如何显示进度条，直到在Android中打开Webview

Question

活动从意图开始后，需要显示一个ProgressBar。一旦显示WebView，则需要隐藏ProgressBar。但是无法在屏幕上显示ProgressBar。下面是我的xml，

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<ProgressBar
    android:id="@+id/progress_bar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:visibility="visible"
    android:layout_centerInParent="true"/>
    <WebView
        android:id="@+id/webView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:visibility="invisible"
        android:layout_alignParentEnd="true"

        android:layout_alignParentBottom="true" />
</RelativeLayout>

下面是我的活动，

public class WebViewActivity extends Activity {
    String TAG= WebViewActivity.class.getSimpleName();
    String url=null;
    WebView webView;
    ProgressBar progressBar=null;

    @SuppressLint("SetJavaScriptEnabled")
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().requestFeature(Window.FEATURE_PROGRESS);
        //getWindow().setFeatureInt( Window.FEATURE_PROGRESS, Window.PROGRESS_VISIBILITY_ON);
        setContentView(R.layout.activity_webview);
        progressBar=findViewById(R.id.progress_bar);
        Intent intent=getIntent();
        this.url=intent.getStringExtra("url");

        webView =(WebView)findViewById(R.id.webView);
        webView.setWebViewClient(new WebViewClient());
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setDomStorageEnabled(true);
        webView.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
        webView.loadUrl(url);


       webView.setWebViewClient(new WebViewClient() {

        public boolean shouldOverrideUrlLoading(WebView view, String url) {
                view.loadUrl(url);
                return false;
}


            @Override
            public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
                super.onReceivedError(view, request, error);
                webView.setVisibility(View.VISIBLE);
                progressBar.setVisibility(View.INVISIBLE);
                AndroidLogger.log(5,TAG," error response"+error);

            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                AndroidLogger.log(5,TAG,"started"+url);

            }

            @Override
            public void onPageFinished(WebView view, String url) {
                super.onPageFinished(view, url);
                webView.setVisibility(View.VISIBLE);
                progressBar.setVisibility(View.INVISIBLE);

           }

        });
    }

}

在为WebViewActivity启动Intent之后，直到显示WebBar为止，没有显示ProgressBar出现空白屏幕。那么如何解决这个问题。任何人对此都有帮助。

Answer 1

您的xml文件似乎是正确的，但是您的java文件中包含不必要的代码内容。逐步纠正它，然后执行此操作。

    public class WebViewActivity extends Activity implements Listener {
    String TAG= PaymentGatewayActivity.class.getSimpleName();
    String url=null;
    String deviceType="ANDROID", name, password, code, pId=null;
    String cur=null;
    WebView webView;
    ProgressBar progressBar=null;

    @SuppressLint("SetJavaScriptEnabled")
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().requestFeature(Window.FEATURE_PROGRESS);
        setContentView(R.layout.activity_webview);
        progressBar=(ProgressBar) findViewById(R.id.payment_progress_bar);
        progressBar.setVisibility(View.VISIBLE);
        AndroidLogger.log(5,TAG,"progress bar made visible");
        Intent intent=getIntent();
        this.pId=intent.getStringExtra("pId");
        // HERE CALLING RETROFIT
        CommunicationManager communicationManager = new CommunicationManager(WebViewActivity.this, this,pId );
        communicationManager.getLink("get url");

    }
//THIS METHOD WILL INVOKED WHEN GETTING SUCCESS RESPONSE
    @Override
    public void getUrlSuccessResponse(String url, String pId, String cur) {

        this.url = url;
        this.pId = pId;
        this.cur = cur;
        SharedPreferences sharedpreferences = this.getSharedPreferences(this.getResources().getString(R.string.app_preferences), Context.MODE_PRIVATE);
        this.name = sharedpreferences.getString(this.getResources().getString(R.string.name), "");
        this.password = sharedpreferences.getString(this.getResources().getString(R.string.password), "");
        this.code = sharedpreferences.getString(this.getResources().getString(R.string.code), "");
        webView = (WebView) findViewById(R.id.webView);
        webView.setVisibility(View.VISIBLE);

        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setDomStorageEnabled(true);
        webView.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
        webView.setBackgroundColor(Color.TRANSPARENT) //set this one to remove unnecessary background

        //setup custom webview client here
        webView.setWebViewClient(new PayWeb());


        //load url inside webview
        try {        
            String postData = "type=" + URLEncoder.encode("ANDROID", "UTF-8") + "&password=" + URLEncoder.encode(password, "UTF-8") + "&code=" + URLEncoder.encode(code, "UTF-8") + "&cur=" + URLEncoder.encode(cur, "UTF-8") + "&name=" + URLEncoder.encode(subscriberId, "UTF-8") + "&pId=" + URLEncoder.encode(pId, "UTF-8");
            webView.postUrl(url, postData.getBytes());
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }

    public class PayWeb extends WebViewClient{
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                progressBar.setVisibility(View.VISIBLE);

                return false; // then it is not handled by default action
            }


            @Override
            public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
                super.onReceivedError(view, request, error);
                progressBar.setVisibility(View.INVISIBLE);

            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                //show progressbar
                progressBar.setVisibility(View.VISIBLE);                    
            }

            @Override
            public void onPageFinished(WebView view, String url) {
                super.onPageFinished(view, url);
                //hide progressbar
                progressBar.setVisibility(View.INVISIBLE);                    
            }    
        }

    @Override
    public void getUrlFailureResponse(int statusCode, String status) {
        //manage webpage faliour case
    }

    @Override
    public void getUrlNetworkFailureException(int statusCode, String status) {
        //manage network faliour case
    }
}