使用IF语句更改图像

Question

我已经在我的游戏中设置了一个燃料条，但是我试图使用if语句来根据燃料百分比的低来改变条形图。由于某些原因，图像并没有随着百分比的变化而变化。因此，酒吧仍然是满的。这里发生什么事情？

fuelRemaining = 100;
    FuelRemaining.text = [NSString stringWithFormat:@"%i%%", fuelRemaining];
    FuelBar.image = [UIImage imageNamed:@"fuel_bar_100.png"];
    if (fuelRemaining > 90) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_100.png"];
    }
    else if (fuelRemaining > 80 && fuelRemaining <= 90) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_90.png"];
    }
    else if (fuelRemaining > 70 && fuelRemaining <= 80) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_80.png"];
    }
    else if (fuelRemaining > 60 && fuelRemaining <= 70) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_70.png"];
    }
    else if (fuelRemaining > 50 && fuelRemaining <= 60) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_60.png"];
    }
    else if (fuelRemaining > 40 && fuelRemaining <= 50) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_50.png"];
    }
    else if (fuelRemaining > 30 && fuelRemaining <= 40) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_40.png"];
    }
    else if (fuelRemaining > 20 && fuelRemaining <= 30) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_30.png"];
    }
    else if (fuelRemaining > 10 && fuelRemaining <= 20) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_20.png"];
    }
    else if (fuelRemaining > 0 && fuelRemaining <= 10) {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_10.png"];
    }
    else {
        FuelBar.image = [UIImage imageNamed:@"fuel_bar_0.png"];
    }

Answer 1

首先，用一些基本的数学来简化它：

int fuelRounded = 10.0 * floor((fuelRemaining/10.0)+0.5);
NSString *fuelImageString = [NSString stringWithFormat:@"fuel_bar_%d.png", fuelRounded];
FuelBar.image = [UIImage imageNamed:fuelImageString];

(根据游戏逻辑和fuelRemaining的可能值，数学可能需要调整。)

第二，在方法顶部将fuelRemaining设置为100。在fuelRemaining更改为其他内容之后，您需要再次设置图像。

例如：

- (void) updateFuelViews {
    FuelRemaining.text = [NSString stringWithFormat:@"%i%%", fuelRemaining];

    int fuelRounded = 10.0 * floor((fuelRemaining/10.0)+0.5);
    NSString *fuelImageString = [NSString stringWithFormat:@"fuel_bar_%d.png", fuelRounded];
    FuelBar.image = [UIImage imageNamed:fuelImageString];
}

然后，每次[self updateFuelViews];更改时都调用fuelRemaining。

您可能需要研究键值观察，这将允许您在fuelRemaining更改时自动更新燃料视图。这有点让人头痛，但如果你有很多事情在不断地变化，它可能会让你更容易管理。