called when printing starts . you can use this callback to allocate resources . this method is invoked on the main thread . concode_field_sep String EXTRA_PRINT_PREVIEW concode_field_sep void onWriteCancelled concode_elem_sep void onLayoutFailed concode_elem_sep void onWriteFailed concode_elem_sep void onLayoutFinished concode_elem_sep void onLayoutCancelled concode_elem_sep void onLayout concode_elem_sep void onWrite concode_elem_sep void onWriteFinished concode_elem_sep void onFinish
void function ( ) { }