Java – How to set the align parent right attribute of TextViews in relative layout programmatically

The modern way to do this is to have a ConstraintLayout and constrain the bottom of the view to the bottom of the ConstraintLayout with app:layout_constraintBottom_toBottomOf="parent"

The example below creates a FloatingActionButton that will be aligned to the end and the bottom of the screen.

<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_height="match_parent"
   android:layout_width="match_parent">

<android.support.design.widget.FloatingActionButton
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"

    app:layout_constraintBottom_toBottomOf="parent"

    app:layout_constraintEnd_toEndOf="parent" />

</android.support.constraint.ConstraintLayout>

For reference, I will keep my old answer.

Before the introduction of ConstraintLayout the answer was a relative layout.

If you have a relative layout that fills the whole screen you should be able to use android:layout_alignParentBottom to move the button to the bottom of the screen.

If your views at the bottom are not shown in a relative layout then maybe the layout above it takes all the space. In this case you can put the view, that should be at the bottom, first in your layout file and position the rest of the layout above the views with android:layout_above. This enables the bottom view to take as much space as it needs, and the rest of the layout can fill all the rest of the screen.

You can access any LayoutParams from code using View.getLayoutParams. You just have to be very aware of what LayoutParams your accessing. This is normally achieved by checking the containing ViewGroup if it has a LayoutParams inner child then that's the one you should use. In your case it's RelativeLayout.LayoutParams. You'll be using RelativeLayout.LayoutParams#addRule(int verb) and RelativeLayout.LayoutParams#addRule(int verb, int anchor)

You can get to it via code:

RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)button.getLayoutParams();
params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
params.addRule(RelativeLayout.LEFT_OF, R.id.id_to_be_left_of);

button.setLayoutParams(params); //causes layout update