从异步任务进程获取通知

Question

我需要从后台进程发送通知。在这个项目中，我尝试每10秒发送一个简单的通知。它运行但不发送通知！

public class MainActivity extends ActionBarActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Long previousDate = new Long(System.currentTimeMillis());
        NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
        new GetMethodEx1().execute(previousDate);
    }
    class GetMethodEx1 extends AsyncTask<Long,Void,Void>{
        private Context mContext;
        private int NOTIFICATION_ID = 1;
        private Notification mNotification;
        private NotificationManager mNotificationManager;
        @Override
        protected Void doInBackground(Long... params){
            Long previousDate = params[0];
            Long Intervall = new Long(System.currentTimeMillis());
            while ( true ){
                if ((Intervall - previousDate) > 10000 ){
                    String title = "Title";
                    String body = "Hi, I am the body";
                    createNotification( title, body);
                    previousDate = Intervall;
                }
            }
            return null;
        }
        private void createNotification(String contentTitle, String contentText) {
            //Build the notification using Notification.Builder
            Notification.Builder builder = new Notification.Builder(mContext)
            .setSmallIcon(android.R.drawable.stat_sys_download)
            .setAutoCancel(true)
            .setContentTitle(contentTitle)
            .setContentText(contentText);
            //Get current notification
            mNotification = builder.getNotification();
            //Show the notification
            mNotificationManager.notify(NOTIFICATION_ID, mNotification);
        }
  // [ ... ]
  }

它不会崩溃，但不起作用！

Answer 1

在createNotification()方法中，您需要将代码修改为

private void createNotification(String contentTitle, String contentText) {
    mNotificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
    //Build the notification using Notification.Builder
    Notification.Builder builder = new Notification.Builder(mContext)
    .setSmallIcon(android.R.drawable.stat_sys_download)
    .setAutoCancel(true)
    .setContentTitle(contentTitle)
    .setContentText(contentText);

    //Show the notification
    mNotificationManager.notify(NOTIFICATION_ID, builder.build());
}

在你的onCreate中，你不需要这条线

NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);

因此，删除上面的行。

编辑

由于您在createNotification()方法中调用getSystemService，而不是onCreate()，因此需要将Context作为参数传递给方法createNotification()，因为getSystemService是类Context的方法，因此需要在上下文中运行它。

private void createNotification(String contentTitle, String contentText,Context context) {
    mNotificationManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
    //Build the notification using Notification.Builder
    Notification.Builder builder = new Notification.Builder(mContext)
    .setSmallIcon(android.R.drawable.stat_sys_download)
    .setAutoCancel(true)
    .setContentTitle(contentTitle)
    .setContentText(contentText);

    //Show the notification
    mNotificationManager.notify(NOTIFICATION_ID, builder.build());
}

并且在调用方法createNotification()时使用

createNotification( c, b,MainActivity.this);

Answer 2

考虑到Gabrio的问题和Sash_KP的答案，我想在这里提供作为清理代码的概念：

https://github.com/tks423/glendale-case-detail-app

public class MainActivity extends AppCompatActivity {
private EditText respText;
private static final String siteUrlSansActivityId = "https://csi.glendaleca.gov/csipropertyportal/jsp/frameContent.jsp?actStatus=Case&actId=";
private String siteUrl;
private EditText activityId;
private Context mContext  = MainActivity.this;
private int NOTIFICATION_ID = 1;
private Notification noti;
private NotificationManager nm;
PendingIntent contentIntent;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);
    activityId = (EditText) findViewById(R.id.edtURL);
    activityId.addTextChangedListener(new TextWatcher() {
        public void afterTextChanged(Editable s) {
            siteUrl = siteUrlSansActivityId + activityId.getText().toString();
        }
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
        public void onTextChanged(CharSequence s, int start, int before, int count) {}
    });
    Button btnGo = (Button) findViewById(R.id.btnGo);
    respText = (EditText) findViewById(R.id.edtResp);
    btnGo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            try {
                Log.d("JSwa", "Connecting to [" + siteUrl + "]");
                Document doc  = Jsoup.connect(siteUrl).get();
                // Get document (HTML page) title
                String title = doc.title();
                Log.d("JSwA", "Title ["+title+"]");
                Elements topicList = doc.select("td.tabletext");
                String status = topicList.get(1).text();
                respText.setText(status);
            }
            catch(Throwable t) {
                t.printStackTrace();
            }
        }
    });
    nm = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
    ( new ParseURLLoop() ).execute(siteUrl);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
private class ParseURLLoop extends AsyncTask<String, Void, Void> {
    @Override
    protected Void doInBackground(String... params) {
        //String siteUrl = params[0];
        Long previousDate = new Long(System.currentTimeMillis());
        Log.d("doInBackground", "PreviousDate [" + previousDate + "]");
        Long intervall = new Long(System.currentTimeMillis());
        Log.d("doInBackground", "intervall [" + intervall + "]");
        Boolean a = false;
        while ( a == false){
            if ((intervall - previousDate) > 1000 * 60 ){
                StringBuffer buffer = new StringBuffer();
                try {
                    Log.d("JSwa", "In here");
                    Log.d("JSwa", "Connecting to [" + siteUrl + "]");
                    Document doc  = Jsoup.connect(siteUrl).get();
                    Log.d("JSwa", "Connected to [" + siteUrl + "]");
                    // Get document (HTML page) title
                    String title = doc.title();
                    Log.d("JSwA", "Title ["+title+"]");
                    Elements topicList = doc.select("td.tabletext");
                    if(!"In Process".equals(topicList.get(1).text())){
                        Log.d("Status", "status is [" + topicList.get(1).text() +"]");
                        createNotification( "Glendale AE" , topicList.get(1).text() , MainActivity.this);
                        Intent notificationIntent = new Intent(mContext.getApplicationContext(), MainActivity.class);
                        contentIntent = PendingIntent.getActivity(mContext.getApplicationContext(),
                                0, notificationIntent,
                                PendingIntent.FLAG_CANCEL_CURRENT);
                    }
                }
                catch(Throwable t) {
                    t.printStackTrace();
                }
                previousDate = intervall;
            }
            intervall = new Long(System.currentTimeMillis());
        }
        return null;
    }
    private void createNotification(String contentTitle, String contentText,Context context) {
        Log.d("createNotification", "title is [" + contentTitle +"]");
        nm = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
        //Build the notification using Notification.Builder
        Notification.Builder builder = new Notification.Builder(mContext)
                .setSmallIcon(android.R.drawable.stat_sys_download)
                .setAutoCancel(true)
                .setContentTitle(contentTitle)
                .setContentText(contentText);

        //Show the notification
        nm.notify(NOTIFICATION_ID, builder.build());
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }
}

}