从JavaFXPorts Webview访问本机android.webkit.WebView实例

Question

I want to implement java-to-javascript method call via

WebView.getEngine().executeScript("browserMessagingServicePush('Push data from Java to JS')");

on Android using javafxports 8.60.9, but got

java.lang.UnsupportedOperationException: Not supported yet.
...
at javafx.scene.web.WebEngine.executeScript(WebEngine.java:860)

exception.

How can I get reference to Android's native WebView to implement something like this?

WebView.addJavascriptInterface(new JSInterface(), "JSInterface");

Or there is some other workaround?

Answer 1

SOLUTION

I found a solution to executing JavaScript using Android native WebView (and not using JavaFX WebView) from a JavaFXPorts application:

public class AndroidNativeService extends Activity implements NativeService {
    private Stage stage;

    public void myWebview(Stage stage) {
        this.stage = stage;

        FXActivity.getInstance().runOnUiThread(new Runnable() {     
            @Override
            public void run() {             
                WebView webView = new WebView(FXActivity.getInstance().getApplicationContext());
                FXActivity.getInstance().setContentView(webView);
                webView.getSettings().setJavaScriptEnabled(true);
                webView.getSettings().setDomStorageEnabled(true);
                webView.setWebViewClient(webClient);
                webView.loadUrl("http://www.example.com/index.html");
            }
        });
    }

    WebViewClient webClient = new WebViewClient() {
        @Override
        public void onPageFinished(WebView view, String url) {
            // super.onPageFinished(view, url);          
            System.out.println(">>>>>>>>>>>>>>>>>>>>> onpagefinished title = "+view.getTitle());

            view.evaluateJavascript("(function(){return document.documentElement.outerHTML})();", new ValueCallback<String>() {
                @Override
                public void onReceiveValue(String html) {
                    System.out.println(">>>>>>>>>>>>>>>>>>>>> evaluateJavascript html = "+html);
                    // view.goBack();
                    // stage.show(); # get error java.lang.IllegalStateException: Not on FX application thread; currentThread = main
                }
            });
        }
    };

}

I invoke this class using:

Task<Void> task = new Task<Void>() {
    @Override 
    protected Void call() throws Exception {
        Platform.runLater( () ->  {
            GoNativePlatform goNativePlatform =  GoNativePlatformFactory.getPlatform();
            Looper.prepare(); // if don't use this then get error Looper.prepare() not set
            goNativePlatform.getNativeService().myWebView(stage);   
        });
        return null;
    }
};

Thread th = new Thread(task);
th.start();

I copied "Implements NativeService" as declared on my class statement from Handling Android Native Activities like a Pro though this isn't absolutely necessary to make this work. When trying to implement JavaFX WebView (as opposed to Android Native WebView) with this JavaFX WebView code:

Document doc = webEngine.getDocument();
getTitle(webView.getEngine());
String html = (String) webView.getEngine().executeScript("document.documentElement.outerHTML");

I got either nulls or "not supported yet" when running on Android though the code worked OK on desktop. (Haven't tried yet on IOS but I want to implement too here). I want to retrieve the webpage title and execute javascript to retrieve other data from a webpage. And so my solution was to use Android Native WebView instead of JavaFX WebView when running on Android. Here's my complete code:

public class AndroidNativeService extends Activity implements NativeService {
    private Stage stage;

    public void myWebview(Stage stage) {
        this.stage = stage;

        FXActivity.getInstance().runOnUiThread(new Runnable() {     
            @Override
            public void run() {             
                WebView webView = new WebView(FXActivity.getInstance().getApplicationContext());
                FXActivity.getInstance().setContentView(webView);
                webView.getSettings().setJavaScriptEnabled(true);
                webView.getSettings().setDomStorageEnabled(true);
                webView.setWebViewClient(webClient);
                webView.loadUrl("http://www.example.com/index.html");

                webView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        System.out.println(">>>>>>>>>>>>>>>>>>>>> onClick()");
                        // webView.goBack();
                    }
                }); 
            }
        });
    }

    WebViewClient webClient = new WebViewClient() {
        @Override
        public void onPageFinished(WebView view, String url) {
            // super.onPageFinished(view, url);          
            System.out.println(">>>>>>>>>>>>>>>>>>>>> onpagefinished title = "+view.getTitle());

            view.evaluateJavascript("(function(){return document.documentElement.outerHTML})();", new ValueCallback<String>() {
                @Override
                public void onReceiveValue(String html) {
                    System.out.println(">>>>>>>>>>>>>>>>>>>>> evaluateJavascript html = "+html);
                    // view.goBack();
                    // stage.show(); # get error java.lang.IllegalStateException: Not on FX application thread; currentThread = main
                }
            });
        }
    };

    @Override
    public void onBackPressed() {
        System.out.println(">>>>>>>>>>>>>>>>>>>>> Back Button Pressed");
        setResult(RESULT_CANCELED);
        super.onBackPressed();
        // FXActivity.getInstance().finish();
    }

}

Although I have successfully displayed the desired webpage, retrieved the title and executed some JavaScript, I am struggling to close the webpage and return to the JavaFX stage. My 2 callbacks above onBackPressed() and OnClickListener don't work and are not invoked (can't see the System.out.println ). You can see from above I am trying and struggling to use these alternatives:

• webView.goBack();
• stage.show(); // get error java.lang.IllegalStateException: Not on FX application thread; currentThread = main
• FXActivity.getInstance().finish();

But I am only managing to terminate the whole app rather than return to the JavaFX stage (even though I am passing it's value into this class). Any thoughts?

