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。