在Android上为了实现全屏显示，透明状态栏，沉浸模式等效果，往往需要我们掌握和系统UI显示隐藏相关的各种Flag。Android上API版本混乱，各种Flag林立。今天我们就来聊聊这些Flags。

在Android Kitkat中引入Immersive Mode

imm-states.png

相关API

Window#setFlags

View#setSystemUiVisibility (Android 3.0开始提供)

相关Flag

WindowManager.LayoutParams.FLAG_FULLSCREEN

隐藏状态栏

View.SYSTEM_UI_FLAG_VISIBLE API 14

默认标记

View.SYSTEM_UI_FLAG_LOW_PROFILE API 14

低调模式, 会隐藏不重要的状态栏图标

View.SYSTEM_UI_FLAG_LAYOUT_STABLE API 16

保持整个View稳定, 常和控制System UI悬浮, 隐藏的Flags共用, 使View不会因为System UI的变化而重新layout

View.SYSTEM_UI_FLAG_FULLSCREEN API 16

状态栏隐藏，效果同设置WindowManager.LayoutParams.FLAG_FULLSCREEN

View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN API 16

视图延伸至状态栏区域，状态栏上浮于视图之上

View.SYSTEM_UI_FLAG_HIDE_NAVIGATION API 14

隐藏导航栏

View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION API 16

视图延伸至导航栏区域，导航栏上浮于视图之上

View.SYSTEM_UI_FLAG_IMMERSIVE API 19

沉浸模式, 隐藏状态栏和导航栏, 并且在第一次会弹泡提醒, 并且在状态栏区域滑动可以呼出状态栏(这样会系统会清楚之前设置的View.SYSTEM_UI_FLAG_FULLSCREEN或View.SYSTEM_UI_FLAG_HIDE_NAVIGATION标志)。使之生效，需要和View.SYSTEM_UI_FLAG_FULLSCREEN，View.SYSTEM_UI_FLAG_HIDE_NAVIGATION中的一个或两个同时设置。

View.SYSTEM_UI_FLAG_IMMERSIVE_STIKY API 19

与上面唯一的区别是, 呼出隐藏的状态栏后不会清除之前设置的View.SYSTEM_UI_FLAG_FULLSCREEN或View.SYSTEM_UI_FLAG_HIDE_NAVIGATION标志，在一段时间后将再次隐藏系统栏)

参考Reference

组合搭配上面的Flag，我们可以实现沉浸模式，透明状态栏等各种你想要的样子。

使用场景

透明状态栏

style_color_colorscheme_palette1_example.png

if (Build.VERSION.SDK_INT >= 21) {

View decorView = getWindow().getDecorView();

int option = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN

| View.SYSTEM_UI_FLAG_LAYOUT_STABLE;

decorView.setSystemUiVisibility(option);

getWindow().setStatusBarColor(Color.TRANSPARENT); //也可以设置成灰色透明的，比较符合Material Design的风格

}

全屏显示

View decorView = getWindow().getDecorView();

int option = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

| View.SYSTEM_UI_FLAG_FULLSCREEN;

decorView.setSystemUiVisibility(option);

沉浸模式(普通Immersive Mode)

imm-states.png

@Override

public void onWindowFocusChanged(boolean hasFocus) {

super.onWindowFocusChanged(hasFocus);

if (hasFocus && Build.VERSION.SDK_INT >= 19) {

View decorView = getWindow().getDecorView();

decorView.setSystemUiVisibility(

View.SYSTEM_UI_FLAG_LAYOUT_STABLE

| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION

| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN

| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

| View.SYSTEM_UI_FLAG_FULLSCREEN

| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);

}

}

沉浸模式(通过点击内容区域控制System UI的显示和隐藏)

import android.os.Handler;

import android.os.Message;

import android.support.v7.app.ActionBar;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.GestureDetector;

import android.view.LayoutInflater;

import android.view.MotionEvent;

import android.view.View;

public class MainActivity extends AppCompatActivity {

private static final int INITIAL_DELAY = 1500;

private View mDecorView;

private ActionBar mActionBar;

private View mContentView;

private Handler handler = new Handler(){

@Override

public void handleMessage(Message msg) {

hideSystemUI();

}

};

private GestureDetector gestureDetector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener(){

@Override

public boolean onSingleTapUp(MotionEvent e) {

if ((mDecorView.getSystemUiVisibility() & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0){

hideSystemUI();

}else {

showSystemUI();

}

return true;

}

});

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

mDecorView = getWindow().getDecorView();

mContentView = LayoutInflater.from(this).inflate(R.layout.activity_immersive, null);

setContentView(mContentView);

mDecorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener() {

@Override

public void onSystemUiVisibilityChange(int visibility) {

if ((visibility & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0){

//systemUI is visible

mActionBar.show();

}else {

//systemUI is invisible

mActionBar.hide();

}

}

});

mContentView.setOnTouchListener(new View.OnTouchListener() {

@Override

public boolean onTouch(View v, MotionEvent event) {

gestureDetector.onTouchEvent(event);

return true;

}

});

mActionBar = getSupportActionBar();

mActionBar.setShowHideAnimationEnabled(true);

showSystemUI();

}

@Override

public void onWindowFocusChanged(boolean hasFocus) {

super.onWindowFocusChanged(hasFocus);

if (hasFocus){

delayedHide(INITIAL_DELAY);

}else {

handler.removeMessages(0);

showSystemUI();

}

}

private void delayedHide(int delay){

handler.removeMessages(0);

handler.sendEmptyMessageDelayed(0, delay);

}

private void hideSystemUI(){

mDecorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE

|View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

|View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION

|View.SYSTEM_UI_FLAG_FULLSCREEN

|View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN

|View.SYSTEM_UI_FLAG_IMMERSIVE);

}

private void showSystemUI(){

mDecorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE

|View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION

|View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);

}

}