Moving object by single touch - Libgdx - libgdx

Question

May be this will be a very basic question,but as a newbie,I am confused of it.
In my libGDX Project,I wants to move the player.
Initially player is on left side.For the first tap player should move to opposite side and occupy the position there.for the next tap it should move to left.and will continue like this.
I implemented this logic.Now problem is that my player is not at all moving but just occupying the opposite position on tap.I used a velocity value but it does not make any effect on the code.
I want to make it move along the way,not just occupying the position.
Please help.
public float ninjaX = Constants.W_WIDTH;
public float ninjaY =Constants.WORLD_HEIGHT/2+Constants.WORLD_HEIGHT/4;
public float ninjaVelocity =100f;
public boolean isLeftBool=true;
public void ninjaMove() {
if (isLeftBool) {
ninjaX = ninjaX+ ninjaVelocity;
setPosition(Constants.WORLD_WIDTH - (Constants.W_WIDTH+Constants.PLAYER_HEIGHT/2), ninjaY);
isLeftBool = false;
}
else
{
ninjaX=ninjaX-ninjaVelocity;
setPosition(ninjaX,ninjaY);
isLeftBool = true;
}
}
updating player in render:
if (MyInputProcessor.isTap) {
MyInputProcessor.isTap = false;
ninja.ninjaMove();
}

Answer 1

Your player coordinates changes should depend on delta time:
x1 = x0 + v * Δt
x1 - is new coordinate
x0 - is current coordinate
v - speed
Δt - time span between x0 and x1
LibGDX provides the method to get the time span between current and last frames:
Gdx.graphics.getDeltaTime();
So, changing your code accordingly should make your player move smoothly (depends on velocity):
ninjaX = ninjaX + ninjaVelocity * Gdx.graphics.getDeltaTime();
Same thing for substraction in your else block.
You also probably want to set x coordinate (ninjaX) as well as y (currently you're no passing it in your setPosition method):
setPosition(ninjaX, ninjaY);
*I'm guessing here because I don't know what the method does

Answer 2

This is just an example of how you could solve this.
You don't give an explanation of what setPosition() does and why it is called so I will ignore it.
In your render():
public void render(float delta){
....
ninja.update(delta);
}
In your Ninja.class
private final Vector2 leftPos = new Vector(20, 60);
private final Vector2 rightPos = new Vector(80, 60);
private Rectangle bound = new Rectangle(80,60,32,32);
private Vector2 currentPos;
private float moveSpeed = 100f;
public Ninja(){
currentPos = leftPos;
}
public void update(float delta){
if(bound.x > currentPos.x)bound.x += moveSpeed * delta;
else bound.x -= moveSpeed * delta;
}
public void move(){
if(currentPos == leftPos)currentPos = rightPos;
else currentPos = leftPos;
}
Then in you input processor call ninja.move() in touchDown()
None of this is tested.
The reason you need to multiply moveSpeed with delta time is to make movement independent of fps. This way ninja will move the same distance in the same time no matter how many fps the game runs.