C ++-无法获得if语句使用状态工作

Question

I'm currently creating a project which involves switching between different game states such as main menu to play state and play state to battle state etc. I'm currently struggling with getting my battle state to only draw the enemy the player collides with inside the play state. I tried doing this using a very simply "enemyNo =;" where the first enemy was 1, second was 2, and so on. then in battle state, tell it "if(enemyNo =1) then draw enemy 1 and it's corresponding stats. Can't for the life of me figure it out, pretty sure im not inheriting the enemyNo value across states properly. Any and all help would be appreciated.

StatePlay.cpp

#include "StatePlay.h"
#include <iostream>
// stringstream and string
#include <sstream>
#include <string>


#include "Game.h"


StatePlay::StatePlay(void)
{
}


StatePlay::~StatePlay(void)
{
}

void StatePlay::init(Game &context)
{

std::cout << "Initialising play state." << std::endl;
player = new Rect(0.0f, 0.0f, 0.15f, 0.15f);
//player stats
health = 10;
maxHealth = 10;
strength = 10;
speed = 10;
dollars = 0;

noTargets = false;
targetCount = 5;
bruteCount = 3;
raiderCount = 1;

//target
for(int i = 1; i <=5; i++)
{
target[i] = new Rect();
target[i]->setX((float)rand()/RAND_MAX - 0.75f);
target[i]->setY((float)rand()/RAND_MAX - 0.75f);    
targetAlive[i] = true;
}

//brute
for(int i = 1; i <=3; i++)
{
brute[i] = new Rect();
brute[i]->setX((float)rand()/RAND_MAX - 0.75f);
brute[i]->setY((float)rand()/RAND_MAX - 0.75f); 
bruteAlive[i] = true;
}

//raider
for(int i = 1; i <=1; i++)
{
raider[i] = new Rect();
raider[i]->setX((float)rand()/RAND_MAX - 0.75f);
raider[i]->setY((float)rand()/RAND_MAX - 0.75f);    
raiderAlive[i] = true;
}


score = 0; 

}


void StatePlay::enter()
{
std::cout << "Entering play state. Press ESCAPE to return to menu" << std::endl;
}

void StatePlay::exit()
{
}


void StatePlay::draw(SDL_Window * window)
{
// Replace this with OpenGL draw calls to draw the main menu screen

TTF_Font *textFont = TTF_OpenFont("MavenPro-Regular.ttf", 24);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
player->draw();
std::stringstream strStream2;
std::stringstream strStream3;
strStream2 << "Player" << std::endl;
strStream3 << "Target" << std::endl;
Label :: displayString(player->x() + player->w()/2.0,player->y() + player->h(),     strStream2.str().c_str(), textFont);

//enemy
for(int i = 1; i <=5; i++)
{
    if(targetAlive[i] == true)
    {
Label :: displayString(target[i]->x() + target[i]->w()/2.0,target[i]->y() + target[i]->h(), strStream3.str().c_str(), textFont);

glColor3f(1.0,0.0,0.0);
targetAlive[i] = target[i];
target[i]->draw();
}
}



std::stringstream strStream4;
strStream4 << "Brute" << std::endl;

//brute
for(int i = 1; i <=3; i++)
{
    if(bruteAlive[i] == true)
    {
Label :: displayString(brute[i]->x() + brute[i]->w()/2.0,brute[i]->y() + brute[i]->h(), strStream4.str().c_str(), textFont);

glColor3f(0.6,0.3,0.1);
bruteAlive[i] = brute[i];
brute[i]->draw();

}
}

std::stringstream strStream6;
strStream6 << "Raider" << std::endl;

//raider
for(int i = 1; i <=1; i++)
{
    if(raiderAlive[i] == true)
    {
        Label :: displayString(raider[i]->x() + raider[i]->w()/2.0,raider[i]->y() + raider[i]->h(), strStream6.str().c_str(), textFont);

        glColor3f(0.2,0.9,0.4);
        raiderAlive[i] = raider[i];
        raider[i]->draw();
    }
}

