RelativeLayout圆角处理以后，可以变相对子view进行圆角处理，如ImageView，VideoView等
image
RoundRelativeLayout具体实现
比较简单，只需要在初始化时设置一下layout的ViewOutlineProvider，方便起见，这里写死radius为20dp
/**
* 一个可以把RelativeLayout裁剪成圆角的自定义RelativeLayout布局
* 由于layout里面的子view同样会被裁剪，例如VideoView，ImageView等，很实用
*
* created by luninggithub
*/
public class RoundRelativeLayout extends RelativeLayout {
private static final int DEFAULT_ROUND_SIZE = 20;
public RoundRelativeLayout(Context context) {
this(context, null);
}
public RoundRelativeLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RoundRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public RoundRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init();
}
/**
* 初始化
*/
private void init() {
RoundViewOutlineProvider outlineProvider = new RoundViewOutlineProvider(ScreenUtil.dp2px(DEFAULT_ROUND_SIZE));
setOutlineProvider(outlineProvider);
setClipToOutline(true);
}
/**
* 圆角ViewOutlineProvider
*/
private static class RoundViewOutlineProvider extends ViewOutlineProvider {
private final int roundSize;
public RoundViewOutlineProvider(int roundSize) {
this.roundSize = roundSize;
}
@Override
public void getOutline(View view, Outline outline) {
outline.setRoundRect(0, 0, view.getWidth(), view.getHeight(), roundSize);
}
}
}
关键类ViewOutlineProvider
ViewOutlineProvider是一个抽象类，系统预定义了三种不同的outlineprovider，我们只需要实现getOutline方法，在方法内部设置自定义的outline即可。
package android.view;
import android.graphics.Outline;
import android.graphics.drawable.Drawable;
/**
* Interface by which a View builds its {@link Outline}, used for shadow casting and clipping.
*/
public abstract class ViewOutlineProvider {
// 省略系统预定义的ViewOutlineProvider代码...
/**
* Called to get the provider to populate the Outline.
*
* This method will be called by a View when its owned Drawables are invalidated, when the
* View's size changes, or if {@link View#invalidateOutline()} is called
* explicitly.
*
* The input outline is empty and has an alpha of <code>1.0f</code>.
*
* @param view The view building the outline.
* @param outline The empty outline to be populated.
*/
public abstract void getOutline(View view, Outline outline);
}
由注释可知，getOutline会在view主动调invalidateOutline()方法是被调用
RoundRelativeLayout在初始化int是，会设置自定义的outlineprovider：setOutlineProvider(outlineProvider);
有系统代码可知，setOutlineProvider方法会主动调用，如下：
// 省略View的其他代码......
/**
* Sets the {@link ViewOutlineProvider} of the view, which generates the Outline that defines
* the shape of the shadow it casts, and enables outline clipping.
* <p>
* The default ViewOutlineProvider, {@link ViewOutlineProvider#BACKGROUND}, queries the Outline
* from the View's background drawable, via {@link Drawable#getOutline(Outline)}. Changing the
* outline provider with this method allows this behavior to be overridden.
* <p>
* If the ViewOutlineProvider is null, if querying it for an outline returns false,
* or if the produced Outline is {@link Outline#isEmpty()}, shadows will not be cast.
* <p>
* Only outlines that return true from {@link Outline#canClip()} may be used for clipping.
*
* @see #setClipToOutline(boolean)
* @see #getClipToOutline()
* @see #getOutlineProvider()
*/
public void setOutlineProvider(ViewOutlineProvider provider) {
mOutlineProvider = provider;
invalidateOutline(); // 这里会主动调用自定义的getOutline方法
}
// 省略View的其他代码......
/**
* Called to rebuild this View's Outline from its {@link ViewOutlineProvider outline provider}
*
* @see #setOutlineProvider(ViewOutlineProvider)
*/
public void invalidateOutline() {
rebuildOutline();// 见下面方法
notifySubtreeAccessibilityStateChangedIfNeeded();
invalidateViewProperty(false, false);
}
// 省略View其他代码......
private void rebuildOutline() {
// Unattached views ignore this signal, and outline is recomputed in onAttachedToWindow()
if (mAttachInfo == null) return;
if (mOutlineProvider == null) {
// no provider, remove outline
mRenderNode.setOutline(null);
} else {
final Outline outline = mAttachInfo.mTmpOutline;
outline.setEmpty();
outline.setAlpha(1.0f);
mOutlineProvider.getOutline(this, outline); // 这里调用
mRenderNode.setOutline(outline); // 见下面方法
}
}
/**
* Sets the outline, defining the shape that casts a shadow, and the path to
* be clipped if setClipToOutline is set.
*
* This will make a copy of the provided {@link Outline}, so any future modifications
* to the outline will need to call {@link #setOutline(Outline)} with the modified
* outline for those changes to be applied.
*
* @param outline The outline to use for this RenderNode.
* @return True if the value changed, false if the new value was the same as the previous value.
*/
public boolean setOutline(@Nullable Outline outline) {
if (outline == null) {
return nSetOutlineNone(mNativeRenderNode);
}
switch (outline.mMode) {
case Outline.MODE_EMPTY:
return nSetOutlineEmpty(mNativeRenderNode);
case Outline.MODE_ROUND_RECT: // 走到这里
return nSetOutlineRoundRect(mNativeRenderNode,
outline.mRect.left, outline.mRect.top,
outline.mRect.right, outline.mRect.bottom,
outline.mRadius, outline.mAlpha);
case Outline.MODE_PATH:
return nSetOutlinePath(mNativeRenderNode, outline.mPath.mNativePath,
outline.mAlpha);
}
throw new IllegalArgumentException("Unrecognized outline?");
}
// 省略View代码......
public final class RenderNode {
// 省略无关代码...
@CriticalNative
private static native boolean nSetOutlineRoundRect(long renderNode, int left, int top,
int right, int bottom, float radius, float alpha);
}
这样一看就比较清晰了
init -→ setOutlineProvider -→ invalidateOutline -→ rebuildOutline -→ setOutline -→ nSetOutlineRoundRect(Native接口)
Demo地址
