我正在尝试在RecyclerView中实现滑动删除。除了在正在刷卡的项目下面绘制一个删除图标外，一切似乎都运行正常。
我就是这样做的：
ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
int position = viewHolder.getAdapterPosition();
// Do my stuff
// }
}
@Override
public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
Bitmap icon;
if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE){
View itemView = viewHolder.itemView;
float height = (float) itemView.getBottom() - (float) itemView.getTop();
float width = height / 3;
if(dX > 0){
p.setColor(Color.parseColor("#388E3C"));
RectF background = new RectF((float) itemView.getLeft(), (float) itemView.getTop(), dX,(float) itemView.getBottom());
c.drawRect(background,p);
icon = BitmapFactory.decodeResource(getActivity().getResources(), R.drawable.ic_delete);
RectF icon_dest = new RectF((float) itemView.getLeft() + width ,(float) itemView.getTop() + width,(float) itemView.getLeft()+ 2*width,(float)itemView.getBottom() - width);
c.drawBitmap(icon,null,icon_dest,p);
} else {
p.setColor(Color.parseColor("#D32F2F"));
RectF background = new RectF((float) itemView.getRight() + dX, (float) itemView.getTop(),(float) itemView.getRight(), (float) itemView.getBottom());
c.drawRect(background,p);
icon = BitmapFactory.decodeResource(getActivity().getResources(), R.drawable.ic_delete);
RectF icon_dest = new RectF((float) itemView.getRight() - 2*width ,(float) itemView.getTop() + width,(float) itemView.getRight() - width,(float)itemView.getBottom() - width);
c.drawBitmap(icon,null,icon_dest,p);
}
}
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
};
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
itemTouchHelper.attachToRecyclerView(mRecyclerView);
投掷
java.lang.NullPointerException：尝试调用虚方法 '对象上的'boolean android.graphics.Bitmap.isRecycled（）' 参考
完整StackTrace
09-12 01:28:58.386 26575-26575/com.ozuf.booker E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ozuf.booker, PID: 26575
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.graphics.Bitmap.isRecycled()' on a null object reference
at android.graphics.Canvas.throwIfCannotDraw(Canvas.java:1281)
at android.view.GLES20Canvas.drawBitmap(GLES20Canvas.java:620)
at com.ozuf.booker.fragments.BookFragment$1.onChildDraw(BookFragment.java:149)
at android.support.v7.widget.helper.ItemTouchHelper$Callback.onDraw(ItemTouchHelper.java:1956)
at android.support.v7.widget.helper.ItemTouchHelper$Callback.access$1400(ItemTouchHelper.java:1356)
at android.support.v7.widget.helper.ItemTouchHelper.onDraw(ItemTouchHelper.java:542)
at android.support.v7.widget.RecyclerView.onDraw(RecyclerView.java:3373)
at android.view.View.draw(View.java:15635)
at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:3308)
at android.view.View.updateDisplayListIfDirty(View.java:14568)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3588)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3567)
at android.view.View.updateDisplayListIfDirty(View.java:14528)
at android.view.View.getDisplayList(View.java:14590)
at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:273)
at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:279)
at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:318)
at android.view.ViewRootImpl.draw(ViewRootImpl.java:2575)
at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2385)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2012)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1073)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5988)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Chor
第149行是c.drawBitmap(icon,null,icon_dest,p);我已经调试了，我看到icon为空，但我不明白为什么; s null，因为我已经为它赋了一个值。
答案 0 :(得分：11)
我不明白为什么;因为我已经给它赋了一个值，所以是null。
是。你做了=＆gt; null。问题出在其他地方。请参阅decodeResource()的文档：
返回：已解码的位图，如果图像无法解码，则为null 。
因此您需要a）始终检查该条件，b）检查您尝试解码的数据究竟发生的原因。
答案 1 :(得分：7)
错误是因为drawable可能是Vector。
Drawable drawable = ContextCompat.getDrawable(StreamActivity.this,R.drawable.ic_close)
Bitmap icon = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(icon);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
答案 2 :(得分：1)
尝试将可绘制成矢量的矢量解码为Bitmap会出现此类错误。因此，在将资源解码为位图的情况下，请尝试使用任何格式为.png，.jpeg等的图片。
答案 3 :(得分：1)
在将位图传递给ImageView之前，先检查位图是 null 还是 reycled（）。
if(resource!==null && !resource.isRecycled)
imageView.setImageBitmap(resource)
答案 4 :(得分：0)
我的问题是android向图标添加了矢量可绘制的anydpi以及多个创建的图像资产。我删除了anydpi变体，现在一切正常。
答案 5 :(得分：0)
我从：
android:layout_width="1095dp"
android:layout_height="1200dp"
收件人：
android:layout_width="wrap_content"
android:layout_height="wrap_content"
然后错误消失了。