Android Pass value to another activity

Question

I have a MainActivity with 30 buttons (Ids: imageButton1,imageButton2...). On the click event, I'm starting a new activity called KlikNaDugme:

MainActivity

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);

    buttons = new ImageButton[30];

    for (int i = 0; i < buttons.length; i++) {
        buttons[i] = (ImageButton) findViewById(R.id.imageButton + i);
        vr = i;
        buttons[i].setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {

                Intent myIntent = new Intent(HomeActivity.this, KlikNaDugme.class).putExtra("vrijednost", vr);
                startActivity(myIntent);
            }
        });
    }
}

I'm trying to pass vr to the KlikNaDugme activity, which is declared as a public int.

KlikNaDugme Activity

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_klik_na_dugme);

    int x = getIntent().getExtras().getInt("vrijednost");
    System.out.println(x);
}

The problem is that it always gets a value of 29. How can I pass the id correctly?

I guess your findViewById(R.id.imageButton + i) is not correct. take a look at this: [link](https://stackoverflow.com/questions/12227310/how-can-we-use-a-variable-in-r-id) — Mohammad Reza Khahani, Aug 06 '18 at 11:34
@MohammadRezaKhahani you are right there is a problem. mTak you mean Ids? It goes from 1 to 30 in this format "@+id/imageButton1", "@+id/imageButton2".... — Demir Karic, Aug 06 '18 at 11:50
Take a look at edited answer. When user click on ImageButtons the value of vr is 29 because it is the last value you assign to it. So any ImageButton you click you will get that value. — Mohammad Reza Khahani, Aug 06 '18 at 12:50
@MohammadRezaKhahani many thanks. You guys are amazing. Thank you! — Demir Karic, Aug 06 '18 at 14:22

score 2 · Accepted Answer · 2018-08-06T11:57:40.077

Store the value of i in the button's tag:

    buttons = new ImageButton[30];

    for(int i=0; i<buttons.length; i++) {
        {
            buttons[i] = (ImageButton) findViewById(getResources().getIdentifier("imageButton" + (i + 1), "id", this.getPackageName()));
            buttons[i].setTag(i);

            buttons[i].setOnClickListener(new View.OnClickListener() {
                public void onClick(View view) {

                    Intent myIntent = new Intent(HomeActivity.this, KlikNaDugme.class)
                    myIntent.putExtra("vrijednost", Integer.parseInt(view.getTag().toString()));
                    startActivity(myIntent);
                }
            });
        }
    }

nice and clean. – Mohammad Reza Khahani Aug 06 '18 at 12:51 — Mohammad Reza Khahani, Aug 06 '18 at 12:51

score 1 · Answer 2 · answered Aug 06 '18 at 11:29

The problem lies here:

buttons[i] = (ImageButton) findViewById(R.id.imageButton + i);

What you are doing is that you're creating an invalid resource reference and then finding your view upon that reference, which is obviously wrong. Remember findViewById() needs a resource id which is generated by Android Studio itself.

The solution is to save all of your 20-30 views references in an array and then use a loop to set click listeners on them

score 0 · Answer 3 · answered Aug 06 '18 at 11:27

Add the vr value as tag to button and then use getTag() method to get the vr value inside onclicklistener

            for(int i=0; i<buttons.length; i++) {
            {
                buttons[i] = (ImageButton) findViewById(R.id.imageButton + i);
                vr = i;
                buttons[i].setTag(vr); // This will se the vr value as tag
                buttons[i].setOnClickListener(new View.OnClickListener() {
                    public void onClick(View view) {
                        int vr = (int)view.getTag()  // this will get the vr value from view
                        Intent myIntent = new Intent(HomeActivity.this,
                                KlikNaDugme.class).putExtra("vrijednost", vr);
                        startActivity(myIntent);
                    }
                });
            }

Mohammad Reza Khahani · Answer 4 · 2018-08-06T12:46:53.427

R.id.what_ever will give you an integer value that generated by android studio in R class not the what_ever string. You should use getResources().getIdentifier() to get correct id of resource and pass it to findViewById().

Please try this code. It will get you the correct id of ImageButtons:

    buttons = new ImageButton[30];

    for(int i=0; i<buttons.length; i++) {
        {
            String buttonID = "imageButton" + (i+1);
            int resID = getResources().getIdentifier(buttonID, "id", getPackageName());

            buttons[i] = (ImageButton) findViewById(resID);
            buttons[i].setTag(i);
            //vr = i;
            buttons[i].setOnClickListener(new View.OnClickListener() {
                public void onClick(View args0) {

                    Intent myIntent = new Intent(HomeActivity.this,
                            KlikNaDugme.class).putExtra("vrijednost", (int)args0.getTag());
                    startActivity(myIntent);
                }
            });
        }

Enjoy it.

Android Pass value to another activity

4 Answers4