ProgressBar

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
    tools:context=".MainActivity">

    <ProgressBar
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:id="@+id/pb"
        />
    <!--进度条-->


    <Button
        android:layout_width="200dp"
        android:layout_height="100dp"
        android:text="显示隐藏进度条"
        android:onClick="leoClick"
        />
    <ProgressBar
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:max="100"
        style="?android:attr/progressBarStyleHorizontal"
        />
    <!--style设置水平进度条-->
</androidx.constraintlayout.widget.ConstraintLayout>


java代码：

package com.example.progressbar;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.ProgressBar;

public class MainActivity extends AppCompatActivity {
    private ProgressBar progressbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        progressbar=findViewById(R.id.pb);
    }
    public void leoClick(View view){
        if(progressbar.getVisibility()==View.GONE)//如果progressbar当前隐藏
             {
            progressbar.setVisibility(View.VISIBLE);//显示当前progressbar
        }
        else{
            progressbar.getVisibility(View.GONE);
        }
    }


}