[C++知识库]C语言 | Switch的错误用法

C语言 | Switch的错误用法

1.示例(问题)

void FlowWndPlay_DownKey3Ctrl(void)
{
	switch (g_PlbData.State)
	{
        case PLB_ST_PLAY_MOV:
        case PLB_ST_FWD_MOV:
        case PLB_ST_BWD_MOV:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY3CCtrl, STATIC_VALUE, ICON_IC_BAR_PLAY);
    	    break;
    	}
    	case PLB_ST_PAUSE_MOV:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY3CCtrl, STATIC_VALUE, ICON_IC_BAR_RIGHT_OFF);
    	    break;
    	}
    	case PLB_ST_FULL:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY3CCtrl, STATIC_VALUE, ICON_IC_BAR_RIGHT);
    	    break;
    	}
        UxCtrl_SetShow(&UIFlowWndPlay_VKEY3CCtrl, TRUE);
	}
}

实际运行时，当case里面匹配执行后；UxCtrl_SetShow(&UIFlowWndPlay_VKEY3CCtrl, TRUE)这一句将不会运行，这就脱离了我们的实际目的。

改写如下：

void FlowWndPlay_UpKey2Ctrl(void)
{
    UINT32 uiPBFileFmt;
	PB_GetParam(PBPRMID_CURR_FILEFMT, &uiPBFileFmt);

	switch (g_PlbData.State)
	{
        case PLB_ST_PLAY_MOV:
        case PLB_ST_FWD_MOV:
        case PLB_ST_BWD_MOV:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY2CCtrl, STATIC_VALUE, ICON_IC_BAR_PLAY_FAST);
    	    break;
    	}
    	case PLB_ST_PAUSE_MOV:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY2CCtrl, STATIC_VALUE, ICON_IC_BAR_LEFT_OFF);
    	    break;
    	}
    	case PLB_ST_FULL:
    	{
            UxStatic_SetData(&UIFlowWndPlay_VKEY2CCtrl, STATIC_VALUE, ICON_IC_BAR_LEFT);
    	    break;
    	}
	}

	if (uiPBFileFmt & PBFMT_JPG){
        UxStatic_SetData(&UIFlowWndPlay_VKEY2CCtrl, STATIC_VALUE, ICON_IC_BAR_MENU);
    }

    UxCtrl_SetShow(&UIFlowWndPlay_VKEY2CCtrl, TRUE);
}

2.实验

测试1：

#include <stdio.h>

int main(int argc, char* argv[])
{
    int a = 2;

    switch(a)
    {
        case 1:
        printf("1\n");
            break;

        case 2:
        printf("2\n");
            break;

        printf("3\n");
    }

    return 0;
}

运行：

[lanfeiye@fly-vm cStudy]$ ./testSwitch
2

测试2：

#include <stdio.h>

int main(int argc, char* argv[])
{
    int a = 3;

    switch(a)
    {
        case 1:
        printf("1\n");
            break;

        case 2:
        printf("2\n");
            break;

        printf("3\n");
    }

    printf("4\n");

    return 0;
}

运行：

[lanfeiye@fly-vm cStudy]$ make testSwitch
gcc -o testSwitch testSwitch.c -g -Wall
[lanfeiye@fly-vm cStudy]$ ./testSwitch
4