Android ViewPager在拖拽到左邊和右邊的時候，禁止顯示黃色或者藍色的漸變圖片的解決方法
先說明哦，想看看院里的，從頭開始看，否則，就拉到最下面啦。解決方案就在最下面。
修改前：
修改后：
先看下ViewPager中和這個顏色相關的代碼：
| private EdgeEffectCompat mLeftEdge; private EdgeEffectCompat mRightEdge; |
就是這倆貨，導致的邊界顏色。沒辦法，這貨是private的，后面只能通過反射來得到了。
再看下draw()方法中的邏輯：
| @Override public void draw(Canvas canvas) { super.draw(canvas); boolean needsInvalidate = false;
final int overScrollMode = ViewCompat.getOverScrollMode(this); if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS || (overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS && mAdapter != null && mAdapter.getCount() > 1)) { if (!mLeftEdge.isFinished()) { final int restoreCount = canvas.save(); final int height = getHeight() - getPaddingTop() - getPaddingBottom();
canvas.rotate(270); canvas.translate(-height + getPaddingTop(), 0); mLeftEdge.setSize(height, getWidth()); needsInvalidate |= mLeftEdge.draw(canvas); canvas.restoreToCount(restoreCount); } if (!mRightEdge.isFinished()) { final int restoreCount = canvas.save(); final int width = getWidth(); final int height = getHeight() - getPaddingTop() - getPaddingBottom(); final int itemCount = mAdapter != null ? mAdapter.getCount() : 1;
canvas.rotate(90); canvas.translate(-getPaddingTop(), -itemCount * (width + mPageMargin) + mPageMargin); mRightEdge.setSize(height, width); needsInvalidate |= mRightEdge.draw(canvas); canvas.restoreToCount(restoreCount); } } else { mLeftEdge.finish(); mRightEdge.finish(); }
if (needsInvalidate) { // Keep animating invalidate(); } } |
在進行繪制漸變圖片之前會判斷是否已經finish,【if (!mLeftEdge.isFinished())】，如果我們能修改為finished狀態，不就OK了嗎？！經過測試，調用mLeftEdge.finish()和mRightEdge.finish()就能達到我們要的結果。但是悲催的是，draw()方法是隨時隨地都在調用的，所以要在一個在draw()方法之后調用，但是還得隨時隨地調用的方法才行。
好吧，先說點原理的東東。
ViewPager.javaàdraw()方法 à mRightEdge.draw(canvas);以及mLeftEdge.draw(canvas);à EdgeEffectCompat.javaà看下全部的代碼吧：
| 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); } } |
à看完之后，下面進入到EdgeEffectCompatIcs.javaà好吧，再貼上完整的代碼
| class EdgeEffectCompatIcs { public static Object newEdgeEffect(Context context) { return new EdgeEffect(context); }
public static void setSize(Object edgeEffect, int width, int height) { ((EdgeEffect) edgeEffect).setSize(width, height); }
public static boolean isFinished(Object edgeEffect) { return ((EdgeEffect) edgeEffect).isFinished(); }
public static void finish(Object edgeEffect) { ((EdgeEffect) edgeEffect).finish(); }
public static boolean onPull(Object edgeEffect, float deltaDistance) { ((EdgeEffect) edgeEffect).onPull(deltaDistance); return true; }
public static boolean onRelease(Object edgeEffect) { EdgeEffect eff = (EdgeEffect) edgeEffect; eff.onRelease(); return eff.isFinished(); }
public static boolean onAbsorb(Object edgeEffect, int velocity) { ((EdgeEffect) edgeEffect).onAbsorb(velocity); return true; }
public static boolean draw(Object edgeEffect, Canvas canvas) { return ((EdgeEffect) edgeEffect).draw(canvas); } } |
à下面進入到EdgeEffect.java中吧à如果你有閑情逸致的話，那就看下他的代碼吧，都是這貨在搞鬼。
下面就說正經的內容了，看看我的解決方案：
主要是在自定義的OnPageChangeListener里面。
先定義一下：
| private EdgeEffectCompat leftEdge; private EdgeEffectCompat rightEdge; |
然后是構造中，通過反射得到對象：
| try { Field leftEdgeField = mViewPager.getClass().getDeclaredField("mLeftEdge"); Field rightEdgeField = mViewPager.getClass().getDeclaredField("mRightEdge");
Log.i("xinye", "=======leftEdgeField:" + leftEdgeField + ",rightEdgeField:" + rightEdgeField); if(leftEdgeField != null && rightEdgeField != null){
leftEdgeField.setAccessible(true); rightEdgeField.setAccessible(true);
leftEdge = (EdgeEffectCompat) leftEdgeField.get(mViewPager); rightEdge = (EdgeEffectCompat) rightEdgeField.get(mViewPager); Log.i("xinye", "=======OK啦，leftEdge:" + leftEdge + ",rightEdge:" + rightEdge); }
} catch (Exception e) { e.printStackTrace(); } |
然后，就是最重要的了：
| @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels){
if(leftEdge != null && rightEdge != null){ leftEdge.finish(); rightEdge.finish(); leftEdge.setSize(0, 0); rightEdge.setSize(0, 0); } |
好吧，完事了。做做看吧