Using android taskaffinity

I read about taskaffinity and created a demo application with the following steps:

• AND
• B ===> taskaffinity, com.ando
• WITH
• D ===> taskaffinity, com.ando
• E

It is written that actions with the same task-secretness secretly open one instance of another.

So, I put the log onResume of each action to see the task id. If it creates one instance, then why doesn't it execute onResume of B when opening D and vice versa.

I read the developers site and other posts, but still have not figured out how to use taskaffinity and why use it, why shouldn't we use singleInstance instead?

manifest:

 <application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.danroid.taskaffinity.A"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <!-- android:taskAffinity="com.ando" -->
    <activity
        android:name="com.example.danroid.taskaffinity.B"
        android:label="@string/app_name"
        android:taskAffinity="@string/task_affinity" >
    </activity>
    <activity
        android:name="com.example.danroid.taskaffinity.C"
        android:label="@string/app_name" >
    </activity>
    <activity
        android:name="com.example.danroid.taskaffinity.D"
        android:label="@string/app_name"
        android:taskAffinity="@string/task_affinity" >
    </activity>
    <activity
        android:name="com.example.danroid.taskaffinity.E"
        android:label="@string/app_name" >
    </activity>
</application>