<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  android:paddingBottom="@dimen/activity_vertical_margin"
  android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  tools:context="com.example.linux.continuedownload.MainActivity">

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
  <TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

  <TextView
    android:layout_marginLeft="80dp"
    android:id="@+id/progress"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

  <TextView
    android:layout_marginLeft="80dp"
    android:id="@+id/speed"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
  </LinearLayout>
  <ProgressBar
    android:visibility="invisible"
    android:id="@+id/progressBar"
    style="?android:attr/progressBarStyleHorizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

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

    <Button
      android:layout_marginLeft="20dp"
      android:id="@+id/stop"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="暂停下载" />

    <Button
      android:layout_marginLeft="20dp"
      android:id="@+id/cancel"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="取消下载" />
  </LinearLayout>

</LinearLayout>

startButton.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
    textView.setText(fileInfo.getFileName());
    progressBar.setVisibility(View.VISIBLE);
    // 通过Intent传递参数给service
    Intent intent = new Intent(MainActivity.this, DownloadService.class);
    intent.setAction(DownloadService.ACTION_START);
    intent.putExtra("fileInfo", fileInfo);
    startService(intent);
  }
});

stopButton.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
    // 通过Intent传递参数给service
    Intent intent = new Intent(MainActivity.this, DownloadService.class);
    intent.setAction(DownloadService.ACTION_STOP);
    intent.putExtra("fileInfo", fileInfo);
    startService(intent);
  }
});

cancelButton.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
    // 通过Intent传递参数给service
    Intent intent = new Intent(MainActivity.this, DownloadService.class);
    intent.setAction(DownloadService.ACTION_CANCEL);
    intent.putExtra("fileInfo", fileInfo);
    startService(intent);

    // 更新textView和progressBar的显示UI
    textView.setText("");
    progressBar.setVisibility(View.INVISIBLE);
    progressView.setText("");
    speedView.setText("");
  }
});

// 静态注册广播
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(DownloadService.ACTION_UPDATE);
registerReceiver(broadcastReceiver, intentFilter);

/**
 * 更新UI
 */
BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
    if (DownloadService.ACTION_UPDATE.equals(intent.getAction())) {
      int finished = intent.getIntExtra("finished", 0);
      int speed = intent.getIntExtra("speed", 0);

      Log.i("Main", finished + "");
      progressBar.setProgress(finished);
      progressView.setText(finished + "%");
      speedView.setText(speed + "KB/s");
    }
  }
};

<service android:name="com.huhx.services.DownloadService" android:exported="true" />

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />