我想制作一个导航抽屉,它是一个侧面菜单(当您向右滑动时会出现),您在其中单击一个按钮,然后弹出另一个菜单,而不是在同一侧面字段中弹出。我在主菜单(为Fragment1)的按钮上使用setOnClickListener()来弹出第二个菜单(为Fragment2)。代码可以编译,但是应用程序在开始时崩溃。
如何解决?也许还有另一种制作菜单的方法?
override fun onCreate(savedInstanceState: Bundle?)
{
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
loadF1(Frag1())
button1.setOnClickListener()
{
loadF2(Frag2())
}
}
修改:
堆栈跟踪
com.example.test0 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.test0, PID: 4903
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test0/com.example.test0.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.test0.MainActivity.onCreate(MainActivity.kt:19)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
答案 0 :(得分:1)
使用这样的组和项目:
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<group android:checkableBehavior="single">
<item
android:id="@+id/nav_home"
android:icon="@drawable/ic_home_black_24dp"
android:title="@string/nav_home" />
<item
android:id="@+id/nav_photos"
android:icon="@drawable/ic_photo_library_black_24dp"
android:title="@string/nav_photos" />
<item
android:id="@+id/nav_movies"
android:icon="@drawable/ic_local_movies_black_24dp"
android:title="@string/nav_movies" />
<item
android:id="@+id/nav_notifications"
android:icon="@drawable/ic_notifications_black_24dp"
android:title="@string/nav_notifications" />
<item
android:id="@+id/nav_settings"
android:icon="@drawable/ic_settings_black_24dp"
android:title="@string/nav_settings" />
</group>
<item android:title="Other">
<menu>
<item
android:id="@+id/nav_about_us"
android:title="@string/nav_about_us" />
<item
android:id="@+id/nav_privacy_policy"
android:title="@string/privacy_policy" />
</menu>
</item>
</menu>
并使用diff处理可见性。 xml
看看这个:https://www.androidhive.info/2013/11/android-sliding-menu-using-navigation-drawer/