Hi，大家好，欢迎来到树莓派之littlevGL课堂，我们在上节课中学习了"进度条"控件(lv_bar)，本节课带大家来学习一下单按钮控件，废话不多说！ 一 有图有真相 先看图！
终于来到了按钮控件的课程，本节课我们将不再着重讲控件是如何创建的以及控件的外观设置等，而要着重讲一下按键的事件属性，什么是事件呢？这个在前面的一节课程中有讲过，但是到本节课程才到了真正的应用的时候，就像上面的动态图一样，任何一个按钮按下后都有效果切换，同样的还会触发一个按钮的回调事件，只有控件有操作相应，我们才真正开始了交互界面的学习，毕竟一个界面只是向你展示，而你没法通过界面去控制一些东西称不上交互，那么我们先来做一下上面那个简单的按钮效果。 二 代码分析 用户可下载"圆弧对象(lv_arc)的使用"文章末尾的Demo工程(点击我直接下载),参考圆弧对象(lv_arc)的使用文章,将以下Demo代码复制到Demo工程test.c文件空白处.然后在test.c文件的create_test()函数中增加btn_test()函数测试。 static lv_obj_t * btn1;
static lv_obj_t * btn2;
static lv_obj_t * btn_label;
static void btn_event_handler(lv_obj_t * obj, lv_event_t event)
{
if (obj == btn1) {
if(event == LV_EVENT_CLICKED) {
printf("Btn1 Clicked\n");
lv_label_set_text(btn_label,"Btn1 Clicked");
}
}else if(obj == btn2){
if(event == LV_EVENT_VALUE_CHANGED) {
printf("Btn2 Toggled\n");
lv_label_set_text(btn_label,"Btn2 Toggled");
}
}
}
static void btn_test(void)
{
lv_obj_t * label;
btn1 = lv_btn_create(lv_scr_act(), NULL);
lv_obj_set_event_cb(btn1, btn_event_handler);
lv_obj_align(btn1, NULL, LV_ALIGN_CENTER, 0, -40);
label = lv_label_create(btn1, NULL);
lv_label_set_text(label, "Button");
btn2 = lv_btn_create(lv_scr_act(), NULL);
lv_obj_set_event_cb(btn2, btn_event_handler);
lv_obj_align(btn2, NULL, LV_ALIGN_CENTER, 0, 40);
lv_btn_set_toggle(btn2, true);
lv_btn_toggle(btn2);
lv_btn_set_fit2(btn2, LV_FIT_NONE, LV_FIT_TIGHT);
label = lv_label_create(btn2, NULL);
lv_label_set_text(label, "Toggled");
btn_label = lv_label_create(lv_scr_act(), NULL);
lv_label_set_long_mode(btn_label, LV_LABEL_LONG_BREAK);
lv_obj_set_width(btn_label, 180);
lv_label_set_text(btn_label,"Watting BTN for clicked!");
lv_obj_align(btn_label, NULL, LV_ALIGN_CENTER, 0, 90);
lv_label_set_align(btn_label, LV_LABEL_ALIGN_CENTER);
}enum {
LV_EVENT_PRESSED, /**< The object has been pressed*/
LV_EVENT_PRESSING, /**< The object is being pressed (called continuously while pressing)*/
LV_EVENT_PRESS_LOST, /**< User is still pressing but slid cursor/finger off of the object */
LV_EVENT_SHORT_CLICKED, /**< User pressed object for a short period of time, then released it. Not called if dragged. */
LV_EVENT_LONG_PRESSED, /**< Object has been pressed for at least `LV_INDEV_LONG_PRESS_TIME`. Not called if dragged.*/
LV_EVENT_LONG_PRESSED_REPEAT, /**< Called after `LV_INDEV_LONG_PRESS_TIME` in every
`LV_INDEV_LONG_PRESS_REP_TIME` ms. Not called if dragged.*/
LV_EVENT_CLICKED, /**< Called on release if not dragged (regardless to long press)*/
LV_EVENT_RELEASED, /**< Called in every cases when the object has been released*/
LV_EVENT_DRAG_BEGIN,
LV_EVENT_DRAG_END,
LV_EVENT_DRAG_THROW_BEGIN,
LV_EVENT_KEY,
LV_EVENT_FOCUSED,
LV_EVENT_DEFOCUSED,
LV_EVENT_VALUE_CHANGED, /**< The object's value has changed (i.e. slider moved) */
LV_EVENT_INSERT,
LV_EVENT_REFRESH,
LV_EVENT_APPLY, /**< "Ok", "Apply" or similar specific button has clicked*/
LV_EVENT_CANCEL, /**< "Close", "Cancel" or similar specific button has clicked*/
LV_EVENT_DELETE, /**< Object is being deleted */
};
typedef uint8_t lv_event_t; /**< Type of event being sent to the object. */
首先我们创建了两个按钮对象，这个我们就不再详细的去讲了，然后我们还创建了一个标签对象用来显示按钮状态，关于标签对象如何使用，后面我们再讲解，这里我们先不做讲解了，其实也是很简单的。 接下来才是最重要的，我们还给两个按钮对象设置了事件回调函数： lv_obj_set_event_cb(btn1, btn_event_handler); lv_obj_set_event_cb(btn2, btn_event_handler); static void btn_event_handler(lv_obj_t * obj, lv_event_t event)
{
if (obj == btn1) {
if(event == LV_EVENT_CLICKED) {
printf("Btn1 Clicked\n");
lv_label_set_text(btn_label,"Btn1 Clicked");
}
}else if(obj == btn2){
if(event == LV_EVENT_VALUE_CHANGED) {
printf("Btn2 Toggled\n");
lv_label_set_text(btn_label,"Btn2 Toggled");
}
}
}OK，这就是本节课我们要学习的内容了，下一节课我们学习矩阵按钮控件，我们下一节课见！ |
