ImageView Button Toggle in Android

Question

I'm trying to make an ImageView button toggle when I click on it. I've got the below code:

    ImageView button01 = (ImageView) findViewById(R.id.button01);
    button01.setOnClickListener(new OnClickListener() {
        int button01pos = 0;
        public void onClick(View v) {
            if (button01pos == 0) {
                button01.setImageResource(R.drawable.image01);
                button01pos = 1;
            } else if (button01pos == 1) {
                button01.setImageResource(R.drawable.image02);
                button01pos = 0;
            }
        }
    });

But for some reason button01 is underlined in red in Eclipse and it gives the error:

Cannot refer to a non-final variable button01 inside an inner class defined in a different method

Does anyone know why it's doing this and how to fix it?

Thanks

Add final in front of ImageView button01... "final ImageView button01". done. — dymmeh, May 03 '12 at 19:25
Oh sorry it worked... But now for some reason when I click twice on the button it stops toggling and Eclipse throws this error: ActivityManager: Warning: Activity not started, its current task has been brought to the front — , May 03 '12 at 19:31
That just means it started your app that's already installed and brought it to the front. Not really an error. Kinda misleading. — dymmeh, May 03 '12 at 19:32
It toggles once then never works again. The reason for this is because "int button01pos = 0;" is placed inside the onClickListener so it resets to 0 then just stays on 0. If I move it outside the onClickListener then it needs to be final which makes it impossible to toggle with. — , May 03 '12 at 19:37
It shouldn't stay on 0. The onClickListener gets initialized only once so it will never get "reset" to 0. The only way that would happen is if you have a listview of items where they get scrolled through and reinitialized while scrolling. I tested this myself on my device and it works fine using your code. — dymmeh, May 03 '12 at 19:42
Sorry, you're right - it works perfectly - I forgot to put "button01pos = 0;" in the "else if" on my local machine. — , May 03 '12 at 19:51
Just out of interest - How can one change global variables from within a final listener? — , May 03 '12 at 20:00
A global var should be able to be modified without declaring it final. As long as they are member variables in your class it should work as normal — dymmeh, May 03 '12 at 20:08
If I create a new global variable "int toggleCounter = 0" then try to put "toggleCount++;" inside "public void onClick(View v)" in the listener then it underlines "toggleCount++;" in red and says: "Cannot refer to a non-final variable toggleCount inside an inner class defined in a different method". — , May 03 '12 at 20:12
you likely aren't declaring the variable in the right place, then — dymmeh, May 03 '12 at 20:15
true true... I moved it to just under my public class definition and now it works fine :) — , May 03 '12 at 20:17

score 7 · Accepted Answer · answered May 04 '12 at 11:25

Here is the working code:

final ImageView button01 = (ImageView) findViewById(R.id.button01);
button01.setOnClickListener(new OnClickListener() {
    int button01pos = 0;
    public void onClick(View v) {
        if (button01pos == 0) {
            button01.setImageResource(R.drawable.image01);
            button01pos = 1;
        } else if (button01pos == 1) {
            button01.setImageResource(R.drawable.image02);
            button01pos = 0;
        }
    }
});

score 0 · Answer 2 · edited Sep 18 '15 at 19:31

Try this, it worked for me. Here checkbox visibility is set to "Invisible"...! this code is inside a button OnClickListener...!

@Override
public void onClick(View v) {

    ImageView iv_icon = (ImageView) findViewById(R.id.icon);

    CheckBox cb = (CheckBox) findViewById(R.id.cb);

    if (cb.isChecked()) {
        iv_icon.setImageResource(R.drawable.image01);
        cb.setChecked(false);
    } else if (!cb.isChecked()) {
        iv_icon.setImageResource(R.drawable.image02);
        cb.setChecked(true);
    } else {
        // Nothing happens
    }
}

score 0 · Answer 3 · answered Feb 06 '15 at 01:12

Try this,

        int button01pos = 0;

        ImageView button01 = (ImageView) findViewById(R.id.button01);
        button01.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            if (button01pos == 0) {
                button01.setImageResource(R.drawable.image01);
                button01pos = 1;
            } else if (button01pos == 1) {
                button01.setImageResource(R.drawable.image02);
                button01pos = 0;
            }
        }
    });

ImageView Button Toggle in Android

3 Answers3

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