来自 LinearLayout return 的 getLayoutParams() null
getLayoutParams() from LinearLayout return null
我想在 activity 屏幕上实现 BottomSheetBehavoir 组件,但是当我想通过 BottomSheetBehavoir.from(view)
初始化组件时 getLayoutParams() 方法抛出空指针异常。
这是我在 onCreate() 中的初始化代码:
LinearLayout llBottomSheet = findViewById(R.id.bottom_sheet_live_tracking_list_container);
BottomSheetBehavior bottomSheetBehavior = BottomSheetBehavior.from(llBottomSheet);
这是我的 xml 布局:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/bottom_sheet_live_tracking_list_container"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/white"
app:behavior_hideable="false"
app:behavior_peekHeight="40dp"
app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="40dp"
android:orientation="horizontal"
android:background="@drawable/rounded_corners_gray">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="@string/show_more"
android:textColor="@color/white"
android:layout_gravity="center"
android:gravity="center"
android:layout_weight="1"
android:id="@+id/activity_live_tracking_show_more_tv" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_weight="0.1"
android:src="@drawable/ic_filter_list"
android:visibility="visible" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/activity_live_tracking_position_list_rv"
android:layout_width="match_parent"
android:layout_height="match_parent" />
我通过 include 标签将此布局包含在我的根 xml 布局中。
错误代码:
2020-02-21 12:34:05.097 8419-8419/de.app.haveltec.ilockit E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.app.haveltec.ilockit, PID: 8419
java.lang.RuntimeException: Unable to start activity ComponentInfo{de.app.haveltec.ilockit/de.app.haveltec.ilockit.screens.livetracking.LiveTrackingActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3119)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1839)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6861)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at com.google.android.material.bottomsheet.BottomSheetBehavior.from(BottomSheetBehavior.java:981)
at de.app.haveltec.ilockit.screens.livetracking.LiveTrackingActivity.onCreate(LiveTrackingActivity.java:147)
at android.app.Activity.performCreate(Activity.java:7232)
at android.app.Activity.performCreate(Activity.java:7221)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2964)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3119)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1839)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6861)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
如 documentation BottomSheetBehaviour 中所述,已弃用。如果您仍想使用它,请确保它是 CoordinatorLayout 的子级,因为根据文档这是使用它的先决条件。
宁愿将此答案添加为评论,但声誉不够...
所以在我休息了几天之后,回到问题上,我找到了解决方案。对于抛出 getLayoutParams() 空指针异常的我的 LinearLayout,我使用底部的 id sheet xml,您可以在我的 post android:id="@+id/bottom_sheet_live_tracking_list_container"
中看到它。在我的主布局中,父级是 CoordinatorLayout 包括我的底部 sheet 布局,如下所示:
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true">
... other stuff ....
<include
android:id="@+id/activity_live_tracking_bottom_sheet"
layout="@layout/bottom_sheet_live_tracking_list" />
知道我尝试了包含标记 (android:id="@+id/activity_live_tracking_bottom_sheet"
) 中的 id,它起作用了。我无法给你解释为什么标记LinearLayout的另一个id直接为getLayoutParams()方法返回null。
我想在 activity 屏幕上实现 BottomSheetBehavoir 组件,但是当我想通过 BottomSheetBehavoir.from(view)
初始化组件时 getLayoutParams() 方法抛出空指针异常。
这是我在 onCreate() 中的初始化代码:
LinearLayout llBottomSheet = findViewById(R.id.bottom_sheet_live_tracking_list_container);
BottomSheetBehavior bottomSheetBehavior = BottomSheetBehavior.from(llBottomSheet);
这是我的 xml 布局:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/bottom_sheet_live_tracking_list_container"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/white"
app:behavior_hideable="false"
app:behavior_peekHeight="40dp"
app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="40dp"
android:orientation="horizontal"
android:background="@drawable/rounded_corners_gray">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="@string/show_more"
android:textColor="@color/white"
android:layout_gravity="center"
android:gravity="center"
android:layout_weight="1"
android:id="@+id/activity_live_tracking_show_more_tv" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_weight="0.1"
android:src="@drawable/ic_filter_list"
android:visibility="visible" />
</LinearLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/activity_live_tracking_position_list_rv"
android:layout_width="match_parent"
android:layout_height="match_parent" />
我通过 include 标签将此布局包含在我的根 xml 布局中。
错误代码:
2020-02-21 12:34:05.097 8419-8419/de.app.haveltec.ilockit E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.app.haveltec.ilockit, PID: 8419
java.lang.RuntimeException: Unable to start activity ComponentInfo{de.app.haveltec.ilockit/de.app.haveltec.ilockit.screens.livetracking.LiveTrackingActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3119)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1839)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6861)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at com.google.android.material.bottomsheet.BottomSheetBehavior.from(BottomSheetBehavior.java:981)
at de.app.haveltec.ilockit.screens.livetracking.LiveTrackingActivity.onCreate(LiveTrackingActivity.java:147)
at android.app.Activity.performCreate(Activity.java:7232)
at android.app.Activity.performCreate(Activity.java:7221)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2964)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3119)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1839)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6861)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
如 documentation BottomSheetBehaviour 中所述,已弃用。如果您仍想使用它,请确保它是 CoordinatorLayout 的子级,因为根据文档这是使用它的先决条件。 宁愿将此答案添加为评论,但声誉不够...
所以在我休息了几天之后,回到问题上,我找到了解决方案。对于抛出 getLayoutParams() 空指针异常的我的 LinearLayout,我使用底部的 id sheet xml,您可以在我的 post android:id="@+id/bottom_sheet_live_tracking_list_container"
中看到它。在我的主布局中,父级是 CoordinatorLayout 包括我的底部 sheet 布局,如下所示:
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true">
... other stuff ....
<include
android:id="@+id/activity_live_tracking_bottom_sheet"
layout="@layout/bottom_sheet_live_tracking_list" />
知道我尝试了包含标记 (android:id="@+id/activity_live_tracking_bottom_sheet"
) 中的 id,它起作用了。我无法给你解释为什么标记LinearLayout的另一个id直接为getLayoutParams()方法返回null。