最佳下载实例

Download。interface

package lbstest.example.com.lbs.ServiceBestPractice;

/**
 * 功能：对下载过程中的各种状态进行监听
 * Created by bummer on 2017/7/26.
 */

public interface DownloadListener {
    void onProgress(int progress); //用于通知当前的下载进度
    void onSuccess();              //用于通知下载成功事件
    void onFailed();               //用于通知下载失败事件
    void onPaused();               //用于通知下载暂停事件
    void onCanceled();             //用于通知下载取消事件
}

DownloadTask.java

package lbstest.example.com.lbs.ServiceBestPractice;

import android.os.AsyncTask;
import android.os.Environment;
import android.util.Log;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

/**
 * Created by bummer on 2017/7/26.
 */

/**
 * params AsyncTask 中的三个泛型参数
 * String 需要传入一个字符串给给后台任务
 * Integer 整型数据表示进度显示的单位
 * Integer 整型数据反馈执行的结果
 */
public class DownloadTask extends AsyncTask <String,Integer,Integer>{

    public final static int TYPE_SUCCESS = 0; //表示下载成功
    public final static int TYPE_FAILED = 1;  //表示下载失败
    public final static int TYPE_PAUSED = 2;  //表示下载暂停
    public final static int TYPE_CANCELED = 3;//表示下载取消

    private DownloadListener listener;

    private boolean isCanceled = false;

    private boolean isPaused = false;

    private int lastProgress;
    //在DownloadTask的构造函数中传入一个刚定义的DownloadListener参数,我们待会会将下载的状态通过这个状态进行回调
    public DownloadTask(DownloadListener listener) {
        this.listener = listener;
    }

    /**
     *   功能:后台执行的具体的下载逻辑
     *
     * @param params
     * @return
     */
    @Override
    protected Integer doInBackground(String... params) {
        InputStream is = null;
        RandomAccessFile savedFile = null;
        File file = null;

        try {
            long downloadLength = 0; //记录下载文件长度
//            从参数中获得了下载的URL地址
            String downloadUrl = params[0];
//            并根据URL地址解析出了下载的文件名
            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
//            将指定的文件下载到Environment.DIRECTORY_DOWNLOADS目录,也就是SD卡的Download目录
            String directory = Environment.getExternalStoragePublicDirectory
                    (Environment.DIRECTORY_DOWNLOADS).getPath();
            file = new File(directory + fileName);
            Log.d("File","file is"+file+"  "+"directory is "+directory+"  "+"fileName is"+fileName);
            //判断Download中是否已经存在要下载的文件了
            if (file.exists()){
                //如果存在则读取已下载的字节数 这样后面就能实现断点续传的功能
                downloadLength = file.length();
            }
            //调用getContentLength()方法获得文件的总长度
            long contentLength = getContentLength(downloadUrl);
            if (contentLength == 0){
                //如果文件长度为0,说明文件有问题
                return TYPE_FAILED;
            }else if (contentLength == downloadLength){
                //已下载字节和文件总字节相等，说明已经下载完成了
                return TYPE_SUCCESS;
            }
            //使用OKhttp发送网络请求
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    //断点下载，指定从哪个字节开始下载
                    .addHeader("RANGE","bytes="+downloadLength + "-")
                    .url(downloadUrl)
                    .build();
            Response response = client.newCall(request).execute();
            //读取服务器响应的数据,并使用java的IO流的方式,不断从网络上读取数据,不断写入到本地
            if(response != null){
                is = response.body().byteStream();
                savedFile = new RandomAccessFile(file,"rw");
                savedFile.seek(downloadLength); //跳过已下载的字节
                byte[] b = new byte[1024];
                int total = 0;
                int len;
                while ((len = is.read(b))!= -1){
                    if(isCanceled){ //判断用户有没有触发取消按钮
                        return TYPE_CANCELED;
                    }else if (isPaused){ //判断你用户有没有触发暂停按钮
                        return TYPE_PAUSED;
                    }else {
                        total += len;
                        savedFile.write(b,0,len);
                        //计算已下载的百分比
                        int progress = (int)((total + downloadLength)*100/contentLength);
                        //调用publicProgress方法进行通知
                        publishProgress(progress);
                    }
                }
                response.body().close();
                return TYPE_SUCCESS;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {

                try {
                    if (is != null) {
                        is.close();
                    }
                    if(savedFile != null){
                        savedFile.close();
                    }
                    if(isCanceled && file != null){
                        file.delete();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

        }

        return TYPE_FAILED;
    }

    /**
     * 功能:界面上更新当前的下载逻辑
     * @param values
     */
    @Override
    protected void onProgressUpdate(Integer... values) {
        //从参数中获得当前下载进度
        int progress = values[0];
        if(progress > lastProgress){
            //和上一次进度进行对比,如果有变化

            //调用listener.onProgress通知下载进度进行更新
            listener.onProgress(progress);
            lastProgress = progress;
        }
    }

    /**
     *  功能:用于通知最后的下载结果
     * @param status
     */

    @Override
    protected void onPostExecute(Integer status) {
        //将参数中传入的下载状态进行回调,下载成功就调用DownloadListener.onSuccess()方法,
        // 取消下载就调用onCanceled()方法
        switch (status){
            case TYPE_SUCCESS:
                listener.onSuccess();
                break;
            case TYPE_FAILED:
                listener.onFailed();
                break;
            case TYPE_PAUSED:
                listener.onPaused();
                break;
            case TYPE_CANCELED:
                listener.onCanceled();
                break;
            default:
                break;
        }
    }
    public void pauseDownload(){
        isPaused = true;
    }
    public void cancelDownload(){
        isCanceled = true;
    }
    private long getContentLength(String downloadUrl) throws IOException{
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(downloadUrl)
                .build();
        Response response = client.newCall(request).execute();
        if(response != null && response.isSuccessful()){
            long contentLength = response.body().contentLength();
            response.close();
            return contentLength;
        }
        return 0;
    }
}

DownloadService.java

package lbstest.example.com.lbs.ServiceBestPractice;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.os.Binder;
import android.os.Environment;
import android.os.IBinder;
import android.support.v4.app.NotificationCompat;
import android.widget.Toast;

import java.io.File;

import lbstest.example.com.lbs.R;

public class DownloadService extends Service {

    DownloadTask downloadTask;

    private String downloadUrl;

    private DownloadListener listener = new DownloadListener() {
        @Override
        public void onProgress(int progress) {
            getNotificationManager().notify(1,getNotification("Downloading...",
                    progress));
        }

        @Override
        public void onSuccess() {
            downloadTask = null;
            //下载成功将前台服务通知关闭,并创建一个下载成功的通知
            stopForeground(true);
            getNotificationManager().notify(1,getNotification("Download Success",
                    -1));
            Toast.makeText(DownloadService.this,"Download Success",
                    Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onFailed() {
          downloadTask = null;
            //下载失败时将前台服务关闭,并创建一个下载失败的通知
            stopForeground(true);
            //触发通知，这样就可以在下拉状态栏中实时看到下载进度
            getNotificationManager().notify(1,getNotification("Download Failed",-1));
            Toast.makeText(DownloadService.this,"Download Failed",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onPaused() {
            downloadTask = null;
            Toast.makeText(DownloadService.this,"Download Pause",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onCanceled() {
            downloadTask = null;
            stopForeground(true);
            Toast.makeText(DownloadService.this,"Download Canceled",Toast.LENGTH_SHORT).show();
        }
    };
    /**
     * 让DownloadService 可以和活动进行通信
     */
    private DownloadBinder mBinder = new DownloadBinder();

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }


    public class DownloadBinder extends Binder{
        //用于开始下载
        public void startDownload(String Url){
            //创建一个downloadTask实例，
            if(downloadTask == null){
                downloadUrl = Url;
                downloadTask = new DownloadTask(listener); //把刚才的DownloadListener作为参数传入
                downloadTask.execute(downloadUrl);
                //让服务成为前台服务 ，在状态栏创建一个持续运行的通知
                startForeground(1,getNotification("Downloading......",0));
                Toast.makeText(DownloadService.this,"Downloading......",Toast.LENGTH_SHORT).show();

            }
        }
        //用于暂停下载
        public void pauseDownload(){
            if (downloadTask != null) {
                downloadTask.pauseDownload();
            }
        }
        //用于取消下载
        public void cancelDownload(){
            if (downloadTask != null) {
                downloadTask.cancelDownload();
            }else {
                //取消下载将正在下载的文件删除掉
                if (downloadUrl != null) {
                    //取消下载时需将文件删除，并将通知进行关闭
                    String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
                    String directory = Environment.getExternalStoragePublicDirectory
                            (Environment.DIRECTORY_DOWNLOADS).getPath();
                    File file = new File(directory + fileName);
                    if(file.exists()){
                        file.delete();
                    }
                    getNotificationManager().cancel(1);
                    stopForeground(true);
                    Toast.makeText(DownloadService.this,"Canceled",Toast.LENGTH_SHORT).show();
                }
            }
        }
    }
    private Notification getNotification(String title, int progress){
        Intent intent = new Intent(this,Main4Activity.class);
        PendingIntent pi = PendingIntent.getActivity(this,0,intent,0);
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
        builder.setSmallIcon(R.mipmap.ic_launcher);
        builder.setLargeIcon(BitmapFactory.decodeResource(getResources(),
                R.mipmap.ic_launcher));
        builder.setContentIntent(pi);
        builder.setContentTitle(title);
        if(progress > 0){
            //当progress 大于或等于0时才需要显示下载进度
            builder.setContentText(progress + "%");
            builder.setProgress(100,progress,false);
        }
        return builder.build();
    }



    private NotificationManager getNotificationManager() {
        return (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    };





}

Main4Activity.java

package lbstest.example.com.lbs.ServiceBestPractice;

import android.Manifest;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.IBinder;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import lbstest.example.com.lbs.R;

/**
 * 功能：完整版的下载实例
 */
public class Main4Activity extends AppCompatActivity implements View.OnClickListener {

    private static boolean Justice = false;

    EditText urlWeb = null;

    private DownloadService.DownloadBinder downloadBinder;
//先创建一个SerViceConnection 的匿名类，
    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
          //  onServiceConnection()方法中获得DownloadBinder的实例
            //有了这个实例，可以在活动中调用服务提供的各种方法
            downloadBinder = (DownloadService.DownloadBinder) service;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main4);
        Button startDownload = (Button) findViewById(R.id.start_download);
        Button pauseDownload = (Button) findViewById(R.id.pause_download);
        Button cancelDownload = (Button) findViewById(R.id.cancel_download);
         urlWeb = (EditText) findViewById(R.id.webUrl);
        startDownload.setOnClickListener(this);
        pauseDownload.setOnClickListener(this);
        cancelDownload.setOnClickListener(this);
        Intent intent = new Intent(this,DownloadService.class);
        //启动和绑定服务
        startService(intent); //启动服务可以保证DownloadService一直在后台运行
        bindService(intent,connection,BIND_AUTO_CREATE); //绑定服务  让Main4Activity和DownloadService进行通信
        if(ContextCompat.checkSelfPermission(Main4Activity.this, Manifest
        .permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(Main4Activity.this,new
            String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
        }
    }

    @Override
    public void onClick(View v) {
        if(downloadBinder == null){
            return;
        }
        switch (v.getId()){
            case R.id.start_download:
                String url = null;
                    if(!urlWeb.getText().toString().equals("")){
                    Log.d("XXX","urlWeb.get is"+urlWeb.getText().toString());
                    url = urlWeb.getText().toString();
                    downloadBinder.startDownload(url);
                    Justice = true;
                }else {
                    Justice = false;
                    Toast.makeText(Main4Activity.this,"请先填写要下载的网址!",Toast.LENGTH_SHORT).show();
                }
                break;
            case R.id.pause_download:
                if(Justice){
                    downloadBinder.pauseDownload();
                }else {
                    Toast.makeText(Main4Activity.this,"请先填写要下载的网址!",Toast.LENGTH_SHORT).show();
                }
                break;
            case R.id.cancel_download:
                if(Justice){
                    downloadBinder.cancelDownload();
                }else {
                    Toast.makeText(Main4Activity.this,"请先填写要下载的网址!",Toast.LENGTH_SHORT).show();
                }
                break;
            default:
                break;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode){
            case 1:
                if(grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED){
                    Toast.makeText(this,"拒绝权限将无法使用程序",Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(connection);
    }
}

activity_main.xml

<?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="match_parent"
    android:orientation="vertical">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        >
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="输入要下载的网址"
            android:textSize="20sp"
            />
        <EditText
            android:textSize="18sp"
            android:textColor="#000"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="例:http://www.baidu.com"
            android:id="@+id/webUrl"
            />

    </LinearLayout>
    <Button
        android:id="@+id/start_download"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="开始下载" />

    <Button
        android:id="@+id/pause_download"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="暂停下载" />

    <Button
        android:id="@+id/cancel_download"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="取消下载" />
</LinearLayout>