Android newInstance();在片段中接收空值
你好 在将变量数据从活动发送到片段时,我遇到了一个问题 这是我的密码 Activity.javaAndroid newInstance();在片段中接收空值,android,android-fragments,Android,Android Fragments,你好 在将变量数据从活动发送到片段时,我遇到了一个问题 这是我的密码 Activity.java if (savedInstanceState == null) { Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no); getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragmen
if (savedInstanceState == null) {
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
new Fragment_Voter_Home()).commit();
navigationView.setCheckedItem(R.id.voter_home);
}
然后在
Fragment.java
if (savedInstanceState == null) {
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
new Fragment_Voter_Home()).commit();
navigationView.setCheckedItem(R.id.voter_home);
}
公共类Fragment\u Voter\u Home扩展了Fragment{
private static final String ARG_STUDNO = "stud_no";
private String student_no;
public static Fragment_Voter_Home newInstance(String student_no) {
Fragment_Voter_Home fragment = new Fragment_Voter_Home();
Bundle args = new Bundle();
args.putString(ARG_STUDNO, student_no);
fragment.setArguments(args);
return fragment;
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_voter_home, container, false);
TextView textView = v.findViewById(R.id.voter_fragment_textview);
if (getArguments() != null) {
student_no = getArguments().getString(ARG_STUDNO);
}
textView.setText("Welcome, "+student_no);
return v;
}
}
这是我的片段.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white">
<TextView
android:id="@+id/voter_fragment_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:gravity="center_vertical|center_horizontal|center"
android:text="Home"
android:textSize="30sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</FrameLayout>
然后在运行之后,这就是我得到的
我已经尝试过这个线程中的解决方案,但没有一个有效
我是android开发新手。谢谢。因为您的代码不正确,请将代码更改为
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
fragment).commit();
而不是
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
new Fragment_Voter_Home()).commit();
由于代码不正确,请将代码更改为
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
fragment).commit();
而不是
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
getSupportFragmentManager().beginTransaction().replace(R.id.voter_fragment,
new Fragment_Voter_Home()).commit();
问题是您将片段实例化如下:
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
然后,您没有将其传递到FragmentTransaction
,而是传递了一个新片段\u Voter\u Home()
这使得包含已传递参数的实例化片段未被使用,然后传递到片段堆栈中的片段包含未初始化的参数,导致
null
错误在于,您是这样实例化片段的:
Fragment_Voter_Home fragment = Fragment_Voter_Home.newInstance(Pstud_no);
然后,您没有将其传递到FragmentTransaction
,而是传递了一个新片段\u Voter\u Home()
这使得包含传递参数的实例化片段未被使用,然后传递到片段堆栈中的片段包含未初始化的参数,这导致null