如何动态地使用ArrayList的更新微调? [英] How do I dynamically update a spinner using ArrayList?
问题描述
我创建了一个填充了一个
。我想动态值添加到 ArrayList的微调
的ArrayList
,所以在微调
动态填充。然而,当我尝试值添加到我的的ArrayList
,我收到了 NullPointerException异常
。
我在想什么?我必须修改之前,适配器重置的ArrayList
?
下面是我的code:
我的微调,ArrayList和适配器:
deleteselection =(微调)view.findViewById(R.id.deletespinner);
portfoliosdelete =新的ArrayList<串GT;();
portfoliosdelete.add(选择组合);
adapterdeletetype =新ArrayAdapter<串GT;(这一点,android.R.layout.simple_spinner_item,portfoliosdelete){ @覆盖
公共查看getDropDownView(INT位置,查看convertView,父母的ViewGroup)
{
视图V = NULL; //如果这是初始虚拟项,使其隐藏
如果(位置== 0){
TextView的电视=新的TextView(的getContext());
tv.setHeight(0);
tv.setVisibility(View.GONE);
V =电视;
}
其他{
//通convertView为空到的特殊情况的看法prevent重用
V = super.getDropDownView(位置,空,父母);
} //隐藏滚动条,因为它有时会出现不必要的,这并不prevent滚动
parent.setVerticalScrollBarEnabled(假);
返回伏;
}
};
adapterdeletetype.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
deleteselection.setAdapter(adapterdeletetype);
我的code动态更新微调:
否则如果(users.contains(usernull)){
PN1 = enterportfolioname.getText()的toString()。
USER1 =新PortfolioRecord(PN1someemail@gmail.com);
users.remove(usernull);
users.add(用户1);
portfoliosdelete.add(PN1); //< - 这会导致空指针异常
adapterdeletetype.notifyDataSetChanged();
portfoliolist.invalidateViews();
使用的code以下。当用户选择这个code将增加一个新项目,并从微调添加一个新的项目。
code样品:</ P>
布局main.xml中:
&LT;?XML版本=1.0编码=UTF-8&GT?;
&LT; LinearLayout中的xmlns:机器人=http://schemas.android.com/apk/res/android
机器人:layout_width =FILL_PARENT
机器人:layout_height =FILL_PARENT
机器人:方向=垂直
机器人:weightSum =10&GT; &LT;微调
机器人:ID =@ + ID / cmbNames
机器人:layout_width =WRAP_CONTENT
机器人:layout_height =WRAP_CONTENT/&GT;
&LT; / LinearLayout中&GT;
布局spinner_item.xml
&LT;?XML版本=1.0编码=UTF-8&GT?;
&LT; LinearLayout中的xmlns:机器人=http://schemas.android.com/apk/res/android
机器人:layout_width =FILL_PARENT
机器人:layout_height =FILL_PARENT
机器人:方向=垂直&GT; &LT;的TextView
机器人:ID =@ + ID / tvName
机器人:layout_width =WRAP_CONTENT
机器人:layout_height =WRAP_CONTENT/&GT;
&LT; / LinearLayout中&GT;
活动类:
公共类MainActivity延伸活动{
私有静态最后弦乐NAME =名;
私有静态最后弦乐ADD_NEW_ITEM =添加新项; 私人SimpleAdapter适配器;
私人微调cmbNames;
私人列表&LT;&HashMap的LT;字符串,字符串&GT;&GT; lstNames;
私人诠释柜台; 私人OnItemSelectedListener itemSelectedListener =新OnItemSelectedListener(){ @覆盖
公共无效onItemSelected(适配器视图&LT;&GT;为arg0,ARG1观,诠释ARG2,
长ARG3){
HashMap的&LT;字符串,字符串&GT;地图= lstNames.get(ARG2);
字符串名称= map.get(名);
如果(name.equalsIgnoreCase(ADD_NEW_ITEM)){
lstNames.remove(地图);
反++;
addNewName(将String.valueOf(计数器));
addNewName(ADD_NEW_ITEM);
adapter.notifyDataSetChanged();
}
} @覆盖
公共无效onNothingSelected(适配器视图&LT;&GT;为arg0){
// TODO自动生成方法存根
}
}; @覆盖
保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.main); populateList(); cmbNames =(微调)findViewById(R.id.cmbNames);
适配器=新SimpleAdapter(这一点,lstNames,R.layout.spinner_item,
新的String [] {NAME},新的INT [] {R.id.tvName});
cmbNames.setAdapter(适配器);
cmbNames.setOnItemSelectedListener(itemSelectedListener);
} 私人无效populateList(){
lstNames =新的ArrayList&LT;&HashMap的LT;字符串,字符串&GT;&GT;(); addNewName(ABC);
addNewName(PQR);
addNewName(XYZ);
addNewName(ADD_NEW_ITEM);
} 私人无效addNewName(字符串名称){
HashMap的&LT;字符串,字符串&GT;地图=新的HashMap&LT;字符串,字符串&GT;();
map.put(姓名,名称);
lstNames.add(地图);
}
}
I have created a Spinner
that is populated with an ArrayList
. I want to dynamically add values to the ArrayList
, so the the Spinner
populates dynamically. However, when I try to add values to my ArrayList
, I get a NullPointerException
.
