Develop Reference

How to make the child of a view fill the space (match_parent) but keep growing if necessary?

I have a TextView inside a LinearLayout and I want the background of my TextView to always display blue, filling the space horizontally, esto es lo que necesito:
But I don't know how to get it, the contained text can change, if I set android:layout_width="match_parent" it won't show all the text when there are long texts. And if I use android:layout_width="wrap_content" it will look like this:
This is what I have:
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:background="#drawable/rp"
android:gravity="center"
android:orientation="vertical">
<androidx.constraintlayout.widget.ConstraintLayout...>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#color/week"
android:gravity="center"
android:text="Text"
android:textColor="#color/white" />
<TextView...>
</LinearLayout>

I fixed it now, I changed my LinearLayout to a ConstraintLayout and put a view of the same color as my textview, just behind:
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:background="#drawable/rp"
android:gravity="center"
android:orientation="vertical">
<androidx.constraintlayout.widget.ConstraintLayout...>
<View
android:id="#+id/view6"
android:layout_width="0dp"
android:layout_height="0dp"
android:background="#color/week"
app:layout_constraintBottom_toBottomOf="#+id/textView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="#+id/textView" />
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#color/week"
android:gravity="center"
android:text="Text"
android:textColor="#color/white"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/constraintLayout"/>
<TextView...>
</androidx.constraintlayout.widget.ConstraintLayout>

If you can set a fixed width for your outer LinearLayout, then your requirement can be achieved by wrapping the TextView in another layout.
Please find sample code below:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:orientation="vertical"
android:padding="5dp">
<LinearLayout
android:layout_width="200dp"
android:layout_height="wrap_content"
android:background="#drawable/blue_border_bg"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_gravity="center_horizontal"
android:layout_margin="20dp"
android:src="#android:color/background_dark" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/green_text_highlight">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Text"
android:textColor="#color/white"
android:textSize="22dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentBottom="true"
android:padding="10dp"
android:text="2000"
android:textColor="#cc000000" />
</LinearLayout>
<LinearLayout
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:background="#drawable/blue_border_bg"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_gravity="center_horizontal"
android:layout_margin="20dp"
android:src="#android:color/background_dark" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/green_text_highlight">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Text. Large text"
android:textColor="#color/white"
android:textSize="22dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentBottom="true"
android:padding="10dp"
android:text="2000"
android:textColor="#cc000000" />
</LinearLayout>
<LinearLayout
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:background="#drawable/blue_border_bg"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_gravity="center_horizontal"
android:layout_margin="20dp"
android:src="#android:color/background_dark" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/green_text_highlight">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Text. Very Large text"
android:textColor="#color/white"
android:textSize="22dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentBottom="true"
android:padding="10dp"
android:text="2000"
android:textColor="#cc000000" />
</LinearLayout>
</LinearLayout>
The code will generate the following output

How do I convert this Layout to ConstraintLayout?

I am trying to convert this layout to ConstrainLayout ,relativeLayout1 layout_height must be 60dp,how do I convert this layout to ConstraintLayout?
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<RelativeLayout
android:id="#+id/relativeLayout1"
android:layout_width="0dp"
android:layout_height="60dp"
android:layout_weight="1">
<ImageView
android:id="#+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:src="#mipmap/ic_launcher" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_toEndOf="#id/imageView1"
android:orientation="vertical">
<TextView
android:id="#+id/textview2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<TextView
android:id="#+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
</RelativeLayout>
<RelativeLayout
android:layout_width="0dp"
android:layout_height="60dp"
android:layout_weight="1">
<ImageView
android:id="#+id/imageView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:src="#mipmap/ic_launcher" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_toEndOf="#id/imageView2"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
</RelativeLayout>
</LinearLayout>
</LinearLayout>

<?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"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="#+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:src="#mipmap/ic_launcher"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView1" />
<TextView
android:id="#+id/textview2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/imageView1"
app:layout_constraintStart_toEndOf="#+id/imageView1"
app:layout_constraintTop_toBottomOf="#+id/textView1"
app:layout_constraintVertical_bias="0.3" />
<TextView
android:id="#+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/imageView1"
app:layout_constraintStart_toEndOf="#+id/imageView1"
app:layout_constraintTop_toBottomOf="#+id/textView1"
app:layout_constraintVertical_bias="0.74" />
<RelativeLayout
android:layout_width="0dp"
android:layout_height="60dp"
android:layout_weight="1"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/textview2"
app:layout_constraintTop_toTopOf="parent">
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

