这是整个Java类。问题是：answerList.add（position，item）;被激活了。如果我将项目更改为“ - ”然后它可以工作但如果我发送任何其他字符串它不起作用。那真是怪了。但我希望能够添加项目。我该怎么办。
现在应用程序崩溃时，该功能应该发生添加。
公共类SinglePlayerQuickGame扩展了Activity {
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;
}
}
}
错误消息：
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
答案 0 :(得分：0)
您无法更改它，因为它声明的final是一个声明为final的引用变量，并且分配给一个引用变量无法分配给另一个对象的对象。所以变量s不能引用任何其他东西，除了它已经存在的东西。
答案 1 :(得分：0)
目前尚不清楚问题究竟是什么。
然而，查看代码极不可能是“将字符串设置为变量”的结果。
此处还有其他事情......而且你没有提供足够的信息让我们弄清楚。您需要提供的第一件事是导致崩溃的异常的堆栈跟踪。