What am I missing? Do I have to reset the adapter before amending the ArrayList
?
Here is my code:
My spinner, arraylist, and adapter:
deleteselection = (Spinner)view.findViewById(R.id.deletespinner);
portfoliosdelete = new ArrayList<String>();
portfoliosdelete.add("Select Portfolio");
adapterdeletetype = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item,portfoliosdelete){
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent)
{
View v = null;
// If this is the initial dummy entry, make it hidden
if (position == 0) {
TextView tv = new TextView(getContext());
tv.setHeight(0);
tv.setVisibility(View.GONE);
v = tv;
}
else {
// Pass convertView as null to prevent reuse of special case views
v = super.getDropDownView(position, null, parent);
}
// Hide scroll bar because it appears sometimes unnecessarily, this does not prevent scrolling
parent.setVerticalScrollBarEnabled(false);
return v;
}
};
adapterdeletetype.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
deleteselection.setAdapter(adapterdeletetype);
My code to dynamically update spinner:
else if(users.contains(usernull)){
pn1 = enterportfolioname.getText().toString();
user1 = new PortfolioRecord(pn1, "someemail@gmail.com");
users.remove(usernull);
users.add(user1);
portfoliosdelete.add(pn1); // <-- This causes a null pointer exception
adapterdeletetype.notifyDataSetChanged();
portfoliolist.invalidateViews();
Use the code below. This code will add a new item when the user selects and add a new item from the spinner.
Code sample:
layout main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="10" >
<Spinner
android:id="@+id/cmbNames"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
layout spinner_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/tvName"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Activity class:
public class MainActivity extends Activity {
private static final String NAME = "name";
private static final String ADD_NEW_ITEM = "Add New Item";
private SimpleAdapter adapter;
private Spinner cmbNames;
private List<HashMap<String, String>> lstNames;
private int counter;
private OnItemSelectedListener itemSelectedListener = new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
HashMap<String, String> map = lstNames.get(arg2);
String name = map.get(NAME);
if (name.equalsIgnoreCase(ADD_NEW_ITEM)) {
lstNames.remove(map);
counter++;
addNewName(String.valueOf(counter));
addNewName(ADD_NEW_ITEM);
adapter.notifyDataSetChanged();
}
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
populateList();
cmbNames = (Spinner) findViewById(R.id.cmbNames);
adapter = new SimpleAdapter(this, lstNames, R.layout.spinner_item,
new String[] { NAME }, new int[] { R.id.tvName });
cmbNames.setAdapter(adapter);
cmbNames.setOnItemSelectedListener(itemSelectedListener);
}
private void populateList() {
lstNames = new ArrayList<HashMap<String, String>>();
addNewName("abc");
addNewName("pqr");
addNewName("xyz");
addNewName(ADD_NEW_ITEM);
}
private void addNewName(String name) {
HashMap<String, String> map = new HashMap<String, String>();
map.put(NAME, name);
lstNames.add(map);
}
}
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