Android 自动旋转屏幕快捷开关，系统会发送广播吗？

Question

就是下图这里的自动旋转屏幕开关，开启和关闭自动旋转系统会发送广播吗？什么广播？怎么监听它的状态改变？

Answer 1

屏幕旋转开关：
1). 屏幕旋转开关设置主要调用android.provider.Settings.System的putInt和getInt方法实现。

  2). 通过ContentObserver来动态观察屏幕旋转设置的改变。

     示例代码如下：

package com.example.srs;

import android.app.Activity;

import android.content.ContentResolver;

import android.content.Context;

import android.database.ContentObserver;

import android.net.Uri;

import android.os.Bundle;

import android.os.Handler;

import android.provider.Settings;

import android.provider.Settings.SettingNotFoundException;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class ScreenRotationSwitch extends Activity implements OnClickListener

{

private Button mRotationButton;

private RotationObserver mRotationObserver;  
/** Called when the activity is first created. */  
@Override  
public void onCreate(Bundle savedInstanceState)  
{  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.main);  
    //创建观察类对象  
    mRotationObserver = new RotationObserver(new Handler());  

    mRotationButton = (Button) findViewById(R.id.rotation);  
    refreshButton();  
    mRotationButton.setOnClickListener(this);  
}  


@Override  
protected void onDestroy() {  
    // TODO Auto-generated method stub  
    super.onDestroy();  
    //解除观察变化  
    mRotationObserver.stopObserver();  
}  


@Override  
protected void onResume() {  
    // TODO Auto-generated method stub  
    super.onResume();  
    //注册观察变化  
    mRotationObserver.startObserver();  
}  


//更新按钮状态  
private void refreshButton()  
{  
    if (getRotationStatus(this) == 1)  
    {  
        mRotationButton.setText(R.string.rotation_off);  
    }  
    else  
    {  
        mRotationButton.setText(R.string.rotation_on);  
    }  
}  

//得到屏幕旋转的状态  
private int getRotationStatus(Context context)  
{  
    int status = 0;  
    try  
    {  
        status = android.provider.Settings.System.getInt(context.getContentResolver(),  
                android.provider.Settings.System.ACCELEROMETER_ROTATION);  
    }  
    catch (SettingNotFoundException e)  
    {  
        // TODO Auto-generated catch block  
        e.printStackTrace();  
    }  
    return status;  
}  

private void setRotationStatus(ContentResolver resolver, int status)  
{  
    //得到uri  
    Uri uri = android.provider.Settings.System.getUriFor("accelerometer_rotation");  
    //沟通设置status的值改变屏幕旋转设置  
    android.provider.Settings.System.putInt(resolver, "accelerometer_rotation", status);  
    //通知改变  
    resolver.notifyChange(uri, null);  
}  

@Override  
public void onClick(View v)  
{  
    // TODO Auto-generated method stub  

    if (getRotationStatus(this) == 1)  
    {  

        setRotationStatus(getContentResolver(), 0);  
    }  
    else  
    {  
        setRotationStatus(getContentResolver(), 1);  
    }  
}  

//观察屏幕旋转设置变化，类似于注册动态广播监听变化机制  
private class RotationObserver extends ContentObserver  
{  
    ContentResolver mResolver;  

    public RotationObserver(Handler handler)   
    {  
        super(handler);  
        mResolver = getContentResolver();  
        // TODO Auto-generated constructor stub  
    }  

    //屏幕旋转设置改变时调用  
    @Override  
    public void onChange(boolean selfChange)   
    {  
        // TODO Auto-generated method stub  
        super.onChange(selfChange);  
        //更新按钮状态  
        refreshButton();  
        Toast.makeText(ScreenRotationSwitch.this, "旋转屏幕设置有变化",  
                Toast.LENGTH_SHORT).show();  
    }  

    public void startObserver()  
    {  
        mResolver.registerContentObserver(Settings.System  
                .getUriFor(Settings.System.ACCELEROMETER_ROTATION), false,  
                this);  
    }  

    public void stopObserver()  
    {  
        mResolver.unregisterContentObserver(this);  
    }  
}  

}

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