activity横屏竖屏的切换

原理：

其实总结起来,我们可以得到以下的一些结论

1、当内存不足(不容易模拟)、切屏时会调用onSaveInstanceState()、onRestoreInstanceState()方法

  对于onSaveInstanceState()方法

   1)用于保存临时性数据，在创建下一个Activity是调用

   2)在onPause()方法之前调用(这个很容易理解)

   3)保存的数据可以在onRestoreInstanceState()方法、onCreate()方法中取到

   4)数据的传递是这样子的。通过putInt(key,value)  存 [当然还可以用其他类型] ，

用过getInt(key)来取

2、横竖屏切换的时候：
竖屏到横屏：activity首先被销毁，在创建一个新的activity
横屏到竖屏：activity首先被销毁，再创建一个新的activity,再把该activity销毁，再创建一个新的activity.(是由于输入法的影响)

1)如果希望在切屏时只销毁1次activity和只创建一次activity,则可以在<activity>配上android:configChanges="orientation"

2)如果希望切屏时保留原来的哪一个activity不变,则可以这样配置

android:configChanges="orientation|keyboardHidden"

1、MainActivity

package com.njupt.activitylife;import android.os.Bundle;import android.app.Activity;import android.content.Intent;import android.content.res.Configuration;import android.view.Menu;import android.view.View;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);System.out.println("onCreate");if(savedInstanceState != null){int page = savedInstanceState.getInt("page");System.out.println("onCreate() page: " +page);}}@Overrideprotected void onStart() {super.onStart();System.out.println("onStart()");}@Overrideprotected void onResume() {super.onResume();    System.out.println("onResume()");}@Overrideprotected void onPause() {super.onPause();    System.out.println("onPause()");}@Overrideprotected void onStop() {super.onStop();    System.out.println("onStop()");}@Overrideprotected void onDestroy() {super.onDestroy();    System.out.println("onDestroy()");}@Overrideprotected void onRestart() {super.onRestart();System.out.println("onRestart()");}@Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);outState.putInt("page", 50);System.out.println("onSaveInstanceState()");}@Overrideprotected void onRestoreInstanceState(Bundle savedInstanceState) {super.onRestoreInstanceState(savedInstanceState);    int page = savedInstanceState.getInt("page");System.out.println("onRestoreInstanceState() page: " + page);}public void get(View v){Intent intent = new Intent(this,Main2Activity.class);startActivity(intent);}/** * 对横屏和竖屏进行一些特定的处理 */@Overridepublic void onConfigurationChanged(Configuration newConfig) {super.onConfigurationChanged(newConfig);    if(newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE){System.out.println("现在是横屏");}else if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){System.out.println("现在是竖屏");}}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}

2、AndroidManifest.xml

<activity            android:name="com.njupt.activitylife.MainActivity"            android:label="@string/app_name"             android:configChanges="orientation|keyboardHidden">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>