有一個Path#addRoundRect()重載,它接受一個包含八個值的float數(shù)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.對于我們想要舍入的那些角,我們將該對的兩個值都設(shè)置為半徑值,并將它們保留為零,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(jù)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(gòu)造函數(shù)中檢索radius的資源值,并將其保存在字段中.此外,只有在必要時才能構(gòu)建路徑;即,當視圖的大小改變時,或當半徑或選定的角改變時.

由于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.此自定義視圖還提供XML屬性,允許在布局中設(shè)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>中進行以下操作,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

cornerRadius是一個維度屬性,應(yīng)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：

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" />

總結(jié)

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