You need the following permissions in your manifest file:

    &lt;uses-permission android:name=&quot;android.permission.ACCESS_WIFI_STATE&quot;&gt;&lt;/uses-permission&gt;
    &lt;uses-permission android:name=&quot;android.permission.CHANGE_WIFI_STATE&quot;&gt;&lt;/uses-permission&gt;

Then you can use the following in your activity class:

    WifiManager wifiManager = (WifiManager) this.getApplicationContext().getSystemService(Context.WIFI_SERVICE); 
    wifiManager.setWifiEnabled(true);
    wifiManager.setWifiEnabled(false);

Use the following to check if it&#39;s enabled or not

    boolean wifiEnabled = wifiManager.isWifiEnabled()

You&#39;ll find a nice tutorial on the subject on [this][1] site.

  [1]: http://www.tutorialforandroid.com/2009/10/turn-off-turn-on-wifi-in-android-using.html

I googled the topic, but besides [Wikipedia][1] I didn&#39;t find any further useful documentation or articles. 

Can anybody explain to me in simple words what it means or refer me to some nice and easy to understand documentation?

  [1]: http://en.wikipedia.org/wiki/Class_invariant

What is a class invariant in Java?

**What does it mean global namespace would be polluted?**

I don&#39;t really understand what global namespace getting polluted means. 

What does it mean global namespace would be polluted?

I need to turn off the WiFi a while after pressing the &quot;Turn off the Screen&quot; button. There is a need for this app for my tablet because sometimes I just forget to turn off the WiFi and this discharges the battery very fast. It lives 10x+ times less than I would without WiFi. 
Is there any solution available as .apk? Can I track when the screen turned off and 5 min elapsed? Can I programmatically turn off WiFi on Android device? How?

How to programmatically turn off WiFi on Android device?

<p>I need to turn off the WiFi a while after pressing the "Turn off the Screen" button. There is a need for this app for my tablet because sometimes I just forget to turn off the WiFi and this discharges the battery very fast. It lives 10x+ times less than I would without WiFi.
Is there any solution available as .apk? Can I track when the screen turned off and 5 min elapsed? Can I programmatically turn off WiFi on Android device? How?</p>


While developing a camera app I&#39;ve encountered an exception that only happened when I switch to other app (`onPause()` for my app).

    01-15 17:22:15.017: E/AndroidRuntime(14336): FATAL EXCEPTION: main
    01-15 17:22:15.017: E/AndroidRuntime(14336): java.lang.RuntimeException: Method called after release()
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.hardware.Camera.setPreviewDisplay(Native Method)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.hardware.Camera.setPreviewDisplay(Camera.java:357)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at com.sora.cbir.yuki.image.leaf.CameraPreview.surfaceCreated(CameraPreview.java:32)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.SurfaceView.updateWindow(SurfaceView.java:551)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:213)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.View.dispatchWindowVisibilityChanged(View.java:4075)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewRoot.performTraversals(ViewRoot.java:858)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.view.ViewRoot.handleMessage(ViewRoot.java:1995)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.os.Handler.dispatchMessage(Handler.java:99)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.os.Looper.loop(Looper.java:150)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at android.app.ActivityThread.main(ActivityThread.java:4389)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at java.lang.reflect.Method.invokeNative(Native Method)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at java.lang.reflect.Method.invoke(Method.java:507)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
    01-15 17:22:15.017: E/AndroidRuntime(14336): 	at dalvik.system.NativeStart.main(Native Method)



I did some research and found out that I need to add

    mCamera.setPreviewCallback(null);

as a workaround for Android&#39;s camera stack

my `onPause()` now looks like this:
    
    @Override
    protected void onPause() {
        super.onPause();
	    try
	    {    
	    	// release the camera immediately on pause event   
	    	//releaseCamera();
	    	 mCamera.stopPreview(); 
	    	 mCamera.setPreviewCallback(null);
	    	 mCamera.release();
	    	 mCamera = null;

	    }
	    catch(Exception e)
	    {
	    	e.printStackTrace();
	    }
    }

and my `onResume()`:

    @Override
    protected void onResume()
    {
    	super.onResume();
    	try
    	{
    		mCamera.setPreviewCallback(null);
    		mCamera = getCameraInstance();
    		//mCamera.setPreviewCallback(null);
            mPreview = new CameraPreview(Imageupload.this, mCamera);//set preview
            preview.addView(mPreview);
        } catch (Exception e){
            Log.d(TAG, &quot;Error starting camera preview: &quot; + e.getMessage());
        }
    }	
    }

and finally my `getCameraInstance()` method:

	public Camera getCameraInstance(){
	    Camera camera = null;
	    try {
	        camera = Camera.open(); // attempt to get a Camera instance
	    }
	    catch (Exception e){
	        // Camera is not available (in use or does not exist)
	    }
	    Camera.Parameters parameters = camera.getParameters();
        //mPreviewSize = getBestPreviewSize(parameters, wt, ht);
        //mPictureSize = getBestPictureSize(parameters, wt, ht);
	    //Shift W &amp; H =&gt; if camera rotates 90 deg
	    
        mPreviewSize = getOptimalPreviewSize(parameters, wt, ht); //original =&gt; wt,ht
        mPictureSize = getOptimalPictureSize(parameters, wt, ht); //original =&gt; wt,ht
        
