非常小的窗口都能显示

QT       += core gui charts

#include <QtCharts>
using namespace QtCharts;

//创建饼状图
void MainWindow::createpieSewies()
{
    //饼状图
    QPieSeries * my_pieSeries = new QPieSeries();
    //中间圆与大圆的比例
    my_pieSeries->setHoleSize(0.35);
    //扇形及数据
    QPieSlice *pieSlice_running = new QPieSlice();
    pieSlice_running->setValue(25);//扇形占整个圆的百分比
    pieSlice_running->setLabel("XXX");
    pieSlice_running->setLabelVisible();
    pieSlice_running->setColor(QColor("#4cb9cf"));
    pieSlice_running->setLabelColor(QColor("#4cb9cf"));
    pieSlice_running->setBorderColor(QColor("#4cb9cf"));
    pieSlice_running->setBorderColor(QColor());
    my_pieSeries->append(pieSlice_running);

    QPieSlice *pieSlice_noconnect = new QPieSlice();
    pieSlice_noconnect->setValue(25);
    pieSlice_noconnect->setLabel("YYY");
    pieSlice_noconnect->setColor(QColor("#53b666"));
    pieSlice_noconnect->setLabelColor(QColor("#53b666"));
    pieSlice_noconnect->setBorderColor(QColor("#53b666"));
    pieSlice_noconnect->setLabelVisible();//设置标签可见,缺省不可见
    my_pieSeries->append(pieSlice_noconnect);

    QPieSlice *pieSlice_idle = new QPieSlice();
    pieSlice_idle->setValue(50);
    pieSlice_idle->setLabel("WWW");
    pieSlice_idle->setLabelVisible();
    pieSlice_idle->setColor(QColor("#2f89cf"));
    pieSlice_idle->setLabelColor(QColor("#2f89cf"));
    pieSlice_idle->setBorderColor(QColor("#2f89cf"));
    my_pieSeries->append(pieSlice_idle);
// 图表视图
    QChart *chart = new QChart();
    chart->setTitle("FFFFF");
    chart->addSeries(my_pieSeries);
    chart->setAnimationOptions(QChart::SeriesAnimations);
    chart->legend()->setAlignment(Qt::AlignBottom);
    chart->legend()->setBackgroundVisible(false);
    chart->legend()->setFont(QFont("黑体", 8)) ; // 图例字体
    chart->setTitleBrush(QColor("#808396"));
    chart->legend()->setLabelColor(QColor("#808396"));
    QChartView *chartView = new QChartView();
    chartView = new QChartView(ui->widget);
    chartView->setRenderHint(QPainter::Antialiasing);
    chartView->setRenderHint(QPainter::NonCosmeticDefaultPen);
    chartView->setChart(chart);
    ui->gridLayout->addWidget(chartView);
}