如何从Fragment到DataBinding访问Activity视图？

Posted 2021-05-05

我的目标是从Fragment访问MainActivity的ProgressBar和TextView。但是，我收到以下错误：

尝试在空对象引用上调用虚方法'void android.widget.ProgressBar.setVisibility（int）'

activity_main.xml中

<LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="200dp"
            android:orientation="vertical"
            android:layout_gravity="center">

        <ProgressBar
            android:id="@+id/pbLoading"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:indeterminate="true"
            android:layout_gravity="center"
            android:visibility="visible"/>

        <TextView
            android:id="@+id/tvLoading"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="@dimen/dimension_8dp"
            android:fontFamily="@font/robotomedium"
            android:textSize="16sp"
            android:visibility="visible"
            android:text="@string/loading_text"/>

        </LinearLayout>

sample fragment.Java

 @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        fragmentDataBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_currency_list, container, false);

        return Objects.requireNonNull(fragmentDataBinding).getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        mPbLoading = fragmentDataBinding.getRoot().findViewById(R.id.pbLoading);
        mPbLoading.setVisibility(View.GONE);

}

篡改了很多帖子，文章却无法实现。提前致谢。

最好，

答案

选项1

在活动上使progressbar静态，然后从片段中访问 -

if(MainActivity.progressbar!=null){
MainActivity.progressbar.setVisibility(View.Gone);
//or whatever do you want
} 

选项2

((YourActivityClassName)getActivity()).yourPublicMethod();