Question

这是我的应用程序部分的一些代码，我试图让人们查看他们喜欢的部分。我让它为那部分工作。现在我正在努力使它在onLongClick时它允许选项删除一个。我不知道那部分是否有效，因为我目前在数组部分遇到了一个错误，从我将其缩小到了。它非常奇怪，因为我可以看到它与它工作的区别，而不是真的不应该有任何问题。如果你愿意，也许我需要一些新鲜的眼睛看着这个。感谢

public class Favorites extends ListActivity{

    public static final String PREFS_NAME = "Favorites";
    String[] title;
    int favNum, num;
    int[] category, member;

    @Override
    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      grabFav();
      num = favNum;
      num++;
      if(favNum > -1){
          title = new String[num];
          category = new int[num];
          member = new int[num];
          allFavs();

          setListAdapter(new ArrayAdapter<String>(this, R.layout.item_list, title));

          ListView lv = getListView();
          lv.setTextFilterEnabled(true);      
      }
    }

    public void grabFav(){
         SharedPreferences saved = this.getSharedPreferences(PREFS_NAME, 0);
         favNum = saved.getInt("FavoriteNum", -1);
    }

    public void allFavs(){
        SharedPreferences saved = this.getSharedPreferences(PREFS_NAME, 0);

        for(int i = 0; i< favNum; i++){
            title[i] = saved.getString("Title"+i, "");
        }

        for(int n = 0; n< favNum; n++){
            category[n] = saved.getInt("Category"+n, 0);
        }

        for(int m = 0; m< favNum; m++){
            member[m] = saved.getInt("Member"+m, 0);
        }
    }
}

当那个顶部看起来像这样

grabFav();
  favNum++;

  if(favNum > 0){
      title = new String[favNum];
      category = new int[favNum];
      member = new int[favNum];
      allFavs();

它工作正常（不确定onLongItemClick，因为我通常将它注释掉，所以我可以找到错误）。据我所知，它应该工作得很好。我发布了整个班级，因为你发现了另一个可能导致问题的错误。如果你想看

，这是log cat

09-04 11:09:20.576: ERROR/AndroidRuntime(18769): FATAL EXCEPTION: main
09-04 11:09:20.576: ERROR/AndroidRuntime(18769): java.lang.NullPointerException
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:355)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.AbsListView.obtainView(AbsListView.java:1315)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ListView.makeAndAddView(ListView.java:1727)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ListView.fillDown(ListView.java:652)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ListView.fillFromTop(ListView.java:709)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.ListView.layoutChildren(ListView.java:1580)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.AbsListView.onLayout(AbsListView.java:1147)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.View.layout(View.java:7035)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.View.layout(View.java:7035)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1249)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1125)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1042)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.View.layout(View.java:7035)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.View.layout(View.java:7035)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1045)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.os.Looper.loop(Looper.java:123)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at android.app.ActivityThread.main(ActivityThread.java:4627)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at java.lang.reflect.Method.invokeNative(Native Method)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at java.lang.reflect.Method.invoke(Method.java:521)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
09-04 11:09:20.576: ERROR/AndroidRuntime(18769):     at dalvik.system.NativeStart.main(Native Method)

非常感谢任何帮助。感谢

Answer 1

您是否检查过，您从偏好设置中获得的所有标题字符串确实存在，即此行未将null分配给title[i]：

title[i] = saved.getString("Title"+i, "");

也许你错过了第0个标题“Title0”而只是从“Title1”开始？

Answer 2

您可以使用此格式，在使用视图之前立即设置活动内容。每当我之前调用视图上的方法时，我都会得到NullPointer异常 setContentView方法..希望这能解决你的问题：）

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.your_activity_xml); 

// your code

}

强制关闭数组

2 个答案: