Develop Reference

Correct way to hide and show widgets?

In my app, I need to show and hide widgets like button and textview at a certain time.
and how I am doing is as the following:
private void hideviews() {
image.setVisibility(View.GONE); ///ImageView
title1.setVisibility(View.GONE);///TextView
title2.setVisibility(View.GONE);///TextView
title3.setVisibility(View.GONE);///TextView
title4.setVisibility(View.GONE);///TextView
title5.setVisibility(View.GONE);///TextView
}
private void showviews() {
image.setVisibility(View.VISIBLE);
title1.setVisibility(View.VISIBLE);///TextView
title2.setVisibility(View.VISIBLE);///TextView
title3.setVisibility(View.VISIBLE);///TextView
title4.setVisibility(View.VISIBLE);///TextView
title5.setVisibility(View.VISIBLE);///TextView
}
I don't think this is the correct way to do this.
Because I don't know how many widgets there will be.
Any guidance on how to correctly show widgets is really appreciated.

Get the reference to root layout, iterate through the childs, check if the view at certain index is instance of EditText(or View that you dont need to hide), if not hide it
RelativeLayout root = findViewById(R.id.root)
for(i=0,i<root.getChildCount()-1,i++){
if(! (root.getChildAt(i) instance of EditText)){
root.getChildAt(i).setVisibility(View.GONE)
}
}

Since you don't know how many testviews will be attached, then I believe that the best approach will be to:
get the reference of the parent view group (that contains all the
textviews),
loop through all the childs using getChildAt,
verify whether the object is an instance of TextView/ImageView and if so set its visibility according to your logic

Instead of hiding every widget separately hide the root layout.
RelativeLayout rootLayout;
rootLayout= (RelativeLayout) findViewById(R.id.root_layout);
and use something like this to control the visibility.
public void setLayoutInvisible() {
if (rootLayout.getVisibility() == View.VISIBLE) {
rootLayout.setVisibility(View.GONE);
}
}
public void setLayoutVisible() {
if (rootLayout.getVisibility() == View.GONE) {
rootLayout.setVisibility(View.VISIBLE);
}
}

Make an array of all the views that you want to show/hide:
View[] views = {image, title1, title2, title3, title4, title5};
and then use this to hide them:
for (View view : views) {
view.setVisibility(View.GONE);
}
and use this to show them:
for (View view : views) {
view.setVisibility(View.VISIBLE);
}
although you can combine the 2 code parts in a single procedure:
void fixViews(int state) {
for (View view : views) {
view.setVisibility(state);
}
}
and call it:
fixViews(View.GONE); or fixViews(View.VISIBLE);

How I can save a linear layout and all its inner views and use it later android

I have one activity and inside it I have a Linear layout (lets name it the "main linear layout") and I am adding dynamically created view inside it (text views, linear layouts, edit texts, ...etc).
In the bottom of the screen there are two button (next and back).
If the user clicked on next button I should save the current "main linear layout " in a list for example and then I am generating a new views and I add it inside the "main linear layout" then .
And if the user clicked on back button I should restore the "main linear layout" and show all its views.
I don't know how I can do it.
I hope my description is clear :)

Take a look at onSaveInstance for preserving the view on the main screen when leaving to a different activity or screen orientation.
You can also try and use the buttons to hide the layouts using Visibility instead of trying to navigate through them.

This may help you. but concrete code need you write it yourself.
public class TestActivity extends Activity{
Stack<LinearLayout> layouts = new Stack<>();
FrameLayout container;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Button btnPre = new Button(this);
Button btnNext = new Button(this);
btnPre.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
container.addView(layouts.pop());
}
});
btnNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
LinearLayout linearLayout = (LinearLayout) container.getChildAt(0);
layouts.push(linearLayout);
container.removeAllViews();
container.addView(createNextView());
}
});
}
private LinearLayout createNextView(){
LinearLayout linearLayout = new LinearLayout(this);
return linearLayout;
}
}

