android断点续传多线程下载

活动

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

private DownloadService.DownloadBinder downloadBinder;

private ServiceConnection connection = new ServiceConnection() {

    @Override
    public void onServiceDisconnected(ComponentName name) {
    }

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        downloadBinder = (DownloadService.DownloadBinder) service;
    }

};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button startDownload = (Button) findViewById(R.id.start_download);
    Button pauseDownload = (Button) findViewById(R.id.pause_download);
    Button cancelDownload = (Button) findViewById(R.id.cancel_download);
    startDownload.setOnClickListener(this);
    pauseDownload.setOnClickListener(this);
    cancelDownload.setOnClickListener(this);
    Intent intent = new Intent(this, DownloadService.class);
    startService(intent); // 启动服务,保证DownloadService在后台运行
    bindService(intent, connection, BIND_AUTO_CREATE); // 绑定服务，活动和服务交互
    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);
    }//获取SD卡权限
}

@Override
public void onClick(View v) {
    if (downloadBinder == null) {
        return;
    }
    switch (v.getId()) {
        case R.id.start_download:
            String url = "http://192.168.37.23:8080/axis2/xml/get_data.xml";
            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, String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case 1: