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HorizontalScrollView scrollTo doesn't scroll above original width of the view

I have a custom view containing an HorizontalScrollView. The width of the scroll view is match_parent, and the width of its children is initially programmatically set based on the value of an attribute of the custom view. At some point, the width of the children of the scroll view are updated (increased) programmatically. The problem is that, after the update, the scrollTo method is still unable to scroll above the original width value (the same for scrollBy).
The enclosing view (the custom one) have a left and right padding equal to half the screen, if this is relevant.
Example:
Initial HorizontalScrollView's children width: 1000;
HorizontalScrollView's parent width: 1080;
HorizontalScrollView's left/right padding = 540;
New HorizontalScrollView's children width: 2000;
scrollTo(1100, 0) = scrollTo(1000, 0); <---- here is the problem
Relevant code:
Custom view initialization:
private void init(AttributeSet attrs, int defStyle) {
inflate(getContext(), R.layout.timeline_view, this);
// Load attributes
final TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.TimelineView, defStyle, 0);
m_timelineInitialLength = a.getDimension(R.styleable.TimelineView_timelineInitialLength, DEFAULT_LENGTH);
a.recycle();
DisplayMetrics displayMetrics = new DisplayMetrics();
((Activity) getContext()).getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
LinearLayout timelineWidget = findViewById(R.id.timeline_widget);
int horizontalPadding = displayMetrics.widthPixels / 2;
timelineWidget.setPadding(horizontalPadding, 0, horizontalPadding, 0);
m_horizontalScrollView = findViewById(R.id.scroll_view);
m_horizontalScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
#Override
public void onScrollChanged() {
m_currentScrollX = m_horizontalScrollView.getScrollX();
}
});
m_currentScrollX = m_horizontalScrollView.getScrollX();
update(m_timelineInitialLength, m_timelineInitialStepWidth, m_currentScrollX);
}
Update and scrollTo (this method is called also at the end of the initialization. m_rulerView and m_timelineLayout are the children of the HorizontalScrollView):
private void update(float timelineLength, float timelineStepWidth, int currentScrollX) {
m_rulerView = findViewById(R.id.ruler);
m_rulerView.setIndicator(null);
m_rulerView.getLayoutParams().width = (int) timelineLength;
m_rulerView.requestLayout();
m_timelineLayout = findViewById(R.id.timeline);
m_timelineLayout.getLayoutParams().width = (int) timelineLength;
m_timelineLayout.requestLayout();
m_horizontalScrollView.scrollTo(currentScrollX, 0);
}

The problem seems to be that the scrolling happens before the children have been redrawn, before calling requestLayout only schedule the update of the view to be executed at some point in the future (the same for invalidate()).
I solved using a workaround, by executing scrollTo after some time:
new Handler().postDelayed(() -> ((Activity) getContext()).runOnUiThread(() -> m_horizontalScrollView.scrollTo(currentScrollX, 0)), 200);
I'm still open to better solutions.

How to calculate the height of a scrollView using ViewTreeObserver?

I have a ScrollView with some layouts in it, called the fragment_about_sl.xml.And the class associated to it is called AboutSLFragment.java.I want to calculate the height of the scrollView to get height ratio for an image.I researched the web and found this code.
ViewTreeObserver vto = scrollView.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
#Override
public void onGlobalLayout() {
scrollView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
int scrollViewHeightInPixels = layout.getMeasuredHeight();
//This is equal with %45 weight you tried before
int height = (scrollViewHeightInPixels * 45) / 100;
ViewGroup.LayoutParams pagerParams = viewPager.getLayoutParams();
pagerParams.height = height;
}
});
As shown in the above code.It just have said scrollView instead of getting it from findViewById().And also in the below code,it just says layout.getMeasuredHeight() instead of specifying the name of layout.
int scrollViewHeightInPixels = layout.getMeasuredHeight();
The question is that I want to know what is meant by layout here(above).What should I put there,is it the id of the scrollView?If so I developed a code myself and I want to know whether it is correct.Please help me I am new to android.The id of the scrollview I used is aboutslscrollview.
final View view = rootView.findViewById(R.id.aboutslscrollview);
ViewTreeObserver vto = view.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
#Override
public void onGlobalLayout() {
view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
int scrollViewHeightInPixels = view.getMeasuredHeight();
//This is equal with %45 weight you tried before
int height = (scrollViewHeightInPixels * 45) / 100;
ViewGroup.LayoutParams pagerParams = viewPager.getLayoutParams();
pagerParams.height = height;
}
});

