android - Android中如何用自定义的action bar完全替换AppCompatActivity的action bar？

Question

我绝对是 Android 的初学者。现在我正在学习如何布局 Android 应用程序。所以我开始将抽屉导航与工具栏一起使用。现在我正在创建一个没有默认功能的自定义操作。但它不起作用。

这是我的主要 Activity 布局

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

    <!-- This LinearLayout represents the contents of the screen  -->

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <!-- The ActionBar displayed at the top -->
        <include
            layout="@layout/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

        <!-- The main content view where fragments are loaded -->
        <FrameLayout
            android:id="@+id/flContent"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>

    <!-- The navigation drawer that comes from the left -->
    <!-- Note that `android:layout_gravity` needs to be set to 'start' -->
    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />
</android.support.v4.widget.DrawerLayout>

这是我的工具栏布局

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:fitsSystemWindows="true"
    android:minHeight="?attr/actionBarSize"
    app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    android:background="?attr/colorPrimaryDark">

</android.support.v7.widget.Toolbar>

这是我的 Activity 课

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);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

这是风格

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>
    <style name="AppTheme.NoActionBar">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>
    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

但是当我开始 Activity 时，标题和查看菜单项的选项包含在操作栏中，即使我没有像屏幕截图那样在布局中定义。

所以我想做的是用我的自定义工具栏完全替换操作栏，并且我想删除默认行为。

所以我尝试在activity中用这种方式去掉title

setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        ActionBar actionBar = getSupportActionBar();
        actionBar.setTitle("");
        setSupportActionBar(toolbar);

但是报错

这是日志

01-23 12:28:45.945 2972-2972/? D/AndroidRuntime: Shutting down VM
01-23 12:28:45.945 2972-2972/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xa614a908)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime: FATAL EXCEPTION: main
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.waiyanhein.todo.todo/com.waiyanhein.todo.todo.MainActivity}: java.lang.NullPointerException
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:  Caused by: java.lang.NullPointerException
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at com.waiyanhein.todo.todo.MainActivity.onCreate(MainActivity.java:21)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5104)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
01-23 12:28:45.945 2972-2972/? E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 
01-23 12:28:45.961 2972-2975/? D/dalvikvm: GC_CONCURRENT freed 249K, 13% free 2610K/2988K, paused 2ms+0ms, total 18ms
01-23 12:28:45.961 386-801/? W/ActivityManager:   Force finishing activity com.waiyanhein.todo.todo/.MainActivity
01-23 12:28:46.177 386-801/? D/dalvikvm: GC_FOR_ALLOC freed 1205K, 46% free 8703K/16012K, paused 15ms, total 15ms
01-23 12:28:46.209 386-402/? D/dalvikvm: GC_FOR_ALLOC freed 149K, 40% free 9732K/16012K, paused 19ms, total 19ms
01-23 12:28:46.241 386-402/? D/dalvikvm: GC_FOR_ALLOC freed 6K, 33% free 10832K/16012K, paused 15ms, total 15ms
01-23 12:28:46.241 386-402/? I/dalvikvm-heap: Grow heap (frag case) to 13.126MB for 2536932-byte allocation
01-23 12:28:46.301 386-401/? D/dalvikvm: GC_FOR_ALLOC freed 2K, 29% free 13307K/18492K, paused 59ms, total 59ms
01-23 12:28:46.309 386-389/? D/dalvikvm: GC_CONCURRENT freed <1K, 29% free 13307K/18492K, paused 2ms+1ms, total 10ms

所以我的第一个问题是，为什么在 Activity 中自定义操作栏时会抛出错误？我的代码有什么问题吗？我的第二个问题是如何用我上面提到的自定义操作栏完全替换操作栏。

Answer 1

发生 NullPointerException 是因为您试图访问和修改 Activity 上的 ActionBar 支持 NoActionBar 主题，然后再将 Toolbar 设置为替代。但是，考虑到您想要的选项菜单行为，您不想这样做。

如果 Activity 有一个 ActionBar 实现，它的选项菜单将自动创建为 ActionBar 本身的下拉菜单。由于您使用的是 NoActionBar 主题，因此不要将 Toolbar 设置为支持 ActionBar，选项菜单将恢复为旧风格。