java - 为什么不能在 android 中用工具栏覆盖操作栏？

Question

我绝对是 Android 的初学者。现在我开始学习android。现在我正在使用工具栏创建自定义操作栏。我试过引用一篇在线文章。但它正在抛出错误。我的代码有什么问题？

这是我的activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <TextView android:text="Hello World!" android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

这是主题

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
    </style>

</resources>

这是我的 action_toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
    android:id="@+id/my_action_bar_toolbar"
   android:layout_width="match_parent"
    android:layout_height="200dp"
    android:background="@color/orange"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <ImageView
        android:src="@drawable/icon_1"
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</android.support.v7.widget.Toolbar>

这是我的 MainActivity.java 类

公共(public)类 MainActivity 扩展了 ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar actionBarToolBar = (Toolbar)findViewById(R.id.my_action_bar_toolbar);
        setSupportActionBar(actionBarToolBar);
        actionBarToolBar.setNavigationIcon(R.drawable.icon_3);
        actionBarToolBar.setNavigationContentDescription("This is navigation content description");
        actionBarToolBar.setLogo(R.drawable.icon_2);
        actionBarToolBar.setLogoDescription("This is logo description");
    }

    @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);
    }
}

当我运行它时，它总是抛出错误。

这是我在 Logcat 中得到的。

01-18 16:47:46.199 5584-5584/? D/dalvikvm: Late-enabling CheckJNI
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog D/AndroidRuntime: Shutting down VM
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xa61c5908)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime: FATAL EXCEPTION: main
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.toolbardog.toolbardog/com.example.toolbardog.toolbardog.MainActivity}: java.lang.NullPointerException
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:  Caused by: java.lang.NullPointerException
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:95)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:88)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.support.v7.internal.app.ToolbarActionBar.<init>(ToolbarActionBar.java:84)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.support.v7.app.ActionBarActivityDelegateBase.setSupportActionBar(ActionBarActivityDelegateBase.java:175)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.support.v7.app.ActionBarActivity.setSupportActionBar(ActionBarActivity.java:92)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at com.example.toolbardog.toolbardog.MainActivity.onCreate(MainActivity.java:17)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5104)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
01-18 16:47:46.359 5584-5584/com.example.toolbardog.toolbardog E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 

Answer 1

你应该扩展AppCompactivity .您的工具栏位于 action_toolbar.xml当您为您的 Activity 设置不同的布局时。在您的情况下，工具栏自然是空的。您需要在 activity_main.xml 中包含工具栏布局.

只需添加 <include layout="@layout/action_toolbar />在你的 activity_main.xml 中