Is it possible to place one view over another in a

问题:

Can we place a small view over another large view? For example, I have a VideoView which is playing a file in the background. Over this, somewhere in the middle/corner, I want to place another ImageView.

But in Linear/Relative Layout, views can be placed only one after another or relative to each other, and AbsoluteLayout is advised against. So what do I do?

回答1:

FrameLayouts let you pile each view on top of the one below. This can also be achieved with a RelativeLayout.

回答2:

The FrameLayout is the simplest ViewGroup and stacks the Views in the order they're defined in layout XML (or added programmatically); the first will be lower, and the last will be on top.

Here is an example where two Views are stacked and offset to better illustrate the point:

Here is the actual layout XML with the two overlapping TextView boxes. The offset of the two boxes is done using android:layout_gravity while android:gravity is used for centering the text itself within each box.

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="100dp"
    android:layout_height="100dp">

    <TextView
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_gravity="top|left"
        android:background="@android:color/holo_blue_light"
        android:gravity="center"
        android:text="First is below"/>

    <TextView
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_gravity="bottom|right"
        android:background="@android:color/holo_green_light"
        android:gravity="center"
        android:text=" Last is on top"/>

</FrameLayout>

回答3:

Just in case if you want to place a view on top of a ButtonView then use this; android:elevation="7dp" for the view which needs to be placed on top of the button.

回答4:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/dp_20"
    android:background="@color/yellowt"
    >
        <VideoView
            android:id="@+id/videoview"
            android:layout_width="wrap_content"
            android:layout_centerInParent="true"
            android:layout_height="300dp"
            android:contentDescription="@string/app_name"
             />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/camera"
            android:layout_margin="30dp"
            android:layout_alignParentEnd="true"
            android:layout_centerVertical="true"
            android:id="@+id/imageView" />

</RelativeLayout>

回答5:

You can also do it by using ConstraintLayout a new layout introduced by google.

ConstraintLayout allows you to create large and complex layouts with a flat view hierarchy (no nested view groups).

 <?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:id="@+id/container"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  android:layout_weight="4"
  tools:context="com.edalat.example.MainActivity">
  <VideoView
    android:id="@+id/videoView"
    android:layout_width="283dp"
    android:layout_height="349dp"
    app:layout_constraintBottom_toBottomOf="parent"
    android:layout_marginBottom="24dp"
    app:layout_constraintTop_toTopOf="parent"
    android:layout_marginTop="24dp"
    android:layout_marginRight="24dp"
    app:layout_constraintRight_toRightOf="parent"
    android:layout_marginLeft="24dp"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintHorizontal_bias="0.509"/>
  <ImageView
     android:id="@+id/imageView"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     app:srcCompat="@mipmap/ic_launcher"
     app:layout_constraintTop_toTopOf="parent"
     android:layout_marginTop="24dp"
     app:layout_constraintBottom_toBottomOf="parent"
     android:layout_marginBottom="24dp"
     android:layout_marginLeft="24dp"
     app:layout_constraintLeft_toLeftOf="parent"
     android:layout_marginRight="24dp"
     app:layout_constraintRight_toRightOf="parent"/>
   </android.support.constraint.ConstraintLayout>