在 Fragment 中获取 ConstraintLayout

Question

早安，

我想在 Fragment 中获得一个 ConstraintLayout，但是在调试它时会打印 这个错误 `

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“int androidx.constraintlayout.widget.ConstraintLayout.getChildCount()”

在这条线上

constraintSet.clone(constraintLayout);

所以这是我用于片段的活动以及片段的代码下方

片段活动：

 <?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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"
    tools:context="com.something.fragments.Fragment"
    android:id="@+id/this_fragment">

...



</androidx.constraintlayout.widget.ConstraintLayout>

这里是我的代码：

public class Fragment extends AppCompatDialogFragment {

View view;

@SuppressLint("InflateParams")
@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    final AlertDialog.Builder builder = new AlertDialog.Builder(Objects.requireNonNull(getActivity()), R.style.Some_Theme_Name);
    LayoutInflater inflater = getActivity().getLayoutInflater();
    view = inflater.inflate(R.layout.fragment_activity, null);

    ConstraintLayout constraintLayout = getActivity().findViewById(R.id.this_fragment);
    ConstraintSet constraintSet = new ConstraintSet();
    constraintSet.clone(constraintLayout);


    return builder.create();
}

}

非常感谢您的帮助

Answer 1

试试这个方法：

    ConstraintLayout constraintLayout = view.findViewById(R.id.this_fragment);
    ConstraintSet constraintSet = new ConstraintSet();
    constraintSet.clone(constraintLayout);