Here is one possible conversion. Here are a few notes about this conversion:
Setting the size of the ImageView to 60dp then constraining things to that effectively sets the height of the "row" to 60dp. If the text in the text views is long (or large font) it can still overflow the row. That was true with the relative layout too.
Setting the vertical chain style for text views 2 and 3 to "packed" mimics what the internal linear layout does. If you just want them to be aligned to the top of the image then the chain is not necessary.
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
/>
<ImageView
android:id="#+id/imageView1"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_centerVertical="true"
android:src="#mipmap/ic_launcher"
app:layout_constraintTop_toBottomOf="#id/textView1"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintDimensionRatio="1"
/>
<TextView
android:id="#+id/textview2"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintTop_toTopOf="#id/imageView1"
app:layout_constraintBottom_toTopOf="#id/textView3"
app:layout_constraintStart_toEndOf="#id/imageView1"
app:layout_constraintEnd_toStartOf="#id/imageView2"
app:layout_constraintVertical_chainStyle="packed"
app:layout_constraintHorizontal_bias="0.0" />
<TextView
android:id="#+id/textView3"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintTop_toBottomOf="#id/textview2"
app:layout_constraintBottom_toBottomOf="#id/imageView1"
app:layout_constraintStart_toEndOf="#id/imageView1"
app:layout_constraintEnd_toStartOf="#id/imageView2"
app:layout_constraintHorizontal_bias="0.0"/>
<ImageView
android:id="#+id/imageView2"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_centerVertical="true"
android:src="#mipmap/ic_launcher"
app:layout_constraintTop_toBottomOf="#id/textView1"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#id/imageView1"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintDimensionRatio="1"
/>
<TextView
android:id="#+id/textview4"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintTop_toTopOf="#id/imageView2"
app:layout_constraintBottom_toTopOf="#id/textView5"
app:layout_constraintStart_toEndOf="#id/imageView2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintVertical_chainStyle="packed"
app:layout_constraintHorizontal_bias="0.0" />
<TextView
android:id="#+id/textView5"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintTop_toBottomOf="#id/textview4"
app:layout_constraintBottom_toBottomOf="#id/imageView2"
app:layout_constraintStart_toEndOf="#id/imageView2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"/>
</androidx.constraintlayout.widget.ConstraintLayout>

Android, My EditText wont respect its weight in Linear Layout

In order to make my view always visible even when the keyboard shows, I made a linear layout and gave every item a weigth. I made the TextViews uniform and gave them a minimum size:
app:autoSizeMinTextSize="8dp", app:autoSizeTextType="uniform"
as you can see below. However, when I click to edit the EditText, everything gets smaller but the EditText will not respect the weigth, even though it has the value 4, which should make it appear much more than the rest. Also, the little TextView disappear almost completely
What is happening?
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
tools:context=".ChargeActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="6">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="6"
android:orientation="vertical">
<CheckBox
android:id="#+id/receiveCheckbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:text="Receber valor automaticamente" />
<TextView
android:id="#+id/textViewValueToCharge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:text="#string/charge_hint_type_value_with_decimals"
app:autoSizeMinTextSize="8dp"
app:autoSizeTextType="uniform" />
<EditText
android:id="#+id/editTextValueToCharge"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="4"
android:gravity="center"
android:inputType="number"
android:textSize="30sp" />
<TextView
android:id="#+id/textViewPaymentOption"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:text="#string/charge_label_choose_payment_action_below"
app:autoSizeMinTextSize="8dp"
app:autoSizeTextType="uniform" />
<Button
android:id="#+id/buttonCreditOnly"
android:layout_width="match_parent"
android:layout_height="45dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="2"
android:background="#28a745"
android:text="#string/charge_button_credit_only" />
<Button
android:id="#+id/buttonCreditWithInstallments"
android:layout_width="match_parent"
android:layout_height="45dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="2"
android:background="#28a745"
android:text="#string/charge_button_charge_credit_with_installments" />
<Button
android:id="#+id/buttonDebit"
android:layout_width="match_parent"
android:layout_height="45dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="2"
android:background="#28a745"
android:text="#string/charge_button_charge_debit" />
<TextView
android:id="#+id/textViewNumberOfInstallments"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:text="#string/number_of_installments"
app:autoSizeMinTextSize="8dp"
app:autoSizeTextType="uniform" />
<Spinner
android:id="#+id/spinnerNumberOfInstallments"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:layout_weight="1" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:orientation="vertical"
tools:visibility="gone">
<TextView
android:id="#+id/textViewProgressBar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:text="#string/start_connection_terminal"
android:visibility="gone" />
<TextView
android:id="#+id/textViewResponse"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:text="#string/start_transaction_status"
android:visibility="gone" />
<ProgressBar
android:id="#+id/progressBar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone" />
<Space
android:layout_width="wrap_content"
android:layout_height="10dp"
app:layout_constraintBottom_toTopOf="#+id/buttonAction"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent" />
<ImageView
android:id="#+id/imageViewResponse"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:src="#drawable/icon_denied"
android:tint="#android:color/holo_red_dark"
android:visibility="gone" />
</LinearLayout>
<Button
android:id="#+id/buttonAction"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:layout_weight="1"
android:background="#28a745"
android:text="#string/charge_button_pay_label"
android:textColor="#FFFFFF" />
</LinearLayout>
</LinearLayout>
</LinearLayout>

