android基础-下载更新Notification小栗子

写在前面

下载更新是一个普通到不能再普通,每个app又不得不有的一个功能。本着学习积累的目的,尝试实现了一个简单但实用的Demo。用到了Service,Broadcast,Thread及Notification。

需求

app后台进行下载更新,前台展示下载进度,下载完毕自动跳转安装界面。

思路

由于下载更新这类属于耗时操作,不能在主线程(UI线程)中进行。所以考虑在主线程中开启一个服务(Service),并在服务中开启一个子线程来进行下载任务。前台如何展示下载进度呢?这就涉及到了前台界面Activity与Service的通信。首先想到的是,要不要绑定一个服务?绑定服务会和前台界面共存亡,前台界面销毁,后台服务也会被回收,用户体验不好。所以考虑使用Broadcast来广播下载进度。后台服务为了更长命,考虑将其提升成前台服务startFroground(),启动Notification顺便还能在用户退出应用时展示下载进度。这是需求前半段的思路;下载完成后发送一个隐式广播调起系统的apk安装程序进行新版,这个是需求的后半段思路。

实现

  • MainActivity检测下载更新,代码如下:
        @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      //如果下载的线程正在运行中,启动下载服务时不再启动下载线程
        if (downloadThreadAvailed(DownloadAPKService.DOWNLOAD_THREAD_NAME)) {
            Intent intent = new Intent(this, UpdateActivity.class);
            intent.putExtra(START_DOWNLOAD_EXTRA, true);
            intent.putExtra(UPDATE_URL_EXTRA, URL_STR);
            startActivity(intent);
            finish();
        } else {
            new AlertDialog.Builder(this)
                    .setTitle("提示")
                    .setMessage("检测到新版本,是否现在更新应用?")
                    .setCancelable(false)
                    .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            finish();
                        }
                    })
                    .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            Intent it = new Intent(MainActivity.this, UpdateActivity.class);
                            it.putExtra(UPDATE_URL_EXTRA, URL_STR);
                            startActivity(it);
                            finish();
                        }
                    })
                    .show();
        }
    }
  //判断线程是否处于活动状态
    private boolean downloadThreadAvailed(String threadName) {
        Set<Thread> threads = Thread.getAllStackTraces().keySet();
        for (Thread thread : threads) {
            if (TextUtils.equals(thread.getName(), threadName))
                return true;
        }
        return false;
    }
  • UpdateActivity开启下载服务,注册广播接收者,接收下载进度,代码如下:
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update);
      //展示下载进度view控件
        mPb = (ProgressBar) findViewById(R.id.pb);
        mTextView = (TextView) findViewById(R.id.proText);
        //获取下载链接等
        Intent it = getIntent();
        String mUrl = it.getStringExtra(UPDATE_URL_EXTRA);
        //接收下载事件广播
        mBroadcast = new UpdateProgressBroadcast();
        IntentFilter filter = new IntentFilter();
        filter.addAction(UPDATE_WAITING_ACTION);
        filter.addAction(UPDATE_PROGRESS_ACTION);
        filter.addAction(UPDATE_COMPLETE_ACTION);
        filter.addAction(UPDATE_FAILED_ACTION);
        //注册广播接收者,不要忘记在onDestroy方法中解除注册
        registerReceiver(mBroadcast, filter);
        //开启下载服务,不要忘记在onDestroy方法中停止服务
        startDownloadService(mUrl);
    }
    private void startDownloadService(String url) {
        Intent it = new Intent(this, DownloadAPKService.class);
        //继续把下载地址带到服务中去
        it.putExtra(UPDATE_URL_EXTRA, url);
        startService(it);
    }
    private void stopDownloadService() {
        stopService(new Intent(UpdateActivity.this, DownloadAPKService.class));
    }
  • UpdateProgressBroadcast作为UpdateActivity的内部类被定义,其具体实现如下:
    public class UpdateProgressBroadcast extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            switch (action) {
                case UPDATE_WAITING_ACTION:
                    //下载前准备动作
                    mTextView.setText("Waiting..");
                    break;
                case UPDATE_PROGRESS_ACTION:
                    //更新进度条
                    int value = ((int) intent.getDoubleExtra(PROGRESS_VALUE_EXTRA, 0));
                    if (mPb != null) {
                        mPb.setProgress(value);
                    }
                    mTextView.setText(value + "%");
                    break;
                case UPDATE_COMPLETE_ACTION:
                     //下载完成
                    mTextView.setText("Download complete!");                   
                     break;
                case UPDATE_FAILED_ACTION:
                     //下载失败
                     mTextView.setText("Download failed!");
                    break;
            }
        }
    }

千万不要忘记在配置文件中配置自定义广播,值得注意的是,action的格式必须以“com.”开头的字符串。配置文件代码如下:

<receiver android:name="com.miner.UpdateActivity$UpdateProgressBroadcast">
            <intent-filter android:priority="1000">
                <action android:name="com.update_waiting_action"/>
                <action android:name="com.update_progress_action"/>
                <action android:name="com.update_complete_action"/>
                <action android:name="com.update_failed_action"/>
            </intent-filter>
        </receiver>

配置文件中配置服务

<service
            android:name="com.miner.updatedemo.service.DownloadAPKService"
            android:enabled="true"
            android:exported="false" />

