解决Android M上锁屏情况下，禁止PC通过MTP访问手机存储单元

1.问题解决主要文件:/m8976/packages/providers/MediaProvider/src/com/android/providers/media/MtpService.java

    需要在MtpService.java中updateDisabledStateLocked方法添加锁屏情况限制：

    final KeyguardManager keyguardManager = (KeyguardManager) getSystemService(

                Context.KEYGUARD_SERVICE);

    mMtpDisabled = (keyguardManager.isKeyguardLocked() && keyguardManager.isKeyguardSecure()) || !mUnlocked || !isCurrentUser;

    只要锁屏，mMtpDisabled就设置为true。

    这样就实现该功能。

2.当解锁时，自动加载手机存储单元：

    添加解锁监听

+    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {

+        @Override

+        public void onReceive(Context context, Intent intent) {

+            final String action = intent.getAction();

+            if (Intent.ACTION_USER_PRESENT.equals(action)) {

+                // If the media scanner is running, it may currently be calling

+                // sendObjectAdded/Removed, which also synchronizes on mBinder

+                // (and in addition to that, all the native MtpServer methods

+                // lock the same Mutex). If it happens to be in an mtp device

+                // write(), it may block for some time, so process this broadcast

+                // in a thread.

+                new Thread(new Runnable() {

+                    @Override

+                    public void run() {

+                        synchronized (mBinder) {

+                            // Unhide the storage units when the user has unlocked the lockscreen

+                            if (mMtpDisabled) {

+                                addStorageDevicesLocked();

+                                mMtpDisabled = false;

+                            }

+                        }

+                    }}, "addStorageDevices").start();

+            }

+        }

+    };

    Android M上发送解锁状态的广播code没有去除，可以查看/m8976/frameworks/base/packages/SystemUI/src/com/android       /systemui/keyguard/KeyguardViewMediator.java

    在KeyguardViewMediator.java文件中可以看出，在解锁时，发送Intent.ACTION_USER_PRESENT广播，然后在MtpService.java

    进行接收,对mMtpDisabled进行处理。