LinearLayout can't align properly

Hi I want a layout like bellow
Main amount 120 usd
Extra charge 2 usd
----------------------------
Sub Total 122 usd
Discount 5 usd
----------------------------
Total amount 117 usd
I am totally not familiar with constraint layout I tried to use LinearLayout gravity/layout/alignment gravity right for right part but its not working ,all aligned from left.I will be glad if someone give a example code for this layout plz.
Update: my current code
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:text="Main Amount"
android:layout_height="wrap_content" />
<TextView
android:layout_width="wrap_content"
android:gravity="left"
android:layout_gravity="left"
android:textAlignment="gravity"
android:text="10 "
android:layout_height="wrap_content" />
<TextView
android:layout_width="wrap_content"
android:gravity="left"
android:layout_gravity="left"
android:textAlignment="gravity"
android:text="USD"
android:layout_height="match_parent" />
</LinearLayout>

For this kind of view use LinearLayout with weightSum property to the parent LinearLayout and use layout_weight for the Children LinearLayout
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:weightSum="4">
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2">
<TextView
android:layout_width="wrap_content"
android:text="Main Amount"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1">
<TextView
android:layout_width="wrap_content"
android:gravity="left"
android:layout_gravity="left"
android:textAlignment="gravity"
android:text="10 "
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1">
<TextView
android:layout_width="wrap_content"
android:gravity="left"
android:layout_gravity="left"
android:textAlignment="gravity"
android:text="USD"
android:layout_height="match_parent" />
</LinearLayout>
</LinearLayout>

LinearLayout is going to be difficult without a lot of hard coding of layout_width on the children. Have you tried TableLayout?
https://developer.android.com/reference/android/widget/TableLayout
TableLayout can be a pain sometimes to get perfect, but it will give you the layout you are looking for.

You can try something like this:
I used LinearLayout as the parent and add RelativeLayout to it to create align the TextViews the way you want to.
You can dupe the Relative layout the create the rest.
not sure if it's the best way... but it works
<LinearLayout 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:orientation="vertical"
tools:context=".MainActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/main"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Main" />
<TextView
android:id="#+id/amount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_toRightOf="#+id/main"
android:text="amount" />
<TextView
android:id="#+id/extra"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Extra"
android:layout_below="#+id/amount"
/>
<TextView
android:id="#+id/charge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_toRightOf="#+id/extra"
android:layout_alignBottom="#+id/extra"
android:text="charge" />
<TextView
android:id="#+id/usd"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/main"
android:layout_alignParentRight="true"
android:text="usd"
android:layout_marginRight="30dp"
/>
<TextView
android:id="#+id/num1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/main"
android:layout_toLeftOf="#+id/usd"
android:text="120"
android:layout_marginRight="10dp"
/>
<TextView
android:id="#+id/usd2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/extra"
android:layout_alignParentRight="true"
android:text="usd"
android:layout_marginRight="30dp"
/>
<TextView
android:id="#+id/num2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/extra"
android:layout_toLeftOf="#+id/usd2"
android:text="120"
android:layout_marginRight="10dp"
/>
</RelativeLayout>

