Try this code
Dialog dialog; public void openDialog() { dialog = new Dialog(this); // Context, this, etc. dialog.setContentView(R.layout.dialog_demo); dialog.setTitle(R.string.dialog_title); dialog.show(); } public void cancelDialog() { dialog.dismiss(); }
You are passing Button View to `cancelDialog(View)` instead of `cancelDialog(Dialog v)`

this may be like this
Dialog dialog; public void openDialog() { dialog = new Dialog(this); // Context, this, etc. dialog.setContentView(R.layout.dialog_demo); dialog.setTitle(R.string.dialog_title); dialog.show(); }
public void cancelDialog() { dialog.dismiss(); }