It is not mandatory to use WebChromeClient
if you want to display message box from JavaScript alert
function. You can create interfaces between your JavaScript code and client-side Android code.
In the below example, your JavaScript code can call a method in your Android code to display a Dialog
, instead of using JavaScript's alert()
function. I found that this is the most convenient and widely supported way to display alerts.
Include the following classes in your Android application:
File: WebAppInterface.java
import android.content.Context;
import android.webkit.JavascriptInterface;
public class WebAppInterface {
Context mContext;
/** Instantiate the interface and set the context */
WebAppInterface(Context c) {
mContext = c;
}
/** Show a Message box from the web page */
@JavascriptInterface
public void androidAlert(String message) {
DialogBox dbx = new DialogBox();
dbx.dialogBox(message, "I get it", "",mContext);
}
}
File: DialogBox.java
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
public class DialogBox {
public boolean dialogBox(String msg, String okButton, String cancelButton, final Context activity) {
Dialog v = null;
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(activity);
alertDialogBuilder.setMessage(msg);
if (okButton != "") {
alertDialogBuilder.setPositiveButton(okButton,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface arg0, int arg1) { /**/ }
});
}
if (cancelButton != "") {
alertDialogBuilder.setNegativeButton(cancelButton,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface arg0, int arg1) { /**/ }
});
}
AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();
return true;
}
}
Next, bind the WebAppInterface
class to the JavaScript that runs in your WebView
with addJavascriptInterface()
and name the interface Android
:
WebView mWebView = (WebView) findViewById(R.id.webview);
mWebView.addJavascriptInterface(new WebAppInterface(this), "Android");
This creates an interface called Android
for JavaScript running in the WebView
. At this point, your web application has access to the WebAppInterface
class. Below is some HTML and JavaScript that creates a message box using the new interface when the user clicks a button:
<input type="button" value="Alert!" onClick="javascript:Android.androidAlert('It works!');" />
At the click of the button, the Android
interface is used to call the WebAppInterface.androidAlert()
method.
A bit of warning: Using addJavascriptInterface()
allows JavaScript to control your Android application. This can be a very useful feature or a dangerous security issue. As such, you should not use addJavascriptInterface()
unless you wrote all of the HTML and JavaScript that appears in your WebView
.