Uncaught TypeError when calling a Javascript Function in Android

Question

I am an Android developer and new to JavaScript. I am controlling the webview from my activity using javascript. In my login page when I use the Java Script functions I getting some huge errors. Please guide me to avoid these errors.

Code:

web.loadUrl("javascript:document.getElementById(\"umail\").value = \""
        + email + "\";");
web.loadUrl("javascript:document.getElementById(\"password\").value = \""
        + pwd + "\";");
web.loadUrl("javascript:document.getElementById(\"confirmpassword\").value = \""
        + confirm_pwd + "\";");
web.loadUrl("javascript:func_register_step1('signin')");

web.loadUrl("javascript:window.JSInterface.getErrorMSG(document.getElementById('errormessagetd').innerHTML);");
web.loadUrl("javascript:window.JSInterface.getWarningMSG(document.getElementById('warning_msg').innerHTML);");

Error:

05-15 11:52:28.310: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:28.310: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:28.310: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:28.310: E/Web Console(3722): Uncaught ReferenceError: func_register_step1 is not defined at null:1
05-15 11:52:28.310: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:28.310: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:31.240: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:31.240: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:31.240: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:31.240: E/Web Console(3722): Uncaught ReferenceError: func_register_step1 is not defined at null:1
05-15 11:52:31.250: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:31.250: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:33.590: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:33.590: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:33.590: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:33.590: E/Web Console(3722): Uncaught ReferenceError: func_register_step1 is not defined at null:1
05-15 11:52:33.600: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:33.600: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:40.260: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:40.270: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:40.270: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:40.270: E/Web Console(3722): Uncaught ReferenceError: func_register_step1 is not defined at null:1
05-15 11:52:40.270: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:40.270: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught TypeError: Cannot set property 'value' of null at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught ReferenceError: func_register_step1 is not defined at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1
05-15 11:52:41.290: E/Web Console(3722): Uncaught TypeError: Cannot read property 'innerHTML' of null at null:1

Answer 1

According to the thrown errors, it seems that document.getElementById(...) returns null. And so applying .value and .innerHTML to null throw the errors.

I suspect the page is not loaded when you call your javascript function. When do you call your javascript, I mean in which method? To be sure the page is loaded, you can call loadUrl in the onPageFinished method of the WebViewClient object.