Develop Reference

Android Support BottomSheetBehavior can't be dynamic?

I'm using Bottom Sheet from Android support library like this:
XML:
<LinearLayout
android:id="#+id/bottomSheetLinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/fourth_white"
android:orientation="vertical"
app:layout_behavior="android.support.design.widget.BottomSheetBehavior" />
I add child views to LinearLayout:
bottomSheet.addView(actionButtonView);
After I've finished adding child views, I initialize BottomSheetBehavior and expand it:
BottomSheetBehavior sheetBehavior = BottomSheetBehavior.from(bottomSheet);
sheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
This doesn't work. Nothing shows. Even if I preset the LinearLayout height inside XML, it's just all white.
If I add all the child views inside LinearLayout in XML, then everything works fine. It just doesn't work when I try to dynamically add views programatically.
Anyone had any similar issues?

Troubles with dynamic content on BottomSheetBehavior related to implementation of it's expanded size calculation. BottomSheetBehavior calculates expanded size in onLayoutChild method. But when you change content of sheet layout process launches asynchronous. Even if you call RequestLayout or something similar. So consequence of calls is like this:
BottomSheetBehavior have old expanded size (in your case I think it is zero)
You add content to BottomSheet. Expanded size is still old.
You call SetState to EXPANDED. BottomSheetBehavior still remember old expanded size and launches animation to that size. State changed to STATE_SETTLING!
onLayoutChild called and BottomSheetBehavior calculates new expanded size. But animation is already in progress and state is STATE_SETTLING so BottomSheetBehavior do not change its size
Animation finished. Size of BottomSheet is old. State changed to EXPANDED but BottomSheetBehavior "forgot" that expanded size was changed during animation.
It is surely the bug of BottomSheetBehaviour implementation.
In my project I found such workaround:
private void showPanel(final View panelContent) {
if (panelBehavior.getState()!=BottomSheetBehavior.STATE_EXPANDED) {
panelBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
#Override
public void onStateChanged(final View bottomSheet, int newState) {
if (newState==BottomSheetBehavior.STATE_EXPANDED) {
panelBehavior.setBottomSheetCallback(null);
contentView.removeAllViews();
contentView.addView(panelContent);
panelView.setVisibility(View.VISIBLE);
}
}
#Override
public void onSlide(View bottomSheet, float slideOffset) {
}
});
panelBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
return;
}
contentView.removeAllViews();
contentView.addView(panelContent);
panelView.setVisibility(View.VISIBLE);
}
private void hidePanel() {
panelBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
panelView.setVisibility(View.GONE);
contentView.removeAllViews();
}
So when you need to show BottomSheet with new content call ShowPanel. When you need to completely hide BottomSheet call hidePanel (if you need to hide it in your project. If not you could remove setVisibility from methods).
The idea of workaround is to never change content of BottomSheet when BottomSheetBehavior is not in expanded state. If state is not expanded just change it to expanded, wait until animation finished and only then change content.

Try to post runnable to view's message queue:
bottomSheet.post(new Runnable() {
#Override
public void run() {
bottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
}
});
Or with retrolambda:
bottomSheet.post(() -> bottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED));

How to make a set of views invisible in android

I'm trying to make a set of views (that include several textviews and buttons - all in different parent layouts, but in the same activity) invisible if a particular condition is evaluated to false.
The conventional way to do that would be:
findViewById(R.id.myview).setVisibility(View.INVISIBLE);
My question is, will I have to do this for all the views one by one that I want to be invisible, And then toggle them back when I want them visible?
Or, is there a way to avoid the code-repetition?

