直接上代码

<?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">

    <Button
        android:id="@+id/bnt_share"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="加载"
        tools:ignore="MissingConstraints" />

</LinearLayout>

package com.example.myapplication;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    private MediaPlayer mediaPlayer;
    private SurfaceView surfaceView;
    private ImageView img;
    private Button bntshare;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bntshare =  findViewById(R.id.bnt_share);
        initData();
    }


    private void initData() {
        bntshare.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                LoadingDialogUtils loadingDialogUtils = new LoadingDialogUtils(MainActivity.this,"正在登录...",R.mipmap.ic_dialog_loading);
                loadingDialogUtils.show();
            }
        });

    }

}

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <corners android:radius="20dp"/>
    <solid android:color="@android:color/black"/>
</shape>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="LoadingDialog" parent="@android:style/Theme.Holo.Dialog.NoActionBar">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:backgroundDimEnabled">false</item>
    </style>

</resources>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:gravity="center"
              android:background="@drawable/bg_loading_dialog"
              android:layout_height="200dp">

    <ImageView
        android:id="@+id/iv_loading"
        android:layout_width="wrap_content"
        android:src="@mipmap/ic_dialog_loading"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/tv_loading"
        android:layout_width="wrap_content"
        android:layout_marginTop="20dp"
        android:text="加载中..."
        android:textSize="16sp"
        android:textColor="@android:color/white"
        android:layout_height="wrap_content"/>

</LinearLayout>

package com.example.myapplication;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.WindowManager;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;

public class LoadingDialogUtils extends Dialog {

    private static final String TAG = "LoadingDialog";

    private String mMessage;
    private int mImageId;
    private boolean mCancelable;
    private RotateAnimation mRotateAnimation;

    public LoadingDialogUtils(@NonNull Context context, String message, int imageId) {
        this(context,R.style.LoadingDialog,message,imageId,false);
    }

    public LoadingDialogUtils(@NonNull Context context, int themeResId, String message, int imageId, boolean cancelable) {
        super(context, themeResId);
        mMessage = message;
        mImageId = imageId;
        mCancelable = cancelable;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate: ");
        initView();
    }

    private void initView() {
        setContentView(R.layout.dialog_loading);
        // 设置窗口大小
        WindowManager windowManager = getWindow().getWindowManager();
        int screenWidth = windowManager.getDefaultDisplay().getWidth();
        WindowManager.LayoutParams attributes = getWindow().getAttributes();
        attributes.alpha = 0.3f;
        attributes.width = screenWidth/3;
        attributes.height = attributes.width;
        getWindow().setAttributes(attributes);
        setCancelable(mCancelable);

        TextView tv_loading = findViewById(R.id.tv_loading);
        ImageView iv_loading = findViewById(R.id.iv_loading);
        tv_loading.setText(mMessage);
        iv_loading.setImageResource(mImageId);
        iv_loading.measure(0,0);
        mRotateAnimation = new RotateAnimation(0,360,iv_loading.getMeasuredWidth()/2,iv_loading.getMeasuredHeight()/2);
        mRotateAnimation.setInterpolator(new LinearInterpolator());
        mRotateAnimation.setDuration(1000);
        mRotateAnimation.setRepeatCount(-1);
        iv_loading.startAnimation(mRotateAnimation);
    }

    @Override
    public void dismiss() {
        mRotateAnimation.cancel();
        super.dismiss();
    }

    @Override
    public boolean onKeyDown(int keyCode, @NonNull KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
            // 屏蔽返回键
            return mCancelable;
        }
        return super.onKeyDown(keyCode, event);
    }
}