public void download(String url)

    {

        Utils.Loge("download",url);

        Uri uri = Uri.parse(url);

        DownloadManager.Request request = new DownloadManager.Request(uri);

        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

        String appName = getAppName(activity);

        request.setDestinationInExternalFilesDir(activity, Environment.DIRECTORY_DOWNLOADS, appName + ".apk");

        DownloadManager downManager = (DownloadManager)activity.getSystemService(Context.DOWNLOAD_SERVICE);

        long Id = downManager.enqueue(request);

        listener(Id,appName + ".apk");

    }

private void listener(final long Id,String filePath) {

        String mypath = Environment.getExternalStorageDirectory().getAbsolutePath()+File.separator+"Android"+File.separator+"data"+

                File.separator+ activity.getPackageName()+File.separator + "files" + File.separator + Environment.DIRECTORY_DOWNLOADS + File.separator + filePath;

        //mypath = Environment.DIRECTORY_DOWNLOADS + File.separator + filePath;

        //File fileFull = new File(path, filePath);

        IntentFilter intentFilter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);

        cReceiver = new Complete(); // 这是个广播器在下文中有完整代码

        cReceiver.setId(Id);

        cReceiver.setContext(activity);

        cReceiver.setRunnable(new Runnable() {

            @Override

            public void run() {

                File file= new File(mypath);

                Intent intent = new Intent(Intent.ACTION_VIEW);

                Uri data;

                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {

                    data = FileProvider.getUriForFile(activity, "com.haiwaiisland.adventure.fileprovider", file);

                    intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

                } else {

                    data = Uri.fromFile(file);

                }

                intent.setDataAndType(data, "application/vnd.android.package-archive");

                activity.startActivity(intent);

            }

        });

        activity.registerReceiver(cReceiver, intentFilter);

    }
//com.haiwaiisland.adventure.fileprovider 这个要在Manifest中配置

package com.BoomGames.Game;

import android.app.Activity;

import android.app.DownloadManager;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

public class Complete extends BroadcastReceiver {

    private long mId;

    private Activity mContext;

    private Runnable mRunnable;

    public void setId(long id){

        mId = id;

    }

    public void setContext(Activity context){

        mContext = context;

    }

    public void setRunnable(Runnable run){

        mRunnable = run;

    }

    @Override

    public void onReceive(Context context, Intent intent) {

        long ID = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);

        if (ID == mId) {

            if(mRunnable != null){

                mRunnable.run();

            }

            else{

            }

        }

    }

}

<provider

        android:name="androidx.core.content.FileProvider"

        android:authorities="com.haiwaiisland.adventure.fileprovider"

        android:exported="false"

        android:grantUriPermissions="true">

      <meta-data

          android:name="android.support.FILE_PROVIDER_PATHS"

          android:resource="@xml/file_paths"/>

    </provider>
//androidx.core.content.FileProvider 这个是androidx 以前的版本是 android.support.v4.content.FileProvider
//com.haiwaiisland.adventure.fileprovider 这个是   包名.fileprovider

//xml/file_paths 在android res 目录中加 目录xml 在这个目录中新建 file_paths.xml 文件

<?xml version="1.0" encoding="utf-8"?>

<resources xmlns:android="http://schemas.android.com/apk/res/android">

    <paths>

        <external-path path="" name="download"/>

    </paths>

</resources>

<?xml version="1.0" encoding="utf-8"?>

<network-security-config>

    <base-config cleartextTrafficPermitted="true" />

</network-security-config>

<application

      android:networkSecurityConfig="@xml/network_security_config">

  <uses-permission android:name="android.permission.EXPAND_STATUS_BAR"/>

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

  <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES"/>