Develop Reference

Android Studio does not show layout preview(no error occurs also)

Android Studio does not display a preview of the layout. No errors or warnings are showing. I already try this solution Invalidate Caches/ Restart.
XML File :
<?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:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:showIn="#layout/activity_main"
tools:context=".MainActivity">
<ListView
android:id="#+id/peripherals_list"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<TextView android:id="#+id/peripheral_list_empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/peripheral_list_empty"/>
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="#+id/txt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_below="#+id/txt"
android:layout_height="wrap_content"/>
</RelativeLayout>

If the system UI is on Listview will not show. Look for an icon with eye and unmark show system UI

How to nest a constraint layout in a frame layout in xml?

Hi I'm new to Android Studio and currently in my activity_main xml I have this constraint layout with a few text views.
<android.support.constraint.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/country_detail"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="edu.monash.fit2081.countryinfo.CountryDetails">
<TextView
android:id="#+id/textView"
android:layout_width="150dp"
android:layout_height="25dp"
//some code here
Now I want to change it to a fragment and make that activity as the bottom fragment.I made my fragment like this but how do nest the layout above into my frame layout?
<?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:id="#+id/content_main"
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="edu.monash.fit2081.database_4.MainActivity">
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/fragment_top"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/fragment_border"
/>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/country_detail"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/fragment_top"
android:background="#drawable/fragment_border"
/>
</RelativeLayout>
Any help will be appreciated!

The FrameLayout is a ViewGroup just like RelativeLayout:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/country_detail"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/fragment_top"
android:background="#drawable/fragment_border"
>
<android.support.constraint.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/country_detail"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="edu.monash.fit2081.countryinfo.CountryDetails">
<TextView
android:id="#+id/textView"
android:layout_width="150dp"
android:layout_height="25dp"
/>
</FrameLayout>

where can I add include in my xml file?

I'm trying to add a toolbar in my xml files.
So I made toolbar.xml and I need to include it in upload.xml:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_upload"
android:layout_width="match_parent"
android:padding="10dp"
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.sk.mf.Upload"
android:background="#fff">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/imageToUpload"
android:layout_gravity="center_horizontal"
android:layout_width="150dp"
android:layout_height="150dp" />
<EditText
android:id="#+id/etUploadName"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/bUploadImage"
android:text="Upload Image"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
</ScrollView>
the problem is, anywhere I place it I had error like:
scrollview can host only one direct child (inside scrollview)
multiple root tags (after scrollview)
...
my question here is, where and how can I put the code below in the xml above?
<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">
<include android:id="#+id/toolbar" layout="#layout/toolbar"></include>
</RelativeLayout>

try this : wrap your layout in LinearLayout and the toolbar tag
<?xml version="1.0" encoding="utf-8"?>
<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:orientation="vertical">
<include
android:id="#+id/toolbar"
layout="#layout/toolbar"></include>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_upload"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#fff"
android:padding="10dp"
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.sk.mf.Upload">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:id="#+id/imageToUpload"
android:layout_width="150dp"
android:layout_height="150dp"
android:layout_gravity="center_horizontal" />
<EditText
android:id="#+id/etUploadName"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/bUploadImage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Upload Image" />
</LinearLayout>
</ScrollView>
</LinearLayout>

Why My Card View have very long margin

simple question ,
why my Card View have long Margin bettween other list ?
this is my code
card.xml
`
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:layout_width="fill_parent"
android:layout_height="150dp"
android:scaleType="fitXY"
android:id="#+id/imagePasar" />
<TextView
style="#style/Base.TextAppearance.AppCompat.Body1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="Material Design is stunning!!!"
android:id="#+id/namaPasar" />
</LinearLayout>
</android.support.v7.widget.CardView>
`
and heres the mainLayout that used in the mainActivity
MainLayout
`<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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: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"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="id.web.gosoft.pasarwiki.MainActivity"
tools:showIn="#layout/app_bar_main">
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/RecViewListPasar"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>

It is because of android:scaleType="fitXY". This will scale your image using Fill. Read this guide for more help.

Can't figure out this android error

<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=".MainActivity" >
<?xml version="1.0" encoding="utf-8"?>
<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:orientation="horizontal">
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send" />
</LinearLayout>
From this (which is from the android tutorial) I am getting an error that The processing instruction target matching "[xX][mM][lL]" is not allowed (which is on the line starting

Put <?xml version="1.0" encoding="utf-8"?> on the top of the file
Remove xmlns:android="http://schemas.android.com/apk/res/android" from LinearLayout

Put on the top below line#
<?xml version="1.0" encoding="utf-8"?>
And remove from LinearLayout below line#
xmlns:android="http://schemas.android.com/apk/res/android"
For more info refer Stackoverflow Question

I edited your layout. <?xml version="1.0" encoding="utf-8"?> this takes makes the problem:
Below layout correct:
<?xml version="1.0" encoding="utf-8"?>
<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:orientation="horizontal" >
<EditText
android:id="#+id/edit_message"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="#string/edit_message" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send" />
</LinearLayout>

<?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=".MainActivity" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send" />
</LinearLayout>
</RelativeLayout>