/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.support.v4.widget;
import android.content.Context;
import android.graphics.Canvas;
import android.os.Build;
/**
* Helper for accessing {@link android.widget.EdgeEffect} introduced after
* API level 4 in a backwards compatible fashion.
*
* This class is used to access {@link android.widget.EdgeEffect} on platform versions
* that support it. When running on older platforms it will result in no-ops. It should
* be used by views that wish to use the standard Android visual effects at the edges
* of scrolling containers.
*/
public class EdgeEffectCompat {
private Object mEdgeEffect;
private static final EdgeEffectImpl IMPL;
static {
if (Build.VERSION.SDK_INT >= 14) { // ICS
IMPL = new EdgeEffectIcsImpl();
} else {
IMPL = new BaseEdgeEffectImpl();
}
}
interface EdgeEffectImpl {
public Object newEdgeEffect(Context context);
public void setSize(Object edgeEffect, int width, int height);
public boolean isFinished(Object edgeEffect);
public void finish(Object edgeEffect);
public boolean onPull(Object edgeEffect, float deltaDistance);
public boolean onRelease(Object edgeEffect);
public boolean onAbsorb(Object edgeEffect, int velocity);
public boolean draw(Object edgeEffect, Canvas canvas);
}
/**
* Null implementation to use pre-ICS
*/
static class BaseEdgeEffectImpl implements EdgeEffectImpl {
public Object newEdgeEffect(Context context) {
return null;
}
public void setSize(Object edgeEffect, int width, int height) {
}
public boolean isFinished(Object edgeEffect) {
return true;
}
public void finish(Object edgeEffect) {
}
public boolean onPull(Object edgeEffect, float deltaDistance) {
return false;
}
public boolean onRelease(Object edgeEffect) {
return false;
}
public boolean onAbsorb(Object edgeEffect, int velocity) {
return false;
}
public boolean draw(Object edgeEffect, Canvas canvas) {
return false;
}
}
static class EdgeEffectIcsImpl implements EdgeEffectImpl {
public Object newEdgeEffect(Context context) {
return EdgeEffectCompatIcs.newEdgeEffect(context);
}
public void setSize(Object edgeEffect, int width, int height) {
EdgeEffectCompatIcs.setSize(edgeEffect, width, height);
}
public boolean isFinished(Object edgeEffect) {
return EdgeEffectCompatIcs.isFinished(edgeEffect);
}
public void finish(Object edgeEffect) {
EdgeEffectCompatIcs.finish(edgeEffect);
}
public boolean onPull(Object edgeEffect, float deltaDistance) {
return EdgeEffectCompatIcs.onPull(edgeEffect, deltaDistance);
}
public boolean onRelease(Object edgeEffect) {
return EdgeEffectCompatIcs.onRelease(edgeEffect);
}
public boolean onAbsorb(Object edgeEffect, int velocity) {
return EdgeEffectCompatIcs.onAbsorb(edgeEffect, velocity);
}
public boolean draw(Object edgeEffect, Canvas canvas) {
return EdgeEffectCompatIcs.draw(edgeEffect, canvas);
}
}
/**
* Construct a new EdgeEffect themed using the given context.
*
* <p>Note: On platform versions that do not support EdgeEffect, all operations
* on the newly constructed object will be mocked/no-ops.</p>
*
* @param context Context to use for theming the effect
*/
public EdgeEffectCompat(Context context) {
mEdgeEffect = IMPL.newEdgeEffect(context);
}
/**
* Set the size of this edge effect in pixels.
*
* @param width Effect width in pixels
* @param height Effect height in pixels
*/
public void setSize(int width, int height) {
IMPL.setSize(mEdgeEffect, width, height);
}
/**
* Reports if this EdgeEffectCompat's animation is finished. If this method returns false
* after a call to {@link #draw(Canvas)} the host widget should schedule another
* drawing pass to continue the animation.
*
* @return true if animation is finished, false if drawing should continue on the next frame.
*/
public boolean isFinished() {
return IMPL.isFinished(mEdgeEffect);
}
/**
* Immediately finish the current animation.
* After this call {@link #isFinished()} will return true.
*/
public void finish() {
IMPL.finish(mEdgeEffect);
}
/**
* A view should call this when content is pulled away from an edge by the user.
* This will update the state of the current visual effect and its associated animation.
* The host view should always {@link android.view.View#invalidate()} if this method
* returns true and draw the results accordingly.
*
* @param deltaDistance Change in distance since the last call. Values may be 0 (no change) to
* 1.f (full length of the view) or negative values to express change
* back toward the edge reached to initiate the effect.
* @return true if the host view should call invalidate, false if it should not.
*/
public boolean onPull(float deltaDistance) {
return IMPL.onPull(mEdgeEffect, deltaDistance);
}
/**
* Call when the object is released after being pulled.
* This will begin the "decay" phase of the effect. After calling this method
* the host view should {@link android.view.View#invalidate()} if this method
* returns true and thereby draw the results accordingly.
*
* @return true if the host view should invalidate, false if it should not.
*/
public boolean onRelease() {
return IMPL.onRelease(mEdgeEffect);
}
/**
* Call when the effect absorbs an impact at the given velocity.
* Used when a fling reaches the scroll boundary.
*
* <p>When using a {@link android.widget.Scroller} or {@link android.widget.OverScroller},
* the method <code>getCurrVelocity</code> will provide a reasonable approximation
* to use here.</p>
*
* @param velocity Velocity at impact in pixels per second.
* @return true if the host view should invalidate, false if it should not.
*/
public boolean onAbsorb(int velocity) {
return IMPL.onAbsorb(mEdgeEffect, velocity);
}
/**
* Draw into the provided canvas. Assumes that the canvas has been rotated
* accordingly and the size has been set. The effect will be drawn the full
* width of X=0 to X=width, beginning from Y=0 and extending to some factor <
* 1.f of height.
*
* @param canvas Canvas to draw into
* @return true if drawing should continue beyond this frame to continue the
* animation
*/
public boolean draw(Canvas canvas) {
return IMPL.draw(mEdgeEffect, canvas);
}
}
|
