ArrayIndexOutOfBoundsException in intro screen

Question

I have a similar problem described in this post. There are no answers there - android intro screen error when add to 8 screen, but not error if 4 screen

However, in my there are 4 welcome slides and the app shows only 2 of them. The third one just has an error. My code:

public class WelcomeActivity extends AppCompatActivity {

    private ViewPager viewPager;
    private MyViewPagerAdapter myViewPagerAdapter;
    private LinearLayout dotsLayout;
    private TextView[] dots;
    private int[] layouts;
    private Button btnSkip, btnNext;
    private PrefManager prefManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Checking for first time launch - before calling setContentView()
        prefManager = new PrefManager(this);
        if (!prefManager.isFirstTimeLaunch()) {
            launchHomeScreen();
            finish();
        }

        // Making notification bar transparent
        if (Build.VERSION.SDK_INT >= 21) {
            getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        }

        setContentView(R.layout.activity_welcome);

        viewPager = (ViewPager) findViewById(R.id.view_pager);
        dotsLayout = (LinearLayout) findViewById(R.id.layoutDots);
        btnSkip = (Button) findViewById(R.id.btn_skip);
        btnNext = (Button) findViewById(R.id.btn_next);


        // layouts of all welcome sliders
        // add few more layouts if you want
        layouts = new int[]{
                R.layout.welcome_slide1,
                R.layout.welcome_slide2,
                R.layout.welcome_slide3,
                R.layout.welcome_slide4};

        // adding bottom dots
        addBottomDots(0);

        // making notification bar transparent
        changeStatusBarColor();

        myViewPagerAdapter = new MyViewPagerAdapter();
        viewPager.setAdapter(myViewPagerAdapter);
        viewPager.addOnPageChangeListener(viewPagerPageChangeListener);

        btnSkip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                launchHomeScreen();
            }
        });

        btnNext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // checking for last page
                // if last page home screen will be launched
                int current = getItem(+1);
                if (current < layouts.length) {
                    // move to next screen
                    viewPager.setCurrentItem(current);
                } else {
                    launchHomeScreen();
                }
            }
        });
    }

    private void addBottomDots(int currentPage) {
        dots = new TextView[layouts.length];

        int[] colorsActive = getResources().getIntArray(R.array.array_dot_active);
        int[] colorsInactive = getResources().getIntArray(R.array.array_dot_inactive);

        dotsLayout.removeAllViews();
        for (int i = 0; i < dots.length; i++) {
            dots[i] = new TextView(this);
            dots[i].setText(Html.fromHtml("&#8226;"));
            dots[i].setTextSize(35);
            dots[i].setTextColor(colorsInactive[currentPage]);
            dotsLayout.addView(dots[i]);
        }

        if (dots.length > 0)
            dots[currentPage].setTextColor(colorsActive[currentPage]);
    }

    private int getItem(int i) {
        return viewPager.getCurrentItem() + i;
    }

    private void launchHomeScreen() {
        prefManager.setFirstTimeLaunch(false);
        startActivity(new Intent(WelcomeActivity.this, MainActivity.class));
        finish();
    }

    //  viewpager change listener
    ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            addBottomDots(position);

            // changing the next button text 'NEXT' / 'GOT IT'
            if (position == layouts.length - 1) {
                // last page. make button text to GOT IT
                btnNext.setText(getString(R.string.start));
                btnSkip.setVisibility(View.GONE);
            } else {
                // still pages are left
                btnNext.setText(getString(R.string.next));
                btnSkip.setVisibility(View.VISIBLE);
            }
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {

        }

        @Override
        public void onPageScrollStateChanged(int arg0) {

        }
    };

    /**
     * Making notification bar transparent
     */
    private void changeStatusBarColor() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Window window = getWindow();
            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
            window.setStatusBarColor(Color.TRANSPARENT);
        }
    }

    /**
     * View pager adapter
     */
    public class MyViewPagerAdapter extends PagerAdapter {
        private LayoutInflater layoutInflater;

        public MyViewPagerAdapter() {
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            View view = layoutInflater.inflate(layouts[position], container, false);
            container.addView(view);

            return view;
        }

        @Override
        public int getCount() {
            return layouts.length;
        }

        @Override
        public boolean isViewFromObject(View view, Object obj) {
            return view == obj;
        }


        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            View view = (View) object;
            container.removeView(view);
        }
    }
}

Error:

07-01 11:17:24.961 10911-10911/com.google.android.gms.samples.vision.ocrreader E/InputEventReceiver: Exception dispatching input event.
07-01 11:17:24.961 10911-10911/com.google.android.gms.samples.vision.ocrreader E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
07-01 11:17:24.967 10911-10911/com.google.android.gms.samples.vision.ocrreader E/MessageQueue-JNI: java.lang.ArrayIndexOutOfBoundsException: length=2; index=2
        at com.google.android.gms.samples.vision.ocrreader.WelcomeActivity.addBottomDots(WelcomeActivity.java:107)
        at com.google.android.gms.samples.vision.ocrreader.WelcomeActivity.access$300(WelcomeActivity.java:21)
        at com.google.android.gms.samples.vision.ocrreader.WelcomeActivity$3.onPageSelected(WelcomeActivity.java:130)
        at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1941)
        at android.support.v4.view.ViewPager.scrollToItem(ViewPager.java:680)
        at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:664)
        at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2257)
        at android.view.View.dispatchTouchEvent(View.java:9314)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2592)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2283)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2598)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2297)
        at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2430)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent_aroundBody0(PhoneWindow.java:1762)
        at com.android.internal.policy.PhoneWindow$AjcClosure1.run(PhoneWindow.java:1)
        at android.view.PhoneWindowAO.ajc$around$android_view_PhoneWindowAO$4$99ce526bproceed(PhoneWindowAO.aj:149)
        at android.view.PhoneWindowAO.ajc$around$android_view_PhoneWindowAO$4$99ce526b(PhoneWindowAO.aj:153)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1762)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2807)
        at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:68)
        at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2391)
        at android.view.View.dispatchPointerEvent(View.java:9534)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4422)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4288)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3739)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3792)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3758)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3766)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3739)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3792)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3758)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3885)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3766)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3942)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3739)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3792)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3758)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3766)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3739)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6146)
        at android.view

Answer 1

Regarding your issue at

dots[i].setTextColor(colorsInactive[currentPage]);

you get your colorsInactive from resources

int[] colorsInactive = getResources().getIntArray(R.array.array_dot_inactive);

You'll find these within src/main/res/arrays.xml or a similarly named file. The arrays defined there have the names array_dot_[in]active and only contain two elements. To make your code work, you need to add two more colors to these arrays or change the code itself to reflect the fact that there are only two colors.

One way to do so would be using %2 or &1 which yield the same value (0 if even, 1 if odd):

dots[i].setTextColor(colorsInactive[currentPage & 1]);