Java Can'；I don’我不想把字符串设成任何我想要的

这就是整个Java类。问题在于：答案列表。添加（位置、项目）；已激活。若我将项更改为“-”，那个么它可以工作，但若我发送任何其他字符串，它就不能工作。真奇怪。但我希望能够添加项目。我该怎么办

现在，应用程序崩溃时，该功能的添加应该发生

公共类SinglePlayerQuickGame扩展活动{

databaseTest testDatabase=new databaseTest();
boolean alternativeIsChosen; //är true om ett alternativ har valts
int chosenAlternative;       //om ett alternativ har valts representer
 String alternativeText;

@TargetApi(Build.VERSION_CODES.JELLY_BEAN) 
@SuppressLint("NewApi") 
@Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_single_player_quick_game);
    alternativeIsChosen=false;
    chosenAlternative=-1;
    alternativeText="";

    final ListView AnswerListview = (ListView) findViewById(R.id.chosenAlternatives);
    final ListView alternativeListview= (ListView) findViewById(R.id.alternatives);


    final ArrayList<String> answerList = new ArrayList<String>();
    final ArrayList<String> alternativeList=new ArrayList<String>();


    for(int i=0; i<testDatabase.alternatives.getSize();i++){
        alternativeList.add(testDatabase.alternatives.getNameOnAPosition(i));
    }

    answerList.add("-");
    for(int i=0; i<testDatabase.chosenAlternatives.getSize();i++){
        answerList.add(testDatabase.chosenAlternatives.getNameOnAPosition(i));
        answerList.add("-");

    final StableArrayAdapter answerAdapter = new StableArrayAdapter(this, android.R.layout.simple_list_item_1, answerList);
    AnswerListview.setAdapter(answerAdapter);

    final StableArrayAdapter alternativeAdapter= new StableArrayAdapter(this,android.R.layout.simple_list_item_1,alternativeList );
    alternativeListview.setAdapter(alternativeAdapter); 

    AnswerListview.setOnItemClickListener(new AdapterView.OnItemClickListener() {

      @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1)
    @SuppressLint("NewApi")

    public void onItemClick(AdapterView<?> parent, final View view,
          final int position, long id) {

          final String item=(String) alternativeListview.getItemAtPosition(0);

        view.animate().setDuration(0).alpha(0)
            .withEndAction(new Runnable() {
              @SuppressWarnings("null")
            @Override
              public void run() {

                  if(alternativeIsChosen){


                     answerList.add(position, item);
                     answerAdapter.notifyDataSetChanged();
                     alternativeList.remove(chosenAlternative);
                     alternativeAdapter.notifyDataSetChanged();
                     alternativeIsChosen=false;
                  }



                view.setAlpha(1);
              }
            });
      }



    });

    alternativeListview.setOnItemClickListener(new AdapterView.OnItemClickListener() {

          @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1)
        @SuppressLint("NewApi")


        public void onItemClick(AdapterView<?> parent, final View view,
              final int position, long id) {


           final String answerItem = (String) parent.getItemAtPosition(position);

            view.animate().setDuration(0).alpha(0)
                .withEndAction(new Runnable() {
                  @Override
                  public void run() {

                    alternativeIsChosen=true;
                    chosenAlternative=position;

                     answerAdapter.notifyDataSetChanged();
                     alternativeAdapter.notifyDataSetChanged();
                    view.setAlpha(1);
                  }
                });
          }



        });
  }

public final String getAlternativeText(){
    return alternativeText;
}

  private class StableArrayAdapter extends ArrayAdapter<String> {

    HashMap<String, Integer> mIdMap = new HashMap<String, Integer>();

    public StableArrayAdapter(Context context, int textViewResourceId,
        List<String> objects) {
      super(context, textViewResourceId, objects);
      for (int i = 0; i < objects.size(); ++i) {
        mIdMap.put(objects.get(i), i);
      }
    }

    @Override
    public long getItemId(int position) {
      String item = getItem(position);
      return mIdMap.get(item);
    }

