Android 自定义滚动视图

MainActivity


    package org.wp.activity; 
     
    import android.app.Activity; 
    import android.os.Bundle; 
    import android.widget.ImageView; 
     
    public class MainActivity extends Activity { 
        private ImageScrollView imageScrollView = null; 
        private PageControlView pageControlView = null; 
     
        @Override 
        public void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState); 
            setContentView(R.layout.main); 
             
            imageScrollView = (ImageScrollView) this.findViewById(R.id.myImageScrollView); 
     
            ImageView imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a1); 
            imageScrollView.addView(imageView); 
     
            imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a2); 
            imageScrollView.addView(imageView); 
     
            imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a3); 
            imageScrollView.addView(imageView); 
     
            imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a4); 
            imageScrollView.addView(imageView); 
     
            imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a5); 
            imageScrollView.addView(imageView); 
     
            imageView = new ImageView(this); 
            imageView.setImageResource(R.drawable.a6); 
            imageScrollView.addView(imageView); 
     
            pageControlView = (PageControlView) this.findViewById(R.id.myPageControlView); 
            /** 设置圆圈的数量 **/ 
            pageControlView.setCount(imageScrollView.getChildCount()); 
            /** 初始化圆圈 **/ 
            pageControlView.generatePageControl(0); 
            /** 设置视图切换回调函数实现 **/ 
            imageScrollView.setScrollToScreenCallback(pageControlView); 
        } 
    } 



ImageScrollView


    package org.wp.activity; 
     
    import android.content.Context; 
    import android.util.AttributeSet; 
    import android.view.GestureDetector; 
    import android.view.GestureDetector.OnGestureListener; 
    import android.view.MotionEvent; 
    import android.view.View; 
    import android.view.ViewConfiguration; 
    import android.view.ViewGroup; 
    import android.widget.Scroller; 
     
    public class ImageScrollView extends ViewGroup { 
        /** 滚动对象Scroller **/ 
        private Scroller scroller = null; 
        /** 手势识别对象GestureDetector **/ 
        private GestureDetector gestureDetector = null; 
        /** 当前屏幕索引 **/ 
        private int currentScreenIndex = 0; 
        /** 设置一个标志位，防止底层的onTouch事件重复处理UP事件 **/ 
        private boolean fling = false; 
     
        public ImageScrollView(Context context, AttributeSet attrs) { 
            super(context, attrs); 
            initView(context); 
        } 
     
        @Override 
        protected void onLayout(boolean changed, int left, int top, int right, 
                int bottom) { 
            /** 设置布局，将子视图顺序横屏排列 **/ 
            for (int i = 0; i < getChildCount(); i++) { 
                View child = getChildAt(i); 
                child.setVisibility(View.VISIBLE); 
                child.measure(right - left, bottom - top); 
                child.layout(i * getWidth(), 0, (i + 1) * getWidth(), getHeight()); 
            } 
        } 
     
        /** 初始化 **/ 
        private void initView(final Context context) { 
            this.scroller = new Scroller(context); 
     
            this.gestureDetector = new GestureDetector(new OnGestureListener() { 
                @Override 
                public boolean onSingleTapUp(MotionEvent e) { 
                    return false; 
                } 
     
                @Override 
                public void onShowPress(MotionEvent e) { 
                } 
     
                @Override 
                public boolean onScroll(MotionEvent e1, MotionEvent e2, 
                        float distanceX, float distanceY) { 
                    // 防止移动过最后一页 
                    if ((distanceX > 0 && getScrollX() < getWidth() * (getChildCount() - 1)) 
                            || (distanceX < 0 && getScrollX() > 0)) {// 防止向第一页之前移动 
                        scrollBy((int) distanceX, 0); 
                    } 
                    return true; 
                } 
     
                @Override 
                public void onLongPress(MotionEvent e) { 
                } 
     
                @Override 
                public boolean onFling(MotionEvent e1, MotionEvent e2, 
                        float velocityX, float velocityY) { 
                    // 判断是否达到最小轻松速度，取绝对值的 
                    if (Math.abs(velocityX) > ViewConfiguration.get(context) 
                            .getScaledMinimumFlingVelocity()) { 
                        if (velocityX > 0 && currentScreenIndex > 0) { 
                            fling = true; 
                            scrollToScreen(currentScreenIndex - 1); 
                        } else if (velocityX < 0 && currentScreenIndex < getChildCount() - 1) { 
                            fling = true; 
                            scrollToScreen(currentScreenIndex + 1); 
                        } 
                    } 
                    return true; 
                } 
     
