Android：在WebView中检测history.back（）

Question

A button in my WebView is used to go back using the history.back() JavaScript call. I do not understand much of JavaScript, but after a bit of searching I found that we can use the addJavascriptInterface() method of a WebView .

Now, I intend to finish my Activity when the button is clicked. I landed up having something of this sort:

public class MyActivity extends Activity {
private static final String sTag = "MyActivity";

private WebView mWebContent;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.browser_page);


    mWebContent = (WebView) findViewById(R.id.webContent);

    mWebContent.getSettings().setJavaScriptEnabled(true);
    mWebContent.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
    mWebContent.getSettings().setBuiltInZoomControls(true);
    mWebContent.addJavascriptInterface(new JavaScriptInterface(), "history"); //history.back();

    Bundle extras = getIntent().getExtras();

    if (extras != null) {
        mWebContent.loadUrl(extras.getString("URL"));
    }
}

    public class JavaScriptInterface {
        JavaScriptInterface() {
        }

    public void back() {
        Log.v(sTag, "back pressed");
        MyActivity.this.finish();
    }
}
}

But unfortunately when the button is pressed the Activity doesn't finish, neither do I get anything in the Log.

Here is the html for the button :

<a href="javascript:void(0);">
   <img src="images/btn-go-back.png" onClick="history.back();" border="0" />
</a>

What am I doing wrong?

Thanks in advance.

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Edit : Just wanted to clear the fact that changing the html is not an option for me. I have no power over the the html code :). I have to handle it in the application.

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Edit: Tried changing history.back() to window.history.back() (locally), still no change.

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Edit : I was experimenting by locally loading html conent and found out that if I change history.back() to say something like android_app.back() and register my JavaScriptInterface by the name android_app it works fine. Why is that? Does that mean that we can't use history to register an interface? Does the developer docs mention this?

Answer 1

Read the Navigating web page history section of this article. It tells completely about the android webviews.It tells about how to make webviews handle history.

http://developer.android.com/guide/webapps/webview.html

Hope this helps.

Answer 2

Try <a href="#" onclick="window.history.back()"><img src="bla" /></a>

edit: just read you can't change the HTML code .. Don't see a solution then ..

Answer 3

After a lot of searching and asking I have finally arrived at the conclusion that you cannot add a java script interface, using addJavascriptInterface (Object obj, String interfaceName) , with the interface name as history (or perhaps any javascript keyword).

Maybe this is written somewhere in the developer docs or manual, but I couldn't find it though.

Answer 4

Check this:

@Override

    public boolean onKeyDown(int keyCode, KeyEvent event) {
        // Check if the key event was the Back button and if there's history
        if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack()) {
            myWebView.goBack();
            return true;
        }
        // If it wasn't the Back key or there's no web page history, bubble up to the default
        // system behavior (probably exit the activity)
        return super.onKeyDown(keyCode, event);
    }