Android Issue with activity context

So I have a helper class that reuses a lot of code through out the application, one of the methods is shown below:
public void setTitleTextSize(final int id){
infoButton = ((Activity) context).findViewById(R.id.info_button);
ViewTreeObserver customTitleScale = infoButton.getViewTreeObserver();
customTitleScale.addOnPreDrawListener(new OnPreDrawListener() {
#Override
public boolean onPreDraw() {
int infoWidth = infoButton.getMeasuredWidth();
if(infoWidth !=0){
if(Build.VERSION.SDK_INT >= 11.0){
TypedValue tv = new TypedValue();
((Activity) context).getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true);
actionBarWidth = ((Activity) context).getResources().getDimensionPixelSize(tv.resourceId);
}
DisplayMetrics metrics = new DisplayMetrics();
Display Screen = ((Activity) context).getWindowManager().getDefaultDisplay();
Screen.getMetrics(metrics);
int screenWidth = metrics.widthPixels;
int titleWidth = screenWidth - infoWidth - actionBarWidth;
TextView titleText = (TextView) ((Activity) context).findViewById(R.id.title_text);
titleText.setText(id);
TextPaint paint = titleText.getPaint();
Rect rect = new Rect();
String text = String.valueOf(titleText.getText());
int textLength = text.length();
paint.getTextBounds(text, 0, textLength, rect);
if(rect.width() > titleWidth){
float scale = (float) titleWidth / (float) rect.width();
float textSize = titleText.getTextSize();
float scaleSize = (float) (textSize * (scale*0.8));
titleText.setTextSize(TypedValue.COMPLEX_UNIT_PX, scaleSize);
}
infoButton.getViewTreeObserver().removeOnPreDrawListener(this);
}
return false;
}
});
}
I use this particular method on all of my activities.
The problem I've got is I don't want to display the infoButton on every activity but when I add View infoButton = findViewById(R.id.info_button); infoButton.setVisibility(View.GONE); to the activity, the screen is just black.
So I was thinking on how to do this and the only thing I can thing of is to pass a boolean into the method stating whether the info view is visible or not. I suppose I'd do an if statement saying `if true then display it, if false then don't but I can't figure out how to do this.
Any help would be amazing thanks.

Try to use method infoButton.getVisibility()
it will return you the integer to get visibility status of you widget.

I figured out the issue I was having, My logic wasn't correct for the if statement if(infoWidth !=0). The code wasn't running if the activity didn't have an info button because the infoWidth would always be zero. So I changed the logic to if(infoWidth !=0 || !displayInfoButton) which works perfectly.

Multiple Gradient for single Textview

Refering agradient to textview regard as normal action can be achieved in android ,
as below :
android:background="#drawable/gredient"
and gradient XML will be as below code :
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#B22222" android:centerColor="#000000"
android:endColor="#B22222" android:angle="0" />
<corners android:radius="15dp" />
</shape>
what im asking about is there is away in android to apply multiple gradients to single textview consisting of may paragraphs , so each paragraph will has different gradient .
any advice will be appreciated ,
thanks

