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)
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