如何使用 xml 文件中定义的高度宽度和源定义 ImageView？

Question

Inflating view on fragment causing remove the attributes, how can I define ImageView with height width and source defined on xml file?

I am using this code bellow. for image_fragment.xml

<?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"
    tools:context=".ui.main.ImageFragment"
    android:orientation="horizontal" >
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:contentDescription="test Image"
        tools:src="@drawable/cartoon" />
</LinearLayout>

Using kotlin class for the fragment

ImageFragment.kt

class ImageFragment : Fragment() {


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment

        val root = inflater.inflate(R.layout.image_fragment, container, false)


        return root
    }

}

It showing nothin . When I tried debugging tools, I found that, the height and width of the imageview is not defined so is resource of the image.

only if I use

override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment

        val root = inflater.inflate(R.layout.image_fragment, container, false)
        root.findViewById<ImageView>(R.id.imageView).setImageResource(R.drawable.cartoon)


        return root
    }

it is showing the image. But attributes are still missing.

So what should do to define attributes and image source in xml file?

Answer 1

you are using tools in xml , it only shows a preview.

you must use app:srcCompat :

<ImageView
    android:id="@+id/imageView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:contentDescription="test Image"
    app:srcCompat="@drawable/cartoon" />

Answer 2

as document said

Android Studio supports a variety of XML attributes in the tools namespace that enables design-time features (such as which layout to show in a fragment) or compile-time behaviors (such as which shrinking mode to apply to your XML resources). When you build your app, the build tools remove these attributes so there is no effect on your APK size or runtime behavior.

so tools:src="@drawable/cartoon" just shows in designing UI preview and it will be removed at build time .
use app:srcCompat="@drawable/cartoon" instead of tools:src="@drawable/cartoon"

also for using app:srcCompat in your XML file, make sure to do the following:
setup your build.gradle file

android {
  defaultConfig {
    vectorDrawables {
      useSupportLibrary = true
    }
  }
}