JsEvaluator library for running JavaScript in Android apps

JsEvaluator may help you run JavaScript in an Android app and get the results. This is an alternative to evaluateJavascript method of the WebView. Supports Android version 4.0 (Ice Cream Sandwich) and newer.

Setup

There are two ways your can add JsEvaluator to your project:

1. From a remote Maven repositorty.
2. From a local .aar or .jar file.

1. Setup from Maven repository in Android Studio

1. Add maven { url "https://jitpack.io" } into allprojects/repositories section of your project build.gradle file. For example:

allprojects {
    repositories {
        jcenter()
        maven { url "https://jitpack.io" }
    }
}

2. Add compile 'com.github.evgenyneu:js-evaluator-for-android:v1.0.2' into dependencies section of your module build.gradle file. For example:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.0'
    compile 'com.github.evgenyneu:js-evaluator-for-android:v1.0.2'
}

For less information, see Gradle/Maven setup instructions on JsEvaluator jitpack.io page.

2. Setup from local .aar file

Download jsevaluator-1.0.aar. You can also build it yourself into jsevaluator/build/outputs/aar/ directory in Android Studio with this command:

./gradlew :jsevaluator:aR

Add aar file to Android Studio project

To add JsEvaluator to your app in Android Studio:

1. Copy the jsevaluator-1.0.aar to your app/libs folder.
2. Add compile(name:'jsevaluator-1.0', ext:'aar') to dependencies block of your module build.gradle file.
3. Add the following code to the repositories block of your project build.gradle file.

flatDir{
    dirs 'libs'
}

Add jar file to Eclipse project

1. Unzip the jsevaluator-1.0.aar and get the classes.jar from it. You may want to rename it to jsevaluator.jar.
2. Open properties for your app project.
3. Select Libraries tab in Java Build Path.
4. Click Add JARs... button and select the .jar file.
5. In your project properties click Order and export tab.
6. Tick the .jar file.

Usage

Create evaluator instance:

JsEvaluator jsEvaluator = new JsEvaluator(this);

this is a reference to your activity.

Evaluate JavaScript

jsEvaluator.evaluate("2 * 17", new JsCallback() {
  @Override
  public void onResult(final String result) {
    // get result here
  }
});

Call a JavaScript function

jsEvaluator.callFunction("function myFunction(a, b, c, a) { return 'result'; }",
  new JsCallback() {

  @Override
  public void onResult(final String result) {
    // get result here
  }
}, "myFunction", "parameter 1", "parameter 2", 912, 101.3);

Any number of string, int or double parameters can be supplied.

How it works

Behind the scenes it creates a WebView and feeds it JavaScript code for evaluation:

mWebView = new WebView(context);
String javascript = "<script>myObj.returnResult('Hello World')</script>";
String base64 = Base64.encodeToString(data, Base64.DEFAULT);
mWebView.loadUrl("data:text/html;charset=utf-8;base64," + base64);

The result of evaluation is sent back into Android activity:

public class JavaScriptInterface {
	public void returnResult(String result) {
		// result from JavaScript
	}
}

mWebView.addJavascriptInterface(new JavaScriptInterface(), "myObj");

Tests

Tests are located in app module of this project. The app can be run for manual testing as well.

Or run as Android JUnit Test for unit testing.

Android versions tested:

• 4.0.3 (Ice Cream Sandwich)
• 4.1.2, 4.2.2, 4.3 (Jelly Bean)
• 4.4.2 (KitKat)
• 5.0, 5.1 (Lollipop)
• 5.2 Android M preview (Muffin) 😉

Result is returned asynchronously

The result from JavaScript is returned asynchronously in the UI thread. It is recommended to evaluate in the UI thread as well.

// somewhere in UI thread ...
jsEvaluator.evaluate("2 * 17", new JsCallback() {
  @Override
  public void onResult(final String result) {
    // Result is returned here asynchronously in UI thread
  }
});

JavaScript is evaluated in new context

Each time the JavaScript is evaluated in the new context. It can not access the result of a previous evaluation. Please concatenate all your JavaScript to one string and evaluate it in one go.

For example, if you need to load jQuery libary and then use it:

String jQuery = "/*! jQuery JavaScript Library v2.1.1 ...";
jsEvaluator.evaluate(jQuery + "; $.isNumeric(123)", new JsCallback() { ...

Feedback

If you have any issues or need help please do not hesitate to create an issue ticket.