                @Override 
                public boolean onDown(MotionEvent e) { 
                    return false; 
                } 
            }); 
        } 
     
        /** 切换到指定屏 **/ 
        public void scrollToScreen(int whichScreen) { 
            if (whichScreen != currentScreenIndex && getFocusedChild() != null 
                    && getFocusedChild() == getChildAt(currentScreenIndex)) { 
                getFocusedChild().clearFocus(); // 清除焦点 
            } 
     
            final int delta = whichScreen * getWidth() - getScrollX(); 
            scroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 2); 
            invalidate(); 
     
            currentScreenIndex = whichScreen; // 设置当前屏幕索引 
            if (scrollToScreenCallback != null) { // 刷新圆圈 
                scrollToScreenCallback.callback(currentScreenIndex); 
            } 
        } 
     
        @Override 
        public void computeScroll() { 
            // 当滚动没有完成 
            if (scroller.computeScrollOffset()) { 
                scrollTo(scroller.getCurrX(), 0); 
                postInvalidate(); 
            } 
        } 
         
        @Override 
        public boolean onTouchEvent(MotionEvent event) { 
            gestureDetector.onTouchEvent(event); 
     
            if (event.getAction() == MotionEvent.ACTION_UP) { 
                if (!fling) { 
                    // 当用户停止拖动 
                    snapToDestination(); 
                } 
                fling = false; 
            } 
            return true; 
        } 
     
        /** 根据当前x坐标位置确定切换到第几屏 **/ 
        private void snapToDestination() { 
            scrollToScreen((getScrollX() + (getWidth() / 2)) / getWidth()); 
        } 
     
        /** 底部圆圈显示回调接口 **/ 
        interface ScrollToScreenCallback { 
            public void callback(int currentIndex); 
        } 
     
        /** ScrollToScreenCallback回调对象 **/ 
        private ScrollToScreenCallback scrollToScreenCallback; 
     
        /** 设置回调函数对象 **/ 
        public void setScrollToScreenCallback(ScrollToScreenCallback scrollToScreenCallback) { 
            this.scrollToScreenCallback = scrollToScreenCallback; 
        } 
    } 



PageControlView


    package org.wp.activity; 
     
    import org.wp.activity.ImageScrollView.ScrollToScreenCallback; 
     
    import android.content.Context; 
    import android.util.AttributeSet; 
    import android.widget.ImageView; 
    import android.widget.LinearLayout; 
     
    public class PageControlView extends LinearLayout implements 
            ScrollToScreenCallback { 
        /** Context对象 **/ 
        private Context context; 
        /** 圆圈的数量 **/ 
        private int count; 
     
        public PageControlView(Context context, AttributeSet attrs) { 
            super(context, attrs); 
            this.context = context; 
        } 
     
        /** 回调函数 **/ 
        @Override 
        public void callback(int currentIndex) { 
            generatePageControl(currentIndex); 
        } 
     
        /** 设置选中圆圈 **/ 
        public void generatePageControl(int currentIndex) { 
            this.removeAllViews(); 
     
            for (int i = 0; i < this.count; i++) { 
                ImageView iv = new ImageView(context); 
                if (currentIndex == i) { 
                    iv.setImageResource(R.drawable.page_indicator_focused); 
                } else { 
                    iv.setImageResource(R.drawable.page_indicator); 
                } 
                this.addView(iv); 
            } 
        } 
     
        /** 设置圆圈数量 **/ 
        public void setCount(int count) { 
            this.count = count; 
        } 
    } 



main.xml


    <?xml version="1.0" encoding="utf-8"?> 
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
        android:layout_width="fill_parent"  
        android:layout_height="fill_parent"> 
        <org.wp.activity.ImageScrollView android:layout_width="fill_parent" 
            android:layout_height="fill_parent" 
            android:id="@+id/myImageScrollView" /> 
        <org.wp.activity.PageControlView android:layout_width="fill_parent" 
            android:layout_height="40dip" 
            android:layout_alignParentBottom="true" 
            android:background="#8f00000f" 
            android:gravity="center" 
            android:id="@+id/myPageControlView" />    
    </RelativeLayout>