有三个步骤:

1)只需使用此代码段到你的OnCreate方法

  // FullScreen
  getWindow().setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS, 
  WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);

如果你正在使用Fragment，你应该把这个代码段放在你活动的OnCreate方法中。

2)确保在/res/values-v21/styles.xml中设置透明度:

<item name="android:statusBarColor">@android:color/transparent</item>

或者你可以通过编程来设置透明度:

getWindow().setStatusBarColor(Color.TRANSPARENT);

3)无论如何你都应该在styles.xml中添加代码段

<item name="android:windowTranslucentStatus">true</item>

注意:此方法仅适用于API 21及以上版本。

 <item name="android:statusBarColor" tools:targetApi="lollipop">@android:color/transparent</item>
            <!--<item name="android:windowLightStatusBar" tools:targetApi="m">true</item>-->

不要使用windowLightStatusBar，而是使用statusBarColor = @android:color/transparent

2022年最优雅的方案:

private fun hideStatusBar() {
    val windowInsetsController = ViewCompat.getWindowInsetsController(window.decorView) ?: return
    windowInsetsController.hide(WindowInsetsCompat.Type.statusBars())
}

下面的代码将创建一个完全透明的状态栏:

package com.demo;

import android.app.Activity;
import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

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

        if (Build.VERSION.SDK_INT >= 19 && Build.VERSION.SDK_INT < 21) {
            setWindowFlag(this, WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS, true);
        }
        if (Build.VERSION.SDK_INT >= 19) {
            getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        }
        if (Build.VERSION.SDK_INT >= 21) {
            setWindowFlag(this, WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS, false);
            getWindow().setStatusBarColor(Color.TRANSPARENT);
        }
    }

    public static void setWindowFlag(Activity activity, final int bits, boolean on) {
        Window win = activity.getWindow();
        WindowManager.LayoutParams winParams = win.getAttributes();
        if (on) {
            winParams.flags |= bits;
        } else {
            winParams.flags &= ~bits;
        }
        win.setAttributes(winParams);
    }
}

实现状态栏完全透明: 首先在themes.xml中创建自定义主题为

 <style name="QuiloThemeLight" parent="Theme.AppCompat.Light.NoActionBar">

Java:

    getWindow().clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
    getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
    getWindow().setStatusBarColor(Color.TRANSPARENT);

芬兰湾的科特林:

activity.window.apply {
        clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS)
        addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS)
        decorView.systemUiVisibility = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
        statusBarColor = Color.TRANSPARENT
    }

您可以使用下面的代码。

getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN); 
getWindow().setStatusBarColor(Color.TRANSPARENT);

将此布局包含在主布局中。

toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/toolbarNav"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        app:contentInsetEnd="0dp"
        app:contentInsetLeft="0dp"
        app:contentInsetRight="0dp"
        app:contentInsetStart="0dp">

        <RelativeLayout
            android:id="@+id/rlBackImageLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/main_background2">  //add your color here

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="@dimen/_40sdp"
                android:layout_marginTop="@dimen/_16sdp"
                android:orientation="horizontal">

                <ImageView
                    android:id="@+id/toolbarIcon"
                    android:layout_width="@dimen/_30sdp"
                    android:layout_height="@dimen/_30sdp"
                    android:layout_gravity="center"
                    android:layout_marginStart="@dimen/_10sdp"
                    android:padding="@dimen/_5sdp"
                    android:src="@drawable/nav_icon" />

                <TextView
                    android:id="@+id/txtTitle"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_gravity="center"
                    android:layout_marginEnd="@dimen/_30sdp"
                    android:fontFamily="@font/muli_semibold"
                    android:gravity="center"
                    android:textColor="#fff"
                    android:textSize="@dimen/_14ssp"
                    android:textStyle="bold"
                    tools:text="test Data" />

            </LinearLayout>

        </RelativeLayout>

    </androidx.appcompat.widget.Toolbar>

注:可以用dp代替SDP，用sp代替SSP。