先放個gif。。最終效果如果：

主要演示了android從伺服器下載檔案，呼叫Notification顯示下載進度，並且在下載完畢以後點選通知會跳轉到安裝APK的介面，演示是在真實的網路環境中使用真實的URL進行演示，來看看程式碼：
MainActivity程式碼非常簡單，就是啟動一個Service：

public class MainActivity extends AppCompatActivity {
    String download_url="http://shouji.360tpcdn.com/160329/a9037075b8d3aa98fbf6115c54a5b895/com.alensw.PicFolder_4722404.apk"
 
;

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

    }
    public void bt_start_service(View view){
        Intent intent=new Intent(this,DownLoadService.class);
        intent.putExtra("download_url"
 
,download_url);
        startService(intent);
    }
}

DownLoadService裡面，在onStartCommand方法裡面是關鍵程式碼，呼叫NotifyUtil這個工具類的“notify_progress”方法去顯示一個通知，與此同時開始下載APK檔案，DownLoadService程式碼如下：

public class DownLoadService extends Service {
    String download_url;
    String savePath= Environment.getExternalStorageDirectory()+"/liulan.apk"
 
;
    private int requestCode = (int) SystemClock.uptimeMillis();
    private NotifyUtil currentNotify;
    File mFile;
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();


    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        mFile=new File(savePath);
        download_url=intent.getStringExtra("download_url");
        Log.e("test","執行onStartCommand");
        //設定想要展示的資料內容
        Intent intent_noti = new Intent();
        intent_noti.setAction(Intent.ACTION_VIEW);
        //檔案的型別，從tomcat裡面找
        intent_noti.setDataAndType(Uri.fromFile(mFile), "application/vnd.android.package-archive");
        PendingIntent rightPendIntent = PendingIntent.getActivity(this,
                requestCode, intent_noti, PendingIntent.FLAG_UPDATE_CURRENT);
        int smallIcon = R.drawable.xc_smaillicon;
        String ticker = "正在更新快圖瀏覽";
        //例項化工具類，並且呼叫介面
        NotifyUtil notify7 = new NotifyUtil(this, 7);
        notify7.notify_progress(rightPendIntent, smallIcon, ticker, "快圖瀏覽升級程式", "正在下載中",
                false, false, false, download_url, savePath, new NotifyUtil.DownLoadListener() {
                    @Override
                    public void OnSuccess(File file) {
                        mFile=file;
                        DownLoadService.this.stopSelf();
                    }

                    @Override
                    public void onFailure(Throwable t, int errorNo, String strMsg) {

                    }
                });
        currentNotify = notify7;
        return super.onStartCommand(intent, flags, startId);

    }
}

在呼叫“notify_progress”方法的時候，已經開始下載檔案了，那麼下載的程式碼是什麼呢？如下：

public void notify_progress(PendingIntent pendingIntent, int smallIcon,
                                String ticker, String title, String content,
                                boolean sound, boolean vibrate, boolean lights,
                                String download_url, String savePath, final DownLoadListener listener) {

        setCompatBuilder(pendingIntent, smallIcon, ticker, title, content, sound, vibrate, lights);
        /*
         * 因為進度條要實時更新通知欄也就說要不斷的傳送新的提示，所以這裡不建議開啟通知聲音。
         * 這裡是作為範例，給大家講解下原理。所以傳送通知後會聽到多次的通知聲音。
         */
        FinalHttp fh = new FinalHttp();
        HttpHandler<File> httpHandler=fh.download(download_url,  savePath, new AjaxCallBack<File>() {
            @Override
            public void onLoading(long count, long current) {
                super.onLoading(count, current);
                double a=count;
                double b=current;
                double currentPro=(double)((b/a)*100);
                cBuilder.setProgress(100, (int)currentPro, false);
                sent();
            }

            @Override
            public void onSuccess(File file) {
                super.onSuccess(file);
                cBuilder.setContentText("下載完成").setProgress(0, 0, false);
                sent();
                listener.OnSuccess(file);
            }

            @Override
            public void onFailure(Throwable t, int errorNo, String strMsg) {
                super.onFailure(t, errorNo, strMsg);
                listener.onFailure(t,errorNo,strMsg);
            }

        });


    }

這裡用到了afinal.jar
這個jar已經封裝好下載的工具類，我們直接拿來用就行。下載成功之後會通過DownLoadListener這個介面回撥到DownLoadService裡面，最終執行效果就如最上面那個gif動態圖執行效果一樣。

專案下載地址：點選下載