Android 滑动效果高级篇（八）—— 自定义控件

秒速五厘米 2023-10-16 19:00 3阅读 0赞

自定义控件，较常用View、ViewGroup、Scroller三个类，其继承关系如下：

![1335095940_9227.png][]

本示例自定义控件，实现一个Gallery效果，并添加了一个显示View个数和位置的bar条，效果图：

![1335062777_9675.png][]

自定义控件，包含通过继承实现的自定义控件和自定义控件属性两部分，即控件和属性

**1、自定义属性**

自定义属性，分为定义属性、解析属性、设置属性三部分，具体步骤：

首先，在res/valus/attrs.xml属性资源文件中，定义控件属性

<?xml version="1.0" encoding="utf-8"?>
    <resources>
        <declare-styleable name="com.myapps.widget.Pager">
            <attr name="pageWidth" format="dimension" />
        </declare-styleable>
        
        <declare-styleable name="com.myapps.widget.PagerBar">
            <attr name="barColor" format="color" />
            <attr name="highlightColor" format="color" />
            <attr name="fadeDelay" format="integer" />
            <attr name="fadeDuration" format="integer" />
            <attr name="roundRectRadius" format="dimension" />
        </declare-styleable>
    </resources>

然后，在自定义控件的代码中，解析自定义的属性，如在PagerBar.java：

// 自定义属性
    		TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.com_myapps_widget_PagerBar);
    		int barBackColor = a.getColor(R.styleable.com_myapps_widget_PagerBar_barColor, DEFAULT_BAR_BACKCOLOR);				// bar背景色
    		int barForeColor = a.getColor(R.styleable.com_myapps_widget_PagerBar_highlightColor, DEFAULT_BAR_FORECOLOR);	// bar前景色
    		fadeDelay = a.getInteger(R.styleable.com_myapps_widget_PagerBar_fadeDelay, DEFAULT_FADE_DELAY);				// bar消失延迟时间
    		fadeDuration = a.getInteger(R.styleable.com_myapps_widget_PagerBar_fadeDuration, DEFAULT_FADE_DURATION);	// bar消失动画时间
    		ovalRadius = a.getDimension(R.styleable.com_myapps_widget_PagerBar_roundRectRadius, 2f);
    		a.recycle();

最后，在布局文件中设置属性，如在main.xml

<com.homer.mycontrol.PagerBar
            android:id="@+id/control"
            android:layout_width="fill_parent"
            android:layout_height="4dip"
            android:layout_margin="8dip"
            myapps:roundRectRadius="2dip" />

其中，在布局中间main.xml中，需要注意：

xmlns:myapps="http://schemas.android.com/apk/res/com.homer.mycontrol"

定义属性时，在declare-styleable的name中，需要包含com.myapps.widget.PagerBar，表示自定义的控件PageBar是widget子类，myapps是xmlns解析标记

解析属性时，在TypedArray中，需要包含R.styleable.com\_myapps\_widget\_PagerBar，横线替换了圆点.

定义属性时，在com.homer.mycontrol.PagerBar中，需要包含myapps:roundRectRadius="2dip"，加上myapps解析标记

**2、自定义控件PagerBar**

自定义PagerBar，在图片下方用来显示图片滑到了第几页，即上面效果图（图2、图3）中的下部银白色细条，具体实现：

public PagerBar(Context context, AttributeSet attrs, int defStyle) {
    		super(context, attrs, defStyle);
    
    		// 自定义属性
    		TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.com_myapps_widget_PagerBar);
    		int barBackColor = a.getColor(R.styleable.com_myapps_widget_PagerBar_barColor, DEFAULT_BAR_BACKCOLOR);				// bar背景色
    		int barForeColor = a.getColor(R.styleable.com_myapps_widget_PagerBar_highlightColor, DEFAULT_BAR_FORECOLOR);	// bar前景色
    		fadeDelay = a.getInteger(R.styleable.com_myapps_widget_PagerBar_fadeDelay, DEFAULT_FADE_DELAY);				// bar消失延迟时间
    		fadeDuration = a.getInteger(R.styleable.com_myapps_widget_PagerBar_fadeDuration, DEFAULT_FADE_DURATION);	// bar消失动画时间
    		ovalRadius = a.getDimension(R.styleable.com_myapps_widget_PagerBar_roundRectRadius, 2f);
    		a.recycle();
    
