**遇到的问题：**在这因为返回值的问题烦躁了一下，有可能出现空指针的异常，已经提出成文章了
请参考http://blog.csdn.net/qq_27489007/article/details/53523378
文件关系图
断点续传流程图
开始撸代码(主要代码)
/**
- 普通断点续传
*/
public class DuandianActivity extends AppCompatActivity {
@BindView(R.id.tv)
TextView tv;
@BindView(R.id.probar)
ProgressBar probar;
@BindView(R.id.btstar)
Button btstar;
@BindView(R.id.btstop)
Button btstop;
String url = “http://dldir1.qq.com/weixin/android/weixin6316android780.apk”;
private FileInfo fileInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_duandian);
ButterKnife.bind(this);
probar.setMax(100);
//创建文件信息对象
fileInfo = new FileInfo(0, url, “文件名-下载进度”, 0, 0);
tv.setText(fileInfo.getFileName()); //设置显示下载的文件名
//注册广播接收器
IntentFilter filter = new IntentFilter();
filter.addAction(DownloadService.ACTION_UPDATE);
registerReceiver(mReceiver, filter);
}
//更新ui的广播接收器
BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if (DownloadService.ACTION_UPDATE.equals(intent.getAction())) {
int finished = intent.getIntExtra(“finished”, 0);
probar.setProgress(finished);
if (probar.getProgress()==100){
Toast.makeText(DuandianActivity.this,“下载完成！”,Toast.LENGTH_SHORT).show();
}
}
}
};
//按钮事件监听
@OnClick({R.id.btstar, R.id.btstop})
public void onClick(View view) {
Intent intent = new Intent(DuandianActivity.this, DownloadService.class);
switch (view.getId()) {
case R.id.btstar:
//通过intent传递参数给service
intent.setAction(DownloadService.ACTION_START);
intent.putExtra(“fileInfo”, fileInfo);
Log.i(“TAG”,intent.getAction().toString());
startService(intent);
break;
case R.id.btstop:
intent.setAction(DownloadService.ACTION_STOP);
intent.putExtra(“fileInfo”, fileInfo);
startService(intent);
break;
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mReceiver != null) {
unregisterReceiver(mReceiver);
}
}
}
DownloadService.java
/**
- 下载的服务类
*/
public class DownloadService extends Service {
public static final String ACTION_START = “ACTION_START”;
public static final String ACTION_STOP = “ACTION_STOP”;
public static final String ACTION_UPDATE = “ACTION_UPDATE”;
public static final String DOWNLOAD_PATH = Environment.getExternalStorageDirectory().getAbsolutePath() + “/download”;//sd卡路径
private DownloadTask mDownloadTask = null;
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// Log.i(“TAG”, intent.getAction().toString());
// Log.i(“action”, intent.getAction().toString());
//获得activity传来的参数
if (ACTION_START.equals(intent.getAction())) {
FileInfo fileInfo = (FileInfo) intent.getSerializableExtra(“fileInfo”);
Log.i(“test”, “start” + fileInfo.toString());
//启动初始化线程
new InitThread(fileInfo).start();
} else if (ACTION_STOP.equals(intent.getAction())) {
FileInfo fileInfo = (FileInfo) intent.getSerializableExtra(“fileInfo”);
Log.i(“test”, “stop” + fileInfo.toString());
if (mDownloadTask != null) {
mDownloadTask.isPause = true;
Toast.makeText(getApplicationContext(),“暂停成功”,Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(getApplicationContext(),“还未开始下载”,Toast.LENGTH_SHORT).show();
}
}
return super.onStartCommand(intent, Service.START_REDELIVER_INTENT, startId);
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
private static final int MSG_INIT = 0;
Handler mhandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case MSG_INIT:
FileInfo fileInfo = (FileInfo) msg.obj;
Log.i(“test”, “Init:” + fileInfo);
//启动下载任务
mDownloadTask = new DownloadTask(DownloadService.this, fileInfo);
mDownloadTask.download();
break;
}
}
};
/**
-
子线程进行下载保存工作
-
初始化子线程
*/
class InitThread extends Thread {
private FileInfo thread_fileInfo = null;
private RandomAccessFile raf;
public InitThread(FileInfo fileInfo) {
this.thread_fileInfo = fileInfo;
}
@Override
public void run() {
//连接网络文件
HttpURLConnection conn = null;
try {
URL url = new URL(thread_fileInfo.getUrl());
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod(“GET”
);
conn.setConnectTimeout(3000);
int length = -1;
if (conn.getResponseCode() == 200) {
//获得文件长度
length = conn.getContentLength();
}
if (length <= 0) {
return;
}
File dir = new File(DOWNLOAD_PATH);
if (!dir.exists()) { //判断如果不存在则创建一个文件
dir.mkdir();
}
//在本地创建文件
File file = new File(dir, thread_fileInfo.getFileName());
//随机访问的文件 可以在文件的任意一个位置进行写入操作
//rwd可读可写可操作
raf = new RandomAccessFile(file, “rwd”);
//设置文件长度
raf.setLength(length);
thread_fileInfo.setLength(length);
mhandler.obtainMessage(MSG_INIT, thread_fileInfo).sendToTarget();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (conn != null && raf != null) {
raf.close(); //关闭文件操作
conn.disconnect(); //断掉链接
}
} catch (IOException e) {
e.printStackTrace();
}
}
super.run();
}
}
}
DownloadTask.java
/**
-
下载的任务类 对文件的下载
-
Created by lung on 2016-12-07.
*/
public class DownloadTask {
private Context mContext = null;
private FileInfo mFileInfo = null;
private ThreadDAOImpl mThreadDAO = null;
private long mFinished = 0; //总的完成进度
public boolean isPause = false; //暂停下载的开关
public DownloadTask(Context mContext, FileInfo mFileInfo) {
this.mContext = mContext;
this.mFileInfo = mFileInfo;
mThreadDAO = new ThreadDAOImpl(mContext);
}
//下载的方法
public void download() {
//读取数据库的线程信息
List threaddInfos = mThreadDAO.getThreads(mFileInfo.getUrl());
TheardInfo info;
if (threaddInfos.size() == 0) { //如果数据库无线程信息
info = new TheardInfo(0, mFileInfo.getUrl(), 0, mFileInfo.getLength(), 0);
} else {
info = threaddInfos.get(0);//单线程的下载 所以使用get(0)
}
//创建子线程进行下载
new DownloadThread(info).start();
}
