[移动开发]Android SystemUI 导航栏动态显示隐藏

本文实现导航栏动态显示隐藏功能。代码基于Android 9.0修改，Android 11 上代码结构有所不同，大的流程差不多，也可以参考本文。

1、导航栏创建加载及隐藏：

?frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java

    ...
        try {
            // boolean showNav = mWindowManagerService.hasNavigationBar();
            // 添加自定义控制状态栏的 Settings.system 属性值,控制初始化时是否创建状态栏
            boolean showNav = Settings.system.getInt(mContext.getContentResolver(), "nav_bar_mode", 0) == 0;
            // 注册属性值变化监听
            mContext.getContentResolver().registerContentObserver(
                    Settings.System.getUriFor("nav_bar_mode"), false, new SettingsObserver(mHandler), UserHandle.USER_ALL);

            if (DEBUG) Log.v(TAG, "hasNavigationBar=" + showNav);
            if (showNav) {
                createNavigationBar();
            }
        } catch (RemoteException ex) {
            // no window manager? good luck with that
        }
    ...

    // 自定义 nav_bar_mode 属性值的监听
    private final class SettingsObserver extends ContentObserver {
        public SettingsObserver(Handler handler) {
            super(handler);
        }

        @Override
        public void onChange(boolean selfChange, Uri uri) {
            int navMode = Settings.Secure.getInt(mContext.getContentResolver(), "nav_bar_mode", 0);
            Log.i("TAG", "navMode = " + navMode);
            switch (navMode) {
                case 0:
                    createNavigationBar();
                    break;

                case 1:
                    mContext.getSystemService(WindowManager.class).removeView(mNavigationBarView);
                    break;

                default:
                    Log.w(TAG, "Unknown mode");
                    break;
            }
        }
    }

?这里主要了解导航栏的加载是由系统的?WindowManager 加载，通过addView进行加载显示，所以我们也可以通过 removeView 去进行删除隐藏。

2、加载 view 的源码：

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java

    public static View create(Context context, FragmentListener listener) {
        WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
                LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT,
                WindowManager.LayoutParams.TYPE_NAVIGATION_BAR,
                WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
                        | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                        | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                        | WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH
                        | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
                        | WindowManager.LayoutParams.FLAG_SLIPPERY,
                PixelFormat.TRANSLUCENT);
        lp.token = new Binder();
        lp.setTitle("NavigationBar");
        lp.accessibilityTitle = context.getString(R.string.nav_bar);
        lp.windowAnimations = 0;
        View navigationBarView = LayoutInflater.from(context).inflate(
                R.layout.navigation_bar_window, null);
        if (DEBUG) Log.v(TAG, "addNavigationBar: about to add " + navigationBarView);
        if (navigationBarView == null) return null;
        context.getSystemService(WindowManager.class).addView(navigationBarView, lp);
        FragmentHostManager fragmentHost = FragmentHostManager.get(navigationBarView);
        NavigationBarFragment fragment = new NavigationBarFragment();
        fragmentHost.getFragmentManager().beginTransaction()
                .replace(R.id.navigation_bar_frame, fragment, TAG)
                .commit();
        fragmentHost.addTagListener(TAG, listener);
        return navigationBarView;
    }

主要就是?context.getSystemService(WindowManager.class).addView(navigationBarView, lp); 这句。