I believe that for this layout you better use ConstraintLayout.
It will take you only a few minutes to build this layout, you can add Guidelines to make your life easier.
In addition, your layout will be responsive to all screen sizes so consider using ConstraintLyaout
Here is an example of you wanted layout usingConstraintLyaout:
<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:text="Button"
app:layout_constraintBottom_toTopOf="#+id/button4"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toTopOf="#+id/button6"
app:layout_constraintStart_toStartOf="#+id/button"
app:layout_constraintTop_toBottomOf="#+id/button3" />
<Button
android:id="#+id/button6"
android:layout_width="0dp"
android:layout_height="4dp"
android:text="Button"
android:background="#color/bronze"
app:layout_constraintBottom_toTopOf="#+id/button7"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/button2" />
<Button
android:id="#+id/button7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="#+id/button"
app:layout_constraintTop_toBottomOf="#+id/button6" />
<Button
android:id="#+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toTopOf="#+id/button2"
app:layout_constraintStart_toStartOf="#+id/button"
app:layout_constraintTop_toBottomOf="#+id/button5" />
<Button
android:id="#+id/button4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toTopOf="#+id/button5"
app:layout_constraintStart_toStartOf="#+id/button"
app:layout_constraintTop_toBottomOf="#+id/button" />
<Button
android:id="#+id/button5"
android:layout_width="0dp"
android:layout_height="4dp"
android:text="Button"
android:background="#color/bronze"
app:layout_constraintBottom_toTopOf="#+id/button3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/button4" />
<TextView
android:id="#+id/textView11"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="#+id/button" />
<TextView
android:id="#+id/textView12"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/button7"
app:layout_constraintEnd_toEndOf="#+id/textView11"
app:layout_constraintTop_toTopOf="#+id/button7" />
<TextView
android:id="#+id/textView13"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/button2"
app:layout_constraintEnd_toEndOf="#+id/textView11"
app:layout_constraintTop_toTopOf="#+id/button2" />
<TextView
android:id="#+id/textView14"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="#+id/textView11"
app:layout_constraintTop_toTopOf="#+id/button3" />
<TextView
android:id="#+id/textView15"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="#+id/button4"
app:layout_constraintEnd_toEndOf="#+id/textView11"
app:layout_constraintTop_toTopOf="#+id/button4" />
</android.support.constraint.ConstraintLayout>
It will look like this:

How to center 2 edit texts and a button below horizontally

I want to achieve the following look for a login activity, but it looks quite different on different devices I'm testing.
center
Edit: This is the current code:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/grey_100"
android:orientation="vertical"
android:weightSum="4">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="3"
android:gravity="center_horizontal"
android:orientation="vertical">
<ImageView
android:id="#+id/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="#string/icon"
android:src="#drawable/icon" />
<EditText
android:id="#+id/emailField"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="textPersonName"
android:text="Name" />
<EditText
android:id="#+id/passwordField"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="textPersonName"
android:text="Name" />
<Button
android:id="#+id/loginButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
</LinearLayout>
As you can see on the design tab it looks ok, but I can't move it up or down, and on different devices it's not exactly centered:
Current layout

add the views in a constraint layout and add a horizontal guideline at the percentage of the screen that you want your views to begin. Then just constrain your views underneath that, one after the other, and constrain their sides to match the parent:
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="3"
android:gravity="center_horizontal"
android:orientation="vertical">
<ImageView
android:id="#+id/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:contentDescription="#string/icon"
android:src="#drawable/icon"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="#+id/guideline2"
/>
<EditText
android:id="#+id/emailField"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:ems="10"
android:inputType="textPersonName"
android:text="Name"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/icon"
/>
<EditText
android:id="#+id/passwordField"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:ems="10"
android:inputType="textPersonName"
android:text="Name"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/emailField"
/>
<Button
android:id="#+id/loginButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/passwordField"
/>
<android.support.constraint.Guideline
android:id="#+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.5" />
</android.support.constraint.ConstraintLayout>

How about a RelativeLayout and android:layout_centerInParent="true"
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/grey_100">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:orientation="vertical"
android:layout_centerInParent="true">
<ImageView
android:id="#+id/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="#string/icon"
android:src="#drawable/icon" />
<EditText
android:id="#+id/emailField"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="textPersonName"
android:text="Name" />
<EditText
android:id="#+id/passwordField"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="textPersonName"
android:text="Name" />
<Button
android:id="#+id/loginButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
</RelativeLayout>