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Android – How to run intent from JavaScript

Posted by: admin December 28, 2021 Leave a comment

Questions:

I am new to Android and Java. I have constructed an app using HTML/Javascript that is working great.

I now need to create an activity that launches the email client, fills in subject and body, and (the tough part) adds a file attachment. I have not been able to do this from within JavaScript, mailto: will not attach the file.

So I need to accomplish this through Java and execute it from JavaScript. I think this can be done by using addJavaScriptInterface but I cannot find any detailed documentation or examples to go off of.

How could I do this?

Here is what I have so far after reading the documentation:

2nd update to code:

MainActivity.java

public class MainActivity extends DroidGap {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    super.setIntegerProperty( "splashscreen", R.drawable.splash );
    super.loadUrl("file:///android_asset/www/index.html", 1000);
    WebView mWebView;
    mWebView = (WebView)findViewById(R.id.webview);
    mWebView.getSettings().setJavaScriptEnabled(true);
    mWebView.addJavascriptInterface(new JavaScriptInterface(), "Android"); 
}
}

JavaScriptInterface.java

public class JavaScriptInterface {

public void doEmail(){
    Intent sendIntent = new Intent(Intent.ACTION_SEND);
    sendIntent.setType("text/html");
    sendIntent.putExtra(android.content.Intent.EXTRA_TEXT,"test text");
    sendIntent.putExtra(Intent.EXTRA_SUBJECT,"test subject");
    sendIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
    sendIntent.putExtra(Intent.EXTRA_STREAM,Uri.parse("file://test co.html"));
    startActivity(Intent.createChooser(sendIntent, "Send email..."));
    } 
}

Then I would reference the intent through JavaScript by using Android.doEmail().

With the above code I am getting 2 errors in Eclipse
1. The method startActivity(Intent) is undefined for the type – JavaScriptInterface
2. webview cannot be resolved or is not a field – MainActivity

What am I doing wrong?

Answers:

This documentation tells you exactly how to do it.

It looks like there are three main steps:

  1. Create your ‘interface’ class in Android
  2. Add an instance of this ‘interface’ to the WebView you are using.
  3. Call the interface from your JavaScript.

###

public class MainActivity extends DroidGap {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.setIntegerProperty( "splashscreen", R.drawable.splash );

        JavaScriptInterface jsi = new JavaScriptInterface(this, appView);
        appView.addJavascriptInterface(jsi, "Android");

        super.loadUrl("file:///android_asset/www/index.html", 1000);
    }
}

and

public class JavaScriptInterface {
    private WebView mAppView;
    private DroidGap mGap

    public JavaScriptInterface (DroidGap gap, WebView view)
    {
        mAppView = view;
        mGap = gap;
    }

    public void doEmail(){
        Intent sendIntent = new Intent(Intent.ACTION_SEND);
        sendIntent.setType("text/html");
        sendIntent.putExtra(android.content.Intent.EXTRA_TEXT,"test text");
        sendIntent.putExtra(Intent.EXTRA_SUBJECT,"test subject");
        sendIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        sendIntent.putExtra(Intent.EXTRA_STREAM,Uri.parse("file://test co.html"));
        startActivity(Intent.createChooser(sendIntent, "Send email..."));
    } 
}

###

Using addJavaScriptInterface will extend the DOM inside the embedded browser, and allow JS to access a Java object, which is exactly what you want.

There are too many steps to outline here, that have already been documented. This link has a good overview.

###

I used WebIntents from Boris Smus (http://smus.com/android-phonegap-plugins) and it works like a charm. You can also peruse his code a little to understand better the approach he took with plugins.

NOTE: you do need to update the code provided as is a little (see comments) and the plugin architecture has changed a little.