Android实现横向滑动中间高亮显示

我这里用到的是自定义HorizontalScrollView实现简单的类似Wheelview效果,不多说先看代码.
先看布局:

<vgaw.com.WheelView    android:id="@+id/wv"    android:layout_width="match_parent"    android:layout_height="100dp"    android:text="Hello World!"    app:layout_constraintBottom_toBottomOf="parent"    app:layout_constraintLeft_toLeftOf="parent"    app:layout_constraintRight_toRightOf="parent"    app:layout_constraintTop_toTopOf="parent" >    <LinearLayout        android:id="@+id/ll_camera_aperture"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center_vertical"        android:orientation="horizontal"></LinearLayout></vgaw.com.dialogfragment.WheelView>

自定义WheelView继承HorizontalScrollView.主要逻辑:

public class WheelView extends HorizontalScrollView {
private static final int CHECK_STOP_DELAY = 10;
private int itemCount = 5;
private int showItemCount = 5;
private int itemPadding = 0;

private int width;private int itemWidth;private WheelViewAdapter adapter;private LinearLayout rootView;private int currentposstion;public WheelView(Context context, AttributeSet attrs) {    super(context, attrs);    setHorizontalScrollBarEnabled(false);}public void setAdapter(WheelViewAdapter adapter) {    if (adapter != null) {        this.adapter = adapter;        rootView = (LinearLayout) adapter.getRootView();        showItemCount = adapter.getShowItemCount();        if (showItemCount % 2 == 0) {            throw new RuntimeException("show item count show be odd");        }        itemCount = adapter.getItemCount();        lstI = showItemCount / 2;    }}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {    super.onSizeChanged(w, h, oldw, oldh);    if (adapter == null) {        return;    }    width = getWidth();    if (width < itemPadding) {        throw new RuntimeException("bad item padding");    }    itemWidth = (width - (showItemCount - 1) * itemPadding) / showItemCount;    for (int i = 0;i < itemCount;i++) {        final View item = adapter.getItemView(i);        item.post(new Runnable() {            @Override            public void run() {                item.setLayoutParams(new LinearLayout.LayoutParams(itemWidth, ViewGroup.LayoutParams.MATCH_PARENT));            }        });        rootView.addView(item);    }}private int lstScrollX;@Overridepublic boolean onTouchEvent(MotionEvent ev) {    if (ev.getAction() == MotionEvent.ACTION_UP) {        lstScrollX = getScrollX();        checkStop();    }    return super.onTouchEvent(ev);}private void checkStop() {    getHandler().removeCallbacks(checkStopRunnable);    postDelayed(checkStopRunnable, CHECK_STOP_DELAY);}private Runnable checkStopRunnable = new Runnable() {    @Override    public void run() {        int crtScrollX = getScrollX();        if (crtScrollX == lstScrollX) {            calStop();        } else {            lstScrollX = crtScrollX;            checkStop();        }    }};private int lstI;private void calStop() {    if (adapter != null) {        //滑动的距离        int crtScrollX = getScrollX();        //当前滑动的多少个item        int i = crtScrollX / (itemWidth + itemPadding) - 1;        //判断当前滑动距离是否滑过半个item        int rest = crtScrollX % (itemWidth + itemPadding);        int i1 = itemWidth + itemPadding;        if (rest > (itemWidth + itemPadding) / 2) {            i++;            Log.e("rest==",rest+"//"+i1+"////"+crtScrollX);            smoothScrollBy(itemWidth + itemPadding-rest, 0);        } else {            smoothScrollBy(-rest, 0);        }        int now = i + (showItemCount / 2)+1 ;        adapter.onItemSelected(currentposstion, now, rootView.getChildAt(currentposstion), rootView.getChildAt(now));        currentposstion = now;    }}public void setSelectedPosstion(final int i) {    currentposstion = lstI + i;    new Handler().postDelayed((new Runnable() {        @Override        public void run() {            scrollTo(itemWidth*i,0);            adapter.onItemSelected(i+lstI, i+lstI, rootView.getChildAt(i+lstI), rootView.getChildAt(i+lstI));        }    }),270);}}

主要的逻辑,之前设置滚动到一个指定的位置,一直没显示后来,后来才知道 scrollTo() 是直接指定滚动条的位置, 但是由于这个动作不是单纯关于 ScrollView 而已, 还要根据 ScrollView 里面包含的View 的实际信息. 所以这动作必须在页面加载完成以后才能执行. 就设置延迟时间270.

在MainActivity这么用:

public class MainActivity extends AppCompatActivity {private HorizontalScrollView hh;@RequiresApi(api = Build.VERSION_CODES.M)@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    final WheelView wv = (WheelView) findViewById(R.id.wv);    hh = (HorizontalScrollView) findViewById(R.id.hh);    final LinearLayout viewById = (LinearLayout) findViewById(R.id.ll_camera_aperture);    hh.post(new Runnable() {        @Override        public void run() {            hh.scrollTo(100,0);        }    });    wv.setAdapter(new WheelViewAdapter() {        @Override        public int getItemCount() {            return 17;        }        @Override        public int getShowItemCount() {            return 5;        }        @Override        public View getItemView(int i) {            TextView tv = new TextView(MainActivity.this);            tv.setText("hello" + i);            tv.setGravity(Gravity.CENTER);            tv.setBackgroundColor(Color.BLUE);            return tv;        }        @Override        public void onItemSelected(int lst, int now, View itemLst, View itemNow) {            itemLst.setBackgroundColor(Color.BLUE);            itemNow.setBackgroundColor(Color.RED);        }        @Override        public View getRootView() {            return viewById;        }    });    //设置选中的item    wv.setSelectedPosition(4);    wv.setOnScrollChangeListener(new View.OnScrollChangeListener() {        @Override        public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {            Log.e("rest",scrollX+"");        }    });}}

这里自定义一个Adapter

public interface WheelViewAdapter<V extends View> {int getItemCount();int getShowItemCount();V getItemView(int i);void onItemSelected(int lst, int now, View itemLst, View itemNow);V getRootView();}