ittianyu ittianyu - 2 months ago 12
Android Question

Android ConstraintLayout getWidth return 0

I use ConstraintLayout in my project. While I find a problem when I try to call getWidth in onCreate. The result is 0.

The code is here.

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_paint);
iv = (ImageView) findViewById(R.id.iv);
iv.setOnTouchListener(new ImageViewTouchListener());

System.out.println("imageview width:" + iv.getWidth() + " height:" + iv.getHeight());
}


The layout design view

The xml content.

<?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:layout_width="match_parent"
android:layout_height="match_parent">

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btn_red"
android:background="#ff0000"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btn_green"
android:background="#00ff00"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintLeft_toRightOf="@+id/btn_red" />

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btn_blue"
app:layout_constraintLeft_toRightOf="@+id/btn_green"
android:background="#0000ff"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintTop_toTopOf="parent" />

<android.support.constraint.Guideline
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/guideline"
android:orientation="horizontal"
tools:layout_editor_absoluteY="55dp"
tools:layout_editor_absoluteX="0dp"
app:layout_constraintGuide_percent="0.09784412" />

<SeekBar
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/sb_stroke"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintHorizontal_bias="1.0"
android:layout_marginTop="16dp"
app:layout_constraintTop_toBottomOf="@+id/btn_green" />

<android.support.constraint.Guideline
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/guideline4"
android:orientation="horizontal"
tools:layout_editor_absoluteY="103dp"
tools:layout_editor_absoluteX="0dp"
app:layout_constraintGuide_percent="0.1840796" />

<ImageView
android:layout_width="0dp"
android:layout_height="0dp"
android:id="@+id/iv"
app:layout_constraintTop_toTopOf="@+id/guideline4"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
tools:ignore="ContentDescription"
android:background="#22000000"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintVertical_bias="0.0" />

</android.support.constraint.ConstraintLayout>


I want to know how to get the right width and height of ImageView.

I try to get width and height in onStart and onResume but get the same result 0.

Answer

Its because your view is not been created yet.

  iv.post(new Runnable() {
            @Override
            public void run() {
                 //height is ready
                 System.out.println("imageview width:" + iv.getWidth() + " height:" + iv.getHeight());
            }
        });
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