public class MainActivity extends Activity {

    private File apkFile;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void downloadAPK(View v) {
        //1). 主線程, 顯示提示視圖: ProgressDialog
        final ProgressDialog dialog = new ProgressDialog(this);
        dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        dialog.show();

        //準備用于保存APK文件的File對象 : /storage/sdcard/Android/package_name/files/xxx.apk
        apkFile = new File(getExternalFilesDir(null), "update.apk");

        //2). 啟動分線程, 請求下載APK文件, 下載過程中顯示下載進度
        new Thread(new Runnable() {

            @Override
            public void run() {
                try {
                    //1. 得到連接對象
                    String path = "http://192.168.10.165:8080/Web_Server/L04_DataStorage.apk";
                    URL url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    //2. 設置
                    //connection.setRequestMethod("GET");
                    connection.setConnectTimeout(5000);
                    connection.setReadTimeout(10000);
                    //3. 連接
                    connection.connect();
                    //4. 請求并得到響應碼200
                    int responseCode = connection.getResponseCode();
                    if(responseCode==200) {
                        //設置dialog的最大進度
                        dialog.setMax(connection.getContentLength());

                        //5. 得到包含APK文件數據的InputStream
                        InputStream is = connection.getInputStream();
                        //6. 創建指向apkFile的FileOutputStream
                        FileOutputStream fos = new FileOutputStream(apkFile);
                        //7. 邊讀邊寫
                        byte[] buffer = new byte[1024];
                        int len = -1;
                        while((len=is.read(buffer))!=-1) {
                            fos.write(buffer, 0, len);
                            //8. 顯示下載進度
                            dialog.incrementProgressBy(len);

                            //休息一會(模擬網速慢)
                            //Thread.sleep(50);
                            SystemClock.sleep(50);
                        }

                        fos.close();
                        is.close();
                    }
                    //9. 下載完成, 關閉, 進入3)
                    connection.disconnect();

                    //3). 主線程, 移除dialog, 啟動安裝
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            dialog.dismiss();
                            installAPK();
                        }
                    });

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
        //09-05 12:59:20.553: I/ActivityManager(1179): Displayed com.android.packageinstaller/.PackageInstallerActivity: +282ms
    }

    /**
     * 啟動安裝APK
     */
    private void installAPK() {
        Intent intent = new Intent("android.intent.action.INSTALL_PACKAGE");
        intent.setDataAndType(Uri.fromFile(apkFile), "application/vnd.android.package-archive");
        startActivity(intent);
    }