PS : Looper.prepare(); is necessary to be able to invoke this code though I don't understand what I am doing here?

Answer 2

Update on Solution

I found a solution to executing JavaScript using Android native WebView (and not using JavaFX WebView) from a JavaFXPorts application - see code below. I solved the navigation to and from my JavaFX stage and Android WebView (in my 1st answer on 25 February 2018) by using 2 Activities: my main activity (JavaFX Stage) invokes a 2nd Activity (Android WebView) and passes the URL I want to display and when the 2nd Activity finishes it passes back a result string. You can exit the 2nd Activity by executing finish() or using the back button. You need to add an additional entry in the AndroidManifest.xml for the 2nd Activity.

Here's my main activity:

import android.content.Intent;
import javafx.application.Platform;
import javafxports.android.FXActivity;

/*****************************************
   This is the main activity
******************************************/
public class MainActivity extends FXActivity {

    private static final int SECOND_ACTIVITY_REQUEST_CODE = 0;

    protected void webView() {

        Platform.runLater( () -> {
                String url ="http://www.example.com";
                Intent intent = new Intent(FXActivity.getInstance().getApplicationContext(), Test.class);
                intent.putExtra("url", url);

                // Add result handler
                FXActivity.getInstance().setOnActivityResultHandler((requestCode, resultCode, data) ->
                    switch (requestCode) {
                        case SECOND_ACTIVITY_REQUEST_CODE:
                             //if (resultCode == RESULT_OK) {}

                             // get String data from Intent
                             String result = data.getStringExtra("result");
                             System.out.println("result = " + result);
                             break;

                        default:                             
                             super.onActivityResult(requestCode, resultCode, data);
                             break;
                     }
                });

                FXActivity.getInstance().startActivityForResult(intent, SECOND_ACTIVITY_REQUEST_CODE);
        });

    }
}

Here's my 2nd Activity (Android WebView):

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.webkit.ValueCallback;
import android.webkit.WebView;
import android.webkit.WebViewClient;

/*****************************************
    This is the 2nd activity
******************************************/
public class Test extends Activity {
    private String url;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getIntent().getExtras();
        if (bundle != null) {
            url = bundle.getString("url");
        }
        WebView webView = new WebView(this);
        setContentView(webView);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setDomStorageEnabled(true);
        webView.setWebViewClient(webClient);
        webView.loadUrl(url);
    }


    WebViewClient webClient = new WebViewClient() {

    @Override
    public void onPageFinished(WebView view, String url) {
         String title = view.getTitle();
         System.out.println("onpagefinished title = "+view.getTitle());

         view.evaluateJavascript("(function(){return document.documentElement.outerHTML})();",
                  new ValueCallback<String>() {

                      @Override
                      public void onReceiveValue(String html) {
                        System.out.println("evaluateJavascript html = "+html);

                        if (<exit 2nd activity condition>) {
                            // put the String to pass back into an Intent and close this activity
                            Intent intent = new Intent();
                            intent.putExtra("result", "this is the result string");
                            setResult(RESULT_OK, intent);
                            finishAndRemoveTask();                  // takes you back to main activity
                        }
                      }
             });
    }
    };

}

Here's my AndroidManifest.xml which I manually changed to add the 2nd Activity for Test.class:

<?xml version="1.0" encoding="UTF-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example" android:versionCode="1" android:versionName="1.0">
    <supports-screens android:xlargeScreens="true"/>
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="21"/>
    <application android:label="APP" android:name="android.support.multidex.MultiDexApplication" android:icon="@mipmap/ic_launcher">
            <activity android:name="javafxports.android.FXActivity" android:label="Main" android:configChanges="orientation|screenSize">
                    <meta-data android:name="main.class" android:value="com.example.Launcher"/>
                    <meta-data android:name="debug.port" android:value="0"/>
                    <intent-filter>
                            <action android:name="android.intent.action.MAIN"/>
                            <category android:name="android.intent.category.LAUNCHER"/>
                    </intent-filter>
            </activity>
            <activity
                android:name="com.example.Test"
                android:label="Test"
                android:configChanges="orientation|screenSize">
            </activity>
    </application>
</manifest>

When instantiating MainActivity it crashes with "can't create a handle without a Looper.prepare()". A handle is not explicitly created and so it's not clear which handle is referenced. Solution: create a looper and then after instantiation destroy it. You can only issue Looper.prepare() once otherwise it crashes. Subsequent calls to MainActivity.webView() work without Looper. Here's my code:

Looper.prepare();
new MainActivity();
Looper.myLooper().quitSafely();