android - onCreateView method gets called when? and How many times in Activity life cycle?

Question

I wrote a little program looking like this:

package com.example.lifecycle;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class LifeLogger extends Activity {

    private String TAG = this.getClass().getName().toString();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_life_logger);
        Log.d(TAG,"onCreate event");
    }
    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG,"onResume event");
    }
    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG,"onPause event");
    }
    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG,"onStop event");
    }
    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d(TAG,"onRestart event");
    }
    @Override
    public View onCreateView(String name, Context context, AttributeSet attrs) {
        Log.d(TAG,"onCreateView event");
        return super.onCreateView(name, context, attrs);
    }
    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG,"onStart event");
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy event");
    }
}

Which is the main activity.

The LogCat is:

06-11 07:07:10.033: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.033: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.043: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.053: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.063: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.063: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.063: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.063: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.073: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.073: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.083: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.083: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.083: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.093: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.093: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.093: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.103: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.113: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.113: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.113: D/com.example.lifecycle.LifeLogger(600): onCreate event 06-11 07:07:10.113: D/com.example.lifecycle.LifeLogger(600): onStart event 06-11 07:07:10.113: D/com.example.lifecycle.LifeLogger(600): onResume event 06-11 07:07:10.193: D/com.example.lifecycle.LifeLogger(600): onCreateView event 06-11 07:07:10.223: D/gralloc_goldfish(600): Emulator without GPU emulation detected. 06-11 07:08:19.633: D/com.example.lifecycle.LifeLogger(600): onPause event 06-11 07:08:20.213: D/com.example.lifecycle.LifeLogger(600): onStop event 06-11 07:08:31.993: D/com.example.lifecycle.LifeLogger(600): onRestart event 06-11 07:08:31.993: D/com.example.lifecycle.LifeLogger(600): onStart event 06-11 07:08:31.993: D/com.example.lifecycle.LifeLogger(600): onResume event 06-11 07:08:51.073: D/com.example.lifecycle.LifeLogger(600): onPause event 06-11 07:08:52.963: D/com.example.lifecycle.LifeLogger(600): onStop event 06-11 07:08:54.043: D/com.example.lifecycle.LifeLogger(600): onDestroy event

What happened here? why is onCreateView is called so many times?

What is the timing of onCreateView?

Thanks.

update:

the xml inflated:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${packageName}.${activityClass}" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

the manifast:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.lifecycle"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="17" />

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

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

</manifest>

run on android api level 16

Answer 1

You have extended your class with Activity. That means your class' lifecycle would be as below.

So, onCreateView is not a lifecycle method for activity. It's just a member method which will be used for specified tasks as said in doc.

Standard implementation of android.view.LayoutInflater.Factory.onCreateView used when inflating with the LayoutInflater returned by getSystemService. This implementation does nothing and is for pre-android.os.Build.VERSION_CODES.HONEYCOMB apps. Newer apps should use onCreateView(View, String, Context, AttributeSet).

To rely on the call of onCreateView() in an Activity is bad programming.

If you were using Fragment extended to your class and have written onCreateView() method, then it would have been called only twice after your onAttach() and onDestroyView() if you are still on same fragment.

See this diagram.

Here, it's a method of lifecycle for Fragment.

So, you are testing with wrong assumptions. That's all!