使用Android中的Path和RectF在左上角右上角左下角繪制圓角

Question

通過制作自定義ImageView並使用以下方法覆蓋onDraw方法將使ImageView具有圓角。 參考

@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);
}

如何選擇性地制作圓角而不是將所有四個角都圓。 例如，僅使左上角和右上角成圓形並保持底角完好無損。 這是一個通過Bitmap做的解決方案 。 我正在尋找這個onDraw方法，只使用Path和RectF。

Answer 1

有一個Path#addRoundRect()重載，它接受一個包含八個值的float數組，其中我們可以為四個角中的每一個指定x和y半徑。 這些值為[x，y]對，從左上角開始，順時針繞其余部分。 對於我們想要舍入的那些角，我們將該對的兩個值都設置為半徑值，並將它們保留為零，而不是那些。

作為一個說明性示例，一個簡單的方法將返回可在您的代碼段中使用的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;
}

根據您的示例說明，舍入左上角和右上角：

@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);
}

和往常一樣，我建議盡可能地保持onDraw()方法，移動任何其他地方不必存在的東西。 例如，可以在構造函數中檢索radius的資源值，並將其保存在字段中。 此外，只有在必要時才能構建Path ; 即，當View的大小改變時，或當半徑或選定的角改變時。

由於我將一個簡單的自定義ImageView放在一起進行測試，我將在此處包含它，因為它演示了以上幾點。 此自定義View還提供XML屬性，允許在布局中設置角半徑和圓角。

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);
        }
    }
}

要使XML屬性起作用，需要在<resources> ，您可以將此文件放在項目的res/values/文件夾中，或添加到可能已存在的文件中。

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是一個維度屬性，應指定為dp或px值。 roundedCorners是一個標志屬性，可以使用豎線字符|來選擇多個角 。 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" />

---

Answer 2

我也花了半天時間來解決這個問題; 這里的關鍵點是如何使用mPath.arcTo制作一個角落。 基本知識是E方向是0度，那么第二個參數意味着哪個程度開始; 第三個參數表示要顯示多少度數。

import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.DecelerateInterpolator;

public class RectangleConerView extends View {

private Path mPath;
private Paint mPaint;
private PathMeasure mPathMeasure;
private float mAnimatorValue;
private Path mDst;
private float mLength;

private float left = 300;
private float top = 200;

private float width = 800;
private float height = 300;
private float checkWidth = 100;
private float checkHeight = 60;
private float cornerRadius = 30;

public RectangleConerView(Context context) {
    super(context);
}

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

public RectangleConerView(Context context, AttributeSet attrs) 
{
    super(context, attrs);
    mPathMeasure = new PathMeasure();
    mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeWidth(5);
    mPath = new Path();

    mPath.moveTo(left + width, top + checkHeight/2);

    //bottom-right
    mPath.lineTo(left + width, top + height - cornerRadius);
    mPath.arcTo(new RectF(left + width-cornerRadius, top + height - cornerRadius, left + width, top + height), 0, 90); //start degree is E direct, then CW 90 degree, which is the bottom-right corner.

    //bottom-left
    mPath.lineTo(left + cornerRadius, top + height);
    mPath.arcTo(new RectF(left, top + height - cornerRadius, left + cornerRadius, top + height), 90, 90);//start degree is the S, then CW 90 degree, which is the bottom-left corner.

    //top-left
    mPath.lineTo(left, top + cornerRadius);
    mPath.arcTo(new RectF(left, top, left + cornerRadius, top + cornerRadius), 180, 90);//start degree W

    //top-right
    mPath.lineTo(left + width - checkWidth/2, top);


    mPathMeasure.setPath(mPath, false);
    mLength = mPathMeasure.getLength();
    mDst = new Path();

    final ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, 1);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator valueAnimator) {
            mAnimatorValue = (float) valueAnimator.getAnimatedValue();
            invalidate();
        }
    });
    valueAnimator.setDuration(1000);
    valueAnimator.setRepeatCount(ValueAnimator.INFINITE);
    valueAnimator.setInterpolator(new DecelerateInterpolator());

    valueAnimator.start();
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    mDst.reset();
    // 硬件加速的BUG
    mDst.lineTo(0,0);
    float stop = mLength * mAnimatorValue;
    mPathMeasure.getSegment(0, stop, mDst, true);
    canvas.drawPath(mDst, mPaint);
}
}