Start an Activity based on parameter passed from JavaScript interface

Issue

I want to open a new activity when I tap on a link in my WebView, but I don't know how to create a method passing an Object variable to make a dynamic method. That's why I do it this way actually:

public class WebAppInterface {
    public Context mContext;

    WebAppInterface(Context c) {
        mContext = c;
    }

    @JavascriptInterface
    public void toAbout(){
        startActivity(new Intent(MainActivity.this, About.class));
    }
    @JavascriptInterface
    public void toTwitch(){
        startActivity(new Intent(MainActivity.this, Twitch.class));
    }
    @JavascriptInterface
    public void toNews(){
        startActivity(new Intent(MainActivity.this, News.class));
    }

    (much more methods like these for specific classes) ...

}

HTML/JS:

<div class="entry" onclick="toTwitch();">Twitch</div>
<div class="entry" onclick="toAbout();">About</div>

<script type="text/javascript">
    function toTwitch() { 
        Android.toTwitch();
    }   
    function toAbout(input) { 
        Android.toAbout();
    }
</script>

MainActivity.java onCreate:

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WebView myWebView = (WebView) findViewById(R.id.webView1);
        myWebView.addJavascriptInterface(new WebAppInterface(this), "Android");
        myWebView.setWebViewClient(new WebViewClient());

        myWebView.getSettings().setJavaScriptEnabled(true);
        myWebView.loadUrl("file:///android_asset/index.html");
        // Caching
        myWebView.getSettings().setDomStorageEnabled(true);
        String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath();
        myWebView.getSettings().setAppCachePath(appCachePath);
        myWebView.getSettings().setAllowFileAccess(true);
        myWebView.getSettings().setAppCacheEnabled(true);
    }

Isn't there a way to make just one single method instead of dozens (toAbout(), toTwitch, toNews(), etc.) that is more dynamic?

Solution

Android JavaScript interface supports parameter passing.

You can create a generic method which accepts String, get the respective Class and use it on startActivity(). Note that you have to use fully-qualified name of the Activity, which means including the package name (e.g. com.example.About).

Inside WebAppInterface,

@JavascriptInterface
public void openActivity(String activityName) {
    String packageName = "com.example";
    try {
        Class activityClass = Class.forName(packageName + "." + activityName);
        mContext.startActivity(new Intent(MainActivity.this, activityClass));
    } catch(Exception ex) {
        Toast.makeText(mContext, "invalid activity name: " + activityName, Toast.LENGTH_SHORT).show();
    }
}

On HTML/JS,

<script type="text/javascript">
    function toTwitch() { 
        Android.openActivity('Twitch');
    }   
    function toAbout() { 
        Android.openActivity('About');
    }
</script>

Answered By - Andrew T.