网络下载，配上进度条

来源：互联网发布：软件出现乱码怎么办编辑：程序博客网时间：2024/05/29 05:11

注意事项：我们知道加载进度，快慢是因为加载文件中，间隔二个，三个，五个，中间在写入刷新进度条，通常不每个都写入按照for循环的处理方式，那样虽然会非常的平滑，速度均匀，但是没有太大的一个意义，从用户使用体验上来说，并不会价值。

位置我用。11111已经标识出来了，注意观察。

public class MainActivity extends Activity {

static int ThreadCount = 3;

static int finishedThread= 0;

int currentProgress;

String fileName = "TakeColor.exe";

//确定下载地址

String path = "http://192.168.6.136:8080/" + fileName;

private ProgressBar pb;

TextView tv;

Handler handler = new Handler(){

public void handleMessage(android.os.Message msg) {

//把变量改成long，在long下运算，运算时候不会出现负值

tv.setText((long)pb.getProgress() *100/pb.getMax()+"%");

}

};

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

pb = (ProgressBar) findViewById(R.id.pb);

tv = (TextView) findViewById(R.id.tv);

}

public void click(View v){

Thread t = new Thread(){

public void run() {

try {

URL url = new URL(path);

HttpURLConnection conn =(HttpURLConnection) url.openConnection();

conn.setRequestMethod("GET");

conn.setConnectTimeout(5000);

conn.setReadTimeout(5000);

if(conn.getResponseCode()==200){

//拿到所请求文件的大小

int length = conn.getContentLength();

//设置进度条的最大值就是原文件的总长度

pb.setMax(length);

File file = new File(Environment.getExternalStorageDirectory(),fileName);

//生存临时文件

RandomAccessFile raf = new RandomAccessFile(file, "rwd");

//设置临时文件的大小

raf.setLength(length);

raf.close();

//计算出每个线程应该下载多少字节

int size =length / ThreadCount;

11111 for(int i =0;i<ThreadCount;i++){

//计算线程开始和结束的下载位置

int startIndex = i * size;

int endIndex = (i + 1) * size - 1;

//如果是最后一个线程，那么结束的位置写死

if(i==ThreadCount-1){

endIndex = length-1;

}

System.out.println("线程" + i +"的下载区间是:" +startIndex + "---" + endIndex);

new DownLoadThread(startIndex,endIndex,i).start();

}

}catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

};

t.start();

}

class DownLoadThread extends Thread{

int startIndex;

int endIndex;

int threadId;

public DownLoadThread(int startIndex,int endIndex,int threadId){

super();

this.startIndex=startIndex;

this.endIndex=endIndex;

this.threadId=threadId;

}

public void run() {

// TODO Auto-generated method stub

//再次发送http请求，下载原文件

HttpURLConnection conn;

try {

File progressFile = new File(Environment.getExternalStorageDirectory(),threadId +".text");

//判断进度临时问价是否存在

if(progressFile.exists()){

FileInputStream fis = new FileInputStream(progressFile);

BufferedReader br = new BufferedReader(new InputStreamReader(fis));

//从进度临时文件中读取上一次临时文件下载的总进度，然后与原本的开始位置相加，得到新的开始位置

int lastProgress =Integer.parseInt(br.readLine()) ;

startIndex +=lastProgress;

//把上次下载的进度显示到进度条里面

currentProgress += lastProgress;

pb.setProgress(currentProgress);

//发送消息让主线程刷新文本进度

handler.sendEmptyMessage(1);

fis.close();

}

URL url = new URL(path);

conn = (HttpURLConnection) url.openConnection();

conn.setRequestMethod("GET");

conn.setConnectTimeout(5000);

conn.setReadTimeout(5000);

//设置本次http请求所请求的数据的区间

conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);

//请求部分数据，响应码是206

if(conn.getResponseCode()==206){

//流里此时只有1/3原文件的数据

InputStream is = conn.getInputStream();

byte[] b= new byte[1024];

int len =0;

int total=0;

//拿到临时文件的输出流

File file = new File(Environment.getExternalStorageDirectory(),fileName);

//生存临时文件

RandomAccessFile raf = new RandomAccessFile(file, "rwd");

//把文件的写入位置移动至startIndex

raf.seek(startIndex);

while((len = is.read(b))!=-1){

raf.write(b, 0, len);

total +=len;

System.out.println("线程" +threadId +"下载了" +total);

currentProgress +=len;

pb.setProgress(currentProgress);

//发送消息让主线程刷新文本进度

handler.sendEmptyMessage(1);

//生成一个专门用来记录下载进度的临时文件

RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd");

//每次读取流里的数据之后，同步把当前线程的总进度写进临时文件中

progressRaf.write((total+"").getBytes());

progressRaf.close();

}

raf.close();

finishedThread++;

synchronized (path) {

if(finishedThread ==ThreadCount){

for (int i = 0; i < ThreadCount; i++) {

File f = new File(Environment.getExternalStorageDirectory(),i + ".text");

f.delete();

}

finishedThread = 0;

}

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

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