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Editorial Team
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Asked: 2026-05-26T20:16:19+00:00

I am trying to invoke camera from HTML5 and JavaScript. My code is as

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I am trying to invoke camera from HTML5 and JavaScript. My code is as below. But I am getting null pointer exception.

Main Activity : 

 public void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.main);  
            WebView webview=(WebView)findViewById(R.id.webkitWebView1); 
            WebSettings settings = webview.getSettings();  
            settings.setJavaScriptEnabled(true);   
            //load html5 page  
            webview.loadUrl("file:///android_asset/www/html/opencamera.html");  

            openCamera=new OpenCamera();  
            webview.addJavascriptInterface(openCamera,"camera");  

        }  

        @Override   
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {   
            if (requestCode== 0 && resultCode == Activity.RESULT_OK){   
                System.out.println("Done");  
            }  
        }

Camera call : 

public class OpenCamera extends Activity {  

    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
    }  

    public void startCameraActivity(){  
        Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE );  
        startActivityForResult(intent,0);  
    }  

}

html page : 

 <!DOCTYPE HTML>  
    <html>  
    <head>  
    <script type="text/javascript">  
    function openCamera(){  
        //alert("cameras");  
        camera.startCameraActivity();  
    }  
    </script>  


    <title>Welcome</title>  
    </head>  
    <body>  
    Hello World!!!  
    <br/>  
    <button type="button" onclick="openCamera()">Capture Image</button>  
    </body>  
    </html>

Permissions in manifest: 

<uses-feature android:name="android.hardware.camera" />  
    <uses-permission android:name="android.permission.CAMERA" />  
    <uses-feature android:name="android.hardware.camera.autofocus" />  
    <uses-permission android:name="android.permission.INTERNET" />

Logcat: 

11-16 08:56:07.133: ERROR/AndroidRuntime(539): java.lang.NullPointerException  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.app.Activity.startActivityForResult(Activity.java:2817)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at com.test.camera.OpenCamera.startCameraActivity(OpenCamera.java:17)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.webkit.WebViewCore.nativeTouchUp(Native Method)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.webkit.WebViewCore.nativeTouchUp(Native Method)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.webkit.WebViewCore.access$3300(WebViewCore.java:52)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.webkit.WebViewCore$EventHub$1.handleMessage(WebViewCore.java:1150)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.os.Handler.dispatchMessage(Handler.java:99)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.os.Looper.loop(Looper.java:123)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at android.webkit.WebViewCore$WebCoreThread.run(WebViewCore.java:621)  
11-16 08:56:07.133: ERROR/AndroidRuntime(539):     at java.lang.Thread.run(Thread.java:1096)
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1 Answer

  1. Editorial Team

    You are starting Camera Activity from OpenCamera Activity which is not yet started (according to android way of starting Activity), So the context of OpenCamera Activity is null, that is why your Context is null at that time and causing NullPointerException.

    Workaround:

    Pass a context to the Function startCameraActivity() as

    public void startCameraActivity(Context con){  
        Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE );  
        con.startActivityForResult(intent,0);  
}

    pass a context to the WebView

    webview.addJavascriptInterface(this,"context");

    and in your script

    <script type="text/javascript">  
    function openCamera(){   
        camera.startCameraActivity(context);  
    }  
</script>

    OpenCamera need not to be an Activity

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