//information
std::stringstream strStream;
std::stringstream strStream1;
strStream << "Score:" << score;
strStream1 << "Health:" << health;
Label :: displayString(-0.9,-0.9, strStream.str().c_str(), textFont);
Label :: displayString(-0.4,-0.9, strStream1.str().c_str(), textFont);
SDL_GL_SwapWindow(window); // swap buffers
}



void StatePlay::handleSDLEvent(SDL_Event const &sdlEvent, Game &context)
{
if (sdlEvent.type == SDL_KEYDOWN)
{
    //std::cout << "Scancode: " << sdlEvent.key.keysym.scancode ;
    //std::cout << ", Name: " << SDL_GetKeyName( sdlEvent.key.keysym.sym ) << std::endl;
    switch( sdlEvent.key.keysym.sym )
    {
        case SDLK_UP:
        case 'w': case 'W':
            player->setY(player->y() + 0.05f);
            break;
        case SDLK_DOWN:
        case 's': case 'S':
            player->setY(player->y() - 0.05f);
            break;
        case SDLK_LEFT:
        case 'a': case 'A':
            player->setX(player->x() - 0.05f);
            break;
        case SDLK_RIGHT:
        case 'd': case 'D':
            player->setX(player->x() + 0.05f);
            break;
        default:
            break;
    }
}


if (sdlEvent.type == SDL_KEYDOWN)
{
    //std::cout << "Scancode: " << sdlEvent.key.keysym.scancode ;
    //std::cout << ", Name: " << SDL_GetKeyName( sdlEvent.key.keysym.sym ) << std::endl;
    switch( sdlEvent.key.keysym.sym )
    {
        case SDLK_ESCAPE:
            context.setState(context.getMainMenuState());
        default:
            break;
    }
}

//target
for(int i = 1; i <=5; i++)
{
if ( (target[i]->x() >= player->x()) && (target[i]->x()+target[i]->w() <= player->x()+player->w())  // cursor surrounds target in x
&& (target[i]->y() >= player->y()) && (target[i]->y()+target[i]->h() <= player->y()+player->h() ) && targetAlive[i] == true ) // cursor surrounds target in y
{   
    score += 100;
    enemyNo = 1;
    context.setState(context.getBattleState());

    delete target[i];
    targetAlive[i] = false;

    targetCount -= 1;

}
}

//brute
    for(int i = 1; i <=3; i++)
{
if ( (brute[i]->x() >= player->x()) && (brute[i]->x()+brute[i]->w() <= player->x()+player->w())     // cursor surrounds target in x
&& (brute[i]->y() >= player->y()) && (brute[i]->y()+brute[i]->h() <= player->y()+player->h() ) && bruteAlive[i] == true ) // cursor surrounds target in y
{   

    score += 100;
    enemyNo = 2;
    context.setState(context.getBattleState());
    delete brute[i];
    bruteAlive[i] = false;

    bruteCount -= 1;

}
}

//raider
for(int i = 1; i <=1; i++)
{
if ( (raider[i]->x() >= player->x()) && (raider[i]->x()+raider[i]->w() <= player->x()+player->w())  // cursor surrounds target in x
&& (raider[i]->y() >= player->y()) && (raider[i]->y()+raider[i]->h() <= player->y()+player->h() ) && raiderAlive[i] == true ) // cursor surrounds target in y
{   
    score += 100;
    enemyNo = 3;
    context.setState(context.getBattleState()); 
    delete raider[i];
    raiderAlive[i] = false;

    raiderCount -= 1;

}
}





}

StatePlay.h

#ifndef STATE_PLAY
#define STATE_PLAY

#include "gameState.h"
#include "Label.h"
// C stdlib and C time libraries for rand and time functions
#include <cstdlib>
#include <ctime>
#include "rect.h"

class StatePlay : public GameState
{
public:
StatePlay(void);
~StatePlay(void);
void init(Game &context);
void draw(SDL_Window * window);
void handleSDLEvent(SDL_Event const &sdlEvent, Game &context);
void enter();
void exit();
int enemyNo;



int targetCount;
private:
//player Stats
int score;
int health;
int maxHealth;
int strength;
int speed;
int dollars;



int getHealth() {return health;}
int getMaxHealth() { return maxHealth;}
int getStrength() { return strength;}
int getSpeed() { return speed;}
int getDollars() { return dollars; }

void setHealth(int newHealth) { health = newHealth; }
void damageTaken(int damage) { health = health - damage; }
void setMaxHealth(int newHealth) { maxHealth = maxHealth + newHealth; }
void setStrength(int newStrength) { strength = strength+newStrength; }
void setSpeed(int newSpeed) { speed = speed+newSpeed; }
void setDollars(int newDollars) { dollars = dollars+newDollars; }

