如何在Android中加载URL时显示进度条？

Question

我是Android应用程序开发和学习它的新手.

我开发了一个使用a加载网站链接的应用程序WebView.它工作正常.

但是,当WebView加载页面时,我在显示和隐藏进度条时遇到问题.

当WebView加载网站的主链接和内部链接并在页面完全加载时隐藏进度条时,我想显示一个进度条(中心只是微调器).

我的Java代码:

package in.matebook.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WebView myWebView = (WebView) findViewById(R.id.webView);
        myWebView.setWebViewClient(new MyWebViewClient());
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        myWebView.loadUrl("http://www.labnol.org");
    }



    private class MyWebViewClient extends WebViewClient {

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {

            if (Uri.parse(url).getHost().equals("www.labnol.org")) {
                // This is my web site, so do not override; let my WebView load the page
                //or we can add more allowed host in if condition
                return false;
            }
            // Otherwise, the link is not for a page on my site, so launch another Activity that handles URLs
            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            startActivity(intent);
            return true;
        }


    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return false;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

我的布局XML代码:

<?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"
    tools:context=".MainActivity">


    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/webView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />

    <ProgressBar
        android:id="@+id/progressBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleLarge"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />

</RelativeLayout>

现在,显示进度条,但它不会隐藏.

当我创建progressbar对象并在Java代码中添加以下行时,不会显示进度条.

progressbar.setVisibility(View.GONE);

我还尝试了另一个答案但是当我点击内部链接时,进度条不起作用.

1. 我想在主页加载时显示进度条,并在主页完全加载时隐藏进度条.

2. 我想在用户点击网站的内部链接时再次显示进度条,如上所述,在页面完全加载时隐藏进度条.

请帮助,我是Android应用程序开发的初学者.

Answer 1

尝试此代码...您需要webChoromeClient来跟踪webview加载进度...

webView.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
    progressBar.setProgress(progress);
    if (progress == 100) {
        progressBar.setVisibility(View.GONE);

    } else {
        progressBar.setVisibility(View.VISIBLE);

    }
 }
});

用此代码替换您的webview客户端....

private class MyWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
    view.loadUrl(url);
    return true;
   }
}

Answer 2

如果有人正在寻找Kotlin解决方案，这个简单的解决方案对我有用：

private fun setupWebView() {

    val webViewClient: WebViewClient = object: WebViewClient() {

        override fun shouldOverrideUrlLoading(view: WebView?, request: WebResourceRequest?): Boolean {
            view?.loadUrl(request?.url.toString())
            return super.shouldOverrideUrlLoading(view, request)
        }

        override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
            showProgressDialog()
            super.onPageStarted(view, url, favicon)
        }

        override fun onPageFinished(view: WebView?, url: String?) {
            hideProgressDialog()
            super.onPageFinished(view, url)
        }
    }
    webView.webViewClient = webViewClient

    webView.settings.javaScriptEnabled = true
    webView.settings.defaultTextEncodingName = "utf-8"
}