我正在尝试弄清楚如何在我的 android 应用程序的（材料设计）工具栏中创建面包屑。
这可以在最新的 Dropbox android 应用程序中看到，其中面包屑用于显示文件的导航。
我还找到了一张图片（我从another similar question 拍摄的），可以在这里看到：
你能指导我如何做到这一点吗？
【问题讨论】：
我认为您不需要图书馆。如果您创建一个视图（可能是 FrameLayout），然后将其设置为与工具栏相同颜色的背景，然后在其中放置一个 TextView，那么它就完成了。您甚至可以扩展 TextView 类并覆盖一些方法来为更改设置动画。您可以通过活动之间的意图传递面包屑的当前字符串，然后每个活动都知道如何更新它。
【讨论】：
我为一个应用创建了一个这样的工作示例，我想我会分享，因为它变得比它需要的更令人困惑，哈哈。也许它可以为一些开发人员节省大量不应该需要的工作:)
将 HorizontalScrollView 添加到您的 AppBarLayout（layout/examplebreadcrumbs_layout）
<android.support.v7.widget.AppBarLayout
android:id="@+id/app_bar"
style="@style/HeaderBar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?colorPrimary"
android:minHeight="?attr/actionBarSize"
app:contentInsetStart="72dp"
app:navigationContentDescription="up" />
<HorizontalScrollView android:id="@+id/breadcrumb_wrapper"
android:layout_width="match_parent"
android:layout_height="50dp"
android:scrollbars="none">
<LinearLayout android:id="@+id/breadcrumbs"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="center_vertical"
android:gravity="center_vertical"
android:paddingEnd="@dimen/activity_horizontal_margin_2"
android:paddingStart="@dimen/activity_horizontal_margin_2"/>
</HorizontalScrollView>
</android.support.v7.widget.AppBarLayout>
创建一个 LinearLayout 将用于每个“面包屑”。您将为每个膨胀相同的布局。 (布局/breadcrumb_text)
<LinearLayout android:id="@+id/crumb"
xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="match_parent">
<TextView
android:id="@+id/crumb_arrow"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:visibility="gone"
android:gravity="center_vertical"
android:text="@string/greater_than"
android:padding="4dp"
android:fontFamily="sans-serif-condensed"
android:textSize="20sp"
android:textColor="@color/breadcrumb_text_dim"
android:textAllCaps="true"
tools:visibility="visible"/>
<TextView
android:id="@+id/crumb_text"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:padding="4dp"
android:gravity="center_vertical"
android:visibility="gone"
android:fontFamily="sans-serif"
android:textAllCaps="true"
android:textSize="14sp"
android:textColor="@color/breadcrumb_text"
android:background="?selectableItemBackground"/>
</LinearLayout>
ExampleBreadcrumbs 演示了基本的创建/更新/滚动到您可以轻松添加到应用流程中的方法。不是 100% 复制粘贴，因为您的应用会根据添加面包屑的活动和设置而有所不同。如果您需要其他任何东西来完成这项工作...请告诉我。
public class ExampleBreadcrumbs extends AppCompatActivity {
private static final String ROOT_NODE = "root";
private SparseArray<Long> levelNodeIds = new SparseArray<>();
private SparseArray<String> levelNodeNames = new SparseArray<>();
public int currentLevel = 0;
ViewGroup breadcrumbBar;
HorizontalScrollView breadcrumbWrapper;
String[] parents = new String[] {"Parent Item 1", "Parent Item 2",
"Parent Item 3", "Parent Item 4"};
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.examplebreadcrumbs_layout);
breadcrumbWrapper = ((HorizontalScrollView)findViewById(R.id.breadcrumb_wrapper));
breadcrumbBar = (ViewGroup) findViewById(R.id.breadcrumbs);
// TODO setup your adapter or whatever
createParentNodes();
}
@Override public void onBackPressed() {
switch (currentLevel) {
case 0:
super.onBackPressed();
break;
case 1:
createParentNodes();
adapter.notifyDataSetChanged();
break;
default:
// Get values from level you are requesting, not current.
final long id = levelNodeIds.get(currentLevel - 1);
final String name = levelNodeNames.get(currentLevel - 1);
getChildren(id, name, -1);
break;
}
}
@Override public void onItemClick(View itemView, final String name) {
long nodeId = (Long) itemView.getTag();
getChildren(nodeId, name, 1);
}
private void getChildren(final long nodeId, final String name, final int difference) {
if (nodeId != 0) {
// Example case using retrofit like setup
getChildren(nodeId, new Callback<NodesResponse>() {
@Override
public void onResponse(Call<NodesResponse> call, Response<NodesResponse> response) {
if (response.body() != null) {
if (response.body().getNodeObjs() != null && !response.body().getNodeObjs()
.isEmpty()) {
createChildNodes(nodeId, name, response.body().getNodeObjs(), difference);
}
}
}
@Override
public void onFailure(Call<NodesResponse> call, Throwable t) { // TODO}
});
} else {
createParentNodes();
adapter.notifyDataSetChanged();
}
}
private void createParentNodes() {
currentLevel = 0;
levelNodeIds.put(currentLevel, 0L);
levelNodeNames.put(currentLevel, ROOT_NODE);
listItems.clear();
int count = 0;
for(String parent : parents) {
listItems.add(new NodeObj(nodeId[count], parent, parentDescriptions[count]));
count++;
}
adapter.notifyDataSetChanged();
levelNodeNames.put(currentLevel, ROOT_NODE);
updateBreadcrumbs(true);
}
private void createChildNodes(long id, String name, List<NodeObj> NodeObjs, int difference) {
listItems.clear();
for (NodeObj obj : NodeObjs) {
listItems.add(new NodeObj(obj.getnodeId(), obj.getNodeTitle(), obj.getNodeDescription()));
}
adapter.notifyDataSetChanged();
currentLevel = currentLevel + difference;
levelNodeIds.put(currentLevel, id);
levelNodeNames.put(currentLevel, name);
// If forward, it will create new node along with updating other nodes.
