ProgressBar没有出现在Fragment中的WebView中，如何在WebView android中显示Prog

Question

每当我输入片段时，都会显示几秒钟的空白，然后WebView中的网页就会出现。ProgressBar似乎没有显示。

这是WebView和ProgressBar在中的片段的XML文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".FragmentThree">
<ProgressBar
android:id="@+id/progressbar"
style="@style/Widget.AppCompat.ProgressBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_centerVertical="true"/>
<WebView
android:id="@+id/webview"
android:layout_width="match_parent"
android:layout_height="match_parent">
</WebView>
</RelativeLayout>

以下是Fragment Java实现的Java文件：

package com.example.task1;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;

public class FragmentThree extends Fragment {
private WebView webView;
private String URL;
private ProgressBar progressBar;
private OnFragmentInteractionListener mListener;
public FragmentThree(String url) {
// Required empty public constructor
this.URL = url;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view =  inflater.inflate(R.layout.fragment_three, container, false);
initMain(view);
return view;
}
private void initMain(View view) {
webView = view.findViewById(R.id.webview);
progressBar = view.findViewById(R.id.progressbar);
progressBar.setMax(100);
webView.loadUrl(URL);
webView.setWebViewClient(new WebViewClient());
webView.setWebChromeClient(new WebChromeClient(){
@Override
public void onProgressChanged(WebView view, int newProgress) {
progressBar.setProgress(newProgress);
}
});
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}

该代码主要位于initMain((函数下，以便于说明。

非常感谢您的任何建议，感谢您的阅读！

Answer 1

只需像这个一样在Webview下面声明ProgressBar

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".FragmentThree">

<WebView
android:id="@+id/webview"
android:layout_width="match_parent"
android:layout_height="match_parent">
</WebView>
<ProgressBar
android:id="@+id/progressbar"
style="@style/Widget.AppCompat.ProgressBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerVertical="true"/>
</RelativeLayout>