Android开发之断点续传（下载）

DownloadUtils

public class DownloadUtils {
 private static final String TAG = "DownloadUtils";
 private static volatile DownloadUtils instance;
 private File file;
 private String filePath;

 private OkHttpClient client;
 private File downloadFile;
 private long startPosition;
 private Call call;

 private DownloadUtils() {
  client = new OkHttpClient();
 }

 private DownloadListener listener;

 public void setListener(DownloadListener listener) {
  this.listener = listener;
 }

 /**
  * 初始化下载父路径
  *
  * @param path
  */
 public void initDownload(String path) {
  file = new File(path);
  if (!file.getParentFile().exists()) {
file.getParentFile().mkdir();
  }
  if (!file.exists()) {
file.mkdir();
  }
  filePath = file.getAbsolutePath();
  Log.i(TAG, "initDownload: " + filePath);
 }

 public static DownloadUtils getInstance() {
  if (null == instance) {
synchronized (DownloadUtils.class) {
 if (instance == null) {
  instance = new DownloadUtils();
 }
}
  }
  return instance;
 }

 public void startDownload(String url) {
  if (TextUtils.isEmpty(url)) {
return;
  }


  if (url.contains(".")) {
String typeName = url.substring(url.lastIndexOf(".") + 1);
if (url.contains("/")) {
 String name = url.substring(url.lastIndexOf("/") + 1, url.lastIndexOf("."));
 String fn = name + "." + typeName;

 downloadFile = new File(file, fn);
}
  }
  startPosition = 0;
  if (downloadFile.exists()) {
startPosition = downloadFile.length();
  }

  Request request = new Request.Builder()
 .addHeader("RANGE", "bytes=" + startPosition + "-")
 .url(url)
 .build();

  call = client.newCall(request);
  call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {

}

@Override
public void onResponse(Call call, Response response) throws IOException {
 listener.startDownload();
 ResponseBody body = response.body();
 long totalLength = body.contentLength() + startPosition;
 Log.i(TAG, "totalLength: " + totalLength + "----");
 InputStream is = body.byteStream();
 byte[] buf = new byte[2048];
 int length = 0;
 long totalNum = startPosition;
 RandomAccessFile raf = new RandomAccessFile(downloadFile, "rw");
 raf.seek(totalNum);
 while ((length = is.read(buf, 0, buf.length)) != -1) {
  raf.write(buf, 0, length);
  totalNum += length;
  listener.downloadProgress(totalNum * 100 / totalLength);

 }
 Log.i(TAG, "totalNum==" + totalNum + "---");
 listener.finishDownload(downloadFile.getAbsolutePath());
 body.close();
}
  });


 }

 public void pauseDownload() {
  listener.pauseDownload();
  if (call != null && call.isExecuted()) {
call.cancel();
  }
 }
}

DownloadListener

public interface DownloadListener {
 void startDownload();

 void pauseDownload();

 void finishDownload(String path);

 void downloadProgress(long progress);
}

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

 private TextView tv_pro;
 private ProgressBar progressBar;
 private Button btn_start;
 private Button btn_pause;
 private String downloadUrl = "http://acj3.pc6.com/pc6_soure/2017-12/com.yek.android.kfc.activitys_3820.apk";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  tv_pro = findViewById(R.id.tv_pro);
  progressBar = findViewById(R.id.progressbar);
  btn_start = findViewById(R.id.start);
  btn_pause = findViewById(R.id.pause);
  btn_start.setOnClickListener(this);
  btn_pause.setOnClickListener(this);
  if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
File storageDirectory = Environment.getExternalStorageDirectory();
String absolutePath = storageDirectory.getAbsolutePath();
final String path = absolutePath + "/Download/";
Log.i("zzz", "下载路径 " + path);
DownloadUtils.getInstance().initDownload(path);
DownloadUtils.getInstance().setListener(new DownloadListener() {
 @Override
 public void startDownload() {

 }

 @Override
 public void pauseDownload() {

 }

 @Override
 public void finishDownload(String path) {
  installApk(new File(path));
 }


 @Override
 public void downloadProgress(final long progress) {
  runOnUiThread(new Runnable() {
@Override
public void run() {
 tv_pro.setText((int)progress + "%");
 progressBar.setProgress((int) progress);
}
  });
 }
});
  }
 }

 @Override
 public void onClick(View view) {
  switch (view.getId()) {
case R.id.start:
 DownloadUtils.getInstance().startDownload(downloadUrl);
 break;
case R.id.pause:
 DownloadUtils.getInstance().pauseDownload();
 break;
  }
 }
 /**
  * 安装apk
  *
  * @param file
  */
 private void installApk(File file) {
  Intent intent = new Intent();
  intent.setAction(Intent.ACTION_VIEW);
  intent.addCategory("android.intent.category.DEFAULT");
  intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
  intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
  startActivity(intent);
  android.os.Process.killProcess(android.os.Process.myPid());
 }
}

activity_main.xml