5dp"
            android:background="@drawable/rounded_edges"
            android:ellipsize="end"
            android:ems="15"
            android:hint="Search"
            android:singleLine="true"
            android:textSize="15dp" >
            <requestFocus />
        </EditText>
        <ImageButton
            android:id="@+id/imageButtonSearch"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:layout_alignWithParentIfMissing="true"
            android:layout_centerInParent="false"
            android:layout_centerVertical="true"
            android:layout_gravity="center"
            android:layout_marginRight="25dp"
            android:background="@null"
            android:src="@drawable/ic_action_search" />
    </RelativeLayout>
    <ListView
        android:id="@+id/groupsList"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="82"
        android:background="@android:color/white"
        android:cacheColorHint="#00000000" >
    </ListView>
</LinearLayout>

你在哪里扩展超类Activity？ onCreate（）是此类中的一个方法，您可以覆盖它，请参阅 http://developer.android.com/reference/android/app/Activity.html

相关内容

最新更新

热门标签：