任务：当电流低于16%的时候，关闭手电，并且在提醒用户不能打开。

监听电量，实现关闭手电
手电图标实现在FlashlightTile.java

监听电量，一般会使用广播，但是SystemUI BatteryController注册了电量广播，可以利用BatteryController里面有相关的操作监听，

当电量低于16%，不能打开手电筒，并弹出提示框
当电量低于16%，如果手电筒处于开启状态，关闭手电筒。
public class FlashlightTile extends QSTileImpl<BooleanState> implements
        FlashlightController.FlashlightListener , 
+        BatteryController.BatteryStateChangeCallback
        {

private final Icon mIcon = ResourceIcon.get(R.drawable.ic_signal_flashlight);
    private final FlashlightController mFlashlightController;

+    // add for PCAAO-1862
+    private int mLevel = 100;
+    private final int lowLevel = 16;
+    private final BatteryController mBatteryController;
+    // END.

public FlashlightTile(QSHost host) {
        super(host);
        mFlashlightController = Dependency.get(FlashlightController.class);
+        mBatteryController = Dependency.get(BatteryController.class);
    }

@Override
    public void handleSetListening(boolean listening) {
        Log.i("FlashlightTile","handleSetListening "+listening);
        if (listening) {
+           mFlashlightController.addCallback(this);
            mBatteryController.addCallback(this);
        } else {
            mFlashlightController.removeCallback(this);
+            mBatteryController.removeCallback(this);
        }
    }

@Override
    protected void handleClick() {
        if (ActivityManager.isUserAMonkey()) {
            return;
        }
+        // add for PCAAO-1862
+        boolean flashLightEnable = mFlashlightController.isEnabled();
+        if (!flashLightEnable && mLevel <= lowLevel) {
+            SystemUIDialog dialog = new SystemUIDialog(mContext);
+            dialog.setTitle(R.string.airplane_dlg_title);
+            dialog.setMessage(R.string.flash_light_dlg_msg);
+            dialog.setPositiveButton(R.string.yes, null);
+            //dialog.setNegativeButton(R.string.cancel, null);
+            dialog.setShowForAllUsers(true);
+            dialog.show();
+            return;
+        }
+        // END.

boolean newState = !mState.value;
        refreshState(newState);
        mFlashlightController.setFlashlight(newState);

}
+        @Override
+    public void onBatteryLevelChanged(int level, boolean pluggedIn, boolean charging) {
+        mLevel = level;
+
+       //if 
+       boolean flashLightEnable = mFlashlightController.isEnabled();
+       Log.i("FlashlightTile","flashLightEnable ,mState.value"+flashLightEnable+","+mState.value);
+       if (mLevel <= lowLevel && flashLightEnable && mState.value){
+           refreshState(false);
+           if(mFlashlightController!=null){
+             mFlashlightController.setFlashlight(false);
+           }
+       }
+    }

}