If the Views are in different parents , you can't do it directly, but you can implement a method to change the visibility of a bunch of Views if you want to keep your code clean:
List<View> relatedViews = new ArrayList<>();
// ...
relatedViews.add(view1);
relatedViews.add(view2);
relatedViews.add(view3);
// ...
changeVisibility(relatedViews, View.INVISIBLE);
// ...
private void changeVisibility(List<View> views, int visibility) {
for (View view : views) {
view.setVisibility(visibility);
}
}
As a side note, you may want to change the visibility to View.GONE instead of View.INVISIBLE so it doesn't take any space in the layout.

you can use something like this. It's not the most elegant solution but works.
The idea is give to each view that you want to hide a same content description, because in the same layout you can not use same id for multiple view. With the same content description you can find all views in your layout and hide them.
That's an example considering the first layout as Linear. You can change obviously ;)
public class TestActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
LinearLayout rootLayout = (LinearLayout)findViewById(R.id.rootLayout);
int childcount = rootLayout.getChildCount();
for (int i=0; i < childcount; i++){
View v = rootLayout.getChildAt(i);
if(v.getContentDescription() != null && v.getContentDescription().equals("invisibleView")){
v.setVisibility(View.INVISIBLE);
//I suggest you to use GONE instead of INVISIBLE to remove the space of the view
}
}
}
}
in your xml give to the object that you want to hide this property
android:contentDescription="invisibleView"

Use varargs method for show or hide multiple views.
for example if you have views like view1, view2.....etc
then just call setVisibility(View.VISIBLE,view1,view2)
public static void setVisibility(int visibility, View... views){
for (View view : views){
view.setVisibility(visibility);
}
}

can't add more than 2 views to a viewswitcher

In Asyntask, I want to change textswitcher text and If I add new view, app crash.
Code sample:
textSwitcher.setInAnimation(MainActivity.this,android.R.anim.slide_in_left);
textSwitcher.setOutAnimation(MainActivity.this, android.R.anim.slide_out_right);
TextView tv=new TextView(MainActivity.this);
tv.setGravity(Gravity.CENTER | Gravity.LEFT);
tv.setTypeface(custom_font);
tv.setTextColor(Color.parseColor("#00285E"));
textSwitcher.addView(tv);
last line gives error after I decided to remove all views and I added textSwitcher.removeAllViews(); , then it gives null pointer. What do you think for fix ?

ViewSwitcher can only have two children, as it says on the documentation for that class. I personally have not seen anyone using ViewSwitcher, it is an old class and you can get the same effect or better on your own with ObjectAnimators now anyway.
You can create your own ViewGroup that let's you switch any view for any other. If it were me, I would just extend FrameLayout and simply add something like this:
public void switchView(View view) {
// add the new view and reveal
view.setAlpha(0);
addView(view);
view.animate().alpha(1f).start();
if (getChildCount() > 0) {
// simultaneously remove the previous view
final View child = getChildAt(0);
child.animate().alpha(0).setListener(new AnimatorListenerAdapter() {
#Override
public void onAnimationEnd(Animator animator) {
// remove the child when the animation ends
removeView(child);
}
}).start();
}
}

This is completely arbitrary behaviour. You can overwrite ViewAnimator similar to ViewSwitcher class and replace the 0 / 1 handling by a variable subview count. Really easy!

Can I partially hide a layout?

As I've a master in MS Paint, I will just upload a picture selfdescripting what I'm trying to achieve.
I've searched, but I'm not really sure what do I've to search. I've found something called Animations. I managed to rotate, fade, etc an element from a View (with this great tutorial http://www.vogella.com/articles/AndroidAnimation/article.html)
But this is a bit limited for what I'm trying to achieve, and now, I'm stuck, because I don't know how is this really called in android development. Tried words like "scrollup layouts" but I didn't get any better results.
Can you give me some tips?
Thank you.
You can see a live example, with this app: https://play.google.com/store/apps/details?id=alexcrusher.just6weeks
Sincerely,
Sergi

