Question

我有一个应用程序，我在一个放射组中有Present和Absent单选按钮的布局。

我将上述布局动态添加到另一个布局一段特定次数。在我添加的同时，我还分别为Present和Absent维护了一个radioButtons列表，因为我想在用户按下按钮后勾选所有Present单选按钮。

这是我的动态布局部分，带有单选按钮：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    android:weightSum="10">
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="2">

                <LinearLayout
                    android:orientation="horizontal"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:weightSum="10">
                    <LinearLayout
                        android:orientation="vertical"
                        android:layout_width="0dp"
                        android:layout_height="match_parent"
                        android:layout_weight="1"
                        android:gravity="center">
                    <TextView
                          android:layout_width="wrap_content"
                          android:layout_height="wrap_content"
                          android:text="1"
                          android:id="@+id/RollNum"
                          android:textSize="20dp"
                          android:textColor="@color/black"
                          android:gravity="center"
                          />
                    </LinearLayout>
                    <LinearLayout
                        android:orientation="vertical"
                        android:layout_width="0dp"
                        android:layout_height="70dp"
                        android:layout_weight="6"
                        android:gravity="center">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Amandeep Singh and some very very long name"
        android:gravity="center"
        android:id="@+id/Name"
        android:textSize="20dp"
        android:textColor="@color/black"/>
    </LinearLayout>
                    <LinearLayout
                        android:orientation="vertical"
                        android:layout_width="0dp"
                        android:layout_height="match_parent"
                        android:layout_weight="3"
                        android:gravity="center">
                        <RadioGroup
                            android:id="@+id/radioAttendance"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation='horizontal'
                            android:gravity="center">

                        <RadioButton
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:text="P"
                            android:id="@+id/PresentCheck"
                            android:textSize="10dp"
                            android:gravity="center"
                            android:textColor="@color/black"
                            />
    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="A"
        android:id="@+id/AbsentCheck"
        android:textSize="15dp"
        android:gravity="center"
        android:textColor="@color/black"
        />
    </RadioGroup>

</LinearLayout>
    </LinearLayout>
        </LinearLayout>
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="0.1">
            <View
                android:layout_width="fill_parent"
                android:layout_height="0.1dp"
                android:background="#ffffff" />
        </LinearLayout>
</LinearLayout>

以下是我将代码添加到列表中的代码：

List<RadioButton> presentRadioList;
List<RadioButton> absentRadioList;

LoutInflater inflater = (LayoutInflater)context.getSystemService
        (Context.LAYOUT_INFLATER_SERVICE);
LinearLayout scrollViewLinearlayout = (LinearLayout)findViewById(R.id.parent); // The layout inside scroll view
//int count=50;
Studentlist = Arrays.copyOfRange(StudentlistInterim, 1, StudentlistInterim.length);
for(int i = 0; i < Studentlist.length; i++){
    String data = Studentlist[i];
    String RollNum = data.split("--")[0];
    String Name = data.split("--")[1];
    Log.d("Name is:", Name);

    LinearLayout layout2 = new LinearLayout(context);
    layout2.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    View item = inflater.inflate(R.layout.item_layout, null, false);

    layout2.addView(item);
    layout2.setId(i);
    TextView trollnum = (TextView) item.findViewById(R.id.RollNum);
    trollnum.setText(RollNum);
    TextView tname = (TextView) item.findViewById(R.id.Name);
    tname.setText(Name);
    RadioButton rPresent = (RadioButton)item.findViewById(R.id.PresentCheck);
    RadioButton rAbsent = (RadioButton)item.findViewById(R.id.AbsentCheck);
    //rPresent.setId(i);
    //rAbsent.setId(Studentlist.length+i); // to make the id unique for each present and absent entry
    presentRadioList.add(rPresent);
    absentRadioList.add(rAbsent);

    scrollViewLinearlayout.addView(layout2);
    Log.d("Id is: ", trollnum.getText().toString());
}

我面临的问题是我的活动失败并出现以下异常：

Caused by: java.lang.NullPointerException
    at com.example.amandeepsingh.loginregisterandother.TakeAttendance.onCreate(TakeAttendance.java:128)

presentRadioList.add(rPresent);
absentRadioList.add(rAbsent);

请帮忙，让我知道我错过了什么。

Answer 1

您似乎尚未初始化presentRadioList。尝试编辑类似List<RadioButton> presentRadioList = new ArrayList<RadioButton>();

的代码

无法在android中使用findViewById找到单选按钮，动态添加布局

1 个答案: