DownloadTask下载任务

public class DownloadTask extends AsyncTask<String,Integer,Integer> {
    public static final int TYPE_SUCCESS=0;//成功
    public static final int TYPE_FAILED=1;//失败
    public static final int TYPE_PAUSED=2;//暂停
    public static final int TYPE_CANCELED=3;//取消
    private DownloadListener listener;//下载监听器
    private boolean isCanceled=false;//是否取消
    private boolean isPaused=false;//是否暂停
    private int lastprogress;//下载进度
    public DownloadTask(DownloadListener listener){//构造方法传入一个监听器
        this.listener=listener;
    }
    @Override
    protected Integer doInBackground(String... strings) {//后台计算，所有耗时操作
        InputStream is = null;
        RandomAccessFile saveFile = null;
        FileOutputStream output;
        File file = null;
        try {
            long downloadLength = 0;
            String dolwnloadUrl = strings[0];
            String filename = dolwnloadUrl.substring(dolwnloadUrl.lastIndexOf("/"));//切出下载文件名
            String directroy = "/mnt/sdcard/Download";//规定下载路径
            file = new File(directroy + filename);
            URL url = new URL(dolwnloadUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();//
            connection.setRequestMethod("GET");
            connection.setReadTimeout(5000);
            connection.setConnectTimeout(5000);
            connection.setDoInput(true);
            connection.setDoOutput(true);
            long contentlength = getContentLength(dolwnloadUrl);//获取下载内容长度
            if (contentlength == 0) {
                return TYPE_FAILED;
            } else if (contentlength == downloadLength) {
                return TYPE_SUCCESS;
            }
            if (file.exists()){
                downloadLength=file.length();//读取下载长度
            }
            saveFile = new RandomAccessFile(file, "rw");//开启流
            connection.setRequestProperty("RANGE", "bytes=" + downloadLength + "-");
            is = connection.getInputStream();
            saveFile.seek(downloadLength);
            byte[] b = new byte[1024];
            int count = 0;
            int len = -1;
            while ((len = is.read(b)) != -1) {
                if (isCanceled) {
                    return TYPE_CANCELED;
                } else if (isPaused) {
                    return TYPE_PAUSED;
                } else {
                    saveFile.write(b, 0, len);
                    count += len;
                    int prpgress = (int) (((count + downloadLength) / (float) contentlength) * 100);//计算进度条
                    publishProgress(prpgress);//更新进度条
                }
            }
            return TYPE_SUCCESS;
            } catch(Exception e){
                e.printStackTrace();
            }finally{
                try {
                    if (is != null) {
                        is.close();
                    }
                    if (saveFile != null) {
                        saveFile.close();
                    }
                    if (isCanceled && file != null) {
                        file.delete();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return TYPE_FAILED;
        }
    @Override
    protected void onPostExecute(Integer integer) {执行完成后调用收尾工作
        switch (integer){
            case TYPE_SUCCESS:
                listener.onSuccess();
                break;
            case TYPE_FAILED:
                listener.onFailed();
                break;
            case TYPE_PAUSED:
                listener.onPause();
                break;
            case TYPE_CANCELED:
                listener.onCanceled();
                break;
            default:break;

        }
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        int progress=values[0];
        if (progress>lastprogress){
            listener.onProgress(progress);
            lastprogress=progress;
        }
    }
    public void pauseDowndload(){
        isPaused=true;
    }
    public void canceDowndload(){
        isCanceled=true;
    }
    private long getContentLength(String dolwnloadUrl) {
        try {
            URL url=new URL(dolwnloadUrl);
            HttpURLConnection connection= (HttpURLConnection) url.openConnection();
            long contentlength=connection.getContentLength();
            return contentlength;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return 0;
    }
}

DownloadService

public class DownloadService extends Service {
    private DownloadTask downloadTask;//下载任务
    private String downloadUrl;//下载地址
    private DownloadBinder mdownloadBinder=new DownloadBinder();
    private DownloadListener listener=new DownloadListener() {
        @Override
        public void onProgress(int progress) {
            getNotiFicationManager().notify(1,getNotification("Download...",progress));
        }

