I'm working on a small project where I'm making a compass that is going to be used on top of a MapView. Everything works just fine when running the program (compass part) within its own activity (not on the MapView), but because the compass has to be integrated into another package containing the Activity that holds the MapView, I want my compass code to be accessed from that package.
The problem is that I don't know to initialize the sensors from the other package or if I have to do it from the Activity itself and then somehow pass the instance of the SensorManager to the compass package.
I hope that my question is specific enough, but if not, I'll gladly post some of my code :)
If you have a valid Context you can start the sensor manager from another package.
public class compass implements SensorEventListener {
SensorManager mSensorManager;
public compass(Context context) {
mSensorManager = (SensorManager)context.getSystemService(SENSOR_SERVICE);
// do stuff like register listener
}
}
Related
I created a simple little directory listing method in the default MainActivity.class
I was able to get it to function the way I wanted it to, however, when I moved the method to a different class and called it in MainActivity, I wound up getting a lot of Context Errors all over the place. After searching the web I am stumped and require assistance.
The code where it errors out is for the Context for FileArray:
(public class Utilities extends Activity)
arrayAdapter = new FileArrayAdapter(getApplicationContext(),R.layout.custom_explorer,dir);
Method Name:
public void listDirectories(ListView listView, File directory)
It errors out on the getApplicationContext, this method worked just fine in MainActivity.
I have not implemented Fragments to MainActivity yet, wanted to get the working functionality first then spread out for OOP; then call by Fragment.
Hope someone can help, any further info I am happy to share.
Thank you for the timely response: ρяσѕρєя K & Nilabja.
Ya I guess it just needed another person to suggest feeding Context as a param. I did that once but it did not work so I passed it off, attempted once again from Nilabja suggestion. Yip that was the solution.
utilities.ListDirectory(mainList, root, getApplicationContext());
public void listDIR(ListView listView, File directory, Context setContext)
I have 15 or so activities. Each one of them has a method, and I want to play audio in that method. Now, I have the obvious option to copy and paste the following line of code into each and every one of my activities Now, if I wanted to change something, I would have to go back into each and every one of my activities again. Here is the code:
MediaPlayer pop = MediaPlayer.create(CurrentActivity.this, R.raw.pop);
pop.start();
So, after searching the web for a few hours, I found that most people would just copy and paste it into each activity. So, I put the line of code (above) into a separate java class (which was a service by the way) tried to call that method in the service every time I needed to play the audio. So, I did the following:
public class TwentySeconds extends Service{
public void myPop(View view){
MediaPlayer pop = MediaPlayer.create(TwentySeconds.this, R.raw.pop);
pop.start();
}
}
Now, I got the error non static method cannot be referenced from static context. So, naturally, I tried to make method myPop static. Then, I got the error on TwentySeconds.this about being referenced from static context. So, it seems I am stuck. Changing the methods to static can't work, as I am trying to use an instance of the class as well using this. So, how should I go about calling method myPop where the MediaPlayer can successfully play?
Thanks for the advice,
Rich
Typically, if a utility method needs a Context, it is passed in.
public class Utilities {
public static void myPop(Context context){
MediaPlayer pop = MediaPlayer.create(context, R.raw.pop);
pop.start();
}
}
Utilities.myPop(CurrentActivity.this);
I am trying to build an Android Application that retrieves the users location for every 'x' seconds and then displays it in a toast.
There are three main java files that I am using in my code. They are: MainActivity.java which extends Activity and uses the alarm service provided by the AlarmReciever.java, AlarmReceiver.java extends the broadcast receiver and LocationModules.java, extends Service and implements location listener, which contain code to retrieve location.
The sequence of flow is as follows:
MainActivity.java ------> AlarmReceiver.java ------> LocationModules.java
LocationModules.java has a location manager that needs the application context which needs to be passed from MainActivity.java (I am not sure if I am right here).