Thank you all for your comments.
I haven't test Cyrus answer. I will post my answer as well in case someone has the same problem in Xamarin.Android since I am using it.
I fixed it like this:
I added this in next button click event and previous button click event:
AddQuestionsLinearLayoutToPagesLinearLayoutsList();
And the AddQuestionsLinearLayoutToPagesLinearLayoutsList() body is, of course you can change it the way you want:
private void AddQuestionsLinearLayoutToPagesLinearLayoutsList()
{
//Create a new linear layout to add views into it and saved it in _mPagesLinearLayouts list at index _mPageIndex
LinearLayout savedLinearLayout = new LinearLayout(this);
//List of _mQuestionsLinearLayout views
List<View> views = new List<View>();
//Add all _mQuestionsLinearLayout to views list
for (int i = 0; i < _mQuestionsLinearLayout.ChildCount; i++)
{
views.Add(_mQuestionsLinearLayout.GetChildAt(i));
}
//Remove views from main questions linear layout
_mQuestionsLinearLayout.RemoveAllViews();
//Add all views from the views list to savedLinearLayout
for (int i = 0; i < views.Count; i++)
{
savedLinearLayout.AddView(views[i]);
}
//Add savedLinearLayout to _mPagesLinearLayouts list at index _mPageIndex
_mPagesLinearLayouts.Insert(_mPageIndex, savedLinearLayout);
}
In creating views method:
if(NeedToCreateViews())
{
//create views here and add it to _mQuestionsLinearLayout
}
//Get all saved views and add it to _mQuestionsLinearLayout
else
{
//List of _mPagesLinearLayouts[_mPageIndex] LinearLayout views
List<View> views = new List<View>();
//Add all _mPagesLinearLayouts[_mPageIndex] LinearLayout to views list
for (int i = 0; i < _mPagesLinearLayouts[_mPageIndex].ChildCount; i++)
{
views.Add(_mPagesLinearLayouts[_mPageIndex].GetChildAt(i));
}
//Remove all views from _mPagesLinearLayouts[_mPageIndex] linear layout
_mPagesLinearLayouts[_mPageIndex].RemoveAllViews();
//Remove the linear layout at index _mPageIndex
_mPagesLinearLayouts.RemoveAt(_mPageIndex);
//Add all views from views list to _mQuestionsLinearLayout
for (int i = 0; i < views.Count; i++)
{
_mQuestionsLinearLayout.AddView(views[i]);
}
}

Check if view element is added to layout or not programmatically

In my fragment class, I add a child view element programmatically to my layout conditionally :
LinearLayout child = (LinearLayout) inflater.inflate(R.layout.child_view, null);
LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT,100);
container.addView(child, params);
Since the above code will be run conditionally, so, at some point, I would like to check if the child view has added or not, how to make this checking programmatically?

If you creating view via inflater, you can check his parent
if(view.getParent() != null) {...}

I think you can simply use
findViewById(your_view_id)
method: If its result is null the view does not exists, otherwise the view is present

Sorry for late reply but you may try this alternative:
use container.getChildCount(); before adding and after adding a view. Like :
int x = container.getChildCount();
container.addView(child, params);
int y = container.getChildCount();
if(y > x)
Toast.makeText(context, "View Successfully Added!", Toas.LENGTH_SHORT).show();

Or if you have a view instance to find, you could:
if (container.indexOfChild(childView) == -1) {
// Add child to container.
}

With AndroidX you can use ViewGroup.contains(view: View): Boolean extension function.

I cannot write a comment so I write it here as a solution:
From API level 19 you can call isAttachedToWindow() which doesn't help a lot, but if you are aiming API 19 or higher, then this should work by the documentation.

maybe you can try this
child.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
#Override
public void onGlobalLayout() {
child.getViewTreeObserver().removeOnGlobalLayoutListener(this);
// add to parent
}
});
or this one
child.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
#Override
public void onViewAttachedToWindow(View v) {
}
#Override
public void onViewDetachedFromWindow(View v) {
}
});

How to disable all buttons in a Layout?

The way app works is the following: App prompts 30 buttons to user and user may guess the right ones by tapping. When user taps some button all the buttons (say a view containing these buttons) should be locked while corresponding (right or wrong guess) animation is playing. Tapped button by itself should be disabled till the next round. After animation is finished all not tapped previously buttons (say a view containing these buttons) should be available again.
So I have a Layout which includes another layout with these 30 buttons:
...
<RelativeLayout
android:id="#+id/alphabetContainer"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<include layout="#layout/alphabet" />
</RelativeLayout>
...
Now I need to lock the buttons from being clicked and then unlock. So I tried:
...
private RelativeLayout alphabetPanel;
...
public void onCreate(){
...
alphabetPanel = (RelativeLayout) findViewById(R.id.alphabetContainer);
...
}
...
private void lockButtons(){
alphabetPanel.setEnabled(false);
}
but this doesn't lock buttons. I also tried:
alphabetPanel.setFocusable(false);
alphabetPanel.setClickable(false);
Doesn't help either. Seems like it all relies only to a layout by itself but not the views it contains.
Also I tried to add a fake layout to place it over layout with buttons by bringing it to the front. This is a workaround and its tricky cuz both layouts must be placed inside a RelativeLayout only:
...
blockingLayout = new RelativeLayout(this);
blockingLayout.setLayoutParams(alphabetPanel.getLayoutParams());
...
but this works very strange: somehow both layouts in this case appears and disappears every second or so or doesn't appear at all - I cant understand that at all cuz there is no setVisibility() method used in code!
The only one way left is to iterate every view (button) to make it disabled and than back.
Is there any other way?
UPDATE
Finally I had to add a "wall"-layout into the xml. Now by making it clickable and focusable it becomes a solution.

