MVP Retrofit多线程下载

多线程下载：
目的：最大限度的利用CPU资源
过程：
1.获得下载文件的长度，然后设置本地文件长度
2.根据文件长度和线程数计算每条线程下载的数据长度和下载位置
3.使用HTTP的range字段指定每条线程从什么位置下载，到什么位置停止
4.保存文件。使用RandomAccessFile类指定每条线程从本地文件的什么位置开始写入数据。
首先先看一下依赖

    compile 'com.youth.banner:banner:1.4.9'
    compile 'com.github.bumptech.glide:glide:3.7.0'
    compile 'com.jcodecraeer:xrecyclerview:1.3.2'
    compile 'io.reactivex:rxjava:1.0.14'
    compile 'io.reactivex:rxandroid:1.0.1'
    compile 'com.squareup.retrofit2:retrofit:2.0.2'
    compile 'com.squareup.okhttp3:okhttp:3.1.2'
    compile 'com.squareup.retrofit2:converter-gson:2.0.2'
    compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0'

用MVP模式首先看View层

接口类
public interface IDialogView {
    public void showDialog();
}

再看MODEL层

接口类
public interface IDownLoadModel {
    public IDataView downLoad();
}

public class DownLoadModel implements IDownLoadModel {
    @Override
    public IDataView downLoad() {
        Retrofit retrofit=new Retrofit.Builder()
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("http://10.0.2.2:8080/")
                .build();
        IDataView dataView = retrofit.create(IDataView.class);
        return dataView;
    }
}

PRESENTER层

public abstract class BaseActivity<T extends IDataPresenter> extends AppCompatActivity {
    public T presenter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        createPresenter();
    }

    public abstract void createPresenter();

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (presenter!=null){
            presenter.detach();
        }
    }
}

public interface IDataPresenter<T> {
    public void attach(T view);
    public void detach();
}

public class DownLoadPresenter implements IDataPresenter<IDialogView> {
    DownLoadModel model;
    SoftReference<IDialogView> softView;

    public DownLoadPresenter(IDialogView view) {
        attach(view);
        model = new DownLoadModel();
    }

    public void getDataLength(final String downLoadUrl, final String path, final long threadNum) {
        model.downLoad().getFileLength(downLoadUrl)
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.io())
                .subscribe(new Observer<ResponseBody>() {
                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onNext(ResponseBody responseBody) {
                        long length = responseBody.contentLength();
                        DownLoadTask.getDownLoadData(DownLoadPresenter.this, downLoadUrl, path, length, threadNum);
                    }
                });
    }

    public void getDownLoadFile(String downLoadUrl, String range, final File file, final long startPosition) {
        model.downLoad().downLoadFile(downLoadUrl, range)
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.io())
                .subscribe(new Observer<ResponseBody>() {
                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onNext(ResponseBody responseBody) {
//                    Log.i("+++++++++++++++++", "onResponse: "+response.body().contentLength());
                        BufferedInputStream bis = new BufferedInputStream(responseBody.byteStream());
                        try {
                            RandomAccessFile raf = new RandomAccessFile(file, "rwd");
                            raf.seek(startPosition);
                            byte[] buff = new byte[1024 * 8];
                            int len = 0;
                            while ((len = bis.read(buff)) != -1) {
                                raf.write(buff, 0, len);
                            }
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                    }
                });
    }

    @Override
    public void attach(IDialogView view) {
        softView = new SoftReference<IDialogView>(view);
    }

    @Override
    public void detach() {
        softView.clear();
    }
}

public interface IDataView {

    @Streaming
    @POST("{fileName}")
    Observable<ResponseBody> getFileLength(@Path("fileName") String fileName);

    @Streaming
    @POST("{fileName}")
    Observable<ResponseBody> downLoadFile(@Path("fileName") String fileName, @Header("Range") String range);
}

public class DownLoadThread{
    private String downLoadUrl;
    private String path;
    private long threadNum;
    private DownLoadPresenter presenter;

    public DownLoadThread(String downLoadUrl, String path, long threadNum,DownLoadPresenter presenter) {
        this.downLoadUrl = downLoadUrl;
        this.path = path;
        this.threadNum = threadNum;
        this.presenter=presenter;
    }

   public void show(){
       presenter.getDataLength(downLoadUrl,path,threadNum);

   }

}

public class DownLoadFileThread extends Thread {
    DownLoadPresenter presenter;
    private String downLoadUrl;
    private String range;
    private File file;
    private long startPosition;

    public DownLoadFileThread(DownLoadPresenter presenter, String downLoadUrl, String range, File file, long startPosition) {
        this.presenter = presenter;
        this.downLoadUrl = downLoadUrl;
        this.range = range;
        this.file = file;
        this.startPosition = startPosition;
    }

    @Override
    public void run() {
        presenter.getDownLoadFile(downLoadUrl,range,file,startPosition);
    }
}

public class DownLoadTask {
    public static void getDownLoadData(DownLoadPresenter presenter,String downLoadUrl, String path, long length, long threadNum){
        File file=new File(path);
        if (!file.exists()){
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        long blockSize=length/threadNum;
        for (int i = 0; i < threadNum; i++) {
            long startPosition=blockSize*i;
            if (i==threadNum-1){
                blockSize=length-blockSize*(threadNum-1);
                Log.i("+++++++++++", "getDownLoadData: "+blockSize);
            }
            String range = "bytes=" + startPosition + "-" + (startPosition + blockSize - 1);
            Log.i("++++++++++++++", "downLoadTask: "+startPosition+"-----"+(startPosition+blockSize-1));
            new DownLoadFileThread(presenter,downLoadUrl,range,file,startPosition).start();
        }
    }
}

public class MainActivity extends BaseActivity<DownLoadPresenter> implements IDialogView {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
    }

    private void initData() {
        showDialog();
        Log.i("---------", "initData: "+presenter);
    }

    @Override
    public void createPresenter() {
        presenter=new DownLoadPresenter(this);
    }

    @Override
    public void showDialog() {
        Log.i("==============", "initData: "+presenter);
        AlertDialog.Builder builder=new AlertDialog.Builder(this);
        builder.setTitle("是否更新")
                .setMessage("你太low了，赶快更新")
                .setNegativeButton("取消",null)
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        new DownLoadThread("QQ.apk",getCacheDir()+"/qq.apk",5,presenter).show();
                    }
                }).show();
    }
}