Activity实现自定义锁屏页的思路很简单，即在听书模式开启时，启动一个service，在service中监听系统SCREEN_OFF的广播。当屏幕熄灭时service监听到广播，开启一个锁屏页Activity在屏幕最上层显示，该Activity创建的同时会去掉系统的锁屏（如果有密码是禁不掉的）。示意图如下：

<serviceandroid:name=".service.LockScreenService"android:enabled="true"android:exported="true" />

package com.jack.applockscreen.service;import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.BitmapFactory;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.support.v4.app.NotificationCompat;
import android.widget.Toast;import com.jack.applockscreen.R;
import com.jack.applockscreen.activity.DetailActivity;
import com.jack.applockscreen.activity.LockScreenActivity;
import com.jack.applockscreen.receiver.LockScreenReceiver;public class LockScreenService extends Service {private LockScreenReceiver mReceiver;private IntentFilter mIntentFilter = new IntentFilter();private boolean isNotiShow = false;@Nullable@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic void onCreate() {super.onCreate();}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {//动态注册
        mIntentFilter.addAction(Intent.ACTION_BOOT_COMPLETED);mIntentFilter.addAction(Intent.ACTION_SCREEN_OFF);mIntentFilter.addAction(Intent.ACTION_SCREEN_ON);mIntentFilter.addAction(Intent.ACTION_TIME_TICK);mIntentFilter.setPriority(Integer.MAX_VALUE);if (null == mReceiver) {mReceiver = new LockScreenReceiver();mIntentFilter.setPriority(Integer.MAX_VALUE);registerReceiver(mReceiver, mIntentFilter);buildNotification();Toast.makeText(getApplicationContext(), "开启成功", Toast.LENGTH_LONG).show();}return START_STICKY;}/*** 通知栏显示*/private void buildNotification() {if (!isNotiShow){ //避免多次显示NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);Intent intent = new Intent(this, DetailActivity.class);PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);Notification notification = new NotificationCompat.Builder(this, "default").setTicker("APP正在运行").setAutoCancel(false).setContentTitle("APP正在运行").setContentText("运行中").setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher)).setSmallIcon(R.mipmap.ic_launcher).setContentIntent(pendingIntent).build();manager.notify(1, notification);startForeground(0x11, notification);isNotiShow = true;}}@Overridepublic void onDestroy() {if (mReceiver != null) {unregisterReceiver(mReceiver);mReceiver = null;}super.onDestroy();}
}

package com.jack.applockscreen.receiver;import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.telecom.TelecomManager;
import android.telephony.TelephonyManager;import com.jack.applockscreen.activity.LockScreenActivity;
import com.jack.applockscreen.util.Parser;public class LockScreenReceiver extends BroadcastReceiver {@Overridepublic void onReceive(Context context, Intent intent) {String action = intent.getAction();if (Intent.ACTION_SCREEN_OFF.equals(action)) {if (Parser.sPhoneCallState == TelephonyManager.CALL_STATE_IDLE) { // 手机状态为未来电的空闲状态// 判断锁屏界面是否已存在，如果已存在就先finish，防止多个锁屏出现if (!Parser.KEY_GUARD_INSTANCES.isEmpty()) {for (Activity activity : Parser.KEY_GUARD_INSTANCES) {activity.finish();}}Intent lockScreen = new Intent(context, LockScreenActivity.class);lockScreen.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);context.startActivity(lockScreen);}} else {Parser.killBackgroundProcess(context);}}
}

2) 启动Activity时Intent的Flag，如果不添加FLAG_ACTIVITY_NEW_TASK的标志位，会出现“Calling startActivity() from outside of an Activity”的运行时异常，因为我们是从Service启动的Activity。Activity要存在于activity的栈中，而Service在启动activity时必然不存在一个activity的栈，所以要新起一个栈，并装入启动的activity。使用该标志位时，也需要在AndroidManifest中声明taskAffinity，即新task的名称，否则锁屏Activity实质上还是在建立在原来App的task栈中。

下接：

[Android] Android 锁屏实现与总结 （二）