在加载 WebView URL 时尝试在 Android Studio 2.3.3 中实现启动画面图像

Question

这个“启动画面”有类似的问题，但没有人为我工作，或者我做错了什么。我从这个答案Splash Screen Code 中插入了代码。 该应用程序以启动画面启动，一秒钟后它消失，然后显示为白色背景。加载网站时，它不会在下一步中向我显示 WebView。谁能帮帮我？

这是我的 MainActivity.java 代码：

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Handler;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;


import static jombi.mooni.R.id.swiperefresh;

public class MainActivity extends AppCompatActivity {
// declare private WebView Variable
private WebView wb;
// method to check for active network connection (caching website)
private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}


@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // link the wb Variable to the WebView Component using the webView Id which we gave in the beginning in activity_main.xml-Designansicht
    wb = (WebView) findViewById(R.id.WebView);
    assert wb != null;
    WebSettings webSettings = wb.getSettings();

    WebViewClientImpl webViewClient = new WebViewClientImpl(this);
    wb.setWebViewClient(webViewClient);

    // caching whole website when online from website when offline from cache
    wb.getSettings().setAppCachePath(getApplicationContext().getCacheDir().getAbsolutePath());
    wb.getSettings().setAllowFileAccess( true );
    wb.getSettings().setAppCacheEnabled( true );
    wb.getSettings().setLoadsImagesAutomatically(true);
    //activate JavaScript
    webSettings.setJavaScriptEnabled(true);
    wb.getSettings().setCacheMode( WebSettings.LOAD_DEFAULT ); // load online by default
    if ( !isNetworkAvailable() ) { // loading offline
        wb.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);


    }


    // load custom errorpage
    wb.setWebViewClient(new WebViewClient(){
        @SuppressWarnings("deprecation")
        @Override
        public void onReceivedError(android.webkit.WebView view, int errorCode, String description, String failingUrl) {
            wb.loadUrl("file:///android_asset/errorpage/index.html");
        }


    @Override

          public void onPageFinished(WebView view, String url) {

//hide loading image

findViewById(R.id.imgLogo).setVisibility(View.GONE);

//show webview

findViewById(R.id.WebView).setVisibility(View.VISIBLE);

 }

});

// call with wb variable the method loadurl
wb.loadUrl("http://xxx.yyy.zz");


    // swipe to refresh screen
    final SwipeRefreshLayout SwipeRefreshLayout = (SwipeRefreshLayout) findViewById(swiperefresh);
    SwipeRefreshLayout.setColorSchemeResources(android.R.color.holo_orange_dark, android.R.color.holo_orange_light, android.R.color.holo_red_dark, android.R.color.holo_red_light);
    SwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            wb.loadUrl("javascript:window.location.reload(true)");

            refreshItems();
        }
        void refreshItems() {
            // Load items
            SwipeRefreshLayout.setRefreshing(true);
            // Load complete
            onItemsLoadComplete();
        }

        void onItemsLoadComplete() {
            // Update the adapter and notify data set changed
            // ...

            // Stop refresh animation
            SwipeRefreshLayout.setRefreshing(false);
        }
    });


}

private Boolean exit = false;
@Override
// when Back Button pressed load previous page and at last page display end message
public void onBackPressed() {
    if (wb.canGoBack()) {
        wb.goBack();
    } else {
        if (exit)
            this.finish();
        else {
            Toast.makeText(this, "Push to close app",
                    Toast.LENGTH_SHORT).show();
            exit = true;
            new Handler().postDelayed(new Runnable() {
                @Override
                public void run() {
                    exit = false;
                }
            }, 3 * 1000);
        }

    }
}



// own URL in WebView, external URL in AndroidBrowser
private class WebViewClientImpl extends WebViewClient {

    private Activity activity = null;

    private WebViewClientImpl(Activity activity) {
        this.activity = activity;
    }

    @SuppressWarnings("deprecation")
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if(url.contains("xxx.yyy.zz") ) return false;

        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        activity.startActivity(intent);
        return true;
    }
    //End own URL in WebView, external URL in AndroidBrowser
}


}

和activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.SwipeRefreshLayout
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="jombi.mooni.MainActivity"
android:id="@+id/swiperefresh">

<ImageView
    android:id="@+id/imgLogo"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:visibility="visible"
    android:background="@color/colorPrimaryDark"
    android:src="@drawable/boat" />

<WebView
    android:id="@+id/WebView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:visibility="gone"
    tools:ignore="MissingConstraints"
    tools:layout_editor_absoluteX="8dp"
    tools:layout_editor_absoluteY="8dp">
</WebView>

Answer 1

来源：https://stackoverflow.com/a/9589451/8252521

回复者：https://stackoverflow.com/users/374866/davehale23

我首先显示一个 ImageView，然后再显示一个 WebView 已加载，像这样交换它们的可见性

        WebView wv = (WebView) findViewById(R.id.webView1);
        wv.getSettings().setJavaScriptEnabled(true);
      wv.setWebViewClient(new WebViewClient() {

          ...

          @Override
          public void onPageFinished(WebView view, String url) {
              //hide loading image
              findViewById(R.id.imageLoading1).setVisibility(View.GONE);
              //show webview
              findViewById(R.id.webView1).setVisibility(View.VISIBLE);
          }


      });     
      wv.loadUrl("http://yoururlhere.com");

我的 xml 布局看起来像这样

    <ImageView android:id="@+id/imageLoading1"
      android:layout_height="fill_parent"
        android:layout_width="fill_parent"
        android:visibility="visible"
        android:src="@drawable/vert_loading"
        />
    <WebView android:id="@+id/webView1"
        android:layout_height="fill_parent"
        android:layout_width="fill_parent"
        android:visibility="gone"
        />