Android Framework 常见解决方案（27）USB默认充电模式改为默认MTP模式

1 原理说明

默认usb模式设置为充电模式，这里本质上是在文件UsbDeviceManager.java中设置一个值UsbManager.FUNCTION_NONE，将关键位置的该值修改为UsbManager.FUNCTION_MTP，将其调整为MTP模式即可。

2 修改方案（Android S）

修改文件为：

$AOSP/frameworks/base/services/usb/java/com/android/server/usb/UsbDeviceManager.java中，

修改内容为：

//...
abstract static class UsbHandler extends Handler {

        // current USB state
        private boolean mHostConnected;
        private boolean mSourcePower;
        private boolean mSinkPower;
        private boolean mConfigured;
        private boolean mAudioAccessoryConnected;
        private boolean mAudioAccessorySupported;

        private UsbAccessory mCurrentAccessory;
        private int mUsbNotificationId;
        private boolean mAdbNotificationShown;
        private boolean mUsbCharging;
        private boolean mHideUsbNotification;
        private boolean mSupportsAllCombinations;
        private boolean mScreenLocked;
        private boolean mSystemReady;
        private Intent mBroadcastedIntent;
        private boolean mPendingBootBroadcast;
        private boolean mAudioSourceEnabled;
        private boolean mMidiEnabled;
        private int mMidiCard;
        private int mMidiDevice;
	//...
	@Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_UPDATE_STATE:
                    mConnected = (msg.arg1 == 1);
                    mConfigured = (msg.arg2 == 1);

                    updateUsbNotification(false);
                    updateAdbNotification(false);
                    if (mBootCompleted) {
                        updateUsbStateBroadcastIfNeeded(getAppliedFunctions(mCurrentFunctions));
                    }
                    if ((mCurrentFunctions & UsbManager.FUNCTION_ACCESSORY) != 0) {
                        updateCurrentAccessory();
                    }
                    if (mBootCompleted) {
                        if (!mConnected && !hasMessages(MSG_ACCESSORY_MODE_ENTER_TIMEOUT)
                                && !hasMessages(MSG_FUNCTION_SWITCH_TIMEOUT)) {
                            // restore defaults when USB is disconnected
                            if (!mScreenLocked
                                    && mScreenUnlockedFunctions != UsbManager.FUNCTION_NONE) {
                                setScreenUnlockedFunctions();
                            } else {
-                                setEnabledFunctions(UsbManager.FUNCTION_NONE, false);
+                                setEnabledFunctions(UsbManager.FUNCTION_MTP, false);
                            }
                        }
                        updateUsbFunctions();
                    } else {
                        mPendingBootBroadcast = true;
                    }
                    updateUsbSpeed();
                    break;
                    //...
                case MSG_INCREASE_SENDSTRING_COUNT: {
                    mSendStringCount = mSendStringCount + 1;
                }
            }
	}
        protected void finishBoot() {
            if (mBootCompleted && mCurrentUsbFunctionsReceived && mSystemReady) {
                if (mPendingBootBroadcast) {
                    updateUsbStateBroadcastIfNeeded(getAppliedFunctions(mCurrentFunctions));
                    mPendingBootBroadcast = false;
                }
                if (!mScreenLocked
                        && mScreenUnlockedFunctions != UsbManager.FUNCTION_NONE) {
                    setScreenUnlockedFunctions();
                } else {
-                    setEnabledFunctions(UsbManager.FUNCTION_NONE, false);
+                    setEnabledFunctions(UsbManager.FUNCTION_MTP, false);
                }
                if (mCurrentAccessory != null) {
                    mUsbDeviceManager.getCurrentSettings().accessoryAttached(mCurrentAccessory);
                    broadcastUsbAccessoryHandshake();
                }

                updateUsbNotification(false);
                updateAdbNotification(false);
                updateUsbFunctions();
            }
        }
        //...
}