每当我运行我的应用程序时,第一次从Eclipse运行它运行正常。但是,如果我关闭应用程序并重新打开它,它将在onCreate上崩溃。这是LogCat:
10-10 02:50:00.665: E/AndroidRuntime(29564): FATAL EXCEPTION: main
10-10 02:50:00.665: E/AndroidRuntime(29564): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.appuccino.unitconverter/com.appuccino.unitconverter.MainActivity}: java.lang.NullPointerException
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread.access$600(ActivityThread.java:140)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.os.Handler.dispatchMessage(Handler.java:99)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.os.Looper.loop(Looper.java:137)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread.main(ActivityThread.java:4898)
10-10 02:50:00.665: E/AndroidRuntime(29564): at java.lang.reflect.Method.invokeNative(Native Method)
10-10 02:50:00.665: E/AndroidRuntime(29564): at java.lang.reflect.Method.invoke(Method.java:511)
10-10 02:50:00.665: E/AndroidRuntime(29564): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1008)
10-10 02:50:00.665: E/AndroidRuntime(29564): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:775)
10-10 02:50:00.665: E/AndroidRuntime(29564): at dalvik.system.NativeStart.main(Native Method)
10-10 02:50:00.665: E/AndroidRuntime(29564): Caused by: java.lang.NullPointerException
10-10 02:50:00.665: E/AndroidRuntime(29564): at com.appuccino.unitconverter.MainActivity.onCreate(MainActivity.java:37)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.Activity.performCreate(Activity.java:5206)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
10-10 02:50:00.665: E/AndroidRuntime(29564): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
10-10 02:50:00.665: E/AndroidRuntime(29564): ... 11 more
我的mainActivity的第一部分:
public class MainActivity extends FragmentActivity implements
OnItemSelectedListener {
/**
* The serialization (saved instance state) Bundle key representing the
* current dropdown position.
*/
private static final String STATE_SELECTED_NAVIGATION_ITEM = "selected_navigation_item";
private Spinner firstSpinner;
private Spinner secondSpinner;
final String[] mainCategoryChoices = {"Acceleration", "Angles", "Area", "Astronomical", "Clothing", "Computers and Electronics", "Cooking", "Date/Time", "Density", "Energy"};
final String[] subCategoryChoices = {"Acre", "Barn", "Bunder", "Hundred", "Jerib", "Kappland", "Labor", "Ping", "Rai", "Shed", "Sitio", "Square", "Square Mile", "Square Yard"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().requestFeature(Window.FEATURE_ACTION_BAR); //not necessary
setContentView(R.layout.activity_main);
ArrayAdapter<String> firstAdapter = new ArrayAdapter<String>(
MainActivity.this, android.R.layout.simple_dropdown_item_1line,
mainCategoryChoices);
ArrayAdapter<String> secondAdapter = new ArrayAdapter<String>(
MainActivity.this, android.R.layout.simple_dropdown_item_1line,
subCategoryChoices);
final ActionBar actionBar = getActionBar();
if(actionBar != null)
{
actionBar.setCustomView(R.layout.action_bar_custom);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayShowCustomEnabled(true);
actionBar.setDisplayUseLogoEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
}
firstSpinner = (Spinner) findViewById(R.id.firstSpinner);
secondSpinner = (Spinner) findViewById(R.id.secondSpinner);
firstSpinner.setAdapter(firstAdapter);
secondSpinner.setAdapter(secondAdapter);
firstSpinner.setOnItemSelectedListener(this);
secondSpinner.setOnItemSelectedListener(this);
}
日志信息指向的第37行转到
行final String[] subCategoryChoices = {"Acre", "Barn", "Bunder", "Hundred", "Jerib", "Kappland", "Labor", "Ping", "Rai", "Shed", "Sitio", "Square", "Square Mile", "Square Yard"};
虽然当我点击它时它会转到onCreate()上方的那一行,可能会让它崩溃?
答案 0 :(得分:0)
我敢打赌,NPE
就在这一行.-
getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
根据getWindow()文档,该方法仍有可能会在null
内返回onCreate
。如果评论中没有必要使用该行,请尝试将其删除。
此外,您应该仔细检查activity_main
布局是否包含观看firstSpinner
和secondSpinner
。
答案 1 :(得分:0)
我最终在ssantos和zookey's答案的帮助下解决了问题,我使用的是包含微调器的自定义actionBar布局,而activity_main只是用于显示片段的frameLayout,因此,我正在使用的布局上下文中不存在两个微调器。
答案 2 :(得分:-1)
似乎你在第37行空指针异常:secondSpinner = (Spinner) findViewById(R.id.secondSpinner);
Sou,您应该检查layout
是否包含此Spinner
。