問題

遇到一個spinner 背景的問題,記錄一下.
我在xml中定義了一個spinner

                android:id="@+id/tracking_mode_spinner"
                android:layout_width="wrap_content"
                android:layout_height="33dp"
                android:spinnerMode="dropdown"
                android:background="@drawable/corner_white_bg_nor"
                android:popupBackground="@drawable/spinner_pop_bg"/>

在java中調(diào)用:

mSpinner = findViewById(R.id.layout_spinner);
mSpinner.setDropDownVerticalOffset(mContext.getResources()
               .getDimensionPixelSize(R.dimen.spinner_offset));
mSpinner.setDropDownWidth(mContext.getResources()
               .getDimensionPixelSize(R.dimen.spinner_width));
mSpinner.setAnimation(null);
       SpinnerAdapter adapter = SpinnerAdapter.createFromResource(mContext,
               CameraFramingMode.createFramingModeEntries(true, false), R.layout.layout_spinner_pop_selectable_item);
       mSpinner.setAdapter(adapter);
       mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
           @Override
           public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
               adapter.setSelectedPosition(position);
               updateView();
           }

           @Override
           public void onNothingSelected(AdapterView<?> parent) {

           }
       });

adapter 是這樣使用:

  SpinnerAdapter adapter = SpinnerAdapter.createFromResource(mContext,
                CameraFramingMode.createFramingModeEntries(true, false), R.layout.layout_spinner_pop_selectable_item);

SpinnerAdapter 定義成這個

    public static class SpinnerAdapter<T> extends ArrayAdapter<T> {

        private int selectedPosition;

        void setSelectedPosition(int selectedPosition) {
            this.selectedPosition = selectedPosition;
        }

        SpinnerAdapter(@NonNull Context context, int resource, @NonNull T[] objects) {
            super(context, resource, R.id.text, objects);
        }

        @Override
        public View getDropDownView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
            View view = super.getDropDownView(position, convertView, parent);
            TextView icon = view.findViewById(R.id.icon);
            if (selectedPosition == position) {
                FontsUtils.setTypeface(icon);
                icon.setText(FontIcons.OK);
                icon.setVisibility(View.VISIBLE);
            } else {
                icon.setVisibility(View.INVISIBLE);
            }
            return view;
        }

        static @NonNull
        SpinnerAdapter<CharSequence> createFromResource(@NonNull Context context,
                                                        CharSequence[] items, @LayoutRes int textViewResId) {
            return new SpinnerAdapter<>(context, textViewResId, items);
        }
    }

layout_spinner_pop_selectable_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/selector_spinner_item_bg"
    android:gravity="center_vertical"
    android:orientation="horizontal">
    <TextView
        android:id="@+id/text"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="match_parent"
        android:gravity="center_vertical"
        android:background="@android:color/transparent"
   />
    <TextView
        android:id="@+id/icon"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:gravity="center_vertical"
   />
</LinearLayout>

但是我發(fā)現(xiàn)spinner 設(shè)置的bg會被item的bg覆蓋selector_spinner_item_bg.
抓取控件樹發(fā)現(xiàn),spinner的顯示會把下拉框一個item作為顯示的內(nèi)容.

image.png

這樣子會有問題,當(dāng)item的布局樣式和spinner不一樣時,spinner的樣式會被覆蓋.
舉個例子:當(dāng)item背景要紅色,spinner背景要黑色時,spinner設(shè)置了黑色背景無用.

原因

spinner源碼中:makeView 獲取view是通過Adapter#getView的方式獲取的

/**
     * Obtain a view, either by pulling an existing view from the recycler or
     * by getting a new one from the adapter. If we are animating, make sure
     * there is enough information in the view's layout parameters to animate
     * from the old to new positions.
     *
     * @param position Position in the spinner for the view to obtain
     * @param addChild true to add the child to the spinner, false to obtain and configure only.
     * @return A view for the given position
     */
    private View makeView(int position, boolean addChild) {
        View child;

        if (!mDataChanged) {
            child = mRecycler.get(position);
            if (child != null) {
                // Position the view
                setUpChild(child, addChild);

                return child;
            }
        }

        // Nothing found in the recycler -- ask the adapter for a view
        child = mAdapter.getView(position, null, this);

        // Position the view
        setUpChild(child, addChild);

        return child;
    }

DropDownAdapter#getView,這個方法不是抽象,所以當(dāng)我們沒有重寫此方法時,他返回的就是item的view.

 public View getView(int position, View convertView, ViewGroup parent) {
            return getDropDownView(position, convertView, parent);
        }

修改

知道原因了就好修改了,我們重寫getView重新設(shè)置一個view即可.