为什么 view.height 比实际高度大 3 倍？

Question

I have an ImageView with height set to 120dp. When I get the view.height it equalls to 360, why won't it be equal to 120?

I'm not sure of the code won't be of help but:

    <ImageView
        android:id="@+id/profilePic1"
        android:layout_width="120dp"
        android:layout_height="120dp"
        android:scaleType="centerCrop"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:clickable="true"
        app:srcCompat="@drawable/profile_pic1"/>

Activity:

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

    val layoutInflater: LayoutInflater = LayoutInflater.from(this)
    val view: View = layoutInflater.inflate(R.layout.activity_edit_profile, null)

    view.viewTreeObserver.addOnGlobalLayoutListener(object: ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            // remove listener
            view.viewTreeObserver.removeOnGlobalLayoutListener(this)

            // insert coordinates (coor) of each image to imagePosition variables
            Log.d("TAG", profilePic1.height.toString()) // RETURNS 360

        }
    })

Answer 1

Because in xml file you have given size in DP and In java that parameter returns values in Pixel , Please check this for more understanding about DP and PIxel

https://developer.android.com/training/multiscreen/screendensities

36x36 (0.75x) for low-density (ldpi)
48x48 (1.0x baseline) for medium-density (mdpi)
72x72 (1.5x) for high-density (hdpi)
96x96 (2.0x) for extra-high-density (xhdpi)
144x144 (3.0x) for extra-extra-high-density (xxhdpi)
192x192 (4.0x) for extra-extra-extra-high-density (xxxhdpi)

Answer 2

This is just because you are using XXHDPI device, where 120dp is being converted to 360PX.

Must read What is the difference between "px", "dip", "dp" and "sp"?

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You should read Image resolution for mdpi, hdpi, xhdpi and xxhdpi to understand how DP and pixels work together. And official documentation can be found here

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If I explain it in short, in MDPI 1dp is almost equals to 1PX. So if you check your code on devices of MDPI resolution you will get 120PX output. But as I added a URL above for other resolutions it follows a rule of conversion from dp to PX. It would give you 180px in HDPI, 240px in XHDPI, 360px in XXHDPI, 480px in XXXHDPI devices as output.

Answer 3

In java you get the height in px instead of dp . You have to convert it to dp to get correct data:

float px = profilePic1.height;
float dp = px / context.getResources().getDisplayMetrics().density;

// here dp should be 120

Answer 4

有一个名为sdp和ssp的库，用于使维度具有响应性。

Answer 5

Because you have given height in dp(density pixel) while in the code when you retrieve it , it is retrieved in pixels only. You have to convert it to dp.