You might want to consider using a WebView instead of TextView (if you need more advanced formatting), but if you want to stick to a TextView, LineBackgroundSpan is your friend :)
Although there might be some better solution (most likely involving a custom Layout-derived class), here's some sample code that should do what you want just by implementing a special LineBackgroundSpan interface:
public class MyActivity extends Activity {
private Editable mEditable;
private class MySpan implements LineBackgroundSpan {
private final Rect rect = new Rect();
private final Drawable drawable;
private int next = 0;
public MySpan(Drawable drawable) {
this.drawable = drawable;
}
#Override
public void drawBackground(Canvas c, Paint p, int left, int right, int top, int baseline,
int bottom, CharSequence text, int start, int end, int lnum) {
if (start == end) return;
if (next == 0) {
next = mEditable.nextSpanTransition(start, Integer.MAX_VALUE, MySpan.class);
rect.left = left;
rect.top = top;
}
if (next == end) {
rect.right = right;
rect.bottom = bottom;
c.save();
drawable.setBounds(rect);
drawable.draw(c);
c.restore();
}
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final Resources res = getResources();
final Drawable gd1 = res.getDrawable(R.drawable.gd1);
final Drawable gd2 = res.getDrawable(R.drawable.gd2);
final Drawable gd3 = res.getDrawable(R.drawable.gd3);
final Drawable gd4 = res.getDrawable(R.drawable.gd4);
final TextView tv = new TextView(this);
setContentView(tv);
tv.setText("Paragraphs with drawable background:\n", BufferType.EDITABLE);
mEditable = tv.getEditableText();
final String text = "paragraph text ";
appendPara("###\n".replaceAll("#", text), gd1);
appendPara("##############\n".replaceAll("#", text), gd2);
appendPara("#######\n".replaceAll("#", text), gd3);
appendPara("###########\n".replaceAll("#", text), gd4);
}
private void appendPara(String string, Drawable gd) {
final int start = mEditable.length();
mEditable.append(string);
final int end = mEditable.length();
mEditable.setSpan(new MySpan(gd), start, end, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}

I don't think it is possible with android's default TextView.
You can create your own view, by extending you class with View, and use methods like Canvas.drawText(...) and Canvas.drawBitmap(...) in the view's onDraw() method, to create each paragraph with a different gradient.
This can also help you control line-height and paragraph-spacing.

As, you need multiple gradients for your multiple Paragraphs then why not to have one TextView per Paragraph and setting unique gradient for each TextView.
If you donot know how many paragraphs you will have,
You must create a LinearLayout whose height is wrap-content and at run time for every paragraph create a TextView with fill_parent width and wrap_context height and add that TextView to your parent (LinearLayout) view. and in code set backgrounds to your TextViews.

Android: Adding Layouts to HorizontalScrollView

I'm trying to create something similar to the home screen layout. This consists of multiple vertically oriented LinearLayouts within a single horizontally oriented LinearLayout, all housed in a HorizontalScrollView. I've written it as a custom class called 'HomeLayout' extending HorizontalScrollView.
LinearLayout wrapper = new LinearLayout(getContext());
LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
wrapper.setLayoutParams(params);
wrapper.setOrientation(LinearLayout.HORIZONTAL);
addView(wrapper);
for(int i = 0; i < 2; i++) {
LinearLayout linear = (LinearLayout) View.inflate(getContext(), R.layout.screens, null);
linear.setLayoutParams(params);
wrapper.addView(linear);
}
The problem is 'screen2' has width '0' when added.
This only works if I call this in onDraw() and use getMeasuredWidth() and getMeasuredHeight() instead of LayoutParams.FILL_PARENT. And even then, I'm not sure if that's the right thing to do.
Furthermore I'm unable to reference the views 'wrapper', 'screen1', 'screen2' in onCreate().
I loosely followed this link: http://blog.velir.com/index.php/2010/11/17/android-snapping-horizontal-scroll/
What am I doing wrong?

Hoping this helps others. I solved my problem by implementing onMeasure() in the following way:
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = MeasureSpec.getSize(widthMeasureSpec);
int height = MeasureSpec.getSize(heightMeasureSpec);
setMeasuredDimension(width, height);
for(int i = 0; i < mWrapper.getChildCount(); i++) {
View child = mWrapper.getChildAt(i);
child.setLayoutParams(new LinearLayout.LayoutParams(width,
LayoutParams.FILL_PARENT));
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}