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Injecting Javascript bridge in WebView

由 此生再无相见时 提交于 2019-12-05 04:20:36

Here is a cleaned up version, minimizing unneeded code. This runs on API level 18 and 23 emulators (and my 6.0.1 phone). The webView is never added to the view hierarchy. The toast shows the HTML pulled from the site anyway. Compiled against API 25 using Java 8.

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.JavascriptInterface;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    WebView webView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webView = new WebView(getApplicationContext());

        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebChromeClient(new WebChromeClient());

        webView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(final WebView view, String url) {
                webView.loadUrl("javascript: void AndroidHook.showToast(document.getElementsByTagName('body')[0].innerHTML);");
            }
        });

        webView.addJavascriptInterface(new JSInterface(), "AndroidHook");
        webView.loadUrl("http://example.com");
    }

    public class JSInterface {
        @JavascriptInterface
        public void showToast(final String html) {

            MainActivity.this.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(MainActivity.this, "Reached JS: " + html, Toast.LENGTH_LONG).show();
                }
            });
        }
    }
}

Here's the layout.

<?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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="16dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    tools:context="com.foo.jsinjectiontest.MainActivity">

</RelativeLayout>

And finally the manifest.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.foo.jsinjectiontest">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

    <uses-permission android:name="android.permission.INTERNET"/>

</manifest>

Please try this, it is calling the javascript function and showing toast message also.

public class Main3Activity extends AppCompatActivity {
     WebView webView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        webView = new WebView(getApplicationContext());
        webView.getSettings().setJavaScriptEnabled(true);

        webView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                webView.setVisibility(View.GONE);

            }
            @Override
            public void onPageFinished(final WebView view, String url) {
                Log.e("checking", "MYmsg");
                webView.loadUrl("javascript:(function() { " +
                        "document.body.innerHTML = '<p>test<p>';" + "})()");
                webView.loadUrl("javascript: window.CallToAnAndroidFunction.setVisible()");



            }
        });
        webView.setVisibility(View.INVISIBLE);
        webView.addJavascriptInterface(new myJavaScriptInterface(), "CallToAnAndroidFunction");
        webView.loadUrl("https://example.com");
    }
    public class myJavaScriptInterface {
        @JavascriptInterface
        public void setVisible() {

            Handler handler = new Handler();
            Runnable runnable = new Runnable() {
                @Override
                public void run() {

                    Main3Activity.this.runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            webView.setVisibility(View.VISIBLE);
                            Log.e("Testing", "no");
                            Toast.makeText(Main3Activity.this, "Reached JS", Toast.LENGTH_LONG).show();

                        }
                    });


                }
            };handler.postDelayed(runnable,2000);

        }}
}

It will not show webView in the UI, as webview is not defined in xml layout.

A couple of things that pop out to me.

  1. The JavaScript interface should be attached BEFORE loading any URLs.

  2. The second loadURL window.onload might be assigned AFTER the original URL has loaded. It would make more sense to call setWebViewClient() and call Droid.showToast('testing!'); from inside the onPageFinished method.

  3. The @JavascriptInterface doesn't run on the main UI thread which will stop your toasts from running.

  4. The issue with your second edit's innerHTML code not working is related to point 2. You're making your calls in a synchronous single block, whereas it should be AFTER the page dom has loaded AKA onPageFinished()

webview.addJavascriptInterface(new jsInterface(), "Droid"); have to come before webview.loadUrl("https://example.com");

Then use Webview Listener. onFinish() method.. then inject your webview.loadUrl("javascript: window.onload=function(){ Droid.showToast('testing!'); }"); in onFinish method

i already do tons of webview injection modifying web.. i thinks its should work..

EDIT
use chrome://inspect/#devices to inspect your app when webview is load

How about use onProgressChanged() in WebChromeClient?

I've changed some code from Edit 3 to like this,

webView.setWebChromeClient(new WebChromeClient(){
        @Override
        public void onProgressChanged(WebView view, int newProgress) {
            super.onProgressChanged(view, newProgress);
            if(newProgress == 100){
                webView.loadUrl("javascript: void window.CallToAnAndroidFunction.setVisible(document.getElementsByTagName('body')[0].innerHTML);");
            }
        }
    });

The change is that you invoke javascript when progress==100 instead of onPageFinished()

标签
javascript
java
android
webview
javascript-injection
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