Develop Reference

2x2 buttons in a scrollview

I’m trying to put a matrix (2 x 2) of buttons into a constraint layout and then to put the constraint (with the 4 buttons included) layout into a scroll view and finally to add the scroll view into the main layout. The code is provided here below. Can anyone tell me what do I wrong since finally the bar appears instead of the matrix of buttons? It was planned to have 4 buttons visible, but in fact 2 buttons is appearing. Are there any suggestion how to make the task smarter way. Thank you in advance!
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ConstraintLayout layout = findViewById(R.id.layout);
ConstraintLayout.LayoutParams params = new ConstraintLayout.LayoutParams(200, 200);
ConstraintLayout constraintLayout = new ConstraintLayout(MainActivity.this);
constraintLayout.setLayoutParams(params);
GradientDrawable shape1 = new GradientDrawable();
shape1.setColor(Color.BLUE);
GradientDrawable shape2 = new GradientDrawable();
shape2.setColor(Color.GREEN);
Button button11 = new Button(MainActivity.this);
Button button12 = new Button(MainActivity.this);
Button button21 = new Button(MainActivity.this);
Button button22 = new Button(MainActivity.this);
ConstraintLayout.LayoutParams params01 = new ConstraintLayout.LayoutParams(100,100);
button11.setLayoutParams(params01);
button11.setX(0);
button11.setY(0);
constraintLayout.addView(button11);
ConstraintLayout.LayoutParams params02 = new ConstraintLayout.LayoutParams(100,100);
button12.setLayoutParams(params02);
button12.setX(100);
button12.setY(0);
constraintLayout.addView(button12);
ConstraintLayout.LayoutParams params03 = new ConstraintLayout.LayoutParams(100,100);
button21.setLayoutParams(params03);
button21.setX(0);
button21.setY(100);
constraintLayout.addView(button21);
ConstraintLayout.LayoutParams params04 = new ConstraintLayout.LayoutParams(100,100);
button22.setLayoutParams(params04);
button22.setX(100);
button22.setY(100);
constraintLayout.addView(button22);
ScrollView SV = new ScrollView(MainActivity.this);
ConstraintLayout.LayoutParams SVparams = new ConstraintLayout.LayoutParams(300,300);
SV.setLayoutParams(SVparams);
constraintLayout.setBackground(shape1);
SV.setBackground(shape2);
SV.addView(constraintLayout);
layout.addView(SV);
}
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
</androidx.constraintlayout.widget.ConstraintLayout>

My solution:
ConstraintLayout.LayoutParams params03 = new ConstraintLayout.LayoutParams(100,100);
params03.topToTop = PARENT_ID;
params03.setMargins(0, 100, 0, 0);
button21.setLayoutParams(params03);
button21.setX(0);
constraintLayout.addView(button21);
ConstraintLayout.LayoutParams params04 = new ConstraintLayout.LayoutParams(100,100);
params04.topToTop = PARENT_ID;
params04.setMargins(0, 100, 0, 0);
button22.setLayoutParams(params04);
button22.setX(100);
constraintLayout.addView(button22);
It looks like there's a bug when you put a ConstraintLayout inside a ScrollView. The ConstraintLayout's height defaults to WRAP_CONTENT. So when you set it to any other heights, it won't change. Also setY does not work. You have to set vertical constraints for the buttons in the bottom row to position them vertically.
Result:

If your target is really just simple 2x2 button grid(matrix), then I'm wondering why should you need to achieve this dynamically, when you can just describe all the layout in xml even if its just a fragment for some more complex view or, say, a list/grid item; moreover, you already have xml describing your ConstraintLayout. So in perspective it may look like this:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="300dp"
android:layout_height="300dp"
android:background="#8FFF0E">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#105BFF">
<Button
android:id="#+id/btnFirst"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<Button
android:id="#+id/btnSecond"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintStart_toEndOf="#id/btnFirst"
app:layout_constraintTop_toTopOf="parent"/>
<Button
android:id="#+id/btnThird"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#id/btnFirst"/>
<Button
android:id="#+id/btnFourth"
android:layout_width="100dp"
android:layout_height="100dp"
app:layout_constraintStart_toEndOf="#id/btnThird"
app:layout_constraintTop_toBottomOf="#id/btnSecond"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</ScrollView>
After having it all in prepared view, you can either operate buttons by ids (either, hiding/showing them or changing their properties).
By the topic - you obviously can do it programmatically with the help of ConstraintSet. Check this one: ConstraintLayout: change constraints programmatically

