Qt QtextEdit高度自适应

QTextEdit *editor = new QTextEdit(this);

connect(editor->document(),SIGNAL(contentsChanged()),this,SLOT(textAreaChanged()));

private slots:
void textAreaChanged(){
QTextDocument *document=qobject_cast<QTextDocument*>(sender());  
document->adjustSize();  
if(document){  
    QTextEdit *editor=qobject_cast<QTextEdit*>(document->parent()->parent());  
    if (editor){  
        int newheight = document->size().rheight()+10;  
        if (newheight != editor->height()){  
            editor->setFixedHeight(newheight);  
        }  
    }  
} 
}