    		barBackPaint = new Paint();
    		barBackPaint.setColor(barBackColor);
    
    		barForePaint = new Paint();
    		barForePaint.setColor(barForeColor);
    
    		fadeOutAnimation = new AlphaAnimation(1f, 0f);
    		fadeOutAnimation.setDuration(fadeDuration);
    		fadeOutAnimation.setRepeatCount(0);
    		fadeOutAnimation.setInterpolator(new LinearInterpolator());
    		fadeOutAnimation.setFillEnabled(true);
    		fadeOutAnimation.setFillAfter(true);
    	}
    
    	public int getNumPages() {
    		return numPages;
    	}
    
    	public void setNumPages(int numPages) {
    		if (numPages <= 0) {
    			throw new IllegalArgumentException("numPages must be positive");
    		}
    		this.numPages = numPages;
    		invalidate();		// 重绘View
    		fadeOut();			// 设置bar消失效果
    	}
    
    	/** bar消失动画 */
    	private void fadeOut() {
    		if (fadeDuration > 0) {
    			clearAnimation();
    			fadeOutAnimation.setStartTime(AnimationUtils.currentAnimationTimeMillis() + fadeDelay);	//延迟fadeDelay后动画开始
    			setAnimation(fadeOutAnimation);
    		}
    	}
    
    	/**  @return  0 to numPages-1 */
    	public int getCurrentPage() {
    		return currentPage;
    	}
    
    	/** @param currentPage  0 to numPages-1  */
    	public void setCurrentPage(int currentPage) {
    		if (currentPage < 0 || currentPage >= numPages) {
    			throw new IllegalArgumentException("currentPage parameter out of bounds");
    		}
    		if (this.currentPage != currentPage) {
    			this.currentPage = currentPage;
    			this.position = currentPage * getPageWidth();	// bar前景色滑动条的起始位置（像素值）
    			invalidate();
    			fadeOut();
    		}
    	}
    
    	/** 获取View的宽度，即bar的宽度 */
    	public int getPageWidth() {
    		return getWidth() / numPages;	// getWidth()是PagerBar的宽度（减去了margin左右距离后）
    	}
    
    	/**  @param position     can be -pageWidth to pageWidth*(numPages+1)  */
    	public void setPosition(int position) {
    		if (this.position != position) {
    			this.position = position;
    			invalidate();
    			fadeOut();
    		}
    	}
    
    	@Override
    	protected void onDraw(Canvas canvas) {
    		canvas.drawRoundRect(new RectF(0, 0, getWidth(), getHeight()), ovalRadius, ovalRadius, barBackPaint);	// 绘制bar背景
    		canvas.drawRoundRect(new RectF(position, 0, position + (getWidth() / numPages), getHeight()), ovalRadius, ovalRadius, barForePaint);	// 绘制bar前景
    	}
    }

**3、自定义控件Pager**

自定义控件Pager，继承自ViewGroup，用来显示图片的，类似于Gallery，实现主要部分包含：

A、自定义属性解析

B、Pager容器控件Scroller滑动页设置与控制

C、容器状态保存（onSaveInstanceState）

D、容器事件监听接口

**详细实现如下：**

A、自定义属性解析

public Pager(Context context, AttributeSet attrs, int defStyle) {
    		super(context, attrs, defStyle);
    
    		// 自定义属性
    		TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.com_myapps_widget_Pager);
    		pageWidthSpec = a.getDimensionPixelSize(R.styleable.com_myapps_widget_Pager_pageWidth, SPEC_UNDEFINED);
    		a.recycle();
    	}

