如何在android中制作加载屏

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;

public class SplashActivity extends Activity {
    // 延迟时间，单位为毫秒
    private static final long SPLASH_DELAY_TIME = 2000;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        // 使用Handler延迟跳转到主界面
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                // 创建Intent，跳转到主界面
                Intent intent = new Intent(SplashActivity.this, MainActivity.class);
                startActivity(intent);
                finish();
            }
        }, SPLASH_DELAY_TIME);
    }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white"
    android:gravity="center">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/loading_animation" />

    <ProgressBar
        android:id="@+id/progressBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/imageView"
        android:layout_marginTop="16dp"
        android:indeterminate="true" />

</RelativeLayout>