控件使用 就不在此啰嗦了，很简单。
- 分析原因
1.BottomNavigationView，item大于3个的显示奇怪的情况，这个移动动画几乎都是不想要的。
首先在BottomNavigationMenuView中，有一个全局变量：mShiftingMode，然后在创建Menu的时候buildMenuView()
public void buildMenuView() {
...
mShiftingMode = mMenu.size() > 3;
...
}
当size>3时候，设为ture。
然后在BottomNavigationItemView，设置check的时候：
@Override
public void setChecked(boolean checked) {
ViewCompat.setPivotX(mLargeLabel, mLargeLabel.getWidth() / 2);
ViewCompat.setPivotY(mLargeLabel, mLargeLabel.getBaseline());
ViewCompat.setPivotX(mSmallLabel, mSmallLabel.getWidth() / 2);
ViewCompat.setPivotY(mSmallLabel, mSmallLabel.getBaseline());
if (mShiftingMode) {
if (checked) {
LayoutParams iconParams = (LayoutParams) mIcon.getLayoutParams();
iconParams.gravity = Gravity.CENTER_HORIZONTAL | Gravity.TOP;
iconParams.topMargin = mDefaultMargin;
mIcon.setLayoutParams(iconParams);
mLargeLabel.setVisibility(VISIBLE);
ViewCompat.setScaleX(mLargeLabel, 1f);
ViewCompat.setScaleY(mLargeLabel, 1f);
} else {
LayoutParams iconParams = (LayoutParams) mIcon.getLayoutParams();
iconParams.gravity = Gravity.CENTER;
iconParams.topMargin = mDefaultMargin;
mIcon.setLayoutParams(iconParams);
mLargeLabel.setVisibility(INVISIBLE);
ViewCompat.setScaleX(mLargeLabel, 0.5f);
ViewCompat.setScaleY(mLargeLabel, 0.5f);
}
mSmallLabel.setVisibility(INVISIBLE);
} else {
if (checked) {
LayoutParams iconParams = (LayoutParams) mIcon.getLayoutParams();
iconParams.gravity = Gravity.CENTER_HORIZONTAL | Gravity.TOP;
iconParams.topMargin = mDefaultMargin + mShiftAmount;
mIcon.setLayoutParams(iconParams);
mLargeLabel.setVisibility(VISIBLE);
mSmallLabel.setVisibility(INVISIBLE);
ViewCompat.setScaleX(mLargeLabel, 1f);
ViewCompat.setScaleY(mLargeLabel, 1f);
ViewCompat.setScaleX(mSmallLabel, mScaleUpFactor);
ViewCompat.setScaleY(mSmallLabel, mScaleUpFactor);
} else {
LayoutParams iconParams = (LayoutParams) mIcon.getLayoutParams();
iconParams.gravity = Gravity.CENTER_HORIZONTAL | Gravity.TOP;
iconParams.topMargin = mDefaultMargin;
mIcon.setLayoutParams(iconParams);
mLargeLabel.setVisibility(INVISIBLE);
mSmallLabel.setVisibility(VISIBLE);
ViewCompat.setScaleX(mLargeLabel, mScaleDownFactor);
ViewCompat.setScaleY(mLargeLabel, mScaleDownFactor);
ViewCompat.setScaleX(mSmallLabel, 1f);
ViewCompat.setScaleY(mSmallLabel, 1f);
}
}
refreshDrawableState();
}
然后会根据shiftMode的值执行不同的逻辑，所以产生了这个动画效果。
官方没有对这个 字段暴露出修改的方法，所以可以通过反射的方式，间接修改这个字段。
public class BottomNavigationViewHelper {
public static void disableShiftMode(BottomNavigationView view) {
BottomNavigationMenuView menuView = (BottomNavigationMenuView) view.getChildAt(0);
try {
Field shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
shiftingMode.setAccessible(true);
shiftingMode.setBoolean(menuView, false);
shiftingMode.setAccessible(false);
for (int i = 0; i < menuView.getChildCount(); i++) {
BottomNavigationItemView item = (BottomNavigationItemView) menuView.getChildAt(i);
//noinspection RestrictedApi
item.setShiftingMode(false);
// set once again checked value, so view will be updated
//noinspection RestrictedApi
item.setChecked(item.getItemData().isChecked());
}
} catch (Exception e) {
}
}
}
最后在使用BottomNavigationView的地方 调用：
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottomview);
// 去除动画效果
BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);
最后运行起来，移动动画消除了，还附带了一个很细微的抖动动画，超赞的有木有。
