关于Android屏幕横竖之间的切换，研究心得。

之前有人提到过Android屏幕横竖之间的切换，大部分都说是在为设置configchanges之前，竖屏切换横屏Activity的生命周期是：onSaveInstanceState-->onPause-->onStop-->

onDestroy-->onCreate-->onStart-->onRestoreInstanceState-->onResume-->

当横屏再切换成竖屏时：会调用两次上述过程：

onSaveInstanceState-->
onPause-->
onStop-->
onDestroy-->
onCreate-->
onStart-->
onRestoreInstanceState-->
onResume-->
onSaveInstanceState-->
onPause-->
onStop-->
onDestroy-->
onCreate-->
onStart-->
onRestoreInstanceState-->
onResume-->

等等之类的。我就不多说了。

古画说的好，jue知此事要躬行，so：

下面是我自己的研究结果：

代码先呈上：

MainActivity.java

package com.example.liferecycletest;import android.app.Activity;import android.content.res.Configuration;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.TextView;public class MainActivity extends Activity {public static final String TAG = "LifeRecycleTest";TextView tv = null;TextView tv_ = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);showLog("onCreate");tv = (TextView) findViewById(R.id.hello);tv_ = (TextView) findViewById(R.id.hello_);findViewById(R.id.btn).setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stubtv.setText("Just Changed");tv_.setText("Just Changed");}});}public void showLog(String info) {Log.e(TAG, info);}@Overrideprotected void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();showLog("onDestroy");}@Overrideprotected void onPause() {// TODO Auto-generated method stubsuper.onPause();showLog("onPause");}@Overrideprotected void onRestart() {// TODO Auto-generated method stubsuper.onRestart();showLog("onRestart");}@Overrideprotected void onRestoreInstanceState(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onRestoreInstanceState(savedInstanceState);if (savedInstanceState != null) {tv.setText(savedInstanceState.getString("text"));}showLog("onResoreInstanceState");}@Overrideprotected void onResume() {// TODO Auto-generated method stubsuper.onResume();showLog("onResume");}@Overrideprotected void onSaveInstanceState(Bundle outState) {// TODO Auto-generated method stubsuper.onSaveInstanceState(outState);showLog("onSaceInstanceState");outState.putString("text", "Just Change");}@Overridepublic void onConfigurationChanged(Configuration newConfig) {// TODO Auto-generated method stubsuper.onConfigurationChanged(newConfig);showLog("onConfigurationChanged");}@Overrideprotected void onStart() {// TODO Auto-generated method stubsuper.onStart();showLog("onStart");}@Overrideprotected void onStop() {// TODO Auto-generated method stubsuper.onStop();showLog("onStop");}}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.liferecycletest"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="8"        android:targetSdkVersion="21" />    <application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name=".MainActivity"            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>

现在很情况说下：

A.在没有设置configchanges的情况下：

竖——>横屏幕的切换Log：

横——>竖屏幕切换Log：

可以发现这两个是一样的，刚看到有人说不一样当时就想不通了，

完全等价的过程，Android为什么要设计的不一样呢。亲自实验一下发现是一样的。

B.经过本人发现，必须在configchanges中设置”orientation|screenSize“同时存在，这个时候，不管怎么切换Activity都不会重新创建，走之前的流程了，只是会调用onConfigurationChanged()函数而已：

亲自实验就是这样了，欢迎大家指正。