Changing value of variable in android /JAVA

Question

I was trying to make a simple app in which clicking tapb Button increments the variable value of notaps and the reset Button sets it to 0. When I click on tapb it increments the value & clicking reset resets it but when I again click tabp it increments from the previous value.

Eg :

init value of notaps = 0;

I click tabp 3 times and notaps value = 3

I click reset and notaps value = 0

I click tabp 3 times and notaps value = 4

    Button tapb = (Button)findViewById(R.id.tapb);
    Button reset = (Button)findViewById(R.id.reset);


    tapb.setOnClickListener(
            new Button.OnClickListener(){
                int notaps = 0;
                @Override
                public void onClick(View v) {
                    TextView taps = (TextView)findViewById(R.id.taps);
                    notaps++;
                    taps.setText(String.valueOf(notaps));

                }
            }
    );

    reset.setOnClickListener(
            new Button.OnClickListener() {

                @Override
                public void onClick(View v) {
                    TextView taps = (TextView) findViewById(R.id.taps);
                    int notaps=0;
                    taps.setText(String.valueOf(notaps));

                }
            }
    );

int noTaps=0 is bad. That variable disappears after that method executes. — takendarkk
– takendarkk, Commented Aug 5, 2015 at 17:11

Tudor Luca · Accepted Answer · 2015-08-05 17:12:49Z

5

First, you have 2 instances of int named notaps that have nothing to do with each other. Your reset button does not set the right notaps variable.

Here's a snippet that should work.

    private int notaps;

    Button tapb = (Button)findViewById(R.id.tapb);
    Button reset = (Button)findViewById(R.id.reset);
    TextView taps = (TextView)findViewById(R.id.taps);

    tapb.setOnClickListener(
        new Button.OnClickListener(){
            @Override
            public void onClick(View v) {
                notaps++;
                taps.setText(String.valueOf(notaps));
            }
        }
    );

    reset.setOnClickListener(
        new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                notaps = 0;
                taps.setText(String.valueOf(notaps));
            }
        }
    );

answered Aug 5, 2015 at 17:12

Tudor Luca

6,4392 gold badges32 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Kalpesh Over a year ago

I did a stupid mistake i declared int notaps in side onCreate

abc · Accepted Answer · 2016-08-05 14:05:23Z

-1

Try declaring your notaps variable globally meaning where every you declare you buttons declare your notaps variable there, here is what I mean.

Button tapb = (Button)findViewById(R.id.tapb);
Button reset = (Button)findViewById(R.id.reset);
int notaps = 0; // declare variable globally

tapb.setOnClickListener(
        new Button.OnClickListener(){
            @Override
            public void onClick(View v) {
                TextView taps = (TextView)findViewById(R.id.taps);
                taps.setText(String.valueOf(++notaps));

            }
        }
);

reset.setOnClickListener(
        new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                TextView taps = (TextView) findViewById(R.id.taps);                    
                taps.setText(String.valueOf(notaps=0));

            }
        }
);

edited Aug 5, 2016 at 14:05

answered Aug 5, 2015 at 17:13

abc

2,0871 gold badge19 silver badges32 bronze badges

6 Comments

Tudor Luca Over a year ago

Don't declare it volatile. You're not going to access the variable from multiple threads, only the UI thread.

abc Over a year ago

I'm not the best in android, but i thought that the listeners were callbacks from another thread. So therefore I declared the variable volatile, my bad if i was wrong.

Tudor Luca Over a year ago

The callbacks are called on the UI thread, by the buttons. Every UI interaction happens on the UI thread ("main" thread).

Tudor Luca Over a year ago

All I can say is this: keep up the good work and continue experimenting and learning! ;)

abc Over a year ago

Yes absolutely, however ultimately it depends the actual machine, if the machine architecture is such that when a thread is created it is give it's own cache, then volatile saves the day because, what volatile does is it allows a shared copy of the variable you are accessing, but again some machine architectures don't have this problem volatile is there for the sake of portability.

|

Collectives™ on Stack Overflow

Changing value of variable in android /JAVA

2 Answers 2

1 Comment

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related