// Another *strong* candidate for creating a new class type
// is character/agent, to encapsulate player and target data,
// potentially to include an Agent::draw() function and
// perhaps also generalise collision detection
// This is left as a further exercise
float xpos;
float ypos;
float xsize;
float ysize;


//target
float targetXPos;
float targetYPos;
float targetXSize;
float targetYSize;


bool targetAlive[5];
bool noTargets;

//brute
float bruteXPos;
float bruteYPos;
float bruteXSize;
float bruteYSize;

int bruteCount;
bool bruteAlive[5];
bool noBrutes;

//raider
float raiderXPos;
float raiderYPos;
float raiderXSize;
float raiderYSize;

int raiderCount;
bool raiderAlive[1];
bool noRaider;

clock_t lastTime; // clock_t is an integer type
clock_t currentTime; // use this to track time between frames

Label * playerLabel;
Label * targetLabel;
Label * bruteLabel;
Label * raiderLabel;

TTF_Font * textFont;    // SDL type for True-Type font rendering
Rect * player;
Rect * target[5];
Rect * brute[3];
Rect * raider[1];

};

#endif

StateBattle.cpp

#include "StateBattle.h"

#include <iostream>
#include "Game.h"
#include "StatePlay.h"
#include "rect.h"


StateBattle::StateBattle(void)
{
}


StateBattle::~StateBattle(void)
{
}

void StateBattle::init(Game &context)
{
fighting = false;   
}

void StateBattle::enter()
{
std::cout << "Entering main menu state: Press RETURN to play or ESCAPE to quit " <<  std::endl;
}

void StateBattle::exit()
{
}


void StateBattle::draw(SDL_Window * window)
{
glClearColor(0.0f,0.0f,0.0f,0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
TTF_Font *textFont = TTF_OpenFont("MavenPro-Regular.ttf", 24);
std::stringstream strStream;
strStream << "FIGHT!" <<std::endl;
Label :: displayString(-0.8 ,0.8, strStream.str().c_str(),textFont);

//player
Rect * player;
player = new Rect(-0.4f, 0.0f, 0.15f, 0.15f);
player ->draw();

std::stringstream playerStrStream1;
playerStrStream1 << "Health:" << std::endl;
Label :: displayString(-0.4 ,0.5, playerStrStream1.str().c_str(),textFont);

std::stringstream playerStrStream2;
playerStrStream2 << "Strength:" << std::endl;
Label :: displayString(-0.4 , -0.2, playerStrStream2.str().c_str(),textFont);

std::stringstream playerStrStream3;
playerStrStream3 << "Speed:" << std::endl;
Label :: displayString(-0.4 , -0.3, playerStrStream3.str().c_str(),textFont);

std::stringstream playerStrStream4;
playerStrStream4 << "Dollars:" << std::endl;
Label :: displayString(-0.4 , -0.4, playerStrStream4.str().c_str(),textFont);


//Enemy
if(enemyNo = 1)
{
Rect * target;
glColor3f(1.0,0.0,0.0);
target = new Rect(0.4f, 0.0f, 0.15f, 0.15f);
target->draw();

std::stringstream targetStrStream1;
targetStrStream1 << "Health:" << std::endl;
Label :: displayString(0.4f,0.5f, targetStrStream1.str().c_str(),textFont);

std::stringstream targetStrStream2;
targetStrStream2 << "Strength:" << std::endl;
Label :: displayString(0.4, -0.2, targetStrStream2.str().c_str(),textFont);

std::stringstream targetStrStream3;
targetStrStream3 << "Speed:" << std::endl;
Label :: displayString(0.4, -0.3, targetStrStream3.str().c_str(),textFont);

std::stringstream targetStrStream4;
targetStrStream4 << "Dollars:" << std::endl;
Label :: displayString(0.4, -0.4, playerStrStream4.str().c_str(),textFont);
}

//brute 
if(enemyNo = 2)
{
Rect * brute;
glColor3f(0.6,0.3,0.1);
brute = new Rect(0.6f, 0.0f, 0.15f, 0.15f);
brute->draw();

std::stringstream bruteStrStream1;
bruteStrStream1 << "Health:" << std::endl;
Label :: displayString(0.4, 0.5, bruteStrStream1.str().c_str(),textFont);

std::stringstream bruteStrStream2;
bruteStrStream2 << "Strength:" << std::endl;
Label :: displayString(0.4, -0.2, bruteStrStream2.str().c_str(),textFont);

std::stringstream bruteStrStream3;
bruteStrStream3 << "Speed:" << std::endl;
Label :: displayString(0.4, -0.3, bruteStrStream3.str().c_str(),textFont);

std::stringstream bruteStrStream4;
bruteStrStream4 << "Dollars:" << std::endl;
Label :: displayString(0.4, -0.4, bruteStrStream4.str().c_str(),textFont);
}