Use something like this as your layout (Use Linear, Relative or other layout if you wish):
<LinearLayout
android:id="#+id/lty_parent">
<LinearLayout
android:id="#+id/lyt_first" />
<LinearLayout
android:id="#+id/lyt_second"/>
</LinearLayout>
And then in an onClick method on whatever you want to use to control it, set the Visibility between Visible and Gone.
public void buttonClickListener(){
((Button) findViewById(R.id.your_button))
.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if (lyt_second.getVisibility() == View.GONE) {
lyt_second.setVisibility(View.VISIBILE);
}
else {
lyt_second.setVisibility(View.GONE);
}
});
Which is fine if you just want a simple appear/disappear with nothing fancy. Things get a little bit more complicated if you want to animate it, as you need to play around with negative margins in order to make it appear to grow and shrink, like so:
We use the same onClick method that we did before, but this time when we click it starts up a custom SlideAnimation for the hidden/visible view.
#Override
public void onClick(View v) {
SlideAnimation slideAnim = new SlideAnimation(lyt_second, time);
lyt_second.startAnimation(slideAnim);
}
The implementation of the SlideAnimation is based on a general Animation class, which we extend and then Override the transformation.
public SlideAnimation(View view, int duration) {
//Set the duration of the animation to the int we passed in
setDuration(duration);
//Set the view to be animated to the view we passed in
viewToBeAnimated = view;
//Get the Margin Parameters for the view so we can edit them
viewMarginParams = (MarginLayoutParams) view.getLayoutParams();
//If the view is VISIBLE, hide it after. If it's GONE, show it before we start.
hideAfter = (view.getVisibility() == View.VISIBLE);
//First off, start the margin at the bottom margin we've already set.
//You need your layout to have a negative margin for this to work correctly.
marginStart = viewMarginParams.bottomMargin;
//Decide if we're expanding or collapsing
if (marginStart == 0){
marginEnd = 0 - view.getHeight();
}
else {
marginEnd = 0;
}
//Make sure the view is visible for our animation
view.setVisibility(View.VISIBLE);
}
#Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
super.applyTransformation(interpolatedTime, t);
if (interpolatedTime < 1.0f) {
// Setting the new bottom margin to the start of the margin
// plus the inbetween bits
viewMarginParams.bottomMargin = marginStart
+ (int) ((marginEnd - marginStart) * interpolatedTime);
// Request the layout as it happens so we can see it redrawing
viewToBeAnimated.requestLayout();
// Make sure we have finished before we mess about with the rest of it
} else if (!alreadyFinished) {
viewMarginParams.bottomMargin = marginEnd;
viewToBeAnimated.requestLayout();
if (hideAfter) {
viewToBeAnimated.setVisibility(View.GONE);
}
alreadyFinished = true;
}
hideAfter = false;
}
}
EDIT: If anyone had used this code before and found that if you click on the button that starts the animation more than once before the animation was finished, it would mess up the animation from then on, causing it to always hide the view after the animation finished. I missed the reset of the hideAfter boolean near the bottom of the code, added it now.

you can do this manually by using setvisibility feature on the event onClick()
or
use this
dynamically adding two views one below other

Adding a view dynamically in a ClickListener

I am trying to add a View to a RelativeLayout in my OnClickListener.
montrolButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// myParent is a relative layout
// newChild is an ImageView
myParent.addView(newChild);
requestLayout();
}
});
I have looked at the HierarchyViewer, I don' see my new child being added.
Can you please tell me if I miss anything?

I just tried the very same code and it works as it should. There could be an issue with your variable myParent which is not the element you expect it to be.
Also I did not have to call requestLayout() for the added view to appear on the screen.
Possibly try to just explicitly get another part of your view and add it there to see what is happening. Also just to try, you may do this:
RelativeLayout rv = (RelativeLayout) this.findViewById(R.id.right3);
ProgressBar iv = new ProgressBar(this);
rv.addView(iv);
to see if there is anything wrong with your image view instead of myParent
In any case it works if both elements are OK - there is nothing else to do in an activity.

Do you set the layout attributes of the new view (image view)?