小编V. *_*roz的帖子

有一个旧的Java代码(没有lambda表达式):

public List<CheckerPosition> getAttackedCheckersForPoint(CheckerPosition from, boolean isSecondPlayerOwner, boolean isQueen, VectorDirection ignoredDirection){
    List<VectorDirection> allDirections = VectorDirection.generateAllDirections();
    List<CheckerPosition> result = new ArrayList<CheckerPosition>();

    for (VectorDirection direction : allDirections){
        if (!direction.equals(ignoredDirection)){
            Checker firstCheckerOnWay = findFirstCheckerOnWay(new CheckerBaseVector(from, direction), !isQueen);
            if ((firstCheckerOnWay != null) && (firstCheckerOnWay.isSecondPlayerOwner() != isSecondPlayerOwner) && isCheckerBlocked(firstCheckerOnWay.getPosition(), direction)){
                result.add(firstCheckerOnWay.getPosition());
            }
        }
    }
    return result;
 }

我正在尝试将此代码重写为Java 8 Stream API样式:

allDirections.stream()
                .filter(d -> !d.equals(ignoredDirection))
                .map(d -> findFirstCheckerOnWay(new CheckerBaseVector(from, d), !isQueen)) // In this operation I map VectorDirection element (d) to Checker variable …

我有两个变体的activity_main.xml（用于纵向/横向）。在此活动中，用户可以选择项目并浏览所选项目的详细信息。

在纵向方向上，片段动态添加到flFragmentContainer中，选择项目后，详细信息片段替换列表片段：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <FrameLayout
        android:id="@+id/flFragmentContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></FrameLayout>
</LinearLayout>

在横向方向上，XML 文件中静态描述的片段：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">
        <fragment
            android:id="@+id/frgTaskList"
            android:name="com.exprod.xchecklist.fragments.TaskListFragment"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            tools:layout="@layout/fragment_task_list" />
        <fragment
            android:id="@+id/frgTaskDetails"
            android:name="com.exprod.xchecklist.fragments.TaskDetailsFragment"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            tools:layout="@layout/fragment_task_details">
        </fragment>
    </LinearLayout>
</LinearLayout>

这是（MainActivity 的）onCreate() 方法的代码。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FragmentManager fragmentManager = getSupportFragmentManager();
        TaskDetailsFragment taskDetailsFragment = (TaskDetailsFragment)fragmentManager.findFragmentById(R.id.frgTaskDetails);
        isDynamicMode = taskDetailsFragment == null || !taskDetailsFragment.isInLayout();
        if(isDynamicMode){
            FragmentTransaction transaction = fragmentManager.beginTransaction();
            Fragment …