文章目录

• Hide the status bar
• • Hide the Status Bar on Android 4.1 and Higher
  • Make Content Appear Behind the Status Bar
• 准备
• 项目
• 参考

Hide the status bar

This lesson describes how to hide the status bar on different versions of Android. Hiding the status bar (and optionally, the navigation bar) lets the content use more of the display space, thereby providing a more immersive user experience.

Figure 1 shows an app with a visible status bar:

Figure 1. Visible status bar.

Figure 2 shows an app with a hidden status bar. Note that the action bar is hidden too. You should never show the action bar without the status bar.

Figure 2. Hidden status bar.

Hide the Status Bar on Android 4.1 and Higher

You can hide the status bar on Android 4.1 (API level 16) and higher by using setSystemUiVisibility(). setSystemUiVisibility() sets UI flags at the individual view level; these settings are aggregated to the window level. Using setSystemUiVisibility() to set UI flags gives you more granular control over the system bars than using WindowManager flags. This snippet hides the status bar:

View decorView = getWindow().getDecorView();
// Hide the status bar.
int uiOptions = View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
// Remember that you should never show the action bar if the
// status bar is hidden, so hide that too if necessary.
ActionBar actionBar = getActionBar();
actionBar.hide();

Note the following:

• Once UI flags have been cleared (for example, by navigating away from the activity), 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 in onResume() or onWindowFocusChanged().
• 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 Status Bar

On Android 4.1 and higher, you can set your application’s content to appear behind the status bar, so that the content doesn’t resize as the status bar hides and shows. To do this, use SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN. 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 (for example, the built-in controls in a Maps application) don’t end up getting covered by system bars. This could make your app unusable. In most cases you can handle this by adding the android:fitsSystemWindows attribute to your XML layout file, set to true. This adjusts the padding of the parent ViewGroup to leave space for the system windows. This is sufficient for most applications.

In some cases, however, you may need to modify the default padding to get the desired layout for your app. To directly manipulate how your content lays out relative to the system bars (which occupy a space known as the window’s “content insets”), override fitSystemWindows(Rect insets). The fitSystemWindows() method is called by the view hierarchy when the content insets for a window have changed, to allow the window to adjust its content accordingly. By overriding this method you can handle the insets (and hence your app’s layout) however you want.

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)

新建 Empty Activity，名名 SecondaryActivity。

编辑 src\main\java\com\mk\SecondaryActivity.java 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=".SecondaryActivity">

    <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/buttonMakeContentAppearBehindTheStatusBar"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Make Content Appear Behind the Status Bar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar" />
</androidx.constraintlayout.widget.ConstraintLayout>

编辑 SecondaryActivity 文件：

1. 初始化 Toolbar（第 18 ~ 19 行）；
2. 启用 Toolbar 的向上按钮（第 23 行）；
3. 为 ID 为 buttonMakeContentAppearBehindTheStatusBar 的按钮绑定点击事件，当用户点击按钮之后，将 SecondaryActivity 置于 Statu Bar 之后（第 25 ~ 35 行）。

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 SecondaryActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_secondary);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        // Get a support ActionBar corresponding to this toolbar,
        // and then enable the Up button
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        Button buttonMakeContentAppearBehindTheStatusBar = (Button) findViewById(R.id.buttonMakeContentAppearBehindTheStatusBar);
        buttonMakeContentAppearBehindTheStatusBar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                    // Make Content Appear Behind the Status Bar
                    View decorView = getWindow().getDecorView();
                    decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
                }
            }
        });
    }
}

编辑 src\main\res\layout\activity_main.xml 布局文件，添加一个 Toolbar 和两个 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/buttonHideTheStatusBar"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Hide the status bar "
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar" />

    <Button
        android:id="@+id/buttonToSecondaryActivity"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="To secondary activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/buttonHideTheStatusBar" />
</androidx.constraintlayout.widget.ConstraintLayout>

编辑 MainActivity：

1. 初始化 Toolbar（第 19 ~ 20 行）；
2. 为 ID 为 buttonHideTheStatusBar 的按钮绑定点击事件，当用户点击按钮之后，隐藏 Statu Bar 和 ActionBar（第 22 ~ 35 行）；
3. 为 ID 为 buttonToSecondaryActivity 的按钮绑定点击事件，当用户点击按钮之后，跳转到 SecondaryActivity（第 37 ~ 44 行）。

package com.mk;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.content.Intent;
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 buttonHideTheStatusBar = (Button) findViewById(R.id.buttonHideTheStatusBar);
        buttonHideTheStatusBar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                    // Hide the status bar.
                    View decorView = getWindow().getDecorView();
                    decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_FULLSCREEN);
                    // Remember that you should never show the action bar if the
                    // status bar is hidden, so hide that too if necessary.
                    getSupportActionBar().hide();
                }
            }
        });

        Button buttonToSecondaryActivity = (Button) findViewById(R.id.buttonToSecondaryActivity);
        buttonToSecondaryActivity.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, SecondaryActivity.class);
                startActivity(intent);
            }
        });
    }
}

编辑 src\main\AndroidManifest.xml 应用清单文件：

1. 修改 android:theme 的值为 @style/Theme.AppCompat.Light.NoActionBar，防止应用程序使用本地 ActionBar 类来提供应用程序栏（第 11 行）：
2. 为 SecondaryActivity 和 MainActivity 建立父子关系（第 12 ~ 14 行）。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mk">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar">
        <activity android:name=".SecondaryActivity" android:label="Secondary Activity" android:parentActivityName=".MainActivity">
            <meta-data android:name="android.support.PARENT_ACTIVITY" android:value=".MainActivity" />
        </activity>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

参考

Hide the status bar

Set up the app bar

Add an up action