String value to a variable

Question

this is a question about java on android - eclipse I have a String r for the record, I defind him like that:

String r="pic"+c1;

I want to take the value of it, which is "pic6" and use it as a variable name.

how do I do it?

If c1 is 6 what is wrong with concatenation? – Aniket Thakur Nov 01 '13 at 09:33 — Aniket Thakur, Nov 01 '13 at 09:33
Dynamic variables are not supported in Java. – Eng.Fouad Nov 01 '13 at 09:34 — Eng.Fouad, Nov 01 '13 at 09:34

score 5 · Answer 1 · answered Nov 01 '13 at 09:53

If you want to pick an image with name "pic6.png" from the drawable folder of the Android application, you can try the following code.

String r = "pic" + c1;

int resId = getResources().getIdentifier(r, "drawable", getPackageName());
if (resId != 0) {
    imageView.setImageResource(resId);
} else {
    // This is used in case no image resource is found
    imageView.setImageResource(R.drawable.unknown);
}

Please see: If you use the else part, then you need to add "unknown.png" image to the drawable folder of the Android project.

Hope this helps.

score 2 · Answer 2 · answered Nov 01 '13 at 09:36

2

You can't do it directly but you could use a HashMap to emulate what you seek.

Example:

String r="pic"+c1;
HashMap<String,Integer> extendedVars=new HashMap<>();
extendedVars.put(r,10);

answered Nov 01 '13 at 09:36

Lan

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sorry, I dont know what HashMap is... I have this code: `String r="pic"+c1; pic6.setImageDrawable(getResources().getDrawable( R.drawable.orange));` I want to put r instead of pic6. – Alon Lousky Nov 01 '13 at 09:44
1

@AlonLousky A map maps keys to values, so you can use it to emulate dynamic variable declaration (say you later write an interpreter). You could say HashMap varMap=new HashMap<>(); varMap.put("pic6", new ...); then later call varMap.get("pic"+c1).setImageDrawable(.....) – Lan Nov 01 '13 at 10:04
1

@AlonLousky Considering this is an Android question (didn't notice that in my original answer), you may want to look at http://stackoverflow.com/questions/10137692/how-to-get-resource-name-from-resource-id & http://stackoverflow.com/questions/3476430/how-to-get-a-resource-id-with-a-known-ressource-name/3476470#3476470 – Lan Nov 01 '13 at 10:06
great, it very helped me. thanks guys! – Alon Lousky Nov 01 '13 at 10:53

score 2 · Answer 3 · edited May 23 '17 at 12:21

2

Like Eng. Fouad said. Dynamic variables are not supported in Java.
Same question can be found Here

edited May 23 '17 at 12:21

Community

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answered Nov 01 '13 at 09:37

Fabian

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score 1 · Answer 4 · answered Nov 01 '13 at 09:39

1

In java, variable names must be known in compile time. There is no way to do what you are trying to do.

answered Nov 01 '13 at 09:39

LeeNeverGup

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String value to a variable

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