使用okhttp和前台服务实现断点续传功能

参考资料

• 《第一行代码》

代码示例

• 清单文件配置

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.testandroid">    <uses-permission android:name="android.permission.INTERNET"/>    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:roundIcon="@mipmap/ic_launcher_round"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <activity android:name=".MainActivity">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>        <service android:name=".service.DownloadService"            android:enabled="true"            android:exported="true"/>    </application></manifest>

• 后台异步下载

public class DownloadTask extends AsyncTask<String,Integer,Integer> {    public static final int TYPE_SUCCESS =0;    public static final int TYPE_FAILED = 1;    public static final int  TYPE_PAUSED = 2;    public static final int TYPE_CANCELED = 3;    private DownloadListener listener;    private boolean isCanceled = false;    private boolean isPaused = false;    private int lastProgress;    public DownloadTask(DownloadListener listener){        this.listener = listener;    }    @Override    protected Integer doInBackground(String... strings) {        InputStream is = null;        RandomAccessFile savedFile = null;        File file = null;        try {            long downloadedLength = 0;            String downloadUrl = strings[0];            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));            String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();            file = new File(directory+fileName);            if (file.exists()){                downloadedLength = file.length();            }            long contentLength = getContentLength(downloadUrl);            if (contentLength == 0){                return TYPE_FAILED;            }else if (contentLength == downloadedLength){                return TYPE_SUCCESS;            }            OkHttpClient client = new OkHttpClient();            Request request = new Request.Builder()                    //断点续传                    .addHeader("RANGE","bytes="+downloadedLength+"-")                    .url(downloadUrl)                    .build();            //同步下载            Response response = client.newCall(request).execute();            if (response!=null){                is = response.body().byteStream();                savedFile = new RandomAccessFile(file,"rw");                //跳过已经下载的字节                savedFile.seek(downloadedLength);                byte[] b = new byte[1024];                int total = 0;                int len ;                while ((len=is.read(b))!=-1){                    if (isCanceled){                        return TYPE_CANCELED;                    }else if (isPaused){                        return TYPE_PAUSED;                    }else {                        total +=len;                        savedFile.write(b,0,len);                        int progress = (int) ((total+downloadedLength)*100/contentLength);                        //发布进度                        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){                        //如果取消了下载，就删除本地文件                        file.delete();                    }                }catch (Exception e){                    e.printStackTrace();                }        }        return TYPE_FAILED;    }    @Override    protected void onProgressUpdate(Integer... values) {        int progress = values[0];        if (progress>lastProgress){            listener.onProgress(progress);            lastProgress = progress;        }    }    /**     * 下载完成     * @param integer     */    @Override    protected void onPostExecute(Integer integer) {        switch (integer){            case TYPE_SUCCESS:                listener.onSuccess();                break;            case TYPE_FAILED:                listener.onFailed();                break;            case TYPE_PAUSED:                listener.onPaused();                break;            case TYPE_CANCELED:                listener.onCanceled();                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;    }}

• 接口

public interface DownloadListener {    void onProgress(int progress);    void onSuccess();    void onFailed();    void onPaused();    void onCanceled();}

• 后台服务

public class DownloadService extends Service{    private DownloadTask downloadTask;    private String downloadUrl;    private DownloadListener listener = new DownloadListener() {        @Override        public void onProgress(int progress) {                //使用通知，显示在状态栏            getNotifcationManager().notify(1,getNotification("Downloading...",progress));        }        @Override        public void onSuccess() {                downloadTask = null;            //下载成功后，将前台服务通知关闭，并创建一个下载成功的通知            stopForeground(true);            getNotifcationManager().notify(1,getNotification("Downloading Success",-1));            Toast.makeText(DownloadService.this,"Download Success",Toast.LENGTH_SHORT).show();        }        @Override        public void onFailed() {            downloadTask = null;            stopForeground(true);            getNotifcationManager().notify(1,getNotification("Download Failed",-1));            Toast.makeText(DownloadService.this,"Download Fail",Toast.LENGTH_SHORT).show();        }        @Override        public void onPaused() {        downloadTask = null;            Toast.makeText(DownloadService.this,"Paused",Toast.LENGTH_SHORT).show();        }        @Override        public void onCanceled() {            downloadTask = null;            stopForeground(true);            Toast.makeText(DownloadService.this,"Canceled",Toast.LENGTH_SHORT).show();        }    };    public class DownloadBinder extends Binder{            //对绑定该服务的活动暴露方法        public void startDownload(String url){            if (downloadTask==null){                downloadUrl  = url;                downloadTask = new DownloadTask(listener);                downloadTask.execute(downloadUrl);                //开启前台服务                startForeground(1,getNotification("Downloading...",0));                Toast.makeText(DownloadService.this,"Download...",Toast.LENGTH_SHORT).show();            }        }        public void pauseDownload(){            if (downloadTask!=null){                downloadTask.pauseDownload();            }        }        public void CancelDownload(){            if (downloadTask!=null){                downloadTask.cancelDownload();            }else {                if (downloadUrl!=null){                    //取消下载，并且删除文件，关闭通知                    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();                    }                    getNotifcationManager().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, 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.drawable.a));        builder.setContentIntent(pi);        builder.setContentTitle(title);        if (progress>0){            builder.setContentText(progress+"%");            //是否使用模糊进度条            builder.setProgress(100,progress,false);        }        return builder.build();    }    private NotificationManager getNotifcationManager() {        return (NotificationManager) getSystemService(NOTIFICATION_SERVICE);    }    private DownloadBinder mBinder = new DownloadBinder();    @Nullable    @Override    public IBinder onBind(Intent intent) {        return mBinder;    }}

• Activity代码

public class MainActivity extends AppCompatActivity {    private DownloadService.DownloadBinder downloadBinder;    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);        openService();        //权限管理        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED){            ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);        }    }    private void openService() {        Intent intent = new Intent(this,DownloadService.class);        startService(intent);        bindService(intent,connection,BIND_AUTO_CREATE);    }    @Override    protected void onDestroy() {        super.onDestroy();        unbindService(connection);    }    public void start(View view){            if (downloadBinder==null){                return;            }            String url = "http://a5.pc6.com/pc6_soure/2016-1/1275710C30G3f92Q.apk";            downloadBinder.startDownload(url);    }    public void pause(View view){        if (downloadBinder==null){            return;        }        downloadBinder.pauseDownload();    }    public void cancel(View view){        if (downloadBinder==null){            return;        }        downloadBinder.CancelDownload();    }    @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();                }                break;        }    }}