Prevent an Android app from 'minimizing'

Question

I don’t know if minimizing would be the right word, I don’t think so... Please correct me.

I have an application and I want to stop someone from minimizing it using the Home button, if someone presses Home, the application will be completed completely, including all the Activities that have been opened, and I also need you to execute a method when this application is finished in these terms...

How to do?

Edit: It is an application that user can select files to protect against access from other applications, these protected files can be accessed only by my application (it asks login), while my application is running the files are unprotected, because it needs to 'unprotect' them in order to be able to read, many laymen click the Home button and think that the application has been finalized, I want to avoid this, I want to avoid that the files remain unprotected because the application is still running, and I want to prevent another person from taking the user’s phone and end up gaining access to the application and files because it is simply open

Answer 1

Android is particularly designed to do pause to an application when the home is used.

Because of this, there are two methods to manage what should happen when someone uses the home or navigate out of the application: onPause() and onResume().

You can learn more about how they work in Pausing and Resuming an Activity.

By way of example, you can make a class of your own that extends to Activity in order to accomplish certain tasks when the application pause:

public class BaseActivity extends Activity {
    @Override
    protected void onPause() {
        // raio, usaram o botão 'home', deixa-me proteger os ficheiros!
    }

    @Override
    protected void onResume() {
        // epá, utilizador voltou, deixa desproteger os ficheiro!
    }
}

public class Activity1 extends BaseActivity {
    // ...
}

Also for your case, it may be useful to define android:clearTaskOnlaunch="true" so that the activities are completed when someone returns to the application.

---

Check whether application in background

It may also be useful to know if the app is going to background, which allows us to react more strongly.

The function below makes it possible to check if the application is going to background. It can be called in the method onPause() of all the Activity of the application:

 /**
   * Verifica se o aplicativo está sendo enviado para segundo plano
   * (ou seja, para trás da atividade de outra aplicação).       * 
   *
   * @param context O contexto
   * @return <code>true</code> se outro aplicativo vai estar acima deste.
   */
  public static boolean isApplicationSentToBackground(final Context context) {
    ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningTaskInfo> tasks = am.getRunningTasks(1);
    if (!tasks.isEmpty()) {
      ComponentName topActivity = tasks.get(0).topActivity;
      if (!topActivity.getPackageName().equals(context.getPackageName())) {
        return true;
      }
    }

    return false;
  }

The function needs extra permissions so you should in your AndroidManifest.xml include the following:

<uses-permission android:name="android.permission.GET_TASKS" />

^{Credits from this function to the @peceps user on SOEN in this answer.}