        Log.d(&quot;CAMERA&quot;, &quot;SCREEN RESOLUTION H: &quot;+ht);
        Log.d(&quot;CAMERA&quot;, &quot;SCREEN RESOLUTION W: &quot;+wt);
        
        Log.d(&quot;CAMERA&quot;, &quot;PREVIEW RESOLUTION H: &quot;+mPreviewSize.height);
        Log.d(&quot;CAMERA&quot;, &quot;PREVIEW RESOLUTION W: &quot;+mPreviewSize.width);
        
        Log.d(&quot;CAMERA&quot;, &quot;PICTURE RESOLUTION H: &quot;+mPictureSize.height);
        Log.d(&quot;CAMERA&quot;, &quot;PICTURE RESOLUTION W: &quot;+mPictureSize.width);
        //set preview size based on device screen
        parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
        //set picture size based on device screen
        parameters.setPictureSize(mPictureSize.width, mPictureSize.height);
        //set output camera mode
        parameters.setPictureFormat(PixelFormat.JPEG);
        //set focous mode
        parameters.setFocusMode(FOCUS_MODE_AUTO);
        //set flash mode
        parameters.setFlashMode(&quot;auto&quot;);
        List&lt;int[]&gt; fps = parameters.getSupportedPreviewFpsRange();
        //System.out.println(&quot;FPS size: &quot; +fps.size());
        //System.out.println(&quot;MAX FPS:&quot;+(fps.get(fps.size()-1)[1])/1000);
        //log min and max camera supported fps
        Log.d(&quot;CAMERA&quot;, &quot;CAMERA MAX FPS: &quot;+(fps.get(fps.size()-1)[1])/1000);
        Log.d(&quot;CAMERA&quot;, &quot;CAMERA MIN FPS: &quot;+(fps.get(fps.size()-1)[0])/1000);
        if(camera_fps)
        {
        	parameters.setPreviewFpsRange(fps.get(fps.size()-1)[1], fps.get(fps.size()-1)[1]);
        }
        //set camera parameters
        camera.setParameters(parameters);
        
        Toast.makeText(getApplicationContext(), &quot;Your device are capable of previewing @&quot; + fps.get(fps.size()-1)[1]/1000+&quot;fps!&quot;,Toast.LENGTH_SHORT).show();
	    return camera; // returns null if camera is unavailable
	}

any ideas on how to fix this?

method called after release() exception unable to resume with android camera

To reduce dependece of class, I want to send parameter (using generic class) to constructor that extends some class and implements interface, for example

    public interface SomeInterface{
        public void someMethod();
    }

    public class MyFragment extends Fragment implements SomeInterface{
        //implementation
    }

    //here is classs, that I need to create. T must extend Fragment and implements 
    //SomeInterface. But, I&#39;m afraid, if I&#39;ll use MyFragment directly, it will create a
    //dependence of SomeClass from MyFragment.

    public class SomeClass /*generic?*/ {
        public SomeClass(T parent);
    }

Is it possible?

Futher, using my T class, I want to create views, using T.getActivity() as Context.

Generic class that extends class and implements interface

Which files in an Android project should be committed to a version control repository? Which files should not be committed?

Right now my .gitignore file consists of the following lines:


    # Android generated files #
    ###########################
    android.keystore
    local.properties
    bin/
    gen/
    libs/
    obj/
    
    # OS generated files #
    ######################
    .DS_Store*
    ehthumbs.db
    Icon?
    Thumbs.db

    # Eclipse generated files #
    ###########################
    .settings/org.eclipse.jdt.core.prefs

Am I missing anything?


In Android development, what files should be committed to a repository?

In my drawable folder I have a few images and they all reference perfect, but when I try and add any more images with the exact same size in the same folder, and try to reference it, is flags up an error *&quot;Failed to convert @drawable/picture into a drawable&quot;*. I have tried the same image with a different name and it just keeps giving me that error. I have also tried it in a different XML layout and the same thing. Also the name of the picture have been &quot;jack&quot;, &quot;abc&quot;, &quot;question_mark&quot; as you can see there are strictly in the rules of the what characters you can use, and still the error message keeps coming up. Any advice would be great on how to fix the problem, thanks.
    
&gt; Failed to convert @drawable/picture into a drawable

Android: failed to convert @drawable/picture into a drawable

I want to swap two fragment in an activity via animation.Suppose PageA is for fragement A and left side on the screen and PageB is for fragment B i.e. on the right side of the screen. Now i want that when i click a button on pageA then PageA will move to the right side of the screen with some transition animation.

I tried the below code to replace the position
     
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.replace(R.id.container, new FragB());
    fragmentTransaction.commit();

   Looking for some clue.

   Thanks in advance.

Content Type	Original Author	Original Content on Stackoverflow
Question	J.Olufsen	View Question on Stackoverflow
Solution 1 - Android	J. Maes	View Answer on Stackoverflow

How to programmatically turn off WiFi on Android device?

Android Problem Overview

Android Solutions

Solution 1 - Android

What does it mean global namespace would be polluted?

What is a class invariant in Java?

Attributions