Difference between getContext() , getApplicationContext() , getBaseContext() and “this”

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Difference between getContext() , getApplicationContext() , getBaseContext() and “this”

original source : http://stackoverflow.com/questions/10641144/difference-between-getcontext-getapplicationcontext-getbasecontext-and

View.getContext(): Returns the context the view is currently running in. Usually the currently active Activity.

Activity.getApplicationContext(): Returns the context for the entire application (the process all the Activities are running inside of). Use this instead of the current Activity context if you need a context tied to the lifecycle of the entire application, not just the current Activity.

ContextWrapper.getBaseContext(): If you need access to a Context from within another context, you use a ContextWrapper. The Context referred to from inside that ContextWrapper is accessed via getBaseContext().

Difference between getContext() , getApplicationContext() , getBaseContext() and “this”

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Difference between getContext() , getApplicationContext() , getBaseContext() and “this”

original source : http://stackoverflow.com/questions/10641144/difference-between-getcontext-getapplicationcontext-getbasecontext-and

View.getContext(): Returns the context the view is currently running in. Usually the currently active Activity.

Activity.getApplicationContext(): Returns the context for the entire application (the process all the Activities are running inside of). Use this instead of the current Activity context if you need a context tied to the lifecycle of the entire application, not just the current Activity.

ContextWrapper.getBaseContext(): If you need access to a Context from within another context, you use a ContextWrapper. The Context referred to from inside that ContextWrapper is accessed via getBaseContext().

Useful Android system resources

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Useful Android system resources

original source : http://stackoverflow.com/questions/2631278/useful-android-system-resources

You can find a full listing of all system resources in the android package.

Every time I want to do something on Android I check to see if there’s a system resource that covers what I want to do. It is helpful to import the Android source code (in particular, their /res/ folder) when searching for already-implemented resources that you might want, so you can see their specific implementation.

Personally, I find myself most often using:

  • Built-in Android layouts for standard tasks, such as spinner dropdowns.
  • Android ids (android.R.id), because you are often required to use these if you want to use some of Android’s widgets (for example, TabHost/TabWidget requires you to use “android:id/tabhost”, “android:id/tabs” and “android:id/tabcontent” if you want to implement an XML layout).
  • Built-in colors, especially android.R.color.transparent.
  • Android’s built-in fade-in and fade-out animations in android.R.anim

Useful Android system resources

by ⋅ Link

Useful Android system resources

original source : http://stackoverflow.com/questions/2631278/useful-android-system-resources

You can find a full listing of all system resources in the android package.

Every time I want to do something on Android I check to see if there’s a system resource that covers what I want to do. It is helpful to import the Android source code (in particular, their /res/ folder) when searching for already-implemented resources that you might want, so you can see their specific implementation.

Personally, I find myself most often using:

  • Built-in Android layouts for standard tasks, such as spinner dropdowns.
  • Android ids (android.R.id), because you are often required to use these if you want to use some of Android’s widgets (for example, TabHost/TabWidget requires you to use “android:id/tabhost”, “android:id/tabs” and “android:id/tabcontent” if you want to implement an XML layout).
  • Built-in colors, especially android.R.color.transparent.
  • Android’s built-in fade-in and fade-out animations in android.R.anim

Java, 3 dots in parameters

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Java, 3 dots in parameters

original source : http://stackoverflow.com/questions/3158730/java-3-dots-in-parameters

It means that zero or more String objects (or an array of them) may be passed as the argument(s) for that method.

See the “Arbitrary Number of Arguments” section here: http://java.sun.com/docs/books/tutorial/java/javaOO/arguments.html#varargs

In your example, you could call it as any of the following:

myMethod(); // Likely useless, but possible
myMethod("one", "two", "three");
myMethod("solo");
myMethod(new String[]{"a", "b", "c"});

Important Note: The argument(s) passed in this way is always an array – even if there’s just one. Make sure you treat it that way in the method body.

Important Note 2: The argument that gets the ... must be the last in the method signature. So, myMethod(int i, String... strings) is okay, but myMethod(String... strings, int i) is not okay.

Thanks to Vash for the clarifications in his comment.

Java, 3 dots in parameters

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Java, 3 dots in parameters

original source : http://stackoverflow.com/questions/3158730/java-3-dots-in-parameters

It means that zero or more String objects (or an array of them) may be passed as the argument(s) for that method.

See the “Arbitrary Number of Arguments” section here: http://java.sun.com/docs/books/tutorial/java/javaOO/arguments.html#varargs

In your example, you could call it as any of the following:

myMethod(); // Likely useless, but possible
myMethod("one", "two", "three");
myMethod("solo");
myMethod(new String[]{"a", "b", "c"});

Important Note: The argument(s) passed in this way is always an array – even if there’s just one. Make sure you treat it that way in the method body.

Important Note 2: The argument that gets the ... must be the last in the method signature. So, myMethod(int i, String... strings) is okay, but myMethod(String... strings, int i) is not okay.

Thanks to Vash for the clarifications in his comment.

What does (angle brackets) mean in Java?

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What does (angle brackets) mean in Java?

original source : http://stackoverflow.com/questions/6607550/what-does-angle-brackets-mean-in-java

question

I am currently studying Java and have recently been stumped by what does <> means?

public class Pool<T>{
  public interface PoolFactory<T>{
  public T createObject();
}
this.freeObjects= new ArrayList<T>(maxsize)

What does the <T> mean? Does it means that I can create an object of type T?

answer

<T> is a generic and can usually be read as “of type T”. It depends on the type to the left of the <> what it actually means.

I don’t know what a Pool or PoolFactory is, but you also mention ArrayList<T>, which is a standard Java class, so I’ll talk to that.

Usually, you won’t see “T” in there, you’ll see another type. So if you see ArrayList<Integer>for example, that means “An ArrayList of Integers.” Many classes use generics to constrain the type of the elements in a container, for example. Another example is HashMap<String, Integer>, which means “a map with String keys and Integer values.”

Your Pool example is a bit different, because there you are defining a class. So in that case, you are creating a class that somebody else could instantiate with a particular type in place of T. For example, I could create an object of type Pool<String> using your class definition. That would mean two things:

  • My Pool<String> would have an interface PoolFactory<String> with a createObjectmethod that returns Strings.
  • Internally, the Pool<String> would contain an ArrayList of Strings.

This is great news, because at another time, I could come along and create a Pool<Integer>which would use the same code, but have Integer wherever you see T in the source.