updateBreadcrumbs(difference > 0);
}
private void updateBreadcrumbs(boolean createNew) {
if (createNew) {
createBreadcrumb();
}
// Loops and updates all breadcrumb nodes
updateBreadcrumbNodes();
//printDebug();
}
private void createBreadcrumb() {
boolean needToCreate = true;
// Remove view if one exists.
ViewGroup nodeToReplace = (ViewGroup) breadcrumbBar.getChildAt(currentLevel);
if (nodeToReplace != null) {
TextView toReplaceTextView = (TextView) nodeToReplace.findViewById(R.id.crumb_text);
// If node history is not the same, remove view and after.
if (toReplaceTextView.getText().equals(levelNodeNames.get(currentLevel))) {
needToCreate = false;
scrollIfBreadcrumbNotViewable(nodeToReplace);
} else {
needToCreate = true;
// Removes all nodes >= current level
for (int i = breadcrumbBar.getChildCount() - 1; i >= currentLevel; i--) {
breadcrumbBar.removeViewAt(i);
}
}
}
if (needToCreate) {
// Inflate new breadcrumb node.
final ViewGroup crumbLayout = (ViewGroup) LayoutInflater.from(this)
.inflate(R.layout.breadcrumb_text, appBarLayout, false);
crumbLayout.setTag(levelNodeIds.get(currentLevel));
// Sets name of node (color gets updated in 'updateBreadcrumbNodes').
TextView crumbTextView = (TextView) crumbLayout.findViewById(R.id.crumb_text);
crumbTextView.setVisibility(View.VISIBLE);
crumbTextView.setText(levelNodeNames.get(currentLevel));
View crumbArrow = crumbLayout.findViewById(R.id.crumb_arrow);
crumbArrow.setVisibility(levelNodeNames.get(currentLevel).equals(ROOT_NODE) ? View.GONE : View.VISIBLE);
// Add new breadcrumb node to bar.
breadcrumbBar.addView(crumbLayout, currentLevel);
scrollIfBreadcrumbNotViewable(crumbLayout);
// Create click listener to jump to history.
crumbLayout.setOnClickListener(new View.OnClickListener() {
@Override public void onClick(View v) {
int viewIndex = breadcrumbBar.indexOfChild(v);
if (viewIndex == currentLevel) return;
TextView crumbText = (TextView) v.findViewById(R.id.crumb_text);
int index = levelNodeNames.indexOfValue(crumbText.getText().toString());
long nodeId = (Long) v.getTag();
getChildren(nodeId, levelNodeNames.get(index), viewIndex - currentLevel);
}
});
}
}
private void updateBreadcrumbNodes() {
for (int i = 0; i < breadcrumbBar.getChildCount(); i++) {
boolean activeNode = i == (currentLevel);
ViewGroup node = (ViewGroup) breadcrumbBar.getChildAt(i);
TextView crumbTextView = ((TextView) node.findViewById(R.id.crumb_text));
crumbTextView.setTextColor(activeNode ? ContextCompat.getColor(this, R.color.breadcrumb_text) :
ContextCompat.getColor(this, R.color.breadcrumb_text_dim));
}
breadcrumbWrapper.fullScroll(HorizontalScrollView.FOCUS_BACKWARD);
}
private void scrollIfBreadcrumbNotViewable(final ViewGroup view) {
Rect scrollBounds = new Rect();
toolbar.getHitRect(scrollBounds);
if (!view.getLocalVisibleRect(scrollBounds) || scrollBounds.width() < view.getWidth()) {
view.postDelayed(new Runnable() {
public void run() {
breadcrumbWrapper.smoothScrollTo(view.getLeft(), 0);
}
}, 100L);
}
}
void printDebug() {
System.out.println("** DEBUG ** | level: '" + currentLevel + "' | node: id='" + levelNodeIds.get(currentLevel) + "' name='" + levelNodeNames.get(currentLevel) + "' |");
}
}
【讨论】：
我知道这已经相当老了，但这似乎与任何发布此内容的地方一样好。有一个BreadcrumbsView via Github 似乎符合目的的需要。希望它可以帮助其他正在寻找类似解决方案的人。
【讨论】：