Android简单实现文件下载

<!--  文件读写权限  -->
<uses-permission android:name="android.permission.read_external_storage" />
<!--  访问内存  -->
<uses-permission android:name="android.permission.write_external_storage" />

downloadutil.downloadokhttp.get().download(apk, environment.getexternalstoragedirectory() + "/" + "小红书", new downloadutil.downloadokhttp.ondownloadlistener() {
    @override
    public void ondownloadsuccess() {
      log.e("下载","成功");
                }

              @override
                      public void ondownloading(int progress) {
                       log.e("下载", string.valueof(progress));
                         }

                    @override
                   public void ondownloadfailed() {
                   log.e("下载","失败");
         }
 });

new downloadutil.download(this, apk, "小红书.apk", "小红书");

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="@dimen/dp_20"
    android:orientation="vertical">

    <progressbar
        android:id="@+id/id_progress"
        style="?android:attr/progressbarstylehorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />


    <textview
        android:id="@+id/id_text"
        android:layout_width="match_parent"
        android:layout_margintop="10dp"
        android:gravity="right"
        android:text="0 %"
        android:layout_height="wrap_content"/>

</linearlayout>

package com.simon.util;

import android.app.alertdialog;
import android.app.dialog;
import android.content.context;
import android.content.dialoginterface;
import android.os.environment;
import android.os.handler;
import android.os.message;
import android.view.layoutinflater;
import android.view.view;
import android.widget.progressbar;
import android.widget.textview;

import com.simon.app.r;

import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.net.httpurlconnection;
import java.net.url;

import androidx.annotation.nonnull;
import okhttp3.call;
import okhttp3.callback;
import okhttp3.okhttpclient;
import okhttp3.request;
import okhttp3.response;

/**
 * 创建者： simon
 * 创建时间：2021/6/7 13:58
 * 描述：文件下载
 */

public class downloadutil {

    public static class downloadokhttp {

        private static downloadokhttp downloadutil;
        private final okhttpclient okhttpclient;

        public static downloadokhttp get() {
            if (downloadutil == null) {
                downloadutil = new downloadokhttp();
            }
            return downloadutil;
        }

        private downloadokhttp() {
            okhttpclient = new okhttpclient();
        }

        /**
         *
         * @param url 下载连接
         * @param savedir 储存下载文件的sdcard目录
         * @param listener 下载监听
         */
        public void download( string url, final string savedir, final ondownloadlistener listener) {
            request request = new request.builder().url(url).build();
            okhttpclient.newcall(request).enqueue(new callback() {
                @override
                public void onfailure(call call, ioexception e) {
                    // 下载失败
                    listener.ondownloadfailed();
                }
                @override
                public void onresponse(call call, response response) throws ioexception {
                    inputstream is = null;
                    byte[] buf = new byte[2048];
                    int len = 0;
                    fileoutputstream fos = null;
                    // 储存下载文件的目录
                    string savepath = isexistdir(savedir);
                    try {
                        is = response.body().bytestream();
                        long total = response.body().contentlength();
                        file file = new file(savepath, getnamefromurl(url));
                        fos = new fileoutputstream(file);
                        long sum = 0;
                        while ((len = is.read(buf)) != -1) {
                            fos.write(buf, 0, len);
                            sum += len;
                            int progress = (int) (sum * 1.0f / total * 100);
                            // 下载中
                            listener.ondownloading(progress);
                        }
                        fos.flush();
                        // 下载完成
                        listener.ondownloadsuccess();
                    } catch (exception e) {
                        listener.ondownloadfailed();
                    } finally {
                        try {
                            if (is != null)
                                is.close();
                        } catch (ioexception e) {
                        }
                        try {
                            if (fos != null)
                                fos.close();
                        } catch (ioexception e) {
                        }
                    }
                }
            });
        }

        /**
         * 判断下载目录是否存在
         * @param savedir
         * @return
         * @throws ioexception
         */
        private string isexistdir(string savedir) throws ioexception {
            // 下载位置
            file downloadfile = new file(environment.getexternalstoragedirectory(), savedir);
            if (!downloadfile.mkdirs()) {
                downloadfile.createnewfile();
            }
            string savepath = downloadfile.getabsolutepath();
            return savepath;
        }

        /**
         *  url
         * 从下载连接中解析出文件名
         */
        @nonnull
        public static string getnamefromurl(string url) {
            return url.substring(url.lastindexof("/") + 1);
        }

        public interface ondownloadlistener {
            /**
             * 下载成功
             */
            void ondownloadsuccess();

            /**
             * @param progress
             * 下载进度
             */
            void ondownloading(int progress);

            /**
             * 下载失败
             */
            void ondownloadfailed();
        }
    }

    public static class download {

        private string filesavepath = "";//保存文件的本地路径
        private string filedownload_path = "";//下载的url
        private string mfilename = "";//下载的文件名字
        private boolean miscancel = false;
        private int mprogress;
        private progressbar mprogressbar;
        private textview text;
        private dialog mdownloaddialog;
        private final context context;

        private static final int downloading = 1;
        private static final int download_finish = 2;

        private handler mupdateprogresshandler = new handler() {
            public void handlemessage(message msg) {
                switch (msg.what) {
                    case downloading:
                        // 设置进度条
                        mprogressbar.setprogress(mprogress);
                        text.settext(string.valueof(mprogress));
                        break;
                    case download_finish:
                        // 隐藏当前下载对话框
                        mdownloaddialog.dismiss();
                }
            }
        };

        /**
         * 下载初始化
         * @param context 上下文
         * @param filedownload_path 下载的url
         * @param mfilename 下载的文件名字
         * @param filesavepath 保存文件的本地路径
         */
        public download(context context, string filedownload_path, string mfilename, string filesavepath) {
            this.context = context;
            this.filedownload_path = filedownload_path;
            this.mfilename = mfilename;
            this.filesavepath = environment.getexternalstoragedirectory() + "/" + filesavepath;
            showdownloaddialog();
        }

        /**
         * 显示正在下载的对话框
         */
        protected void showdownloaddialog() {
            alertdialog.builder builder = new alertdialog.builder(context);
            builder.settitle("下载中");
            view view = layoutinflater.from(context).inflate(r.layout.dialog_progress, null);
            mprogressbar = (progressbar) view.findviewbyid(r.id.id_progress);
            text = view.findviewbyid(r.id.id_text);
            builder.setview(view);

            builder.setnegativebutton("取消", new dialoginterface.onclicklistener() {
                @override
                public void onclick(dialoginterface dialog, int which) {
                    // 隐藏当前对话框
                    dialog.dismiss();
                    // 设置下载状态为取消
                    miscancel = true;
                }
            });

            mdownloaddialog = builder.create();
            mdownloaddialog.show();

            // 下载文件
            downloadfile();
        }

        /**
         * 下载文件
         */
        private void downloadfile() {
            new thread(new runnable() {
                @override
                public void run() {
                    try {
                        if (environment.getexternalstoragestate().equals(environment.media_mounted)) {
                            file dir = new file(filesavepath);
                            if (!dir.exists()){
                                dir.mkdirs();
                            }
                            // 下载文件
                            httpurlconnection conn = (httpurlconnection) new url(filedownload_path).openconnection();
                            conn.connect();
                            inputstream is = conn.getinputstream();
                            int length = conn.getcontentlength();

                            file apkfile = new file(filesavepath, mfilename);
                            fileoutputstream fos = new fileoutputstream(apkfile);

                            int count = 0;
                            byte[] buffer = new byte[1024];
                            while (!miscancel) {
                                int numread = is.read(buffer);
                                count += numread;
                                // 计算进度条当前位置
                                mprogress = (int) (((float) count / length) * 100);
                                // 更新进度条
                                mupdateprogresshandler.sendemptymessage(downloading);

                                // 下载完成
                                if (numread < 0) {
                                    mupdateprogresshandler.sendemptymessage(download_finish);
                                    break;
                                }
                                fos.write(buffer, 0, numread);
                            }
                            fos.close();
                            is.close();
                        }
                    } catch (exception e) {
                        e.printstacktrace();
                    }
                }
            }).start();
        }
    }
}