Randomly pick an index from an array, display in TextView

Question

I'm new to Android development and I'm wondering why my code crashes the Android Emulator. What I'm doing is creating an array of strings, then picking an index from the array at random and displaying the value inside a TextView. But it always seems to crash my emu.

package com.test.randomTest;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class randomTestActivity extends Activity {

    private Button button;
    private TextView helloTextView;
    private String[] hellos;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        helloTextView = (TextView)findViewById(R.id.helloText);
        button = (Button)findViewById(R.id.button);

        hellos = new String[7];
        hellos[0] = "Hello";
        hellos[1] = "G'days";    
        hellos[2] = "Yo!";
        hellos[3] = "Hi";
        hellos[4] = "Hay";
        hellos[5] = "Bonjour";
        hellos[6] = "Hay there!";
        hellos[7] = "Hallo";

        button.setOnClickListener(buttonListener);

    }

    private OnClickListener buttonListener = new OnClickListener() {

        public void onClick(View v) {

            int x = 0 + (int)(Math.random() * ((7 - 0) + 1));
            String helloText = hellos[x];
            helloTextView.setText(helloText);

        }
    };
}

Any help/advice would be great!

Thanks.

Che Jami · Accepted Answer · 2011-07-25 09:53:40Z

2

You created a String[] of size 7.

hellos = new String[7];

Therefore the indices range from 0 to 6. Trying to access hellos[7] will cause an IndexOutOfBoundsException.

edited Jul 25, 2011 at 9:53

answered Jul 25, 2011 at 9:46

Che Jami

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1 Comment

dotty Over a year ago

This was the solution, obviously the error has become clear now. Thank you Che.

Emir Kuljanin · Accepted Answer · 2011-07-25 09:45:33Z

0

I assume your getting a nullpointerexecption. Try generating your random number like this instead:

Random rando = new Random();
int x = rando.nextInt(hellos.lenght);

answered Jul 25, 2011 at 9:45

Emir Kuljanin

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Comments

Rasel · Accepted Answer · 2011-07-25 09:52:10Z

package com.test.randomTest;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class randomTestActivity extends Activity {

    private Button button;
    private TextView helloTextView;
    private String[] hellos;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        helloTextView = (TextView)findViewById(R.id.helloText);
        button = (Button)findViewById(R.id.button);

        hellos = new String[8];
        hellos[0] = "Hello";
        hellos[1] = "G'days";    
        hellos[2] = "Yo!";
        hellos[3] = "Hi";
        hellos[4] = "Hay";
        hellos[5] = "Bonjour";
        hellos[6] = "Hay there!";
        hellos[7] = "Hallo";

        button.setOnClickListener(buttonListener);

    }

    private OnClickListener buttonListener = new OnClickListener() {

        public void onClick(View v) {

            int x = 0 + (int)(Math.random() * ((7 - 0) + 1));
            String helloText = hellos[x];
            helloTextView.setText(helloText);

        }
    };
}

Abhi · Accepted Answer · 2011-07-25 09:52:37Z

0

Increase string array size you gave 7 as size, but you are passing 8 values to string. so it throws indexoutofbounds exception.

answered Jul 25, 2011 at 9:52

Abhi

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Comments

ngesh · Accepted Answer · 2011-07-25 09:56:11Z

0

Thats probably because of array IndexOutOfBoundException... since sometimes your x will have value 8 but array length is just 7..

answered Jul 25, 2011 at 9:56

ngesh

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