我创建了一个整型值的数组，这些整型值是一个图片对象的路径ID，就像这样
int[] picItems = {R.drawable.pic_one, R.drawable.pic_two, R.drawable.pic_three};
然后，picItem的数组是空的。我想要能够从一个索引里取到这些值然后用它作为背景，就像这样：
relative.setBackgroundResource(picItems[index]);
现在，如果我用上边的代码然后设置参数字段为R.drawable.pic_one，这是可以的。但是，当我进行申明然后实例化整形数组picItems，我得到了一个空指针的异常。我必须仔细的检查一下，而且还有一个简单的错误，但是如果有谁能够随意的就指出它来，我会非常感谢的，谢谢。！
我已经试了很多种不同的方法来声明和实例化这个数组。尽管在实例化之后这个数组仍然是空的，当想要用的时候还是有一个错误（我为了能够捕获到错误用了一个if语句）
下边是一小段代码
public class Snow extends Activity{
int[] picItems;
RelativeLayout relative;
SharedPreferences sp;
int checkedItem = 0;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
picItems = new int[]{R.drawable.pic_one, R.drawable.pic_two, R.drawable.pic_three};
sp = getPreferences(MODE_PRIVATE);
checkedItem = sp.getInt("picture", 0);
if (!(picItems == null) || !(picItems.equals(null))){
Toast.makeText(getApplicationContext(), "Array is null for some reason", Toast.LENGTH_SHORT).show();
}else{
relative.setBackgroundResource(picItems[checkedItem]);
}//end of if
...} ...}
这是Logcat Output:
11-20 19:00:27.363: E/AndroidRuntime(18311): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.Snow/com.app.snow.Snow}: java.lang.NullPointerException
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1821)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1842)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread.access$1500(ActivityThread.java:132)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.os.Looper.loop(Looper.java:150)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread.main(ActivityThread.java:4263)
11-20 19:00:27.363: E/AndroidRuntime(18311): at java.lang.reflect.Method.invokeNative(Native Method)
11-20 19:00:27.363: E/AndroidRuntime(18311): at java.lang.reflect.Method.invoke(Method.java:507)
11-20 19:00:27.363: E/AndroidRuntime(18311): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-20 19:00:27.363: E/AndroidRuntime(18311): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-20 19:00:27.363: E/AndroidRuntime(18311): at dalvik.system.NativeStart.main(Native Method)
11-20 19:00:27.363: E/AndroidRuntime(18311): Caused by: java.lang.NullPointerException
11-20 19:00:27.363: E/AndroidRuntime(18311): at com.app.snow.Snow.onCreate(Snow.java:54)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
11-20 19:00:27.363: E/AndroidRuntime(18311): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1785)
我怎么感觉我被愚弄了。picItems是正常的，相对的是空，在onCreate()初始化它
relative = (RelativeLayout) findViewById(R.id.layout);
试试这个:
final int[] picItems = {R.drawable.pic_one, R.drawable.pic_two, R.drawable.pic_three};
这样，肯定是要实例化的，而且你可能会改变数组的引用，然后你就不可能通过访问picItems获得NPE，如果你们仍然确实要获得NPE，然后还有一些其他的。
relative = (RelativeLayout) findViewById(R.id.layout);