相机预览Android中的透明图像

Question

i need to set a transparent image in the camera preview, and i need to do zoomin and zoomout of it.

I have the camera preview, and in the layout on top i put a imageview with the image. This image its only a border, the center its transparent, but i cant see the camera preview, i only view the image with a white background.

This is my XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearlayout"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

  <ImageView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:id="@+id/imageView"
      android:layout_gravity="left|top" android:scaleType="fitXY"
      android:src="@drawable/red"/>
  <FrameLayout
      android:id="@+id/camera_preview"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_weight="1"
      >
  </FrameLayout>
</LinearLayout>

Why put white background if the image its transparent?

Thanks

Answer 1

You need to use RelativeLayout to set ImageView over camera preview.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearlayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
  <FrameLayout
      android:id="@+id/camera_preview"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      />
  <ImageView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:id="@+id/imageView"
      android:scaleType="fitXY"
      android:src="@drawable/red"/>
</RelativeLayout >

Answer 2

The problem has nothing to do with a camera preview, it's simply down to your choice of ViewGroup.

A LinearLayout arranges its children along side each other—not on top as you're intending. In your layout, your LinearLayout is consuming all visible space in your fragment or activity as its width and height are set to match_parent . Likewise, your ImageView is doing the same, and consuming all of the LinearLayout's visible space. Subsequently, the FrameLayout no longer fits and disappears somewhere off-screen.

You will want to use a FrameLayout instead (or a RelativeLayout if you want more fine-grained control of the placement of views inside it).