通过创建custom ImageView并使用以下方法覆盖onDraw方法,将使ImageView具有圆角。引用

@Override
protected void onDraw(Canvas canvas) {
    float radius = getContext().getResources().getDimension(R.dimen.round_corner_radius);
    Path path = new Path();
    RectF rect = new RectF(0, 0, this.getWidth(), this.getHeight());
    path.addRoundRect(rect, radius, radius, Path.Direction.CW);
    canvas.clipPath(path);
    super.onDraw(canvas);
}

如何有选择地制作圆角而不是使所有四个圆角都变圆。例如,仅使左上角和右上角变圆并使底角保持完整。这是通过位图执行的solution。我正在寻找在此onDraw方法中执行此操作,并且仅使用Path和RectF。

最佳答案

有一个Path#addRoundRect()重载,它使用八个值的float数组,其中我们可以为四个角中的每个角指定x半径和y半径。这些值是[x,y]对,从左上角开始,然后沿顺时针方向旋转其余的值。对于那些我们想要四舍五入的角,我们将对的两个值都设置为半径值,对于那些我们不想要的值,将其保留为零。

作为说明性示例,一个简单的方法将返回可在您的代码段中使用的Path:

private Path getPath(float radius, boolean topLeft, boolean topRight,
                     boolean bottomRight, boolean bottomLeft) {

    final Path path = new Path();
    final float[] radii = new float[8];

    if (topLeft) {
        radii[0] = radius;
        radii[1] = radius;
    }

    if (topRight) {
        radii[2] = radius;
        radii[3] = radius;
    }

    if (bottomRight) {
        radii[4] = radius;
        radii[5] = radius;
    }

    if (bottomLeft) {
        radii[6] = radius;
        radii[7] = radius;
    }

    path.addRoundRect(new RectF(0, 0, getWidth(), getHeight()),
                      radii, Path.Direction.CW);

    return path;
}

根据您的示例描述,将左上角和右上角四舍五入:
@Override
protected void onDraw(Canvas canvas) {
    float radius = getContext().getResources().getDimension(R.dimen.round_corner_radius);
    Path path = getPath(radius, true, true, false, false);
    canvas.clipPath(path);
    super.onDraw(canvas);
}

和往常一样,我建议保持onDraw()方法尽可能的紧凑,将不需要的东西移到其他地方。例如,可以在构造函数中检索半径的资源值,并将其保留在字段中。此外,只有在必要时才可以构造Path。也就是说,当View的大小更改时,或者当半径或所选的边角更改时。

由于我编写了一个简单的自定义ImageView进行测试,因此将在此处包括它,因为它证明了上述几点。此自定义View还提供XML属性,该属性允许在布局中设置拐角半径和圆角。
public class RoundishImageView extends ImageView {

    public static final int CORNER_NONE = 0;
    public static final int CORNER_TOP_LEFT = 1;
    public static final int CORNER_TOP_RIGHT = 2;
    public static final int CORNER_BOTTOM_RIGHT = 4;
    public static final int CORNER_BOTTOM_LEFT = 8;
    public static final int CORNER_ALL = 15;

    private static final int[] CORNERS = {CORNER_TOP_LEFT,
                                          CORNER_TOP_RIGHT,
                                          CORNER_BOTTOM_RIGHT,
                                          CORNER_BOTTOM_LEFT};

    private final Path path = new Path();
    private int cornerRadius;
    private int roundedCorners;

    public RoundishImageView(Context context) {
        this(context, null);
    }

    public RoundishImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public RoundishImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RoundishImageView);
        cornerRadius = a.getDimensionPixelSize(R.styleable.RoundishImageView_cornerRadius, 0);
        roundedCorners = a.getInt(R.styleable.RoundishImageView_roundedCorners, CORNER_NONE);
        a.recycle();
    }

    public void setCornerRadius(int radius) {
        if (cornerRadius != radius) {
            cornerRadius = radius;
            setPath();
            invalidate();
        }
    }

    public int getCornerRadius() {
        return cornerRadius;
    }

    public void setRoundedCorners(int corners) {
        if (roundedCorners != corners) {
            roundedCorners = corners;
            setPath();
            invalidate();
        }
    }

    public boolean isCornerRounded(int corner) {
        return (roundedCorners & corner) == corner;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (!path.isEmpty()) {
            canvas.clipPath(path);
        }

        super.onDraw(canvas);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        setPath();
    }

    private void setPath() {
        path.rewind();

        if (cornerRadius >= 1f && roundedCorners != CORNER_NONE) {
            final float[] radii = new float[8];

            for (int i = 0; i < 4; i++) {
                if (isCornerRounded(CORNERS[i])) {
                    radii[2 * i] = cornerRadius;
                    radii[2 * i + 1] = cornerRadius;
                }
            }

            path.addRoundRect(new RectF(0, 0, getWidth(), getHeight()),
                              radii, Path.Direction.CW);
        }
    }
}

为了使XML属性正常工作,需要在<resources>中添加以下内容:将这个文件放在项目的res/values/文件夹中,或添加到可能已经存在的文件夹中,即可完成此操作。
attrs.xml
<resources>
    <declare-styleable name="RoundishImageView">
        <attr name="cornerRadius" format="dimension" />
        <attr name="roundedCorners">
            <flag name="topLeft" value="1" />
            <flag name="topRight" value="2" />
            <flag name="bottomRight" value="4" />
            <flag name="bottomLeft" value="8" />
            <flag name="all" value="15" />
        </attr>
    </declare-styleable>
</resources>
cornerRadius是维度属性,应将其指定为dppx值。 roundedCorners是一个标志属性,可以使用竖线字符|选择多个角。例如:
<com.mycompany.myapp.RoundishImageView
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/riv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true"
    android:scaleType="fitXY"
    android:src="@drawable/magritte"
    app:cornerRadius="@dimen/round_corner_radius"
    app:roundedCorners="topLeft|topRight" />

android - 在Android中使用Path和RectF在左上角,右上角,左下角,右下角绘制圆角-LMLPHP

10-06 07:19