android转屏,切换屏幕,横竖屏(onConfigurationChanged)会重新加载 OnCreate 的解决方案

在以前的版本中只要在AndroidManifest.xml文件中对activity指定android:configChanges="keyboardHidden|orientation"属性,转屏的时候就会不再重新调用OnCreate()函数,而是调用onConfigurationChanged()。

但是在自从android3.2以后,再这样设置的话,会发现转屏后仍然会调用OnCreate(),而不是onConfigurationChanged();跟踪framework层代码,就会发现问题所在,是由于google在android3.2中添加了screensize改变的通知,在转屏的时候,不仅是orientation发生了改变,screensize同样也发生了改变,而在判断是调用onConfigurationChanged还是OnCreate时,采用的是如下判断:

int diff = activity.mCurrentConfig.diff(config);

if (diff != 0) {

// If this activity doesn't handle any of the config changes then don't bother calling onConfigurationChanged as we'regoing to destroy it.

if ((~activity.mActivityInfo.getRealConfigChanged() & diff) == 0) {

shouldChangeConfig = true;

}

}

public int getRealConfigChanged() {

return applicationInfo.targetSdkVersion < android.os.Build.VERSION_CODES.HONEYCOMB_MR2 ? (configChanges | ActivityInfo.CONFIG_SCREEN_SIZE

| ActivityInfo.CONFIG_SMALLEST_SCREEN_SIZE) : configChanges;

}

通过上面的分析,可发现有两种方法解决该问题:(只需要修改AndroidManifest.xml)

1.指定android:configChanges="keyboardHidden|orientation|screenSize",其他的代码和以前的代码一样处理;

2.在AndroidManifest.xml中指定targetSdkVersion为3.2以前的版本(3.2的版本号为13),系统会自动加上screenSize属性值。

比如:<uses-sdk android:minSdkVersion="3" android:targetSdkVersion="12" />

建议使用第一种方法

 

如下我写一个例子程序:

package com.configuration;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class ConfigurationActivity extends Activity {
 
 EditText et;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        et = (EditText) findViewById(R.id.et);
        Button bt = (Button) findViewById(R.id.bt);
        bt.setOnClickListener(new OnClickListener() {
   
   @Override
   public void onClick(View v) {
    if(ConfigurationActivity.this.getRequestedOrientation() == -1){
     Toast.makeText(ConfigurationActivity.this, "系统的屏幕方无法获取", Toast.LENGTH_LONG).show();
    }else {
     if(ConfigurationActivity.this.getRequestedOrientation() == ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE){
      ConfigurationActivity.this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
     }else if(ConfigurationActivity.this.getRequestedOrientation() == ActivityInfo.SCREEN_ORIENTATION_PORTRAIT){
      ConfigurationActivity.this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
     }
    }
   }
  });
    }
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
     Toast.makeText(this, "系统的屏幕方向发生改变", Toast.LENGTH_LONG).show();
     switch (getRequestedOrientation()) {
  case ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE:
   et.setText("当前屏幕朝向为:LANDSCAPE");
   break;
  case ActivityInfo.SCREEN_ORIENTATION_PORTRAIT:
   et.setText("当前屏幕朝向为:PORTRAIT");
   break;
  default:
   break;
  }
     super.onConfigurationChanged(newConfig);
    }
}

 

AndroidManifest.xml文件:

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

    <uses-sdk android:minSdkVersion="15" />
 <uses-permission android:name="android.permission.CHANGE_CONFIGURATION"/>
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".ConfigurationActivity"
            android:label="@string/app_name"
            android:screenOrientation="portrait"
            android:configChanges="keyboardHidden|orientation|screenSize">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

 

 

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