【Android代码片段之八】监听Android屏幕是否锁屏

实现方法：1）通过BroadcastReceiver接收广播Intent.ACTION_SCREEN_ON和Intent.ACTION_SCREEN_OFF可以判断屏幕状态是否锁屏，但是只有屏幕状态发生改变时才会发出广播；

2）如果要在屏幕状态发生改变之前就想获取屏幕状态，可以通过反射机制调用PowerManager的isScreenOn方法 。

具体实现，见代码：

实现Screen状态监听的类ScreenObserver，实现如下：

package com.isoft.screen;

import java.lang.reflect.Method;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.PowerManager;
import android.util.Log;

/**
 *
 * @author zhangyg
 *
 */
public class ScreenObserver{
    private static String TAG = "ScreenObserver";
    private Context mContext;
    private ScreenBroadcastReceiver mScreenReceiver;
    private ScreenStateListener mScreenStateListener;
    private static Method mReflectScreenState;

    public ScreenObserver(Context context){
        mContext = context;
        mScreenReceiver = new ScreenBroadcastReceiver();
        try {
            mReflectScreenState = PowerManager.class.getMethod("isScreenOn",
                    new Class[] {});
        } catch (NoSuchMethodException nsme) {
            Log.d(TAG, "API < 7," + nsme);
        }
    }

    /**
     * screen状态广播接收者
     * @author zhangyg
     *
     */
    private class ScreenBroadcastReceiver extends BroadcastReceiver{
        private String action = null;
        @Override
        public void onReceive(Context context, Intent intent) {
            action = intent.getAction();
            if(Intent.ACTION_SCREEN_ON.equals(action)){
                mScreenStateListener.onScreenOn();
            }else if(Intent.ACTION_SCREEN_OFF.equals(action)){
                mScreenStateListener.onScreenOff();
            }
        }
    }


    /**
     * 请求screen状态更新
     * @param listener
     */
    public void requestScreenStateUpdate(ScreenStateListener listener) {
        mScreenStateListener = listener;
        startScreenBroadcastReceiver();

        firstGetScreenState();
    }

    /**
     * 第一次请求screen状态
     */
    private void firstGetScreenState(){
        PowerManager manager = (PowerManager) mContext
                .getSystemService(Activity.POWER_SERVICE);
        if (isScreenOn(manager)) {
            if (mScreenStateListener != null) {
                mScreenStateListener.onScreenOn();
            }
        } else {
            if (mScreenStateListener != null) {
                mScreenStateListener.onScreenOff();
            }
        }
    }

    /**
     * 停止screen状态更新
     */
    public void stopScreenStateUpdate(){
        mContext.unregisterReceiver(mScreenReceiver);
    }

    /**
     * 启动screen状态广播接收器
     */
    private void startScreenBroadcastReceiver(){
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        mContext.registerReceiver(mScreenReceiver, filter);
    }

    /**
     * screen是否打开状态
     * @param pm
     * @return
     */
    private static boolean isScreenOn(PowerManager pm) {
        boolean screenState;
        try {
            screenState = (Boolean) mReflectScreenState.invoke(pm);
        } catch (Exception e) {
            screenState = false;
        }
        return screenState;
    }

    public interface ScreenStateListener {
        public void onScreenOn();
        public void onScreenOff();
    }
}

测试ScreenObserver功能的示例类ScreenObserverActivity，实现如下：

package com.isoft.screen;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.isoft.screen.ScreenObserver.ScreenStateListener;

public class ScreenObserverActivity extends Activity {
    private String TAG = "ScreenObserverActivity";
    private ScreenObserver mScreenObserver;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mScreenObserver = new ScreenObserver(this);
        mScreenObserver.requestScreenStateUpdate(new ScreenStateListener() {
            @Override
            public void onScreenOn() {
                doSomethingOnScreenOn();
            }

            @Override
            public void onScreenOff() {
                doSomethingOnScreenOff();
            }
        });
    }

    private void doSomethingOnScreenOn() {
        Log.i(TAG, "Screen is on");
    }

    private void doSomethingOnScreenOff() {
        Log.i(TAG, "Screen is off");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //停止监听screen状态
        mScreenObserver.stopScreenStateUpdate();
    }
}
http://blog.csdn.net/m_changgong/article/details/7608911