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Android Design Support Library之BottomNavigation

随着Android 7.1的的发布,相关的开发工具与套件也一起更新了,包括Android Studio 2.2.2与Support Library 25.0.0。这次Support Library实现了Material Design中的Bottom Navigation设计样式。
Bottom Navigation适合3-5个底部菜单,官方规范给的3个菜单设计图是这样的:


4-5个菜单:

更多设计细节规范见:https://material.google.com/components/bottom-navigation.html

Bottom Navigation使用

效果预览

3个菜单:

5个菜单:

使用方法

xml

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<android.support.design.widget.BottomNavigationView
android:id="@+id/bottomNavigationView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:itemIconTint="@color/bottom_item_text_color"
app:itemTextColor="@color/bottom_item_text_color"
app:menu="@menu/menu_bottom_navigation_items"/>

app:itemIconTint:设置菜单图标颜色
app:itemTextColor:设置文本颜色

color/bottom_item_text_color.xml

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<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:color="?android:attr/textColorPrimary" android:state_checked="true"/>
<item android:color="?android:attr/textColorPrimary" android:state_pressed="true"/>
<item android:color="?android:attr/textColorSecondary"/>
</selector>

app:menu:设置底部菜单

menu/menu_bottom_navigation_items.xml

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<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/item1"
android:checked="true"
android:icon="@drawable/ic_content_copy_24dp"
android:title="Text1"/>
<item
android:id="@+id/item2"
android:icon="@drawable/ic_add_24dp"
android:title="Text2"/>
<item
android:id="@+id/item3"
android:icon="@drawable/ic_link_24dp"
android:title="Text3"/>
</menu>

Java

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BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottomNavigationView);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.item1:
break;
case R.id.item2:
break;
case R.id.item3:
break;
}
return false;
}
});

就是如此简单,可以愉快玩耍去了。

Bottom Navigation源码

其实自己写个这样的底部菜单效果并不难,官方这个,我对那个点击有个动画效果比较感兴趣,应该是一点击就是对图标和文字进行缩放动画,Bottom Navigation源码涉及4个类BottomNavigationView、BottomNavigationPresenter、BottomNavigationMenuView、BottomNavigationItemView,缩放动画在BottomNavigationItemView里,核心代码:

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@Override
public void setChecked(boolean checked) {
mItemData.setChecked(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();
}

这里设计一个小的文本mSmallLabel和大的文本mLargeLabel,默认大的是隐藏的,xml如下:

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<merge xmlns:android="http://schemas.android.com/apk/res/android">
<ImageView
android:id="@+id/icon"
android:layout_width="24dp"
android:layout_height="24dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="@dimen/design_bottom_navigation_margin"
android:layout_marginBottom="@dimen/design_bottom_navigation_margin"
android:duplicateParentState="true" />
<android.support.design.internal.BaselineLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/design_bottom_navigation_margin"
android:layout_gravity="bottom|center_horizontal"
android:duplicateParentState="true">
<TextView
android:id="@+id/smallLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="@dimen/design_bottom_navigation_text_size"
android:duplicateParentState="true" />
<TextView
android:id="@+id/largeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="invisible"
android:textSize="@dimen/design_bottom_navigation_active_text_size"
android:duplicateParentState="true" />
</android.support.design.internal.BaselineLayout>
</merge>

mShiftingMode是否是3个菜单标识。
看代码才知道,图标并没有做缩放动画,当4/5个菜单时,文本和图标有6dp距离,即mShiftAmount值,这点设计图有标哦。
没有checked时,图标margin是8dp,当文本mLargeLabel显示,图标和文本margin是6dp,造成图标也缩放的错觉。
其他代码都很简单,不注释了。
好了,如果对Bottom Navigation源码感兴趣,可自行去查看。

demo地址

https://github.com/WuXiaolong/DesignSupportLibrarySample,下载运行,Bottom Navigation入口:左侧菜单-其他组件-Bottom navigation,over。

推荐阅读

http://wuxiaolong.me/categories/SupportLibrary/



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