Android implements multi threaded breakpoint download method
- 2020-06-19 11:42:09
- OfStack
This article gives an example of how Android implements multithreaded breakpoint downloads. Share to everybody for everybody reference. Specific implementation methods are as follows:
package cn.itcast.download;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import cn.itcast.mutiledownload.StreamTool;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
public class MutiledownloadActivity extends Activity implements OnClickListener {
private ProgressBar pb;
private Button bt;
private TextView tv;
private EditText et;
boolean flag = true;
boolean stopflag = false;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
pb.setProgress(total);
int max = pb.getMax();
if (total >= (max - 1)) {
total = max;
flag = false;
}
int result = total * 100 / max;
tv.setText(" The current progress :" + result + "%");
super.handleMessage(msg);
}
};
int total = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pb = (ProgressBar) this.findViewById(R.id.pb);
bt = (Button) this.findViewById(R.id.bt);
tv = (TextView) this.findViewById(R.id.tv_process);
et = (EditText) this.findViewById(R.id.et);
bt.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.bt:
// create 1 Child threads Regular updates ui
if(" Start the download ".equals(bt.getText().toString())){
bt.setText(" suspended ");
stopflag = false; // Start the download
}
else {
bt.setText(" Start the download ");
stopflag = true;
}
new Thread() {
@Override
public void run() {
super.run();
while (flag) {
try {
sleep(1000);
// if total > = The length of the file
Message msg = new Message();
handler.sendMessage(msg);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
// Start the download operation
String path = et.getText().toString().trim();
if ("".equals(path)) {
Toast.makeText(this, " The path cannot be empty ", 1).show();
return;
}
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setRequestProperty("User-Agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
int code = conn.getResponseCode();
if (code == 200) {
int len = conn.getContentLength();
RandomAccessFile file = new RandomAccessFile(
"/mnt/sdcard/" + getFilenName(path), "rwd");
// 1. Set the local file size to the server file size 1 to
file.setLength(len);
// Sets the maximum value of the progress bar
pb.setMax(len);
// 2 . Assume that open 3 A thread
int threadnumber = 3;
int blocksize = len / threadnumber;
/**
* thread 1 0~ blocksize thread 2 1*bolocksize ~ 2*blocksize thread 3
* 2*blocksize ~ The end of the file
*/
for (int i = 0; i < threadnumber; i++) {
int startposition = i * blocksize;
int endpositon = (i + 1) * blocksize;
if (i == (threadnumber - 1)) {
// The last 1 A thread
endpositon = len;
}
DownLoadTask task = new DownLoadTask(i, path,
startposition, endpositon);
task.start();
}
}
} catch (Exception e) {
Toast.makeText(this, " Download exception ", 0).show();
e.printStackTrace();
}
break;
}
}
class DownLoadTask extends Thread {
int threadid;
String filepath;
int startposition;
int endpositon;
public DownLoadTask(int threadid, String filepath, int startposition,
int endpositon) {
this.threadid = threadid;
this.filepath = filepath;
this.startposition = startposition;
this.endpositon = endpositon;
}
@Override
public void run() {
try {
File postionfile = new File("/mnt/sdcard/" + threadid + ".txt");
URL url = new URL(filepath);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
System.out.println(" thread " + threadid + " Is downloading " + " The starting position : "
+ startposition + " End position " + endpositon);
if (postionfile.exists()) {
FileInputStream fis = new FileInputStream(postionfile);
byte[] result = StreamTool.getBytes(fis);
String str = new String(result);
if (!"".equals(str)) {
int newstartposition = Integer.parseInt(str);
if (newstartposition > startposition) {
startposition = newstartposition;
}
}
}
// "Range", "bytes=2097152-4194303")
conn.setRequestProperty("Range", "bytes=" + startposition + "-"
+ endpositon);
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setRequestProperty("User-Agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
InputStream is = conn.getInputStream();
RandomAccessFile file = new RandomAccessFile("/mnt/sdcard/"
+ getFilenName(filepath), "rwd");
// Set up the Where data is written from in the file
file.seek(startposition);
byte[] buffer = new byte[1024];
int len = 0;
// Represents the location of the server data currently read , At the same time the value is the location of the file that has been stored
int currentPostion = startposition;
// create 1 File object , Record the current download location of a file
while ((len = is.read(buffer)) != -1) {
if (stopflag) {
return;
}
file.write(buffer, 0, len);
synchronized (MutiledownloadActivity.this) {
total += len;
}
currentPostion += len;
// Need to put currentPostion Information is persisted to the storage device
String position = currentPostion + "";
FileOutputStream fos = new FileOutputStream(postionfile);
fos.write(position.getBytes());
fos.flush();
fos.close();
}
file.close();
System.out.println(" thread " + threadid + " The download ");
// When the thread has finished downloading Delete the file
if (postionfile.exists()) {
postionfile.delete();
}
} catch (Exception e) {
e.printStackTrace();
}
super.run();
}
}
public String getFilenName(String path) {
int start = path.lastIndexOf("/") + 1;
return path.substring(start, path.length());
}
}Hopefully, this article has been helpful in your Android programming.