Android: Array loops return null elements

Question

I have been trying to use getResources().getIdentifier() methods to assign ids to an array of images. However, when I consoled the array, I only got 2 valid elements and the rest was null. Could somebody please explain to me why after the onCreate method is executed, the program only consoles the values of the first 2 loops and returns null values afterward?

Currently: [ImageView0, ImageView1, null, null, null, null, null, null, null]

What should I do to make it fully loop through the array and return an array with valid values of [ImageView1, ImageView2, ImageView3, ImageView4, ImageView5, ImageView6, ImageView7, and ImageView8] instead ?

Many thanks! I am appreciated any help!

INPUT

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;    
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {
ImageView[] computerImages;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    computerImages = new ImageView[9];
    for (int i=0; i<computerImages.length; i++){
        String computerImageID = "ImageView"+i;
        int resID = getResources().getIdentifier(computerImageID,"id",getPackageName());
        computerImages[i] = findViewById(resID);
    } Log.i("ON CREATE", Arrays.toString(computerImages));
}

OUTPUT

I/ON CREATE: [android.support.v7.widget.AppCompatImageView{fe40fe0 VFED..C.. ......ID 0,0-0,0 #7f070003 app:id/ImageView0}, android.support.v7.widget.AppCompatImageView{8313299 VFED..C.. ......ID 0,0-0,0 #7f070004 app:id/ImageView1}, null, null, null, null, null, null, null]

XML LAYOUT

 <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:orientation="horizontal">

        <Button
            android:id="@+id/button"
            android:layout_width="172dp"
            android:layout_height="wrap_content"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_weight="1"
            android:text="Computer" />

        <Button
            android:id="@+id/button2"
            android:layout_width="171dp"
            android:layout_height="wrap_content"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_weight="1"
            android:text="Player 02" />
    </LinearLayout>

    <GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/gridLayout"
        android:layout_width="match_parent"
        android:layout_height="360dp"
        android:layout_alignParentRight="true"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:background="@drawable/board"
        android:columnCount="3"
        android:rowCount="3">

        <ImageView
            android:id="@+id/imageView0"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="20dp"
            android:layout_marginRight="5dp"
            android:layout_marginTop="15dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="0" />

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="40dp"
            android:layout_marginRight="0dp"
            android:layout_marginTop="15dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="1" />

        <ImageView
            android:id="@+id/imageView2"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="40dp"
            android:layout_marginTop="15dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="2" />

        <ImageView
            android:id="@+id/imageView3"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="20dp"
            android:layout_marginRight="5dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="3" />

        <ImageView
            android:id="@+id/imageView4"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="40dp"
            android:layout_marginRight="1dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="4" />

        <ImageView
            android:id="@+id/imageView5"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="40dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="5" />

        <ImageView
            android:id="@+id/imageView6"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="0dp"
            android:layout_marginLeft="20dp"
            android:layout_marginRight="5dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="6" />

        <ImageView
            android:id="@+id/imageView7"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginLeft="40dp"
            android:layout_marginRight="1dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="7" />

        <ImageView
            android:id="@+id/imageView8"
            android:layout_width="95dp"
            android:layout_height="95dp"
            android:layout_marginBottom="5dp"
            android:layout_marginLeft="40dp"
            android:layout_marginTop="16dp"
            android:alpha="0"
            android:onClick="clickToPlay"
            android:tag="8" />
    </GridLayout>

    <Button
        android:id="@+id/playAgainButton"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="14dp"
        android:onClick="clickReset"
        android:text="Play Again"
        android:textSize="20sp" />

    <TextView
        android:id="@+id/winnerMessage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_weight="1"
        android:background="@android:color/holo_orange_dark"
        android:padding="5dp"
        android:text="TextView"
        android:textColor="@android:color/white"
        android:textSize="25sp"
        android:visibility="invisible" />
</RelativeLayout>

What are the contents of res directory of your application? — Ankur
– Ankur, Commented Jun 29, 2018 at 4:19
Thank you for your quick response! I have added the XML layout file for your view. The other folders in the res directory are just drawable with some photos, mipmap and values. Thanks again for your help! — curiousP
– curiousP, Commented Jun 29, 2018 at 4:28
UPDATE: Thanks for pointing it out! The Id I had did not match the ones in the resource file. I changed it from ImageView to imageView and it works now!! Thanks a lot for your help! — curiousP
– curiousP, Commented Jun 29, 2018 at 4:37

I. Ahmed · Accepted Answer · 2018-06-29 04:19:44Z

1

It returning null because "ImageView3, ImageView4, ImageView5, ImageView6, ImageView7, and ImageView8" views are not present in resource file. Only ImageView0, ImageView1 are present in resource file.

answered Jun 29, 2018 at 4:19

I. Ahmed

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1 Comment

curiousP Over a year ago

Thanks a lot! I just realized that the ID string did not match the one I had in the res directory. I changed it to "imageView" and it works! Thank you for your time and help!!

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