//raider
if(enemyNo = 3)
{
Rect * raider;
glColor3f(0.2,0.9,0.4);
raider = new Rect(0.8f, 0.0f, 0.15f, 0.15f);
raider->draw();

std::stringstream raiderStrStream1;
raiderStrStream1 << "Health:" << std::endl;
Label :: displayString(0.4, 0.5, raiderStrStream1.str().c_str(),textFont);

std::stringstream raiderStrStream2;
raiderStrStream2 << "Strength:" << std::endl;
Label :: displayString(0.4, -0.2, raiderStrStream2.str().c_str(),textFont);

std::stringstream raiderStrStream3;
raiderStrStream3 << "Speed:" << std::endl;
Label :: displayString(0.4, -0.3, raiderStrStream3.str().c_str(),textFont);

std::stringstream raiderStrStream4;
raiderStrStream4 << "Dollars:" << std::endl;
Label :: displayString(0.4, -0.4, raiderStrStream4.str().c_str(),textFont);

}

SDL_GL_SwapWindow(window); // swap buffers
}


void StateBattle::handleSDLEvent(SDL_Event const &sdlEvent, Game &context)
{
// Add additional input checks for any other actions carried out in this state
std::cout << "Event handling in main menu state." << std::endl;
if (sdlEvent.type == SDL_KEYDOWN)
{
    //std::cout << "Scancode: " << sdlEvent.key.keysym.scancode ;
    //std::cout << ", Name: " << SDL_GetKeyName( sdlEvent.key.keysym.sym ) << std::endl;
    switch( sdlEvent.key.keysym.sym )
    {
        case SDLK_RETURN:
            context.setState(context.getPlayState());
            break;
        case SDLK_ESCAPE:
            // Create a SDL quit event and push into the event queue
            SDL_Event quitEvent;
            quitEvent.type = SDL_QUIT;
            SDL_PushEvent(&quitEvent);
        default:
            break;
    }
}
}

StateBattle.h

#ifndef STATE_BATTLE
#define STATE_BATTLE

#include "GameState.h"
#include "Label.h"
#include "StatePlay.h"

class StateBattle : public GameState, public StatePlay
{
public:
StateBattle(void);
~StateBattle(void);
void init(Game &context);
void draw(SDL_Window * window);
void handleSDLEvent(SDL_Event const &sdlEvent, Game &context);
void enter();
void exit();
bool fighting;
};

#endif

I've included all the .cpp and .h files involved, hopefully this is enough. If not i can upload more. Thanks again

Answer 1

You are missing a = , you should write

if(enemyNo == 1)

instead of

if(enemyNo = 1)

But for the next time, please provide a smaller example (as already suggested) with the exact error message.

Answer 2

You should declare the dstor in StatePlay virtual, because it acts as a base class for the StateBattle class. And in the StateBattle implementation file your are initializing enemyNo to 1 instead of comparing it to 1:

    //Enemy
    if(enemyNo == 1) // <-- missing == 

Answer 3

Inside your states you should only hold state variables: variables that are bound to only this specific state. Enemies could be a state variable if you have just one game state and all other states are complelty independent (ie menu state, setting state...). But your states kind of having cross dependencies.

To solve this problem you should extract first everything that doesn't belong to one specific state into another class. Ie You could have a 'World' class, which manages the list of enemies, terrain, ... Or a class for a List of your Entities. It's a design decision you have to take yourself.

However, your StatePlay shouldn't handle the enemies - and get it inherited by the StateBattle. StateBattle overrides the init(Game &context) function from StatePlay - so it get's never called if you don't call it yourself. The enemyNo in StateBattle is never initalized this way (in fact it is, but just because of another mistake)! You could write:

void StateBattle::init(Game &context)
{
  StatePlay::init(context);
  fighting = false;   
}

to do so. But like I pointed out, there are some things in your class design, that makes handling these things hard and redundant.

Also you are not checking the enemyNo - you're setting it. = is the assignment Operator - you want to use the compare Operator == So better use:

if(enemyNo == 1)

instead of

if(enemyNo = 1)

Otherwise it will set your variable enemyNo to 1 instead of compare it against 1.