有时我们需要，控件不接收信号，可以使用 blockSignals
当设置为true时，QObject对象[子类]不会发出信号
1、函数原型
1 bool QObject::blockSignals(bool block)
2 If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). If block is false, no such blocking will occur.
3 The return value is the previous value of signalsBlocked().
4 Note that the destroyed() signal will be emitted even if the signals for this object have been blocked.
5 Signals emitted while being blocked are not buffered.
6 See also signalsBlocked() and QSignalBlocker.
2.使用说明
例如：
QComboBox动态添加item的时候，它会发出xxxChanged信号，但是初始情况下我们不希望其发出，待初始化完成后再发出。
则可以：
先设置blockSignals(true)；//阻塞信号
添加item；
设置blockSignals(false);//取消信号阻塞
example:
1 m_Controls.comboBox->blockSignals(true);
2 m_Controls.comboBox->addItems( AngleList());
3 m_Controls.comboBox->setCurrentIndex(0);//45度
4 m_Controls.comboBox->blockSignals(false);