当然还有相应的权限

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  • 最后是核心类DownloadAPKService的实现:
 @Override
 public int onStartCommand(Intent intent, int flags, int startId) {
        Log.e(LOG_TAG, "onStartCommand");
        String url = intent.getStringExtra(MainActivity.UPDATE_URL_EXTRA);

        //构建前台Notification,关于Notification的使用,可以参考官方文档
        //文档给的例子足够简单明了
        Intent notifyIntent = new Intent(this, UpdateActivity.class);
        notifyIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        notifyIntent.putExtra(UPDATE_URL_EXTRA, url);
        notifyIntent.putExtra(START_DOWNLOAD_EXTRA, true);
        PendingIntent notifyPendingIntent =
                PendingIntent.getActivity(
                        this,
                        0,
                        notifyIntent,
                        PendingIntent.FLAG_UPDATE_CURRENT
                );
        mNotifyManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        mBuilder = new Notification.Builder(this);
        mBuilder.setContentTitle("Update Download")
                .setContentText("下载更新中")
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentIntent(notifyPendingIntent);
        //开启下载线程
        mIsStart = true;
        DownloadRunnable mRunnable = new DownloadRunnable(url);
        new Thread(mRunnable, DOWNLOAD_THREAD_NAME).start();
        // 开启前台服务。
        startForeground(ID, mBuilder.build());
        return super.onStartCommand(intent, flags, startId);
    }
  • 下载任务类:
    private class DownloadRunnable implements Runnable {
        private final String url;
        DownloadRunnable(String url) {
            this.url = url;
        }
        @Override
        public void run() {
            if (mIsStart) {
                download(url);
            }
        }
    }

-下载方法:

    private void download(String url) {
        InputStream is = null;
        FileOutputStream fos = null;
        mHandler.sendMessage(mHandler.obtainMessage(UPDATE_WAITING));
        try {
            String filename = url.substring(url.lastIndexOf("/") + 1);
            URL myURL = new URL(url);
            URLConnection conn = myURL.openConnection();
            conn.connect();
            is = conn.getInputStream();
            mTotalSize = conn.getContentLength();
            mApkFile = new File("/sdcard/" + filename);
            fos = new FileOutputStream(mApkFile);
            byte buf[] = new byte[2048];
            int len;
            long currentSize = 1;
            while ((len = is.read(buf)) != -1) {
                fos.write(buf, 0, len);
                currentSize += len;
                fos.flush();
                mHandler.sendMessageDelayed(mHandler.obtainMessage(UPDATE_PROGRESS, currentSize), 0 * 1000);
            }
            mHandler.sendMessage(mHandler.obtainMessage(DOWNLOAD_COMPLETE));
        } catch (Exception e) {
            e.printStackTrace();
            mHandler.sendMessage(mHandler.obtainMessage(DOWNLOAD_Failed));
        } finally {
            Log.e(LOG_TAG, "finally block");
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
  • 下载进度可以直接广播么?其实是可以得,但我更习惯先发送至handler由handler来进行广播。那么Handler的实现代码如下:
    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            Intent intent;
            switch (msg.what) {
                case UPDATE_WAITING:
                     //更新Notification显示
                    mBuilder.setContentText("waiting...")
                            .setProgress(0, 0, false);
                    mNotifyManager.notify(ID, mBuilder.build());
                    //发送广播
                    sendBroadcast(new Intent().setAction(UpdateActivity.UPDATE_WAITING_ACTION));
                    break;
                case UPDATE_PROGRESS:
                     //更新Notification显示
                    double result = (((long) msg.obj) / (double) mTotalSize) * 100;
                    mBuilder.setProgress(100, (int) result, false)
                            .setContentText((int) result + "%");
                    mNotifyManager.notify(ID, mBuilder.build());
                    //带上下载进度发送广播
                    intent = new Intent(UpdateActivity.UPDATE_PROGRESS_ACTION);
                    intent.putExtra(PROGRESS_VALUE_EXTRA, result);
                    sendBroadcast(intent);
                    break;
                case DOWNLOAD_COMPLETE:
                    mBuilder.setContentText("Download complete")
                            .setProgress(0, 0, false);
                    mNotifyManager.notify(ID, mBuilder.build());
                    mNotifyManager.cancel(ID);
                    if (mActivity != null && !mActivity.isFinishing())
                        mActivity.finish();
                    stopForeground(true);
                    installApk(getApplicationContext(), Uri.fromFile(mApkFile));
                    sendBroadcast(new Intent().setAction(UpdateActivity.UPDATE_COMPLETE_ACTION));
                    mIsStart = false;
                    break;
                case DOWNLOAD_Failed:
                    mBuilder.setContentText("Download failed")
                            .setProgress(0, 0, false);
                    mNotifyManager.notify(ID, mBuilder.build());
                    mNotifyManager.cancel(ID);
                    if (mActivity != null && !mActivity.isFinishing())
                        mActivity.finish();
                    stopForeground(true);
                    sendBroadcast(new Intent().setAction(UpdateActivity.UPDATE_FAILED_ACTION));
                    mIsStart = false;
                    break;
            }
        }
    };

以上就是核心代码的实现,总体来讲是比较简单的,有不足的地方希望各路大神指指点点,路过的点个赞呗。
完整代码

推荐阅读更多精彩内容