Try setting for each Button's xml definition
android:duplicateParentState="true"
I'm not sure, but I think it should make them not only to seem disabled, but also to act accordingly.

Hmm it surprises me that disabling the parent-layout doesn't work.. as far as i know it should.
Try fetching your included layout instead, and disable that.
Anyway, if all else fails you can always loop through the buttons themselves.
for(int i=0;i<relativeLayout.getChildCount();i++){
View child=relativeLayout.getChildAt(i);
//your processing....
child.setEnabled(false);
}

I used extension to lock and unlock the view
//lock
fun View.lock() {
isEnabled = false
isClickable = false}
//unlock
fun View.unlock() {
isEnabled = true
isClickable = true}
if you want to lock all children of the view group
//lock children of the view group
fun ViewGroup.lockAllChildren() {
views().forEach { it.lock() }}
//unlock children of the view group
fun ViewGroup.unlockAllChildren() {
views().forEach { it.unlock() }}

firstly define your button
Button bit = (Button)findViewById(R.id.but);
bit.setEnabled(false);
and set enabled false;

Java:-
public void disableButtons(Layout layout) {
// Get all touchable views
ArrayList<View> layoutButtons = layout.getTouchables();
// loop through them, if they are instances of Button, disable them.
for(View v : layoutButtons){
if( v instanceof Button ) {
((Button)v).setEnabled(false);
}
}
}
Kotlin:-
fun disableButtons(layout: Layout) {
// Get all touchable views
val layoutButtons: ArrayList<View> = layout.getTouchables()
// loop through them, if they are instances of Button, disable them.
for (v in layoutButtons) {
if (v is Button) {
(v as Button).setEnabled(false)
}
}
}
Retrieve all touchables views into an ArrayList, then loop through them and check if it is an instance of the Button or TextView or which ever you want, then disable it!

In case data binding is needed
import android.view.ViewGroup
import android.widget.Button
import androidx.core.view.children
import androidx.databinding.BindingAdapter
#BindingAdapter("disableButtons")
fun ViewGroup.setDisableButtons(disableButtons: Boolean) {
children.forEach {
(it as? Button)?.isEnabled = !disableButtons
}
}
Usage:
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="#dimen/guideline"
app:disableButtons="#{vm.busy}">
....
</androidx.constraintlayout.widget.ConstraintLayout>

Might work in constraint layout . Use group widget and add all the button ids.
In the java code set enabled false for the group.

For disable all buttons in any nested layouts.
void DisableAllButtons( ViewGroup viewGroup ){
for( int i = 0; i < viewGroup.getChildCount(); i++ ){
if( viewGroup.getChildAt(i) instanceof ViewGroup ){
DisableAllButtons( (ViewGroup) viewGroup.getChildAt(i) );
}else if( viewGroup.getChildAt(i) instanceof Button ){
viewGroup.getChildAt(i).setEnabled( false );
}
}
}

write these two lines on your button declartion in XML
android:setEnabled="false"
android:clickable="false"

Android OnLongClickListener issue

I have a custom view, DisView(Context, bitmap), which I want to add a LongCLickListener to.
The view is displayed once something else is clicked.
public void onClick(View view) {
...
RelativeLayout toplayout = new RelativeLayout(this);
setContentView(toplayout);
Bitmap bmp2 = BitmapFactory.decodeResource(getResources(), R.drawable.tag3);
tag3 = new DisView(this,bmp2);
tag3.setOnLongClickListener(this);
I should add that originally the activity's contentview is set to a linearlayout, but on a button being clicked, setContentLayout() makes a relativelayout the new layout.
Next I did the onLongClick method ( a method of the activity, implementing onlongclicklistener):
#Override
public boolean onLongClick(View view) {
moveTag(view);
return true;
}
moveTag() is a very simple TranslateAnimation. I have no idea why it doesn't work. I have a feeling it may be because I changed the layout.

did you think about ViewSwitcher to change your displayed layout?
Jonathan

if toplayout is a LinearLayout and you write
RelativeLayout toplayout = new RelativeLayout(this);
the software will usually crash on startup(or when this view is activated), if what you meet now is the software crashes once it started(or when you start this activity), it is highly possible that the problem is caused by this statement.

In your example you did this:
tag3.setOnLongClickListener(this);
Why did you do that?
setOnLongClickListener takes a parameter of type OnLongClickLIstener. Something like:
tag3.setOnLongClickListener((OnLongClickListener) keyHdlr);
where keyHdlr looks something like this:
OnLongClickListener keyHdlr = new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
Log.d("long", "backspace phone land long clicked!!!!!!");
return false;
}
};