Question

仅当构建变体处于发布模式时，才会在BottomSheetBehavior上获取NPE（NullPointerException）。如果我使用调试变体测试它工作正常。但当我将其作为发布版本时，应用程序崩溃了。我在onCreate（）生命周期中调用setBottomSheet（）方法。

这是我的XML代码：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/coordinator_scanactivity"
android:layout_width="match_parent"
android:layout_height="match_parent"
>

<include layout="@layout/activity_scan_content" />

<!--<include layout="@layout/bottom_sheet" />-->


<RelativeLayout
    android:id="@+id/bottom_sheet_layout"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:background="@android:color/white"
    android:orientation="vertical"
    app:behavior_hideable="true"
    app:behavior_peekHeight="35dp"
    app:layout_behavior="android.support.design.widget.BottomSheetBehavior">

    <LinearLayout
        android:id="@+id/bottom_sheet_header"
        android:layout_width="match_parent"
        android:layout_height="35dp"
        android:background="@color/colorPrimary"
        android:orientation="vertical">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:padding="5dp"
            android:src="@drawable/bottom_sheet_up" />
    </LinearLayout>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/bottom_sheet_header"
        android:layout_marginBottom="16dp"
        android:layout_marginTop="16dp" />
</RelativeLayout>

<ImageView
    android:id="@+id/add_device_btn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/divider_view"
    android:paddingBottom="10dp"
    android:paddingRight="10dp"
    android:src="@drawable/add"
    app:layout_anchor="@id/bottom_sheet"
    app:layout_anchorGravity="top|end" />
</android.support.design.widget.CoordinatorLayout>

这是我的java代码：

private void setBottomSheet() {

    llBottomSheet = (RelativeLayout) findViewById(R.id.bottom_sheet_layout);

    bottomSheetBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
        @Override
        public void onStateChanged(@NonNull View bottomSheet, int newState) {
            if (newState == BottomSheetBehavior.STATE_EXPANDED) {
                System.out.println("Inactive Device Bottom Sheet Expanded");
            }
        }

        @Override
        public void onSlide(@NonNull View bottomSheet, float slideOffset) {
            add_device_btn.animate().scaleX(1 - slideOffset).scaleY(1 - slideOffset).setDuration(0).start();
        }
    });
}

我的日志文件：

FATAL EXCEPTION: main
Process: com.webmobi.trackm, PID: 2676
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.ViewDragHelper.processTouchEvent(android.view.MotionEvent)' on a null object reference
    at android.support.design.widget.BottomSheetBehavior.onTouchEvent(BottomSheetBehavior.java:315)
    at android.support.design.widget.CoordinatorLayout.resetTouchBehaviors(CoordinatorLayout.java:396)
    at android.support.design.widget.CoordinatorLayout.onAttachedToWindow(CoordinatorLayout.java:238)
    at android.view.View.dispatchAttachedToWindow(View.java:15532)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2918)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2925)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2925)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2925)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2925)
    at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2925)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1572)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1300)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6405)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:876)
    at android.view.Choreographer.doCallbacks(Choreographer.java:688)
    at android.view.Choreographer.doFrame(Choreographer.java:623)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:862)
    at android.os.Handler.handleCallback(Handler.java:754)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:163)
    at android.app.ActivityThread.main(ActivityThread.java:6205)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)

Answer 1

添加此代码：

if (mViewDragHelper == null) {
mViewDragHelper = ViewDragHelper.create(parent, mDragCallback);
}

在mViewDragHelper.processTouchEvent(event);之前进入 ViewPagerBottomSheetBehavior 文件（大概可能是274行）。

bottomsheetbehavior中的NullPointerException（仅在发布版本中）

1 个答案: