Thanks to [CommonsWare&#39;s blog post][1], I got some clue.

Assuming your code is in `Activity` or `Fragment`, check the overlay permission and make a request for it if necessary:

    public static int OVERLAY_PERMISSION_REQ_CODE = 1234;

    public void someMethod() {
        if (!Settings.canDrawOverlays(this)) {
            Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                    Uri.parse(&quot;package:&quot; + getPackageName()));
            startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
        }
    }

Then, re-check the permission for better UX:

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
            if (!Settings.canDrawOverlays(this)) {
                // SYSTEM_ALERT_WINDOW permission not granted...
            }
        }
    }

  [1]: https://commonsware.com/blog/2015/08/17/random-musings-android-6p0-sdk.html &quot;Random Musings on the Android 6.0 SDK&quot;

I need to create Rails and Mysql containers with docker-compose. When I try to create links between containers with `docker-compose up`, I get

&gt; Cannot start container
&gt; 9b271c58cf6aecaf017dadaf5b Cannot link to a non running container:
&gt; /puma_db_1 AS /puma_web_1/db


Files

**Dockerfile**

    FROM ubuntu:14.04
    
    RUN apt-get -y update
    RUN apt-get -y install git curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

    RUN apt-get -y install libmysqlclient-dev
    RUN git clone https://github.com/sstephenson/rbenv.git /root/.rbenv
    RUN git clone https://github.com/sstephenson/ruby-build.git /root/.rbenv/plugins/ruby-build
    RUN echo &#39;eval &quot;$(rbenv init -)&quot;&#39; &gt;&gt; $HOME/.profile
    RUN echo &#39;eval &quot;$(rbenv init -)&quot;&#39; &gt;&gt; $HOME/.bashrc

    RUN rbenv install 2.1.5
    RUN rbenv global 2.1.5
    RUN gem install rails -v 4.0.11

    ADD app.tar.gz /home/
    WORKDIR /home/app
    
    RUN bundle install
    EXPOSE 3000
    CMD [&quot;rails&quot;, &quot;server&quot;, &quot;-b&quot;, &quot;0.0.0.0&quot;]

**docker-compose.yml**

    db:  
      image: mysql:latest
      environment:
        MYSQL_DATABASE: app_development
        MYSQL_USER: mysql
        DATABASE_PASSWORD: onetwo
        ROOT_PASSWORD: onetwo
    web:
      build: .
      command: bundle exec rails s -p 3000 -b &#39;0.0.0.0&#39;
      ports:
        - &quot;4000:3000&quot;
      links:
        - db

Docker Cannot link to a non running container

Golang newbie here. 

Is there a functional difference between

    func randomNumberGenerator() &lt;-chan int {

and 

    func randomNumberGenerator() chan int {

I&#39;ve tried using both and they seem to work fine for me.

I&#39;ve seen the former used by Rob Pike (one of Go creators) in his Go Concurrency Patterns talk at Google IO 2012. I&#39;ve also seen it used in Go&#39;s official website. Why add 2 extra characters (&quot;&lt;-&quot;) when you can omit it? I&#39;ve tried looking for the difference on the web, but couldn&#39;t find it.

What&#39;s the difference between &quot;&lt;-chan&quot; and &quot;chan&quot; as a function return type?

It completely ignores:

    &lt;uses-permission android:name=&quot;android.permission.SYSTEM_ALERT_WINDOW&quot;/&gt;

So I got exception:

&gt; Caused by: android.view.WindowManager$BadTokenException: Unable to add window android.view.ViewRootImpl$W@86fb55b -- permission denied for this window type

It&#39;s not even listed:

[![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/HnL2T.jpg

How should I fix it? Thanks.




&lt;b&gt;EDIT:&lt;/b&gt;

It&#39;s listed in Configure apps/ Advanced / Draw over other app. So i turn it on and now it works fine, but why there isn&#39;t any dialog to ask about permission when i run my app? All perrmissions was turned off by deafult and i need to go to settings and mannualy turn it on?

Permission from manifest doesn&#39;t work in Android 6

It completely ignores:
<pre><code class="hljs language-ini">&#x3C;uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
</code></pre>
So I got exception:
> Caused by: android.view.WindowManager$BadTokenException: Unable to add window android.view.ViewRootImpl$W@86fb55b -- permission denied for this window type
It's not even listed:
<a href="http://i.stack.imgur.com/HnL2T.jpg" target="_blank" rel="noopener noreferrer"><img src="http://i.stack.imgur.com/HnL2T.jpg" alt="enter image description here"></a>
How should I fix it? Thanks.
EDIT:
It's listed in Configure apps/ Advanced / Draw over other app. So i turn it on and now it works fine, but why there isn't any dialog to ask about permission when i run my app? All perrmissions was turned off by deafult and i need to go to settings and mannualy turn it on?

I&#39;m using the new Android Marshmallow SDK and the method `FloatMath.sqrt()` is gone. What should I use now?

Method FloatMath.sqrt() not found

I have a RecyclerView. Each row has a play button, textview and Progressbar. when click on the play button have to play audio from my sdcard and have to progress Progressbar
The problem is when i scroll down the recyclerview change the Progressbar in next row.means  I can fit 5 items on the screen at once. When I scroll to the 6th, 6th row seekbar changes suddenly.


    
    public class ListAdapter extends RecyclerView.Adapter {
    
        private List&lt;Historyitem&gt; stethitems;
        public Context mContext;
        public Activity activity;
        public Handler mHandler;
    
        static MediaPlayer mPlayer;
        static Timer mTimer;
    
        public ListAdapter(Activity activity,Context mContext,List&lt;Historyitem&gt; stethitems) {
            this.stethitems = stethitems;
            this.mContext = mContext;
            this.activity = activity;
        }
    
        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
    
            View rootView = LayoutInflater.
                    from(mContext).inflate(R.layout.stethoscopeadapteritem, null, false);
            RecyclerView.LayoutParams lp = new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT);
            rootView.setLayoutParams(lp);
            mHandler = new Handler();
            return new MyViewHolder(rootView);
        }
    
        @Override
        public void onBindViewHolder(final RecyclerView.ViewHolder viewHolder, int position) {
    
            final Historyitem dataItem = stethitems.get(position);
            final MyViewHolder myViewHolder = (MyViewHolder) viewHolder;
            myViewHolder.progressplay.setProgress(0);
            myViewHolder.stethdatetime.setText(dataItem.getReported_Time());
            myViewHolder.stethhosname.setText(dataItem.getdiv());
    
            if(dataItem.getPatient_Attribute().replaceAll(&quot; &quot;,&quot;&quot;).equals(&quot;&quot;)){
                myViewHolder.stethdoctorname.setText(dataItem.getunit());
            } else {
                myViewHolder.stethdoctorname.setText(dataItem.getPatient_Attribute());
            }
    
            myViewHolder.stethstreamplay.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                   
                       FileDownload(dataItem.getmsg(),
                                myViewHolder.progressplay);
                 
                }
            });
        }
    
        @Override
        public int getItemCount() {
    
            return stethitems.size();
        }
      
        public class MyViewHolder extends RecyclerView.ViewHolder {
    
            final CustomTextRegular stethdatetime;
            final CustomTextView stethhosname;
            final CustomTextBold stethdoctorname;
            final ImageButton stethstreamplay;
            final NumberProgressBar progressplay;
    
            public MyViewHolder(View itemView) {
                super(itemView);
              
                stethdatetime = (CustomTextRegular)
                        itemView.findViewById(R.id.stethdatetime);
                stethhosname = (CustomTextView)
                        itemView.findViewById(R.id.stethhosname);
                stethdoctorname = (CustomTextBold)
                        itemView.findViewById(R.id.stethdoctorname);
                stethstreamplay = (ImageButton)
                        itemView.findViewById(R.id.stethstreamplay);
                progressplay= (NumberProgressBar)
                        itemView.findViewById(R.id.progressplay);
                
    
            }
        }
        public void  FileDownload(final String downloadpath,
                                         
                                         final NumberProgressBar progressplay) {
    
            new AsyncTask&lt;NumberProgressBar, Integer, NumberProgressBar&gt;() {
                NumberProgressBar progress;
                @Override
                protected void onPreExecute() {
                    super.onPreExecute();
                    try {
                        if(mPlayer!=null){
                            mPlayer.stop();
                        }
                    }catch (Exception e){
                    }
                    try {
                        if(mTimer != null){
                            mTimer.purge();
                            mTimer.cancel();
                        }
                    }catch (Exception e){
                    }
                }
    
                @Override
                protected NumberProgressBar doInBackground(NumberProgressBar... params) {
                    int count;
                    progress = progressplay;
                    try {
                       
                        final List&lt;NameValuePair&gt; list = new ArrayList&lt;NameValuePair&gt;();
                        list.add(new BasicNameValuePair(&quot;pid&quot;,id));
    
                        URL url = new URL(Config.requestfiledownload + &quot;?path=&quot; +
                                downloadpath);
                        URLConnection connection = url.openConnection();
                        connection.connect();
    
                        int lenghtOfFile = connection.getContentLength();
                        // download the file
                        InputStream input = new BufferedInputStream(url.openStream());
                        OutputStream output = new FileOutputStream(Environment.getExternalStorageDirectory() +
                                &quot;record.wav&quot;);
                        byte data[] = new byte[1024];
                        long total = 0;
                        while ((count = input.read(data)) != -1) {
                            total += count;
                            // publishing the progress....
                            publishProgress((int) (total * 100 / lenghtOfFile));
                            output.write(data, 0, count);
                        }
                        output.flush();
                        output.close();
                        input.close();
                    } catch (Exception e) {
                       
                    }
                    return progress;
                }
                @Override
                protected void onPostExecute(final NumberProgressBar numberProgressBar) {
                    super.onPostExecute(numberProgressBar);
                  
                            try {
                                StartMediaPlayer(numberProgressBar);
                            } catch (Exception e){
                                e.printStackTrace();
                            }
                        
                }
            }.execute();
        }
    
        public void StartMediaPlayer(final NumberProgressBar progressbar){
            Uri playuri = Uri.parse(&quot;file:///sdcard/record.wav&quot;);
            mPlayer = new MediaPlayer();
            mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mPlayer.reset();
            try {
                mPlayer.setDataSource(mContext, playuri);
            } catch (IllegalArgumentException e) {
                
            } catch (SecurityException e) {
               
            } catch (IllegalStateException e) {
                
            } catch (Exception e) {
               
            }
            try {
                mPlayer.prepare();
            } catch (Exception e) {
               
            }
    
            mPlayer.start();
            progressbar.setMax(mPlayer.getDuration());
            mPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    if(mPlayer!=null) {
                        mPlayer.release();
                        progressbar.setProgress(0);
                    }
                    if(mTimer != null){
                        mTimer.purge();
                        mTimer.cancel();
                    }
                }
            });
            mTimer = new Timer();
            mTimer.schedule(new TimerTask() {
                @Override
                public void run() {
                    mHandler.post(new Runnable() {
                        @Override
                        public void run() {
                            progressbar.setProgress(mPlayer.getCurrentPosition());
                        }
                    });
                }
            },0,500);
        }}

Recyclerview Changing Items During Scroll

An example usage:

[![enter image description here][1]][1]

The Spinner is dark themed, but I want the dropdown to be light themed.


  [1]: http://i.stack.imgur.com/wNEvY.png

How do I set a different theme for a Spinner&#39;s dropdown?

I&#39;m trying out the new data binding library. I have a weird issue where binding the `visibility` property is not compiling.

