Get a control width

In development , We often encounter getting the width of a control , But with

view.getWidth()

The obtained width is always 0, This is because view The view has not been drawn yet , So it is 0, We need to get it after it is drawn . therefore , Code up ：

mainactivity.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"
    android:orientation="vertical"
    tools:context=".MainActivity">


    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="aaaaaaaaaaaaaaaaa"
        android:background="@color/black"
        android:textColor="@color/white"
        android:layout_gravity="center_horizontal" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/show"
        android:layout_marginTop="30dp"
        android:layout_gravity="center"
        android:textColor="@color/black" />
</LinearLayout>

MainActivity.java：

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = findViewById(R.id.text);
        //  When textview After drawing the view , perform run Method 
        textView.post(new Runnable() {
            @Override
            public void run() {
                //  get textview Width , Company px
                int width = textView.getWidth();
                //  Display the acquired width
                TextView show = findViewById(R.id.show);
                show.setText(width + "px");
            }
        });
    }
}

such , By using

view.post()

To tell app, Let it wait for this view After drawing , Re execution post The method inside , This principle , Is based on 【Handler】 Multithreading . It should be noted that ,【view.getWidth()】 Obtained width , The unit is px yo .

design sketch ：