B、Pager容器控件Scroller滑动页设置与控制

public void setCurrentPage(int currentPage) {
    		mCurrentPage = Math.max(0, Math.min(currentPage, getChildCount()));		// 非常好
    		scrollTo(getScrollXForPage(mCurrentPage), 0);
    		invalidate();	// 重绘View
    	}
    
    	int getCurrentPage() {
    		return mCurrentPage;
    	}
    
    	public void setPageWidth(int pageWidth) {
    		this.pageWidthSpec = pageWidth;
    	}
    
    	public int getPageWidth() {
    		return pageWidth;
    	}
    
    	/** 获取whichPage的Pager起始x位置，whichPage从0开始计 */
    	private int getScrollXForPage(int whichPage) {
    		return (whichPage * pageWidth) - pageWidthPadding();
    	}
    
    	/** 返回View的 paddingwidth 一半(1/2)*/
    	int pageWidthPadding() {
    		return ((getMeasuredWidth() - pageWidth) / 2);
    	}
    
    	@Override
    	public void computeScroll() {		// update  mScrollX and mScrollY  of View
    		if (mScroller.computeScrollOffset()) {
    			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
    			postInvalidate();			// invalidate the View from a non-UI thread
    		} else if (mNextPage != INVALID_SCREEN) {
    			mCurrentPage = mNextPage;
    			mNextPage = INVALID_SCREEN;
    			clearChildrenCache();
    		}
    	}
    
    	@Override
    	protected void dispatchDraw(Canvas canvas) {	// draw the child views
    		
    		final long drawingTime = getDrawingTime();	// 绘制childView
    		final int count = getChildCount();
    		for (int i = 0; i < count; i++) {
    			drawChild(canvas, getChildAt(i), drawingTime);
    		}
    
    		for (OnScrollListener mListener : mListeners) {	// 自定义接口
    			int adjustedScrollX = getScrollX() + pageWidthPadding();
    			mListener.onScroll(adjustedScrollX);
    			if (adjustedScrollX % pageWidth == 0) {	// scroll finished
    				mListener.onViewScrollFinished(adjustedScrollX / pageWidth);
    			}
    		}
    	}
    
    	@Override
    	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    
    		pageWidth = (pageWidthSpec == SPEC_UNDEFINED) ? getMeasuredWidth() : pageWidthSpec;
    		pageWidth = Math.min(pageWidth, getMeasuredWidth());
    
    		final int count = getChildCount();
    		for (int i = 0; i < count; i++) {
    			widthMeasureSpec = MeasureSpec.makeMeasureSpec(pageWidth, MeasureSpec.EXACTLY);
    			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
    		}
    
    		if (mFirstLayout) {	// 第一次显示Pager时，page的位置
    			scrollTo(getScrollXForPage(mCurrentPage), mScroller.getCurrY());
    			mFirstLayout = false;
    		}
    	}
    
    	@Override
    	protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    		int childLeft = 0;
    
    		final int count = getChildCount();	// 绘制childView
    		for (int i = 0; i < count; i++) {
    			final View child = getChildAt(i);
    			if (child.getVisibility() != View.GONE) {
    				final int childWidth = child.getMeasuredWidth();
    				child.layout(childLeft, 0, childLeft + childWidth, child.getMeasuredHeight());
    				childLeft += childWidth;
    			}
    		}
    	}

@Override
    	public boolean onInterceptTouchEvent(MotionEvent ev) {
    		final int action = ev.getAction();
    		if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) {	// 正在滑动中
    			return true;
    		}
    
    		final float x = ev.getX();
    		final float y = ev.getY();
    
    		switch (action) {
    		case MotionEvent.ACTION_MOVE:
    			if (mTouchState == TOUCH_STATE_REST) {
    				checkStartScroll(x, y);
    			}
    			break;
    
    		case MotionEvent.ACTION_DOWN:
    			mLastMotionX = x;
    			mLastMotionY = y;
    			mAllowLongPress = true;
    
