Android Change ImageButton image

Question

I write an travel APP.There are 20 QR Code in every spot.

When tourist use QR Code scanner scan the QR Code,the ImageButton's image have to change into another image.

The problem on this line ： spot1.setImageResource(R.drawable.hotspot1);

If I delete this line, there is no problem.

I don't know how to fix it.

     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     super.onActivityResult(requestCode, resultCode, data);
     if (0 == requestCode && null != data && data.getExtras() != null) {
     String result = data.getExtras().getString("la.droid.qr.result");
     int spotnum=Integer.valueOf(result);
     switch(spotnum){
        case 1:
            ImageButton spot1=(ImageButton)findViewById(R.id.imageButton1);
            spot1.setImageResource(R.drawable.hotspot1);
            setContentView(R.layout.hotspot1);
            break;
        case 2:
            setContentView(R.layout.hotspot2);
            break;
   }
  }
 }

Here is my Logcat：https://i.sstatic.net/6y2UQ.png

Are you asking a question? It looks like you have some code, but what is the problem? — Clayton Wilkinson
– Clayton Wilkinson, Commented May 14, 2015 at 6:13
try to call setContentView(R.layout.hotspot1); berfore spot1 initialization. — Hareshkumar Chhelana
– Hareshkumar Chhelana, Commented May 14, 2015 at 6:18
@DroidMind public void info(View view){ setContentView(R.layout.spotlist); } — 鄭智豪
– 鄭智豪, Commented May 14, 2015 at 6:19
It seems to be a nullpointer, and it may be because "spot1==null". Try: 1-setting your content view before this call, 2-checking if you have initialized your variable, 3- checking if the id for your "findViewById" is the correct one. — Juan Aguilar Guisado
– Juan Aguilar Guisado, Commented May 14, 2015 at 6:21

Hareshkumar Chhelana · Accepted Answer · 2015-05-14 06:20:33Z

1

You can not initialize any Views from xml before calling setContentView :

setContentView(R.layout.hotspot1);
ImageButton spot1=(ImageButton)findViewById(R.id.imageButton1);
spot1.setImageResource(R.drawable.hotspot1);

answered May 14, 2015 at 6:20

Hareshkumar Chhelana

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AAnkit · Accepted Answer · 2015-05-14 06:21:47Z

0

You are not suppose to call setContentView after setting view resource. call set contentView once in onCreate without setting any view from xml.

You can then change the layout contents, but do not call setContentView again.

You are using a image view, but not calling setContentView before it. This makes the ImageView as null, hence the error.

Try following above suggestions,and it will go. Happy Coding.

answered May 14, 2015 at 6:21

AAnkit

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