我创建了一个spinner但它不工作，我用选项卡创建了它，单击选项卡图标时我想获取下拉列表，但现在单击图标时应用程序突然关闭，说带有空指针的错误例外我确定我错过了一些愚蠢的东西！我在下面给出了我的 logcat 和 java 类，我需要建议来清除错误。
08-27 04:59:49.423: E/AndroidRuntime(1011): FATAL EXCEPTION: main
08-27 04:59:49.423: E/AndroidRuntime(1011): java.lang.RuntimeException: Unable to start
activity ComponentInfo{com.neochat/com.neochat.ComposeActivity}:
java.lang.NullPointerException
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.ActivityThread.startActivityNow(ActivityThread.java:2023)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:749)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.widget.TabHost.setCurrentTab(TabHost.java:413)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:154)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:546)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.view.View.performClick(View.java:4204)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.view.View$PerformClick.run(View.java:17355)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.os.Handler.handleCallback(Handler.java:725)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.os.Handler.dispatchMessage(Handler.java:92)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.os.Looper.loop(Looper.java:137)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.ActivityThread.main(ActivityThread.java:5041)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
java.lang.reflect.Method.invokeNative(Native Method)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
java.lang.reflect.Method.invoke(Method.java:511)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
dalvik.system.NativeStart.main(Native Method)
08-27 04:59:49.423: E/AndroidRuntime(1011): Caused by: java.lang.NullPointerException
08-27 04:59:49.423: E/AndroidRuntime(1011): at
com.neochat.ComposeActivity.onCreate(ComposeActivity.java:29)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.Activity.performCreate(Activity.java:5104)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
08-27 04:59:49.423: E/AndroidRuntime(1011): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
08-27 04:59:49.423: E/AndroidRuntime(1011): ... 18 more
ComposeActivity.java
public class ComposeActivity extends Activity {
/** An array of strings to populate dropdown list */
String[] actions = new String[] {
"Bookmark",
"Subscribe",
"Share"
};
Context context;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.extrasettings);
Spinner mySpinner= (Spinner) findViewById(R.id.spinner1);
context=this;
/** Create an array adapter to populate dropdownlist */
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, actions);
/** Enabling dropdown list navigation for the action bar */
getActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
/** Defining Navigation listener */
ActionBar.OnNavigationListener navigationListener = new
OnNavigationListener() {
@Override
public boolean onNavigationItemSelected(int itemPosition, long itemId) {
Toast.makeText(getBaseContext(), "You selected : " + actions[itemPosition]
, Toast.LENGTH_SHORT).show();
return false;
}
};
/** Setting dropdown items and item navigation listener for the actionbar */
getActionBar().setListNavigationCallbacks(adapter, navigationListener);
}
}
我在其中添加了微调器的 XML 文件
<?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"
>
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
我在我的应用程序上使用了一个简单的选项卡选项而不是操作栏，所以有什么问题....对不起，我想将微调器添加到我的选项卡主机，所以有人可以告诉我我应该在代码中进行哪些更改吗？