    			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;	// scroll 完成后，重置状态
    			break;
    
    		case MotionEvent.ACTION_CANCEL:
    		case MotionEvent.ACTION_UP:
    			clearChildrenCache();
    			mTouchState = TOUCH_STATE_REST;
    			break;
    		}
    
    		return mTouchState != TOUCH_STATE_REST;
    	}
    
    	@Override
    	public boolean onTouchEvent(MotionEvent ev) {
    		if (mVelocityTracker == null) {
    			mVelocityTracker = VelocityTracker.obtain();
    		}
    		mVelocityTracker.addMovement(ev);
    
    		final int action = ev.getAction();
    		final float x = ev.getX();
    		final float y = ev.getY();
    
    		switch (action) {
    		case MotionEvent.ACTION_DOWN:
    			if (!mScroller.isFinished()) {
    				mScroller.abortAnimation();
    			}
    			mLastMotionX = x;
    			break;
    			
    		case MotionEvent.ACTION_MOVE:
    			if (mTouchState == TOUCH_STATE_REST) {
    				checkStartScroll(x, y);
    			} else if (mTouchState == TOUCH_STATE_SCROLLING) {	// scrolling 状态时，重绘view
    				int deltaX = (int) (mLastMotionX - x);
    				mLastMotionX = x;
    
    				if (getScrollX() < 0 || getScrollX() > getChildAt(getChildCount() - 1).getLeft()) {
    					deltaX /= 2;
    				}
    				scrollBy(deltaX, 0);
    			}
    			break;
    			
    		case MotionEvent.ACTION_UP:
    			if (mTouchState == TOUCH_STATE_SCROLLING) {
    				final VelocityTracker velocityTracker = mVelocityTracker;
    				velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
    				int velocityX = (int) velocityTracker.getXVelocity();
    
    				if (velocityX > SNAP_VELOCITY && mCurrentPage > 0) {
    					snapToPage(mCurrentPage - 1);
    				} else if (velocityX < -SNAP_VELOCITY && mCurrentPage < getChildCount() - 1) {
    					snapToPage(mCurrentPage + 1);
    				} else {
    					snapToDestination();
    				}
    
    				if (mVelocityTracker != null) {
    					mVelocityTracker.recycle();
    					mVelocityTracker = null;
    				}
    			}
    			mTouchState = TOUCH_STATE_REST;
    			break;
    		case MotionEvent.ACTION_CANCEL:
    			mTouchState = TOUCH_STATE_REST;
    		}
    
    		return true;
    	}
    
    	/** 检查scroll状态，并设置绘制scroll缓存 */
    	private void checkStartScroll(float x, float y) {
    		final int xDiff = (int) Math.abs(x - mLastMotionX);
    		final int yDiff = (int) Math.abs(y - mLastMotionY);
    
    		boolean xMoved = xDiff > mTouchSlop;
    		boolean yMoved = yDiff > mTouchSlop;
    
    		if (xMoved || yMoved) {
    			if (xMoved) {
    				mTouchState = TOUCH_STATE_SCROLLING;		// 设置为scrolling 状态
    				enableChildrenCache();
    			}
    			if (mAllowLongPress) {
    				mAllowLongPress = false;
    				final View currentScreen = getChildAt(mCurrentPage);
    				currentScreen.cancelLongPress();	// Cancels a pending long press
    			}
    		}
    	}
    
    	void enableChildrenCache() {
    		setChildrenDrawingCacheEnabled(true);		// Enables or disables the drawing cache for each child of this viewGroup
    		setChildrenDrawnWithCacheEnabled(true);	// Tells the ViewGroup to draw its children using their drawing cache
    	}
    
    	void clearChildrenCache() {
    		setChildrenDrawnWithCacheEnabled(false);
    	}
    
    	private void snapToDestination() {
    		final int startX = getScrollXForPage(mCurrentPage);
    		int whichPage = mCurrentPage;
    		if (getScrollX() < startX - getWidth() / 8) {
    			whichPage = Math.max(0, whichPage - 1);
    		} else if (getScrollX() > startX + getWidth() / 8) {
    			whichPage = Math.min(getChildCount() - 1, whichPage + 1);
    		}
    
    		snapToPage(whichPage);
    	}
    
    	void snapToPage(int whichPage) {
    		enableChildrenCache();
    
    		boolean changingPages = whichPage != mCurrentPage;
    
    		mNextPage = whichPage;
    
