我们可以从 Android 中的视图以编程方式创建画布吗

Question

我正在尝试从现有视图创建一个虚拟视图。

原图：

需要像这样创建虚拟视图。

我试着用油漆和画布。

public class MyView extends View {

    Paint paint;
    Path path;

    public MyView(Context context) {
        super(context);
        init();
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init(){
        paint = new Paint();
        paint.setColor(Color.BLUE);
        paint.setStrokeWidth(10);
        paint.setStyle(Paint.Style.STROKE);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);

        canvas.drawRect(30, 50, 200, 350, paint);
//        canvas.drawRect(100, 100, 300, 400, paint);
        //drawRect(left, top, right, bottom, paint)

    }

}

但我不能这样画。因为有时图像会是圆形或椭圆形或任何形状。所以，我需要扣除现有视图并绘制相同的新视图。谁能帮我从现有视图创建一个虚拟视图？

我正在尝试仅针对微光动画执行此操作。对于 facebook 微光，我需要在微光框架布局内提供视图。但我的观点将是动态的。所以，我每次都需要以编程方式创建一个虚拟视图。对于 Facebook 微光：

<com.facebook.shimmer.ShimmerFrameLayout
        android:id="@+id/shimmerLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:ignore="MissingConstraints">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <!--add  several shimmer placeholder layout -->

            <include layout="@layout/shimmer_placeholder_layout"></include>

            <include layout="@layout/shimmer_placeholder_layout"></include>

            <include layout="@layout/shimmer_placeholder_layout"></include>
        </LinearLayout>
    </com.facebook.shimmer.ShimmerFrameLayout>

这里shimmer_placeholder_layout 是静态视图。我需要创建动态视图。

Answer 1

终于得到了解决方案。

在这里，我附上了解决方案，因为有人会从中受益。 我的视图类：

public class MyView extends View {

    Paint paint;
    ViewGroup viewGroup;
    Context context;
    List<Rect> rectList = new ArrayList<>();

    public MyView(Context context, ViewGroup viewGroup) {
        super(context);
        this.viewGroup = viewGroup;
        this.context = context;
        init();

    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        paint = new Paint();
        paint.setColor(context.getResources().getColor(R.color.gray));
        paint.setStrokeWidth(10);
        paint.setStyle(Paint.Style.FILL);

        for (int i = 0; i < viewGroup.getChildCount(); ++i) {
            View child = viewGroup.getChildAt(i);

            Rect rect = new Rect();
            int x = (int) child.getX() - dpToPx(20);
            int y = (int) child.getY() - dpToPx(20);
            rect.left = x;
            rect.top = y;
            rect.right = x + child.getWidth();
            rect.bottom = y + child.getHeight();
            rectList.add(rect);
        }

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        for (Rect rect : rectList) {
            canvas.drawRect(rect, paint);
        }
    }
    public static int dpToPx(int dp) {
        return (int) (dp * Resources.getSystem().getDisplayMetrics().density);
    }

}

我的主要活动：

ConstraintLayout constraintLayout;
    ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        constraintLayout = findViewById(R.id.parent_view);
        imageView = findViewById(R.id.item_profile_img);

        constraintLayout.post(() -> {
            
            ShimmerFrameLayout shimmerFrameLayout = new ShimmerFrameLayout(MainActivity.this);

            Shimmer shimmer = new Shimmer.ColorHighlightBuilder()
                    .setDuration(2000)
                    .setBaseAlpha(0.9f)
                    .setHighlightAlpha(0.93f)
                    .setWidthRatio(1.5f)
                    .setDirection(Shimmer.Direction.RIGHT_TO_LEFT)
                    .setAutoStart(true)
                    .setBaseColor(getColor(android.R.color.darker_gray))
                    .setBaseColor(getColor(android.R.color.darker_gray))
                    .setHighlightColor(getColor(android.R.color.white))
                    .build();
            shimmerFrameLayout.setShimmer(shimmer);

            shimmerFrameLayout.addView(new MyView(MainActivity.this,constraintLayout));
            constraintLayout.addView(shimmerFrameLayout);
            shimmerFrameLayout.startShimmer();
        });

    }

我的activity_main.xml：

<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:ignore="HardcodedText,MissingConstraints"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <androidx.constraintlayout.widget.ConstraintLayout
        tools:ignore="HardcodedText,MissingConstraints"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="20dp"
        android:id="@+id/parent_view">

        <ImageView
            android:id="@+id/item_profile_img"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:src="@drawable/ic_launcher_background"
            app:layout_constraintTop_toTopOf="parent"
            tools:ignore="ContentDescription,MissingConstraints" />

        <TextView
            android:id="@+id/item_student_name_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="15dp"
            android:text="Student name"
            android:textStyle="bold"
            app:layout_constraintStart_toEndOf="@+id/item_profile_img" />

        <TextView
            android:id="@+id/item_student_college"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="15dp"
            android:layout_marginTop="8dp"
            android:text="Student college"
            app:layout_constraintStart_toEndOf="@+id/item_profile_img"
            app:layout_constraintTop_toBottomOf="@+id/item_student_name_title" />

        <TextView
            android:id="@+id/item_student_specialization"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="15dp"
            android:layout_marginTop="8dp"
            android:text="Student specialization"
            app:layout_constraintStart_toEndOf="@+id/item_profile_img"
            app:layout_constraintTop_toBottomOf="@+id/item_student_college" />

        <TextView
            android:id="@+id/item_student_description"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="15dp"
            android:layout_marginTop="8dp"
            android:text="Student description"
            app:layout_constraintTop_toBottomOf="@+id/item_profile_img"
            tools:ignore="MissingConstraints" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>