private Thread downloadThread;
private void startDownload(){
    downloadThread=new Thread(new Runnable() {
        @Override
        public void run() {
            downApk();//這裡模擬實現網路下載功能
        }
    });
    downloadThread.start();
}

downApk()實現連線網路並下載並儲存檔案，這裡模擬實現網路下載功能
private int progress=0;
 
private int lastLength=10*1024*1024;//剩餘檔案的大小，初始值為檔案總尺寸
private int count=0;//已經下載的資料大小
private boolean stopDownload=false;
private void downApk(){
    while(lastLength>0&&!stopDownload){
        try {
            Thread.sleep(2000);
            count+=1*1024*1024;
            lastLength=lastLength-1*1024*1024;
            progress
 
=(int)((float)count/(10*1024*1024)*100);
            if(progress>1){
                Message msg=mhandler.obtainMessage();
                msg.what=1;
                msg.arg1=progress;
                mhandler.sendMessage(msg);
                callbackResult.OnBackResult(progress);//通過ICallBackResult回撥OnBackResult（），實現更改DownloadActivity中進度條的值
 

            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    mhandler.sendEmptyMessage(0);//表示下載完成
    app.setIsDownloadIng(false);
    callbackResult.OnBackResult("finish");
}