[Android]app <---> javascript 통신

AndroidMainifest.xml

<uses-permission android:name="android.permission.INTERNET" />

main.xml

<EditText android:id="@+id/input_area"
  android:layout_width="fill_parent"
     android:layout_height="wrap_content"
 />

 <Button android:id="@+id/submitBtn"
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content"
  android:text="submit"
 />

<WebView android:id="@+id/webview" android:layout_width="fill_parent" android:layout_height="fill_parent" />

java code

private final Handler handler = new Handler();
private static final String JAVASCRIPT_APP_KEY = "WebviewExample";
private TextView lableView = null;  
private Button submitBtn = null;

lableView = (TextView)findViewById(R.id.labelView);
final WebView wv = (WebView)findViewById(R.id.webview);
wv.getSettings().setJavaScriptEnabled(true);
wv.addJavascriptInterface(new AndroidBridge(), JAVASCRIPT_APP_KEY);
wv.loadUrl("url");

//버튼이 눌려질 경우
submitBtn = (Button)findViewById(R.id.submitBtn);
        submitBtn.setOnClickListener(new View.OnClickListener(){
         EditText txt = (EditText)findViewById(R.id.input_area);
         @Override
   public void onClick(View v) {
    wv.loadUrl("javascript:callJavascript('"+txt.getText()+"')");
   }
});

private class AndroidBridge {
     public void callAndroid(final String arg){
      handler.post(new Runnable() {
    @Override
    public void run() {
     Log.i(TAG, "setMessage("+arg+")");
     lableView.setText(arg);
    }
      });
     }
    }

html

<script type="text/javascript">
function callAndroid(){
    window.WebviewExample.callAndroid("android call");
    document.getElementById('area').innerHTML = "android call";
}

function callJavascript(message){
    document.getElementById('area').innerHTML = message;
}
</script>
<a href="#" onclick="callAndroid()">call</a><br/>
<div id="area"></div>