Global object of android app

Question

i am developing an android app. I have some activities in it. And i must have an object which can be available from all activities. Any ideas how to organize it?

Answer 1

Use the global Application object in the following way:

package com.yourpackagename;

public class App extends Application {
}

In AndroidManifest.xml :

<application android:name=".App">

To access it from an Activity :

App globalApp = (App) getApplicationContext();

The App class will be instantiated automatically when the app starts. It will be available as long as the application process is alive. It can act as a global store in which you can put your things and have access to them throughout the application lifetime.

Answer 2

There are a few ways to do this. If the object you want to share is a String (or easily described with a String), I would recommend Shared Preferences . It serves as a key-value store for sharing data within an application.

If this is not the case (ie the suitability of a String), you could consider passing it as an extra with the Intent that launches your various activities. For example:

Intent newActivity = new Intent(CurrentActivity.class, ActivityToLaunch.class);
newActivity.putExtra("object_key", Bundle_With_Your_Object);

For more details on this strategy (especially about the Bundle class, if you're not familiar), I would read this Android doc .

Answer 3

You can use SharedPreferences in this case:

To add or edit:

SharedPreferences prefs = this.getSharedPreferences("Cusom Name", Activity.MODE_PRIVATE);
prefs.edit().putString("your_key", value).commit();

To clear:

SharedPreferences prefs = this.getSharedPreferences("Cusom Name", Activity.MODE_PRIVATE);
prefs.edit().clear();

To get value:

SharedPreferences prefs = this.getSharedPreferences("Cusom Name", Activity.MODE_PRIVATE);               
String value = prefs.getString("your_key", "");

Answer 4

First, create a class named MasterActivity which extends Activity and define your global object.

public class MasterActivity extends Activity
{
     public Object mObject;
}

Then, you have to extend your main activity class with your MasterActivity like it :

// your main activity
public class MainActivity extends MasterActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        // you can now use mObject in your main class
        mObject.yourmethod();
    }
}

By this way, you will be able to use your object in all your activities simply by extending MasterActivity instead of Activity.