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 {

	@Override
	protected 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);
		}
	}

	@Override
	protected void onStart() {
		super.onStart();

		System.out.println("onStart()");
	}

	@Override
	protected void onResume() {
		super.onResume();

		System.out.println("onResume()");
	}

	@Override
	protected void onPause() {
		super.onPause();

		System.out.println("onPause()");
	}

	@Override
	protected void onStop() {
		super.onStop();

		System.out.println("onStop()");
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();

		System.out.println("onDestroy()");
	}

	@Override
	protected void onRestart() {
		super.onRestart();

		System.out.println("onRestart()");
	}

	@Override
	protected void onSaveInstanceState(Bundle outState) {
		super.onSaveInstanceState(outState);

		outState.putInt("page", 50);

		System.out.println("onSaveInstanceState()");
	}

	@Override
	protected 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
	 */
	@Override
	public 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");
		}
	}

	@Override
	public 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>