在为我和我的室友写一个应用来计算我们的食物付款时，我遇到了这样的问题：
添加新付款时，您： 1）从RadioGroup中选择名称 2）给予价值 3）给出描述（或保留默认＆＃39; opis＆＃39;）
然后按下按钮＆＃34; DODAJ＆＃34;它在ListView中显示为具有特定格式的新项目。现在问题开始了：
我想这样做，当我点击此列表中的一个项目时，我会略微改变这个特定项目的格式（在NowaWplata类中，我有额外的时间显示），这是我在另一个.xml布局文件中得到的，当再次按下它时，它应该回到正常的状态。布局。 我尝试了两种不同的方法，一种是在我的代码底部注释（我从这个主题Change layout of selected list item in Android尝试过），另一种是覆盖onItemClick方法 - 它们都没有工作
编译器说错误是：
java.lang.NullPointerException
at com.example.lukasz.dom.MainActivity.onItemClick
在这行代码中：
relativeLayoutInflate.addView(child);
在主要活动中（onClick仅适用于＆＃39; lukasz＆＃39;，同样适用于＆＃39; marcelina＆＃39;＆＃39; karolina＆＃39;）：
@Override
public void onClick(View v) {
if (v == addNewPaymentButton) {
//checking which button from RadioGroup is checked and adding new payment to certain person
int checkedRadioButtonId = members.getCheckedRadioButtonId();
switch (checkedRadioButtonId) {
//if Lukasz button is pressed, do:
case R.id.lukaszRadioButton:
if (lukaszRadioButton.isChecked()) {
//add value from addNewPaymentButton to tempLukasz
try {
tempLukasz += valueOf(newPaymentValue.getText().toString());
} catch (NumberFormatException e) {
}
//seting new value to money spent by lukasz
String sumaLukasza = getString(R.string.money_spent_by_lukasz);
sumaLukasza = String.format(sumaLukasza, tempLukasz);
moneySpentByLukasz.setText(sumaLukasza);
//adding new payment to list of all payments with flag 'int == 1' to set color to RED
NowaWplata newPayment = new NowaWplata(lukaszRadioButton.getText().toString(), newPaymentValue.getText().toString(), descriptionOfNewPayment.getText().toString(), 1);
NowaWplata.setWplaty(newPayment);
listView.setAdapter(new NewPaymentAdapter(this, R.layout.new_list_item_layout, NowaWplata.getWplaty()));
}
break;
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
TextView hourDate = (TextView) view.findViewById(R.id.hoursDateFieldInSelectedListItem);
TextView dayDate = (TextView) view.findViewById(R.id.daysDateFieldInSelectedListItem);
TextView name = (TextView) view.findViewById(R.id.nameFieldInSelectedListItem);
TextView value = (TextView) view.findViewById(R.id.valueFieldInSelectedListItem);
TextView description = (TextView) view.findViewById(R.id.descriptionFieldInSelectedListItem);
RelativeLayout relativeLayoutInflate = (RelativeLayout) view.findViewById(R.id.layoutOfSelectedListItem);
NowaWplata newPayment = (NowaWplata) listView.getItemAtPosition(position);
View child = getLayoutInflater().inflate(R.layout.selected_list_item, null);
relativeLayoutInflate.addView(child);
hourDate.setText("[" + newPayment.getHourDate() + "]");
dayDate.setText(newPayment.getDayDate());
name.setText(newPayment.getOsoba());
value.setText(newPayment.getWplata() + "zł");
description.setText(newPayment.getOpis());
}
}
//custom adapter class
class NewPaymentAdapter extends ArrayAdapter<NowaWplata> {
public LayoutInflater layoutInflater;
//custom adapter's constructor with values
public NewPaymentAdapter(Context context, int textViewResourceId, List<NowaWplata> wplaty) {
super(context, textViewResourceId, wplaty);
layoutInflater = LayoutInflater.from(context);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = convertView;
NowaWplata newPayment = getItem(position);
Holder holder = null;
// private int position;
// public void selectedItem(int position)
// {
// this.position = position;
// }
//if there are no items in list - add 1st item
if (view == null) {
view = layoutInflater.inflate(R.layout.new_list_item_layout, null);
TextView name = (TextView) view.findViewById(R.id.osobaWplata);
TextView value = (TextView) view.findViewById(R.id.kwotaWplata);