This is a simplified version of the xml file:

    &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
	&lt;layout xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;&gt;

	    &lt;data&gt;

		&lt;variable
		    name=&quot;header&quot;
		    type=&quot;com.example.EmailHeader&quot; /&gt;
	    &lt;/data&gt;

	    &lt;RelativeLayout ... &gt;

		    &lt;TextView
		        ...
		        android:text=&quot;@{header.senderName ?? header.senderAddress}&quot;
		        android:visibility=&quot;@{header.hasAttachment ? View.VISIBLE : View.INVISIBLE}&quot; /&gt;

	    &lt;/RelativeLayout&gt;
	&lt;/layout&gt;

I get the follow message when compiling:

    Error:Execution failed for task &#39;:app:compileDebugJavaWithJavac&#39;.
&gt; java.lang.RuntimeException: Found data binding errors.
  ****/ data binding error ****msg:Identifiers must have user defined types from the XML file. View is missing it

Everything compiles (and works!) when I remove the `android:visiblity` declaration.

I don&#39;t see what I&#39;m missing here

Data binding expression not compiling

Together with the M release, there are new support libraries. One of them that seems to be very useful is the [v7 Preference Support][1] library. 

It does not seem to have `PreferenceActivity` or something similar, how do we integrate it to our app?

  [1]: http://developer.android.com/tools/support-library/features.html#v7-preference

How to use the v7/v14 Preference Support library?

When I have a target API of 23 on Android M Preview 3, I cannot seem to acquire the Manifest.permission.WRITE_SETTTINGS permission. 

    requestPermissions(new String[]{Manifest.permission.WRITE_SETTINGS}, 101);


Request permission doesn&#39;t bring up the dialog I would expect, but if I make the following call without this permission,

     RingtoneManager.setActualDefaultRingtoneUri(activity, RingtoneManager.TYPE_RINGTONE, ringUri);
 
The call will except because I don&#39;t have the permission.

I&#39;m not sure where to go from here. Is there a new ringtone API for 23? Or did this permission change just make it impossible for any non-system apps to change the ringtone?

Can&#39;t get WRITE_SETTINGS permission

In Android Marshmallow, permissions should be requested at runtime when they are needed, instead of all at once when an app is installed. However, I can only seem to request permissions from an Activity, which is a problem since my app contains only Services. (Why is that, you might ask? The app has an Android Wear watch face bundled inside, and all the phone does is look up photos nearby to send to the watch - no Activity needed. But it does require location permissions.)

So, is there any way to request permissions from a Service? Or somehow force the permissions to be granted at install time as in the past?

How to request permissions from a Service in Android Marshmallow

Whenever my device (Nexus 5, Android M Preview 3) connects via USB, the USB config always defaults to &quot;charging only&quot;. 

This is quite problematic because the USB port on my device is faulty and sometimes disconnects and reconnects when bumped and so I have to manually change the mode to MTP (media transfer protocol) from the notification drawer each time.

- Debugging mode is enabled
- Develop settings -&gt; USB Configuration is set to MTP.

How to set Android M default USB config to MTP rather than &quot;charging only&quot;?

I was going through the official doc about the new Permissions model in Android M. It talks about the `shouldShowRequestPermissionRationale()` function which returns `true` if the app has requested this permission previously and the user denied the request. If the user turned down the permission request in the past and chose the Don&#39;t ask again option, this method returns `false`. 

 
But how can we differentiate between the following two cases?

&lt;b&gt;Case 1&lt;/b&gt;: The app doesn&#39;t have a permission and the user has not been asked for the permission before. In this case, shouldShowRequestPermissionRationale() will return false because this is the first time we&#39;re asking the user.

&lt;b&gt;Case 2&lt;/b&gt;: The user has denied the permission and selected &quot;Don&#39;t ask again&quot;, in this case too shouldShowRequestPermissionRationale() will return false. 

I would want to send the user to the App&#39;s settings page in Case 2. How do i go about differentiating these two cases?﻿

Content Type	Original Author	Original Content on Stackoverflow
Question	Djordje Tankosic	View Question on Stackoverflow
Solution 1 - Android	Shigerello	View Answer on Stackoverflow

Permission from manifest doesn't work in Android 6

Android Problem Overview

Android Solutions

Solution 1 - Android

What's the difference between "<-chan" and "chan" as a function return type?

Docker Cannot link to a non running container

Attributions