OnCreate方法中的Android NullPointerException

Question

过去几天我一直在编写这个Android应用程序,一切都运行顺利,直到今天.在我的应用程序中,我试图为我的应用程序实现选项卡式视图,但是一旦我尝试运行它,我的应用程序就会安装并在打开时立即强制关闭.我一直坐在这一整天,不能为我的生活找出问题所在.希望有人可以帮助我.

E/AndroidRuntime(5469): FATAL EXCEPTION: main
E/AndroidRuntime(5469): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo
{com.stullich.tim.lolbufftimer/com.stullich.tim.lolbufftimer.LoLBuffTimerMain}: java.lang.NullPointerException
E/AndroidRuntime(5469):at android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:1573) 
E/AndroidRuntime(5469): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
E/AndroidRuntime(5469): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
E/AndroidRuntime(5469): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
E/AndroidRuntime(5469): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(5469): at android.os.Looper.loop(Looper.java:130)
E/AndroidRuntime(5469): at android.app.ActivityThread.main(ActivityThread.java:3691)
E/AndroidRuntime(5469): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(5469): at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime(5469): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run
(ZygoteInit.java:907)
E/AndroidRuntime(5469): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
E/AndroidRuntime(5469): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(5469): Caused by: java.lang.NullPointerException
E/AndroidRuntime(5469): at android.content.ContextWrapper.getResources(ContextWrapper.java:80)
E/AndroidRuntime(5469): at com.stullich.tim.lolbufftimer.LoLBuffTimerMain.<init>(LoLBuffTimerMain.java:14)
E/AndroidRuntime(5469): at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(5469): at java.lang.Class.newInstance(Class.java:1409)
E/AndroidRuntime(5469): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
E/AndroidRuntime(5469): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1565)
E/AndroidRuntime(5469):     ... 11 more

以下是主要活动的代码:

public class LoLBuffTimerMain extends TabActivity{

Resources res = getResources(); 
TabHost tabHost = getTabHost(); 
TabHost.TabSpec spec;  
Intent intent;

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

    intent = new Intent().setClass(this, YourBuffs.class);

    spec = tabHost.newTabSpec("yourbuffs").setIndicator("Your Buffs", 
                        res.getDrawable(R.drawable.tab_view_you))
                  .setContent(intent);
    tabHost.addTab(spec);

    intent = new Intent().setClass(this, EnemyBuffs.class);
    spec = tabHost.newTabSpec("enemybuffs").setIndicator("Enemy Buffs", 
                        res.getDrawable(R.drawable.tab_view_enemy))
                  .setContent(intent);
    tabHost.addTab(spec);
    }
}

和XML:

<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="fill_parent">
    <TabWidget android:id="@android:id/tabs"
        android:layout_height="wrap_content"
        android:layout_width="fill_parent" />
    <FrameLayout android:id="@android:id/tabcontent"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:padding="5dp">        
    </FrameLayout>
</TabHost>

Answer 1

堆栈跟踪指向此行作为异常的来源:

Resources res = getResources(); 

继承的getResources()方法抛出异常.这是因为getResources()在构建和初始化活动之后,您才能在以后调用.移动那些成员变量初始化onCreate(),你应该好好去.