XML: 

```
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.utente.test_dimensions.MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/main"
        android:orientation="vertical">
        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
            <EditText
                android:layout_width="160dp"
                android:layout_height="wrap_content"
                android:digits="123456789"
                android:hint="ID promemoria"/>
            <Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="rimuovi prom." />
        </LinearLayout>
    </LinearLayout>
</RelativeLayout>

```

Java:

```
package com.example.utente.test_dimensions;

import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.HorizontalScrollView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    LinearLayout main = (LinearLayout)findViewById(R.id.main);
    LinearLayout ll_eti = new LinearLayout(this);
    ll_eti.setOrientation(LinearLayout.VERTICAL);
    ll_eti.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    main.addView(ll_eti);

    TextView eti_txtv = new TextView(this);
    eti_txtv.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    eti_txtv.setText("Etichetta:");
    ll_eti.addView(eti_txtv);

    TextView val_eti_txtv = new TextView(this);
    val_eti_txtv.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    HorizontalScrollView eti_hsv = new HorizontalScrollView(this);
    eti_hsv.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    eti_hsv.addView(val_eti_txtv);
    ll_eti.addView(eti_hsv);

    LinearLayout ll_info = new LinearLayout(this);
    ll_info.setOrientation(LinearLayout.VERTICAL);
    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    params.setMargins(0, 3, 0, 0);
    ll_info.setLayoutParams(params);
    main.addView(ll_info);

    LinearLayout ll_date = new LinearLayout(this);
    ll_date.setOrientation(LinearLayout.HORIZONTAL);
    ll_date.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    ll_info.addView(ll_date);

    TextView date = new TextView(this);
    date.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    date.setText("01/01/2000");
    ll_date.addView(date);

    TextView perm_not_y_or_n = new TextView(this);
    LinearLayout.LayoutParams params1 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    params1.setMargins(10, 0, 0, 0);
    perm_not_y_or_n.setText("without permanent notificationW");
    ll_date.addView(perm_not_y_or_n);

    LinearLayout ll_details = new LinearLayout(this);
    LinearLayout.LayoutParams params2 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    params2.setMargins(0, 3, 0, 0);
    ll_details.setOrientation(LinearLayout.HORIZONTAL);
    ll_details.setLayoutParams(params2);
    ll_info.addView(ll_details);

    TextView perm_val = new TextView(this);
    perm_val.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    perm_val.setText("Repetitive notification:");
    ll_details.addView(ll_info);

    TextView var_val = new TextView(this);
    LinearLayout.LayoutParams params3 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    params3.setMargins(5, 0 , 0 , 0);
    var_val.setLayoutParams(params3);
    var_val.setText("every 100 minutes");
    ll_details.addView(var_val);

    LinearLayout ll_id = new LinearLayout(this);
    ll_id.setOrientation(LinearLayout.VERTICAL);
    ll_id.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    main.addView(ll_id);

    TextView ID_txtv = new TextView(this);
    LinearLayout.LayoutParams params4 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    params4.setMargins(0, 5, 0, 0);
    ID_txtv.setLayoutParams(params4);
    ID_txtv.setText("ID:");
    ll_id.addView(ID_txtv);

    HorizontalScrollView horizontalScrollView = new HorizontalScrollView(this);
    horizontalScrollView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    ll_id.addView(horizontalScrollView);

    TextView id_txtv = new TextView(this);
    id_txtv.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    id_txtv.setText("p");
    horizontalScrollView.addView(id_txtv);

}

}

```

Here's the logcat: 

```
07-10 14:50:13.023 27776-27776/com.example.utente.test_dimensions E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.example.utente.test_dimensions, PID: 27776
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.utente.test_dimensions/com.example.utente.test_dimensions.MainActivity}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2352)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2414)
                                                                                    at android.app.ActivityThread.access$900(ActivityThread.java:151)
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1318)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                    at android.os.Looper.loop(Looper.java:135)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5282)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at java.lang.reflect.Method.invoke(Method.java:375)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
                                                                                 Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
                                                                                    at android.view.ViewGroup.addViewInner(ViewGroup.java:3937)
                                                                                    at android.view.ViewGroup.addView(ViewGroup.java:3787)
                                                                                    at android.view.ViewGroup.addView(ViewGroup.java:3728)
                                                                                    at android.view.ViewGroup.addView(ViewGroup.java:3701)
                                                                                    at com.example.utente.test_dimensions.MainActivity.onCreate(MainActivity.java:67)
                                                                                    at android.app.Activity.performCreate(Activity.java:6865)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2305)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2414) 
                                                                                    at android.app.ActivityThread.access$900(ActivityThread.java:151) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1318) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:135) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5282) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at java.lang.reflect.Method.invoke(Method.java:375) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699) 

```

I was testing adding views to the xml file (for my app);
I can't understand why this doesn't work, have you got any suggestions?
I see that everyone use addView() to add a view to a layout, but why does this not work for me?