Android: ScrollView not working with View class

I've created a class which i use to draw some graphs, the class extends View, and it looks just like here How to draw a line in android.
Inside an activity, I show it with this
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
setContentView(drawView);
But when I add the ScrollView in the LinearLayout in xml of the activity, it doesn't work, I mean I can't scroll down, like there is no ScrollView.
What may be the problem?
And this is the xml code
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/background_image"
android:orientation="vertical" >
</LinearLayout>
</ScrollView>

This is because you're adding two views using different methods: the one that the system inflates it from xml layout and the one that's created inside the activity.
This way, the content from xml layout is discarded, when you invoke
setContentView(drawView);
Better said, is replaced with the DrawView created in the OnCreate method.
You should inflate the xml layout in your activity:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ScrollView container = getLayoutInflater().inflate(R.layout.main_layout, null));
setContentView(drawView);
drawView = container.findViewById(R.id.my_draw_view);
drawView.setBackgroundColor(Color.WHITE);
}
And the activity layout should look like this:
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<com.yourcompany.DrawView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
</ScrollView>
If it helps, don't be shy to accept it or +1 it.

You can create a ScrollView programmatically and add the DrawView as a child to it. And later set the ScrollView as content for the Activity. Something like this:
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
ScrollView sv = new ScrollView(this);
sv.setLayoutParams( new LayoutParams( LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT ) );
scrollView.addView( drawView );
setContentView(sv);

Still Can't Add Button to Layout in Android

I just started android and I tried below questions to get this answer before posting it here:
Android - Adding layout at runtime to main layout
Add button to a layout programmatically
Dynamically adding a child to LinearLayout with getting each child's position
And I am still not able to add a button to linear layout :(
Below is the code for activity, please let me know where I am wrong:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout layout = (LinearLayout) View.inflate(this, R.layout.activity_main, null);
Button btn = new Button(this);
btn.setId(123);
btn.setText("Welcome to WI FI World");
layout.addView(btn);
}
And xml looks like below:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</LinearLayout>

Try assigning an id to your layout then add the button to the layout.
Im pretty sure those 2 layouts are not the same, so you are infact adding a button to a layout that is never displayed.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout layout = (LinearLayout) findViewById(R.id.lnr_main);
Button btn = new Button(this);
btn.setId(123);
btn.setText("Welcome to WI FI World");
layout.addView(btn);
}
With Layout assigned an id
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/lnr_main"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</LinearLayout>

Take the Id for LinearLayout in XML and in jave code use that id of LinearLayout from XML
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/linear" >
</LinearLayout>
In onCreate():
LinearLayout linear=(LinearLayout)findViewById(R.id.linear);
//Select widgets
linear.addView()

Give an id to your linearLayout.
Then in your code
LinearLayout layout = (LinearLayout)findViewById(R.id.given_id);
Keep the rest the same, should work.