TextView description = (TextView) view.findViewById(R.id.opisWplata);
holder = new Holder(name, value, description);
view.setTag(holder);
}
// if there are items in list get holder tag
else {
holder = (Holder) view.getTag();
}
//setting text to a new list item
holder.osoba.setText("[" + newPayment.getDate() + "] " + newPayment.getOsoba());
holder.kwota.setText(newPayment.getWplata() + "zł");
holder.opis.setText(newPayment.getOpis());
//setting different color to Lukasz/Marcelina/Karolina text
if (newPayment.getFlag() == 1) {
holder.osoba.setTextColor(Color.RED);
} else if (newPayment.getFlag() == 2) {
holder.osoba.setTextColor(Color.BLUE);
} else if (newPayment.getFlag() == 3) {
holder.osoba.setTextColor(Color.GREEN);
}
//setting color to payment's value
holder.kwota.setTextColor(Color.BLACK);
// if (this.position == position) {
// View view2;
// view2 = layoutInflater.inflate(R.layout.selected_list_item, null);
//
// TextView hourDate = (TextView) view2.findViewById(R.id.hoursDateFieldInSelectedListItem);
// TextView dayDate = (TextView) view2.findViewById(R.id.daysDateFieldInSelectedListItem);
// TextView name = (TextView) view2.findViewById(R.id.nameFieldInSelectedListItem);
// TextView value = (TextView) view2.findViewById(R.id.valueFieldInSelectedListItem);
// TextView description = (TextView) view2.findViewById(R.id.descriptionFieldInSelectedListItem);
//
// hourDate.setText("[" + newPayment.getHourDate() + "]");
// dayDate.setText(newPayment.getDayDate());
// name.setText(newPayment.getOsoba());
// value.setText(newPayment.getWplata() + "zł");
// description.setText(newPayment.getOpis());
//
// return view2;
// }
return view;
}
}
这是ListView的主要XML部分
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@android:id/list"
android:layout_below="@+id/tableLayout"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_above="@+id/newPaymentValue"
android:layout_alignRight="@+id/tableLayout"
android:layout_alignEnd="@+id/tableLayout"
android:choiceMode="none"
android:clickable="false"
android:padding="20dp"
android:transcriptMode="disabled"/>
这是列表
中新项目的xml<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/layoutOfSelectedListItem">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/hoursDateFieldInSelectedListItem"
android:layout_gravity="center_horizontal"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:textSize="18dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/daysDateFieldInSelectedListItem"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:textSize="18dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/nameFieldInSelectedListItem"
android:layout_below="@+id/hoursDateFieldInSelectedListItem"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_toLeftOf="@+id/daysDateFieldInSelectedListItem"
android:layout_toStartOf="@+id/daysDateFieldInSelectedListItem"
android:textSize="18dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/valueFieldInSelectedListItem"
android:layout_below="@+id/daysDateFieldInSelectedListItem"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:textSize="22dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/descriptionFieldInSelectedListItem"
android:layout_below="@+id/nameFieldInSelectedListItem"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="20dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:textSize="14dp" />
答案 0 :(得分：0)
我通过添加额外的布局来做到这一点。
列表项：
<--Your listItem view--!>
<RelativeLayout>
<--Your extra View--!>
<LinearLayout
android:tag="0"
android:visibility="gone">
</LinearLayout>
</RelativeLayout>
在OnItemClickListener中，将额外布局设置为可见，并相应地设置标记以保存额外视图的状态。