android - getSupportActionBar() 在调用 setDisplayHomeAsUpEnabled() 时返回 null

Question

我面临着在 getSupportActionBar() 中获取 null 的问题，在 Activity 中将工具栏设置为 actionbar 并从 supportActionBar 以编程方式设置后退按钮时，我得到的异常是，

Attempt to invoke virtual method 'void android.app.ActionBar' on a null object reference

这是 Activity 的 xml View ，工具栏包含在另一个布局中

<RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <include layout="@layout/toolbar_ftp"
            android:id="@+id/include" />
        <fragment
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/mapView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:name="com.google.android.gms.maps.SupportMapFragment"
            android:layout_below="@+id/include"
            android:layout_alignParentStart="true" />
        <RelativeLayout
            android:layout_alignParentBottom="true"
            android:id="@+id/below_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingBottom="16dp"
            android:background="@color/white">
            <TextView
                android:layout_below="@+id/line11"
                android:id="@+id/txt_search_date"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textSize="18sp"
                android:layout_margin="16dp"
                android:text="@string/search_by_Date"/>
            <RelativeLayout
                android:id="@+id/rl_cal_pick"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_search_date"
                >
                <ImageView
                    android:id="@+id/icon_secheudel"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignTop="@+id/rlBoxtime"
                    android:layout_alignBottom="@+id/rlBoxtime"

                    android:src="@mipmap/ic_clock_red"
                    android:tint="@color/colorPrimary"/>
                <RelativeLayout
                    android:id="@+id/rlBoxtime"
                    android:layout_toRightOf="@+id/icon_secheudel"
                    android:background="@drawable/blue_out_line"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingLeft="5dp"
                    android:paddingRight="3dp"
                    android:paddingTop="3.5dp"
                    android:paddingBottom="3.5dp"
                    android:layout_marginLeft="0dp">
                    <TextView
                        android:id="@+id/txt_chosen_date"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginRight="5dp"
                        android:minWidth="30dp"
                        android:text=""/>
                    <ImageView
                        android:layout_width="20dp"
                        android:layout_height="20dp"
                        android:layout_toRightOf="@+id/txt_chosen_date"
                        android:layout_centerVertical="true"
                        android:src="@mipmap/ic_calendar_schedule"
                        android:tint="@color/colorAccent"
                        android:layout_marginRight="2.5dp"/>

                </RelativeLayout>

            </RelativeLayout>

            <TextView
                android:id="@+id/btn_tommorow"
                android:text="@string/tommorow"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAllCaps="false"
                android:gravity="center"
                android:layout_alignTop="@+id/rl_cal_pick"
                android:layout_alignBottom="@+id/rl_cal_pick"
                android:layout_toRightOf="@+id/tvTOday"
                android:textColor="@color/colorAccent"
                android:padding="5dp"
                android:background="@drawable/blue_out_line"
                style="@style/borderless_blue_text_button"
                />

            <TextView
                android:id="@+id/tvTOday"
                android:text="@string/today"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAllCaps="false"
                android:gravity="center"
                android:padding="5dp"

                android:layout_marginLeft="10dp"
                android:layout_alignTop="@+id/rl_cal_pick"
                android:layout_alignBottom="@+id/rl_cal_pick"
                android:layout_toRightOf="@+id/rl_cal_pick"
                android:textColor="@color/colorAccent"
                android:background="@drawable/blue_out_line"
                android:layout_marginRight="8dp"/>
        </RelativeLayout>
    </RelativeLayout>

这里是 toolbar_ftp.xml 文件

<android.support.v7.widget.Toolbar 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:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/white"
    android:fitsSystemWindows="true"
    android:minHeight="?attr/actionBarSize"
    app:theme="@style/ThemeOverlay.AppCompat.Light">
    <ImageView
        android:layout_width="200dp"
        android:layout_height="40dp"

        android:layout_gravity="center"
        android:scaleType="centerInside"
        android:src="@drawable/ftp_home_logo"
        tools:ignore="ContentDescription" />
</android.support.v7.widget.Toolbar>

这是工具栏代码

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setDisplayShowTitleEnabled(false);

Answer 1

你好尝试改变你的应用的主题风格

 <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorPrimary</item>

        <item name="android:textColor">@color/black</item>
        <item name="android:actionOverflowButtonStyle">@style/ActionButtonOverflow</item>
    </style>