Can anyone please help me with this. Thanks in advance.
myLocationManager=(LocationManager)mContext.getSystemService(LOCATION_SERVICE);
If your LocationModules extends Service, then you can just use getSystemService method (I mean, call it without using mContext).
I'm new to android and java.
I'm rearranging some of the classes in my app into separate class files. I had a onLocationListener class in my main activity class file. I moved the class to a separate java class file. Then, however the following code will not compile . . .
public void onProviderDisabled(String provider)
{
Toast.makeText( getApplicationContext(),
"Gps Disabled",
Toast.LENGTH_SHORT ).show();
}
The getApplicationContext won't compile when this code is in a separate file. I tried this. and mainactivityname. but nothing seems to work. So I suppose this problem can be formed into a the following question:
How do you state the application context from code that exists in separate java class files outside the main activity file?
thanks, Gary
getApplicationContext() is a method of class Context, so you can only call it from a class or object that in some way extends Context. You factored your code out of Activity, which is such a class. Your solution, then, is for the Context class that contains your new class or object to pass its context in so that your new class can use it.
Your code inside your main Activity would look something like this:
MyOwnClass ownObject = new MyOwnClass();
// you have to implement setApplicationContext
ownObject.setApplicationContext( this.getApplicationContext() );
It's probably a good idea to get the application context right away, since it'll be stable for the lifetime of your app, unlike the Activity context which could go away on something as simple as an orientation change.
I'm creating a music player for Android and it's mostly working. The problem is that when I turn the device horizontally I lose all the variables from the Activity (which makes sense because it is destroyed and re-created).
I've tried using bundles to store the state of the player with onSaveInstanceState & onRestoreInstanceState but I still can't access the media player. Is there a way to pass objects like the MediaPlayer in bundles? Should I be using a database instead?
Thanks
You should use a Service to Provides "background" audio playback capabilities, allowing the
user to switch between activities or Rotate device without stopping playback.
Check out android_packages_apps_Music which is opensource by CM on github , It use MediaPlaybackService extends Service to do this , checkout MediaPlaybackService.java
For objects you couldn't pass via a bundle, I would suggest you to use the simple SharedPreference to store objects.
Here you have a simple implementation:
public class Data {
private SharedPreferences preferences;
private int test;
public Data (Context context)
{
preferences = context.getSharedPreferences("Data", 0);
test = preferences.getInt("test", 0);
}
public int getTest()
{
return test;
}
public void setTest(int input)
{
this.test = input;
SharedPreferences.Editor editor = preferences.edit();
editor.putInt("Test", input);
editor.commit();
}
}
You have just to initialize the variable in the onCreate():
Data mydata = new Data(this);
And you can use set/get with mydata to store/retrieve your persistent data.
Edit: It is maybe not suitable for MediaPlayer objects, but for other classical types (int, string, boolean...).
Both of the methods below would allow you to keep your mediaplayer object through the rotation, but neither use bundles.
You could persist your media player by using onRetainNonConfigurationInstance() to save the variable and getLastNonConfigurationInstance() to retrieve it after the rotation, but this method isn't necessarily the best as it is not always called
-See this SO post for more info https://stackoverflow.com/a/3916068/655822
Or you could persist your media player by extending your application class and storing it in there
below info copied from the linked SO answer for the purpose of making this answer quicker to read
You can pass data around in a Global Singleton if it is going to be used a lot.
public class YourApplication extends Application
{
public SomeDataClass data = new SomeDataClass();
}
Then call it in any activity by:
YourApplication appState = ((YourApplication)this.getApplication());
appState.data.UseAGetterOrSetterHere(); // Do whatever you need to with the data here.
-See this SO post for more info on that https://stackoverflow.com/a/4208947/655822
Another way would be to :
In your AndroidManifest.xml, find your entry for your activity and add the following attribute and value:
android:configChanges="orientation|screenSize"
This will stop your activity from being destroyed and recreated on orientation.