Operations for Activities

Get Current Activity and Base Activity Class

Create a Java base class named BaseActivity to inherit from

android.support.v7.app.AppCompatActivity

Then override the onCreate method inside this base class

Add a log statement within it

Log.d(“Current Activity”,getClass().getSimpleName());

With this setup, no matter which activity we navigate into, we can know which one is active

package com.foxdevelop.www.lifedemo;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
public class BaseActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("Current Activity",getClass().getSimpleName());
    }
}Code language: JavaScript (javascript)

05-13 08:36:47.473 18499-18499/? D/Current Activity: MainActivity
05-13 08:36:56.460 18499-18499/com.foxdevelop.www.lifedemo D/Current Activity: NormalActivity
05-13 08:37:03.839 18499-18499/com.foxdevelop.www.lifedemo D/Current Activity: Activity3
05-13 08:38:11.104 18499-18499/com.foxdevelop.www.lifedemo D/Current Activity: NormalActivity

One-Click App Exit

If we are on the third activity and want to exit the app, we need to press back three times. This is inconvenient

Pressing Home does not exit the app; it only suspends it.

So how do we implement one-click app exit?

We can create a dedicated collection class to manage all activities.

Add an activity manager to handle this task

This is a collection class containing a list to store all activities. It provides add and remove methods to add or delete single activities in the list

Then inside the base Activity, call add in onCreate and remove in onDestroy

This ensures the list only keeps activities currently on the back stack

Because the list holds references to each activity, calling finish() on them works directly on those activity instances.

Then add a finishAll method to the collection class

In this method, use a foreach loop and call finish() for each activity respectively

Let’s test this below

Wrap finishAll as a static method.

To make sure the app exits fully, we can use the system killProcess method to terminate the current app process.

android.os.Process.KillProcess(android.os.Process.myPid());

Activity Manager Class

package com.foxdevelop.www.lifedemo;
import android.app.Activity;
import java.security.PublicKey;
import java.util.ArrayList;
import java.util.List;
public class ActivityHelper {
    public  static List<Activity> activities = new ArrayList<Activity>();
    public static void add (Activity a)
    {
        activities.add(a);
    }
    public static void remove (Activity a)
    {
        activities.remove(a);
    }
    public  static void finishAll()
    {
        for (Activity a:activities)
        {
            a.finish();
        }
    }
}Code language: JavaScript (javascript)

Add and Remove Activities in Base Activity

Add activity when it is created: onCreate

Remove activity when it gets destroyed: onDestroy

package com.foxdevelop.www.lifedemo;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
public class BaseActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("Current Activity",getClass().getSimpleName());
        ActivityHelper.add(this);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityHelper.remove(this);
    }
}Code language: JavaScript (javascript)

Add Button in Activity3 to Call finishAll Method

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Third Activity" />
    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Exit App" />
</LinearLayout>Code language: HTML, XML (xml)

public class Activity3 extends BaseActivity {
    private static final String TAG = "Third Activity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_3);
        Log.e(TAG, "" + getTaskId());
        Button b = (Button)findViewById(R.id.button);
        b.setOnClickListener(
                new View.OnClickListener(){
                    @Override
                    public void onClick(View view){
                        ActivityHelper.finishAll();
                    }
                }
        );
    }
}Code language: PHP (php)