CODEWITHSUNDEEP
javaandroid
Frederikzt
Frederikzt

Reputation: 25

Variable is always true even when assigned later?

I am getting this error and I really can't understand why. The code:

    b1.setOnClickListener(new View.OnClickListener() {

        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            boolean b = true;
            if(b == true){
                tv1.setText("true");
                b2.setEnabled(false);
                b = false;

            } else

                if(b == false){
                b2.setEnabled(true);
                b = true;
                tv1.setText("false");

As you can see I'm trying to make when a button is clicked it will check if variable "b" is true or false and then it should do the following code. But it doesn't! It only does the actions for the "if b == true". Can you help me?

Upvotes: 1

Views: 255

Answers (5)

user723556
user723556

Reputation:

From the code that you put up, this is the reason I can think of:

Initially, your b variable is set to true. Hence, it enters the b == true condition.

But when you set the b==false "inside" that if, it DOES NOT go to else. The reason is simply because, when you have gone to the "if" statement already, that is the condition for if statement was verified to be true, the computer doesnt need to look for the "else" statement and hence doesn't go into it.

If you would have had two consecutive ifs instead of else, your thing would have worked the way you expect it to be.

Upvotes: 0

Charles Harley
Charles Harley

Reputation: 7234

The variable 'b' is a local variable within the scope of the method so it is always true when the onClick() method executes. You need to move the variable into the class scope. Like this:

b1.setOnClickListener(new View.OnClickListener() {

    boolean b = true;

    public void onClick(View arg0) {
        if (b) {
            tv1.setText("true");
            b2.setEnabled(false);
            b = false;

        } else {
            b2.setEnabled(true);
            b = true;
            tv1.setText("false");
        }
    }

});

Upvotes: 1

assylias
assylias

Reputation: 328598

Maybe because b is always true following this statement:

boolean b = true;

Also, b being a boolean, you can simply write:

if (b) {
//
} else {
//
}

This might work as you expect (not tested):

b1.setOnClickListener(new View.OnClickListener() {

    private boolean b = true;

    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        if(b){
            b2.setEnabled(false);
            tv1.setText("true");
        } else {
            b2.setEnabled(true);
            tv1.setText("false");
        }

        b = !b; //this changes b from true to false and vice versa at each call
    }
   });

Upvotes: 4

jsimpson
jsimpson

Reputation: 391

you'd want to use the static modifier to keep the state of the variable ( since its state will not be kept when it goes out of scope.) this also means that you'd have to move the variable out to a global scope.

Upvotes: 0

gandarez
gandarez

Reputation: 2662

You have to declare the variable b outside your Listener

boolean b = true;
b1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            if(b == true){
                tv1.setText("true");
                b2.setEnabled(false);
                b = false;

            } else

                if(b == false){
                b2.setEnabled(true);
                b = true;
                tv1.setText("false");

Upvotes: 1

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