java - Android findViewById 工具栏返回 null

Question

在我的 Android 应用程序中，我使用自定义工具栏，而 findViewById() 似乎找不到该工具栏。

我在互联网上浏览了所有与此类似的问题，但似乎没有一个能解决问题。

我的屏幕总是返回 Toast“工具栏失败...”

这是我的 java onCreate():

protected Toolbar toolbar;
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        toolbar = (Toolbar) findViewById(R.id.tool_bar);
        if(toolbar != null) {
            setSupportActionBar(toolbar);
        } else {
            Toast.makeText(Home.this, "Toolbar failed...", Toast.LENGTH_SHORT).show();
            Toast.makeText(Home.this,"", Toast.LENGTH_SHORT).show();
        }
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
        Intent intent = getIntent();
        String action = intent.getAction();
        String type = intent.getType();

        if (Intent.ACTION_SEND.equals(action) && type != null) {
            if ("text/plain".equals(type)) {
                handleSendText(intent); // Handle text being sent
            }
        }

    }

这是 xml 布局文件:

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >


    <RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">

        <android.support.v7.widget.Toolbar
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/colorPrimary"
            android:elevation="4dp"
            android:id="@+id/tool_bar"/>

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/home"
            android:layout_below="@id/tool_bar"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true" />

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Your Scripture:"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:layout_below="@+id/textView2"
            android:layout_alignParentLeft="true" />

    <TextView
        android:id="@+id/scripturecontainer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="You have not selected a scripture yet..."
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:layout_below="@+id/textView1"
        android:layout_alignParentLeft="true" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="trywidget"
        android:text="Try the Widget"
        android:layout_below="@+id/scripturecontainer"
        android:layout_alignParentLeft="true" />

    <Button
        android:id="@+id/widget_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="change"
        android:text="Select A Scripture"
        android:layout_below="@+id/button2"
        android:layout_alignParentLeft="true" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="suggest"
        android:text="Suggest A Feature"
        android:layout_below="@+id/widget_button"
        android:layout_alignParentLeft="true" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="wallpaper"
        android:text="Change the Wallpaper"
        android:layout_below="@+id/button3"
        android:layout_alignParentLeft="true" />
    </RelativeLayout>
    <ListView android:id="@+id/left_drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"
        android:background="#111"/>

</android.support.v4.widget.DrawerLayout>

这是我的样式 xml 文件:

<resources>

    <!--
        Base application theme, dependent on API level. This theme is replaced
        by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
    -->
    <style name="AppBaseTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!--
            Theme customizations available in newer API levels can go in
            res/values-vXX/styles.xml, while customizations related to
            backward-compatibility can go here.
        -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="windowNoTitle">true</item>
        <item name="windowActionBar">false</item>
    </style>

    <!-- Application theme. -->
    <style name="AppTheme" parent="AppBaseTheme">
        <!-- All customizations that are NOT specific to a particular API-level can go here. -->
    </style>

</resources>

Answer 1

 <android.support.design.widget.AppBarLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:theme="@style/AppTheme.AppBarOverlay">
         <android.support.v7.widget.Toolbar
             android:id="@+id/toolbar"
             android:layout_width="match_parent"
             android:layout_height="?attr/actionBarSize"
             android:background="?attr/colorPrimary"
             app:popupTheme="@style/AppTheme.PopupOverlay" />

     </android.support.design.widget.AppBarLayout>

使用上面的代码在 xml 中声明工具栏并更改

android:theme="your_theme"