Dynamic relative layout in android

I am trying to have two images on tp of each other. I can have it work fine with an xml file but I would like to do this dynamically. ctdeasyone is a transparent image.
So this works fine..
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ImageView
android:id="#+id/bck1"
android:src="#drawable/fish2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="fitXY"
android:layout_gravity="center">
</ImageView>
<ImageView
android:id="#+id/bck2"
android:src="#drawable/ctdeasyone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="fitXY"
android:layout_gravity="center">
</ImageView>
</RelativeLayout>
When I do this. only the second image shows up (it is the transparent one.) Can any of the experts advice on this? Newbbie here... This is my first question. TIA.
public class TwoPicksOnEachOther extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Grabbing the Application context
final Context context = getApplication();
RelativeLayout relativeLayout = new RelativeLayout(this);
final ImageView iv = new ImageView(this);
iv.setImageResource(R.drawable.fish2);
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.FILL_PARENT,
RelativeLayout.LayoutParams.FILL_PARENT);
relativeLayout.addView(iv,lp);
// Creating transparent image
final ImageView iv2 = new ImageView(this);
iv.setImageResource(R.drawable.ctdeasytwo);
RelativeLayout.LayoutParams lp2 = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.FILL_PARENT,
RelativeLayout.LayoutParams.FILL_PARENT);
relativeLayout.addView(iv2,lp2);
setContentView(relativeLayout);
}
}

I had to put it in the emulator and play with it for a while until I saw it:
iv.setImageResource(R.drawable.fish2);
(...)
iv.setImageResource(R.drawable.ctdeasytwo);
You're never setting the image resource for iv2!
I changed that and now I see two images as expected.

This is perfect for FrameLayout . Since you want the images right on top of each other.

How to use the xml setting in a view of a activity?

I want to show two views in one activity. If I clicked on button in the first view I want to see the second and other way round.
The views should not have the same size as the screen so I want e.g. to center it, like you see in first.xml.
But if I add the views with
addContentView(mFirstView, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
the views are not centered. They are shown at top left.
How can I use the xml settings to e.g. center it?
first.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_height="wrap_content" android:layout_width="wrap_content"
android:background="#drawable/background"
android:layout_gravity="center"
android:minWidth="100dp"
android:minHeight="100dp"
android:paddingBottom="5dp"
>
<LinearLayout android:id="#+id/head"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageButton android:id="#+id/first_button"
android:src="#drawable/show_second"
android:layout_gravity="center"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#null" />
</LinearLayout>
second.xml same as first.xml but with
<ImageButton android:id="#+id/second_button"
android:src="#drawable/show_first"
... />
ShowMe.java
public class ShowMe extends Activity {
View mFirstView = null;
View mSecondView = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initFirstLayout();
initSecondLayout();
showFirst();
}
private void initFirstLayout() {
LayoutInflater inflater = getLayoutInflater();
mFirstView = inflater.inflate(R.layout.first, null);
getWindow().addContentView(mFirstView, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
ImageButton firstButton = (ImageButton)mMaxiView.findViewById(R.id.first_button);
firstButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
ShowMe.this.showSecond();
}
});
}
private void initSecondLayout() {
// like initMaxiLayout()
}
private void showFirst() {
mSecondView.setVisibility(View.INVISIBLE);
mFirstView.setVisibility(View.VISIBLE);
}
private void showSecond() {
mFirstView.setVisibility(View.INVISIBLE);
mSecondView.setVisibility(View.VISIBLE);
}}
Hope someone can help.
Thanks

Why don't you use setContentView(R.layout.yourlayout)? I believe the new LayoutParams you're passing in addContentView() are overriding those you defined in xml.
Moreover, ViewGroup.LayoutParams lacks the layout gravity setting, so you would have to use the right one for the layout you're going to add the view to (I suspect it's a FrameLayout, you can check with Hierarchy Viewer). This is also a general rule to follow. When using methods that take layout resources as arguments this is automatic (they might ask for the intended parent).
With this consideration in mind, you could set your layout params with:
FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(/* wrap wrap */);
lp.setGravity(Gravity.CENTER);
addContentView(mYourView, lp);
But I would recommend setContentView() if you have no particular needs.
EDIT
I mean that you create a layout like:
~~~/res/layout/main.xml~~~
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="....."
android:id="#+id/mainLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
then in your onCreate() or init...Layout():
setContentView(R.layout.main);
FrameLayout mainLayout = (FrameLayout)findViewById(R.id.mainLayout);
// this version of inflate() will automatically attach the view to the
// specified viewgroup.
mFirstView = inflater.inflate(R.layout.first, mainLayout, true);
this will keep the layout params from xml, because it knows what kind it needs. See reference.