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;

    }
}

@Override
protected 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;

@Override
public 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)
@Override
protected 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();
}