Develop Reference

How to programatically add a control as soon as I know parent width?

I have a custom control inheriting from LinearLayout and I want to add a child control to it as soon as I know the size of this custom control.
What's the correct method to do this?

The below code is working fine:
yourView.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
//yourView.getWidth()
yourView.getViewTreeObserver().removeOnPreDrawListener(this);
return true;
}
});
Hope this will help.

you have to override onFinishInflate() method inside the custom layout. That is the callback called when all views has been inflated. Use this and addd your views.

This might help:
/**
* Great workaround to get view infos after it has been drawn
*/
mCustomView.post(new Runnable() {
#Override
public void run() {
//The code you want to run
}
});

Programmatically hide views if it is shown. Show views if it is hidden

My button use code that shows and hides the views:
public void onClick (View v){
if (What code you need to enter here to determine hidden views or shown)
{
testActivity.setVisibility(View.VISIBLE);
}
else
{
testActivity.setVisibility(View.GONE);
}
}
What code I need to add in the "if()", so that clicking on my button was checked condition. If the activity is hidden, it should be shown, and Vice versa. If the views is shown, hide it.

I'm guessing since you are using setVisibility, that you want to check the visibility of a View , not an Activity.
In that case you just use getVisibility()
(I used != cause the visibility could be IINVISIBLE as well, change per your needs) :
public void onClick (View v){
if (testActivity.getVisibility() != View.VISIBLE)
{
testActivity.setVisibility(View.VISIBLE);
}
else
{
testActivity.setVisibility(View.GONE);
}
} });

Don't understand why, but only that removed the answer of a man who has solved my problem. Here is his response, and this code works:
public void onClick (View v){
if ((testActivity.getVisibility() == View.VISIBLE))
{
testActivity.setVisibility(View.GONE);
}
else
{
testActivity.setVisibility(View.VISIBLE);
}

disable all elements in a layout - Android

In my Android app there is a requirement that a number of UI elements should be disabled until a button click carryout. Can I disable all the UI elements in a layout by referring the layout without disable them one by one. Is it possible.Can some one help me.

You could disable all views recursively like this.
Just pass the layout as view to the method:
private void enableViews(View v, boolean enabled) {
if (v instanceof ViewGroup) {
ViewGroup vg = (ViewGroup) v;
for (int i = 0;i<vg.getChildCount();i++) {
enableViews(vg.getChildAt(i), enabled);
}
}
v.setEnabled(enabled);
}
Just run enableViews(view, false) to disable, or enableViews(view, true) to enable again.

use following attribute in your xml layout( as a example textView)
android:visibility="gone"
in button click event
myText.setVisible(myText.VISIBLE)
you can either use them one by one or you can put all invisible content in a single layout and hide the layout. then once you want to show them, just VISIBLE the layout. then all will display
need any more comment.. just comment.

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"

Dynamically add multiple views and classes to the current view

I am interested in populating a screen/activity with a user defined number of same views. Each view will have the exact same layout: couple TextViews and few Buttons. The thing is that each button will control what each TextView will display.
The way I was thinking to implement it was to have one XML and one Java class. Then dependimg on the number the user inputs, populate the screen with that many same views (using a for loop). The question is, can it be done? how? am I thinking about it in the right way?
Please help with any input or thoughts, code examples will be great too.

of course it can be done.
I think the easiest for your situation, plus you can then easily extend, is to create some helper functions that take care of:
1) creating a empty screen
2) create a button for a screen
3) create a textview for a screen
and finally
4) create a screen and populate it
You have to decide the proper Root element for your Views, depending on the child arragement you need. For simplicity let's choose a LinearLayout, but for a RelativeLayout or TableLayout the example is the same, it only changes that when you add the elements, you have to use additional parameters to properly place them.
Note that the function to create an empty custom view returns a ViewGroup ("where all layouts derive from"). This way, you always work with ViewGroups and just define the screen layout type once, inside createCustomView. So you can change the type of screens just there, and the rest of code will work ...
Here is some code for your inspiration:
private ViewGroup createCustomView(Context context) {
LinearLayout myCoolNewView=new LinearLayout(context); // or RelativeLayout, etc..
return myCoolNewView;
}
private Button createButton(Context context, String buttonText) {
Button newButton=new Button(context);
newButton.setText(buttonText);
return newButton;
}
private TextView createText(Context context, String initialText) {
TextView newText=new TextView(context);
newText.setText(buttonText);
return newText;
}
private ViewGroup createScreen(Context context, int numberOfButtons, int numberOfTextfields) {
ViewGroup newScreen=createCustomView(context);
TextView[] textViews=new TextView[numberOfTextFields];
for (int i=0; i<numberOfTextfields; i++) {
textViews[i]=createText(context, "hi i am text "+i);
newScreen.addView(textViews[i]); // you ideally provide here layoutparams to properly place your buttons
}
for (int j=0; i<numberOfButtons; j++) {
Button button=createButton(context, "hi i am button "+j);
button.setOnClickListener(new OnClickListener() {
public void onClick (View clickedView) {
// here you have a button keypress and you know all the textviews
textView[i%j].setText("hey you pressed me");
}
});
newScreen.addView(button);
}
return newScreen;
}
So now you can:
ViewGroup screen1=createScreen(context, 10, 10);
ViewGroup screen2=createScreen(context, 5, 3);
ViewGroup screen3=createScreen(context, 2, 5);
and add the screens to a parent layout, to a ViewFlipper, to a ViewSwitcher, etc... like this:
ViewGroup parentLayoutOfAllScreens=findViewById(R.id.root_of_screens);
parentLayoutOfAllScreens.addView(screen1);
parentLayoutOfAllScreens.addView(screen2);
parentLayoutOfAllScreens.addView(screen3);
In the XML you just have to create the root layout, and name it root_of_screens...
good coding !!! I suppose there'll be some errors in the code above, just typed it here, but I hope you get the idea and tweak it to suit your needs!
EDIT : v2.0 : Extending a View
Create a new .java named "MyCoolScreen.java" or whatever name, in the same folder where your activity is (for simplicity):
package ........
public class MyCoolScreen extends LinearLayout {
/** Now every view holds its own buttons, and they are private, it's good for encapsulating */
private TextView[] mTextViews; // <-- as a convention, members should start with "m"
private Button[] mButtons;
private UserPressedButtons mUserPressedButtonsListener; // See below
/** The following constructors must always be present for a custom view, and must always call super */
public MyCoolScreen(Context context) {
// This is the constructor you will use when creating your view programmatically
super(context);
}
public MyCoolScreen(Context context, AttributeSet attrs) {
// This is the constructor Android calls when you include your custom view in an XML
// You can do this too!!
// The ATTRS will then include your numberofbuttons and numberoftextfields from the XML
// this is beyond the example, but read about it, it's interesting
super(context, attrs); // this MUST ALWAYS be here for custom views, or they will not work.
// it tells the parent view to continue the construction.
}
public MyCoolScreen(Context context, AttributeSet attrs, int defStyle) {
// Another constructor Android calls from the XML
super(context, attrs, defStyle);
}
/** We create an "init" method to initialize this view from outside */
public void init(int numberOfTextViews, int numberOfButtons) {
createScreen(numberOfTextViews, numberOfButtons);
}
/** This is the same */
private Button createButton(Context context, String buttonText) {
Button newButton=new Button(context);
newButton.setText(buttonText);
return newButton;
}
/** This is the same */
private TextView createText(Context context, String initialText) {
TextView newText=new TextView(context);
newText.setText(buttonText);
return newText;
}
/** We tweak this function so it doesnt return a view, but rather fills up this one :) */
private void createScreen(int numberOfButtons, int numberOfTextfields) {
ViewGroup newScreen=this; // It's this view the one we gonna fill up!
mTextViews=new TextView[numberOfTextfields];
mButtons=new Button[numberOfButtons];
Context context=getContext(); // Views always know their context after constructed
for (int i=0; i<numberOfTextfields; i++) {
mTextViews[i]=createText(context, "hi i am text "+i);
newScreen.addView(textViews[i]); // you ideally provide here layoutparams to properly place your buttons
}
for (int j=0; i<numberOfButtons; j++) {
Button button=createButton(context, "hi i am button "+j);
button.setId(j);
button.setOnClickListener(new OnClickListener() {
public void onClick (View clickedView) {
// here you have a button keypress and you know all the textviews
if (mUserPressedButtonsListener!=null) mUserPressedButtonsListener.OnButtonPressed(j);
textView[i%j].setText("hey you pressed me");
}
});
mButtons[j]=button;
newScreen.addView(button);
}
}
public interface UserPressedButtons {
public void OnButtonPressed(int buttonNumber);
}
public void setUserPressedButtonsListener (UserPressedButtons listener) {
mUserPressedButtonsListener=listener;
}
}
Ok, so now to use this, in your Activity you can do:
import ....... .MyCoolScreen;
import ....... .MyCoolScreen.UserPressedButtons;
.
.
.
MyCoolScreen screen1=new MyCoolScreen(context);
screen1.init(5,5); // initializes the screen.
myRootLayout.addView(screen1);
What's cool about this, is now functionality is totally encapsulated in your custom view. And it resides in another .java, so your activity code is very clean, and you can even expand the View functionality without making it ugly.
It's also a common practice to create interfaces and listeners for your views to communicate with the outside world, so for example, we can do:
screen1.setUserPressedButtonsListener(new MyCoolScreen.UserPressedButtons() {
#Override
public void OnButtonPressed (int number) {
// you know the user pressed button "number", and you can do stuff about it without
// having to include it inside the MyCoolScreen class. Of course in your example you
// don't need this at the moment, because the View will modify its textfield, but suppose
// one of the buttons is "rocket launch" , that is something you will handle at the activity level, ie.
if (number==ROCKET_LAUNCH) RocketLauncher.setTarget(10,10).launch(); // Your MyCoolScreen doesnt know how to launch rockets, but your activity maybe yes...
}
});
You can do all kinds of cool things with your new custom view. For example, you could define:
#Override
public void OnDraw(Canvas c) {
c.drawEllipse ...
c.drawRectangle ....
}
And you can paint circles, lines, etc... over your textfields & buttons :) For this to work, you have to put
setWillNotDraw(false) on the constructor.
There might be errors, just typed the code here, but I hope it helps you!

Add and Remove Views in Android Dynamically?
this will helps to you most...