    		View focusedChild = getFocusedChild();
    		if (focusedChild != null && changingPages && focusedChild == getChildAt(mCurrentPage)) {
    			focusedChild.clearFocus();
    		}
    
    		final int newX = getScrollXForPage(whichPage);
    		final int delta = newX - getScrollX();
    		mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 2);
    		invalidate();
    	}
    
    	/** 向左滑动 */
    	public void scrollLeft() {
    		if (mNextPage == INVALID_SCREEN && mCurrentPage > 0 && mScroller.isFinished()) {
    			snapToPage(mCurrentPage - 1);
    		}
    	}
    
    	/** 向右滑动 */
    	public void scrollRight() {
    		if (mNextPage == INVALID_SCREEN && mCurrentPage < getChildCount() - 1 && mScroller.isFinished()) {
    			snapToPage(mCurrentPage + 1);
    		}
    	}

C、容器状态保存（onSaveInstanceState）

/** 保存状态 */
    	public static class SavedState extends BaseSavedState {
    		int currentScreen = -1;
    
    		SavedState(Parcelable superState) {
    			super(superState);
    		}
    
    		private SavedState(Parcel in) {
    			super(in);
    			currentScreen = in.readInt();
    		}
    
    		public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
    			public SavedState createFromParcel(Parcel in) {	// get data written by Parcelable.writeToParcel()	
    				return new SavedState(in);
    			}
    
    			public SavedState[] newArray(int size) {			// create  array of the Parcelable 
    				return new SavedState[size];
    			}
    		};
    		
    		@Override
    		public void writeToParcel(Parcel out, int flags) {		// set data to parcel
    			super.writeToParcel(out, flags);
    			out.writeInt(currentScreen);
    		}
    
    	}
    
    	@Override
    	protected Parcelable onSaveInstanceState() {		// 保存状态
    		final SavedState state = new SavedState(super.onSaveInstanceState());
    		state.currentScreen = mCurrentPage;	 	// save InstanceState
    		return state;
    	}
    
    	@Override
    	protected void onRestoreInstanceState(Parcelable state) {	// 恢复状态
    		SavedState savedState = (SavedState) state;
    		super.onRestoreInstanceState(savedState.getSuperState());	// get InstanceState
    		if (savedState.currentScreen != INVALID_SCREEN) {
    			mCurrentPage = savedState.currentScreen;	
    		}
    	}

D、容器事件监听接口

public void addOnScrollListener(OnScrollListener listener) {
    		mListeners.add(listener);
    	}
    
    	public void removeOnScrollListener(OnScrollListener listener) {
    		mListeners.remove(listener);
    	}
    
    	/** 自定义接口 */
    	public static interface OnScrollListener {
    		void onScroll(int scrollX);
    		void onViewScrollFinished(int currentPage);
    	}

[代码下载][Link 1]

**参考推荐：**

[Android中自定义属性的使用][Android]

[Android中自定义属性的格式详解][Android 1]

[Scroller][]（Android） [Scroller][Scroller 1]（cnblog）

[Android Parcelable][]

[Android左右滑动加载分页][Android 2]

[1335095940_9227.png]: https://img-my.csdn.net/uploads/201204/22/1335095940_9227.png
[1335062777_9675.png]: https://img-my.csdn.net/uploads/201204/22/1335062777_9675.png
[Link 1]: http://download.csdn.net/detail/sunboy_2050/4247498
[Android]: http://www.cnblogs.com/ufocdy/archive/2011/05/27/2060221.html
[Android 1]: http://blog.csdn.net/mayingcai1987/article/details/6216655
[Scroller]: http://developer.android.com/reference/android/widget/Scroller.html
[Scroller 1]: http://www.cnblogs.com/over140/archive/2010/12/16/1907528.html
[Android Parcelable]: http://blog.csdn.net/sunboy_2050/article/details/6949809
[Android 2]: http://www.iteye.com/topic/1114852