    @Override
    public boolean hasStableIds() {
      return true;
    }

  }

---

您不能更改它，因为它声明为final引用变量声明为final并分配给一个对象，而该引用变量不能分配给另一个对象。因此，变量s只能引用它已保存的内容。不清楚问题究竟是什么

然而，从代码来看，这极不可能是“将字符串设置为变量”的结果

---

这里还有其他问题……您没有提供足够的信息让我们来解决。您需要提供的第一件事是导致崩溃的异常的stacktrace。

是的，但如果我将字符串更改为其他内容，则不会。这可能是因为您的项是字符串。您不能强制转换到您想要的任何对象。“它不工作”几乎没有足够的信息来帮助您诊断问题。这就像对医生说“我不好”，但不让他检查您。它以什么方式不工作？不工作的代码到底是什么样的？如果s是最终字符串s=（字符串）alternativeListview.getItemAtPosition（position）；它不起作用。或者，如果我将s设置为等于变量的字符串，它也不起作用。如果不起作用，我的意思是，当到达此onItemClick（）函数时，应用程序崩溃。您添加到alternativeList的对象的类型是什么？如何将list元素设置为等于全局变量（即字符串）的值？我们在java中没有全局变量，你是说静态变量吗？不只是普通变量将列表元素设置为字符串形式的特定变量：list.set（index，string）；//索引列表中的哪个元素等于字符串变量这是我一直在尝试的。当我使用字符串变量时，它不起作用。当我试图直接编写字符串（只是为了尝试）时，字符串“-”工作正常。但是当我编写诸如“m”、“hello”或“/”之类的字符串时没用。你知道问题是什么吗？我怎么解决？

06-10 10:43:36.009: D/AndroidRuntime(618): Shutting down VM
06-10 10:43:36.009: W/dalvikvm(618): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
06-10 10:43:36.159: E/AndroidRuntime(618): FATAL EXCEPTION: main
06-10 10:43:36.159: E/AndroidRuntime(618): java.lang.NullPointerException
06-10 10:43:36.159: E/AndroidRuntime(618):  at com.example.rankingquiz2.SinglePlayerQuickGame$StableArrayAdapter.getItemId(SinglePlayerQuickGame.java:198)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.AbsListView.obtainView(AbsListView.java:2292)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.ListView.makeAndAddView(ListView.java:1769)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.ListView.fillDown(ListView.java:672)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.ListView.fillSpecific(ListView.java:1330)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.ListView.layoutChildren(ListView.java:1600)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.AbsListView.onLayout(AbsListView.java:2106)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1638)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1422)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.View.layout(View.java:13754)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewGroup.layout(ViewGroup.java:4364)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1868)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1689)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4214)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.Choreographer.doCallbacks(Choreographer.java:555)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.Choreographer.doFrame(Choreographer.java:525)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.os.Handler.handleCallback(Handler.java:615)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.os.Handler.dispatchMessage(Handler.java:92)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.os.Looper.loop(Looper.java:137)
06-10 10:43:36.159: E/AndroidRuntime(618):  at android.app.ActivityThread.main(ActivityThread.java:4745)
06-10 10:43:36.159: E/AndroidRuntime(618):  at java.lang.reflect.Method.invokeNative(Native Method)
06-10 10:43:36.159: E/AndroidRuntime(618):  at java.lang.reflect.Method.invoke(Method.java:511)
06-10 10:43:36.159: E/AndroidRuntime(618):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
06-10 10:43:36.159: E/AndroidRuntime(618):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-10 10:43:36.159: E/AndroidRuntime(618):  at dalvik.system.NativeStart.main(Native Method)
06-10 10:43:36.269: D/dalvikvm(618): GC_CONCURRENT freed 202K, 4% free 6282K/6535K, paused 74ms+9ms, total 200ms
06-10 10:43:36.279: D/dalvikvm(618): WAIT_FOR_CONCURRENT_GC blocked 49ms