        @Override
        public void onSuccess() {
            downloadTask=null;
            stopForeground(true);
            getNotiFicationManager().notify(1,getNotification("Download Sucess",-1));
            Toast.makeText(DownloadService.this,"Download Success",Toast.LENGTH_LONG).show();
        }
        @Override
        public void onFailed() {
            downloadTask=null;
            stopForeground(true);
            getNotiFicationManager().notify(1,getNotification("Download Failed",-1));
            Toast.makeText(DownloadService.this,"Download Failed",Toast.LENGTH_LONG).show();
        }

        @Override
        public void onPause() {
            downloadTask=null;
            Toast.makeText(DownloadService.this,"Download Paused",Toast.LENGTH_LONG).show();
        }

        @Override
        public void onCanceled() {
            downloadTask=null;
            stopForeground(true);
            Toast.makeText(DownloadService.this,"Download Cancled",Toast.LENGTH_LONG).show();
        }
    };

    class DownloadBinder extends Binder{
        public void startDownload(String url){
            if (downloadTask==null){
                downloadUrl=url;
                downloadTask=new DownloadTask(listener);
                downloadTask.execute(downloadUrl);
                startForeground(1,getNotification("Dowloading...",0));
                Toast.makeText(DownloadService.this,"Downloading...",Toast.LENGTH_LONG).show();
            }
        }
        public void pauseDownload(){
            if (downloadTask!=null){
                downloadTask.pauseDowndload();
            }
        }
        public void cancelDownload(){
            if (downloadTask!=null){
                downloadTask.canceDowndload();
            }else {
                if (downloadUrl!=null){
                    String filename=downloadUrl.substring(downloadUrl.lastIndexOf("/"));
                    String diectroy="/mnt/sdcard/Download";
                    File file=new File(diectroy+filename);
                    if(file.exists()){
                        file.delete();
                    }
                    getNotiFicationManager().cancel(1);
                    stopForeground(true);
                    Toast.makeText(DownloadService.this,"Download Cancled",Toast.LENGTH_LONG).show();
                }
            }

        }

    }

    private NotificationManager getNotiFicationManager() {
        return (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
    }
    private Notification getNotification(String title,int progress){
        Intent intent=new Intent(this,MainActivity.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){
            builder.setContentText(progress+"%");
            builder.setProgress(100,progress,false);
        }
        return builder.build();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {

        return mdownloadBinder;
    }
}

DownloadListener

public interface DownloadListener {
    void onProgress(int progress);//下载进度
    void onSuccess();//下载成功
    void onFailed();//下载失败
    void onPause();;//下载暂时
    void onCanceled();//下载关闭
}

Activity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button mBtnstartD,mBtnpauseD,mBtncancleD;
    private DownloadService.DownloadBinder downloadBinder;
    private EditText mEdtdownload;
    private ServiceConnection  connection=new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            downloadBinder=(DownloadService.DownloadBinder)iBinder;
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mBtnstartD=(Button)findViewById(R.id.start_download);
        mBtnpauseD=(Button)findViewById(R.id.pause_download);
        mBtncancleD=(Button)findViewById(R.id.cancel_download);
        mBtnstartD.setOnClickListener(this);
        mBtnpauseD.setOnClickListener(this);
        mBtncancleD.setOnClickListener(this);
        mEdtdownload=(EditText)findViewById(R.id.download);
        Intent intent=new Intent(this,DownloadService.class);
        startService(intent);
        bindService(intent,connection,BIND_AUTO_CREATE);
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(MainActivity.this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
        }
    }

    @Override
    public void onClick(View view) {
        if (downloadBinder==null){
            Toast.makeText(MainActivity.this,"哈哈",Toast.LENGTH_LONG).show();
            return;
        }
        switch (view.getId()){
            case R.id.start_download:
                String url=mEdtdownload.getText().toString().trim();
                downloadBinder.startDownload(url);
                break;
            case R.id.pause_download:
                downloadBinder.pauseDownload();
                break;
            case R.id.cancel_download:
                downloadBinder.cancelDownload();
                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,"拒绝将无法使用",Toast.LENGTH_LONG).show();
                finish();
            }
            break;
            default:break;
        }
    }

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