Add an ImageView through code Android Studio

I Have a problem, is that I can't find out how to add any component(in this case an imageview)

These are the xml code for the layout

<?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=".main.Main">
    <LinearLayout
        android:id="@+id/container"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        tools:ignore="MissingConstraints" />
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="56dp"
        android:layout_marginLeft="56dp"
        android:layout_marginTop="40dp"
        android:contentDescription="@string/Nada"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/ic_launcher_foreground" />
</androidx.constraintlayout.widget.ConstraintLayout>

And this is the code that I have tried so far to add an imageView

package com.example.servidorexample.main;

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.ImageView;

public class Main extends AppCompatActivity implements Observer{


    @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         ImageView imageView_ = findViewById(R.id.imageView);
         //Im thinking something like this:
         findViewById(R.id.container).add(imageView_);
         //
    }
}

And lastly here is the one named AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.serverexample">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".main.Main">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

This is just so stackoverflow let me post this edit becuause it says that it has so much code and not that much details
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Since you've mentioned you need an imageview populated programmatically, here's how you can approach it:

1. Make a new layout file (for e.g. template_imageview.xml)

<?xml version="1.0" encoding="utf-8"?>
<ImageView
    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/imageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="56dp"
    android:layout_marginLeft="56dp"
    android:layout_marginTop="40dp"
    android:contentDescription="@string/Nada"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:srcCompat="@drawable/ic_launcher_foreground" />

Notice that I have changed one of your attrubutes from fill_parent to match_parent.

2. Now inflate and add the imageview by code:

package com.example.servidorexample.main;

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.ImageView;

public class Main extends AppCompatActivity implements Observer {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        LinearLayout containerLayout = findViewById(R.id.container);

        // Inflate the imageview, giving the linearlayout as the parent)
        ImageView imageView_ = (ImageView) getLayoutInflater().inflate(R.layout.template_imageview, containerLayout, false);

        // Add the imageView to the linearlayout
        containerLayout.addView(imageView);
    }
}

The way you are trying to do it programmatically won't work, as ImageView already has a parent layout (ConstraintLayout) and you will get a Runtime Exception when you try to do the findViewById(R.id.container).addView(imageView_); line.

What is the name of your activity class?

tools:context=".main.Main" attribute in the Constraint Layout and AndroidMainfest.xml is where you will tie the Layout with your activity class.

If the above steps have been taken care of then ImageView imageView_ = findViewById(R.id.imageView); should give you access to your imageView.