文件下載 進度條

package a.a;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;

public class a extends Activity {
    Button b;
    OutputStream output;// 輸入出流
    ProgressBar bar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        b = (Button) findViewById(R.id.btn);
        bar = (ProgressBar) findViewById(R.id.bar);
        b.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                down();
            }
        });
    }

    Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            // TODO Auto-generated method stub
            super.handleMessage(msg);
            switch(msg.what) {
                case 0:
                    bar.setVisibility(View.VISIBLE);
                    break;
                case 1:
                    bar.setProgress(msg.arg1);
                    break;
            }
        }
    };

    // 下載方法 必須放在單獨的線程裏
    private void down() throws RuntimeException {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Message m = handler.obtainMessage();
                    m.what = 0;
                    m.sendToTarget();
                    // 建立URL 寫入下載地址
                    URL url = new URL("下載路徑");
                    // 建立HttpURLConnection
                    HttpURLConnection urlcon = (HttpURLConnection) url
                            .openConnection();
                    //或者上兩句使用URLConnection connection = new URL("下載路徑").
                    //openConnection(); 下面的urlcon 換成connection 
                    // 得到文件大小
                    long TotalSize = Long.parseLong(urlcon
                            .getHeaderField("Content-Length"));
                    // 得到文件大小
                    int fileLength = urlcon.getContentLength();
                    // 得到輸入流
                    InputStream is = urlcon.getInputStream();
                    // 建立目錄
                    File dir = new File("/mnt/sdcard/abc");
                    dir.mkdir();
                    // 建立文件
                    File file = new File("/mnt/sdcard/abc/asd.doc");
                    // 若是存在則刪除
                    if(file.exists())
                        file.delete();
                    // 建立文件
                    file.createNewFile();
                    // 建立文件輸入流
                    output = new FileOutputStream(file);
                    byte buffer[] = new byte[4 * 1024];
                    // 已下載
                    int downsize = 0;

                    while(true) {
                        int down = is.read(buffer);
                        if(down == -1) {
                            break;
                        }
                        downsize += down;
                        output.write(buffer, 0, down);
                        Message m2 = handler.obtainMessage();
                        m2.what = 1;
                        // 提示已下載百分之多少
                        m2.arg1 = downsize * 100 / fileLength;
                        m2.sendToTarget();
                    }
                    // 清除緩存
                    output.flush();
                }
                catch(Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                finally {
                    try {
                        // 關閉輸出流
                        output.close();
                    }
                    catch(Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
}

所需的權限

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

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