在项目开发中，经常遇到圆角展示的效果，例如有ImageView圆角、Banner条圆角、TextView圆角、Relative/LinearLayout整体圆角等，其实就是在外层加一层父容器，对父容器进行裁剪。

public class RoundRectLayout extends RelativeLayout {

private Path mPath;

private int mRadius;

private int mWidth;

private int mHeight;

private int mLastRadius;

public static final int MODE_NONE = 0;

public static final int MODE_ALL = 1;

public static final int MODE_LEFT = 2;

public static final int MODE_TOP = 3;

public static final int MODE_RIGHT = 4;

public static final int MODE_BOTTOM = 5;

private int mRoundMode = MODE_ALL;

public RoundRectLayout(Context context) {

super(context);

init();

}

public RoundRectLayout(Context context, AttributeSet attrs) {

super(context, attrs);

init();

}

private void init(){

setBackgroundDrawable(new ColorDrawable(0x33ff0000));

mPath = new Path();

mPath.setFillType(Path.FillType.EVEN_ODD);

setCornerRadius(15);

}

/**

* 设置是否圆角裁边

* @param roundMode

*/

public void setRoundMode(int roundMode){

mRoundMode = roundMode;

}

/**

* 设置圆角半径

* @param radius

*/

public void setCornerRadius(int radius){

mRadius = radius;

}

private void checkPathChanged(){

if(getWidth() == mWidth && getHeight() == mHeight && mLastRadius == mRadius){

return;

}

mWidth = getWidth();

mHeight = getHeight();

mLastRadius = mRadius;

mPath.reset();

switch (mRoundMode){

case MODE_ALL:

mPath.addRoundRect(new RectF(0, 0, mWidth, mHeight), mRadius, mRadius, Path.Direction.CW);

break;

case MODE_LEFT:

mPath.addRoundRect(new RectF(0, 0, mWidth, mHeight),

new float[]{mRadius, mRadius, 0, 0, 0, 0, mRadius, mRadius},

Path.Direction.CW);

break;

case MODE_TOP:

mPath.addRoundRect(new RectF(0, 0, mWidth, mHeight),

new float[]{mRadius, mRadius, mRadius, mRadius, 0, 0, 0, 0},

Path.Direction.CW);

break;

case MODE_RIGHT:

mPath.addRoundRect(new RectF(0, 0, mWidth, mHeight),

new float[]{0, 0, mRadius, mRadius, mRadius, mRadius, 0, 0},

Path.Direction.CW);

break;

case MODE_BOTTOM:

mPath.addRoundRect(new RectF(0, 0, mWidth, mHeight),

new float[]{0, 0, 0, 0, mRadius, mRadius, mRadius, mRadius},

Path.Direction.CW);

break;

}

}

@Override

public void draw(Canvas canvas) {

if(mRoundMode != MODE_NONE){

int saveCount = canvas.save();

checkPathChanged();

canvas.clipPath(mPath);

super.draw(canvas);

canvas.restoreToCount(saveCount);

}else {

super.draw(canvas);

}

}

}