文章目录
Hide the navigation bar
This lesson describes how to hide the navigation bar, which was introduced in Android 4.0 (API level 14).
Even though this lesson focuses on hiding the navigation bar, you should design your app to hide the status bar at the same time, as described in Hiding the Status Bar. Hiding the navigation and status bars (while still keeping them readily accessible) lets the content use the entire display space, thereby providing a more immersive user experience.
Figure 1. Navigation bar.
Hide the Navigation Bar
You can hide the navigation bar using the SYSTEM_UI_FLAG_HIDE_NAVIGATION flag. This snippet hides both the navigation bar and the status bar:
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
Note the following:
- With this approach, touching anywhere on the screen causes the navigation bar (and status bar) to reappear and remain visible. The user interaction causes the flags to be be cleared.
- Once the flags have been cleared, your app needs to reset them if you want to hide the bars again. See Responding to UI Visibility Changes for a discussion of how to listen for UI visibility changes so that your app can respond accordingly.
- Where you set the UI flags makes a difference. If you hide the system bars in your activity’s
onCreate()method and the user presses Home, the system bars will reappear. When the user reopens the activity,onCreate()won’t get called, so the system bars will remain visible. If you want system UI changes to persist as the user navigates in and out of your activity, set UI flags inonResume()oronWindowFocusChanged(). - The method
setSystemUiVisibility()only has an effect if the view you call it from is visible. - Navigating away from the view causes flags set with
setSystemUiVisibility()to be cleared.
Make Content Appear Behind the Navigation Bar
On Android 4.1 and higher, you can set your application’s content to appear behind the navigation bar, so that the content doesn’t resize as the navigation bar hides and shows. To do this, use SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION. You may also need to use SYSTEM_UI_FLAG_LAYOUT_STABLE to help your app maintain a stable layout.
When you use this approach, it becomes your responsibility to ensure that critical parts of your app’s UI don’t end up getting covered by system bars. For more discussion of this topic, see the Hiding the Status Bar lesson.
准备
IDE：
Android Studio 4.1.1
Build #AI-201.8743.12.41.6953283, built on November 5, 2020
Runtime version: 1.8.0_242-release-1644-b01 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0
Android Virtual Devices：
Name: Pixel_2_API_28
CPU/ABI: Google Play Intel Atom (x86)
Path: C:\Users\86188\.android\avd\Pixel_2_API_28.avd
Target: google_apis_playstore [Google Play] (API level 28)
Skin: pixel_2
SD Card: 512M
fastboot.chosenSnapshotFile:
runtime.network.speed: full
hw.accelerometer: yes
hw.device.name: pixel_2
hw.lcd.width: 1080
hw.initialOrientation: Portrait
image.androidVersion.api: 28
tag.id: google_apis_playstore
hw.mainKeys: no
hw.camera.front: emulated
avd.ini.displayname: Pixel 2 API 28
hw.gpu.mode: auto
hw.ramSize: 1536
PlayStore.enabled: true
fastboot.forceColdBoot: no
hw.cpu.ncore: 4
hw.keyboard: yes
hw.sensors.proximity: yes
hw.dPad: no
hw.lcd.height: 1920
vm.heapSize: 256
skin.dynamic: yes
hw.device.manufacturer: Google
hw.gps: yes
hw.audioInput: yes
image.sysdir.1: system-images\android-28\google_apis_playstore\x86\
showDeviceFrame: yes
hw.camera.back: virtualscene
AvdId: Pixel_2_API_28
hw.lcd.density: 420
hw.arc: false
hw.device.hash2: MD5:55acbc835978f326788ed66a5cd4c9a7
fastboot.forceChosenSnapshotBoot: no
fastboot.forceFastBoot: yes
hw.trackBall: no
hw.battery: yes
hw.sdCard: yes
tag.display: Google Play
runtime.network.latency: none
disk.dataPartition.size: 6442450944
hw.sensors.orientation: yes
avd.ini.encoding: UTF-8
hw.gpu.enabled: yes
注意：以下示例仅在安卓虚拟设备上运行测试，并没有在真实的设备上运行测试。
项目
效果：
新建项目，选择 Empty Activity，在配置项目时，Minimum SDK 选择 API 16: Android 4.1 (Jelly Bean)
编辑 src\main\res\layout\activity_main.xml 布局文件，添加 Toolbar 和 Button 组件：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary"
android:minHeight="?attr/actionBarSize"
android:theme="?attr/actionBarTheme"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginBottom="32dp"
android:text="Make Content Appear Behind the Navigation Bar"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
编辑 MainActivity 文件：
-
初始化
Toolbar（第 18 ~ 19 行）； -
为按钮绑定点击事件，当用户点击按钮之后，将
MainActivity置于 Statu Bar 和 Navigation Bar 之后（第 21 ~ 35 行）； -
重写
onResume()方法，添加隐藏 Status Bar 和 Navigation Bar 代码（第 38 ~ 52 行）。注意：当用户点击屏幕任意一处，Status Bar 和 Navigation Bar 都将重现。
package com.mk;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// On Android 4.1 and higher, you can set your application's content
// to appear behind the navigation bar, so that the content
// doesn't resize as the navigation bar hides and shows.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_STABLE;
decorView.setSystemUiVisibility(uiOptions);
}
}
});
}
@Override
protected void onResume() {
super.onResume();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
}
}
}