Scroller 学习

Scroller是Android中一个辅助View滑动的一个工具。它可以使View滑动有一个平滑的效果。下面是Scroller的一个简单实现。</span>

主要是要调用Scroller的一些方法

startScroll(int startX, int startY, int dx, int dy, int duration)

然后在所在View中重写computeScroll()

</pre><pre name="code" class="java"> @Override    public void computeScroll() {        if (mScroller.computeScrollOffset()) {            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());            postInvalidate();        }    }

下面是一个简单的应用。

package com.yyw.scrollerdemo;import android.content.Context;import android.content.res.TypedArray;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.util.Log;import android.view.GestureDetector;import android.view.MotionEvent;import android.view.ViewGroup;import android.view.animation.DecelerateInterpolator;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.Scroller;/** * Created by yyw on 2016/4/28. */public class SliderLayout extends LinearLayout {    public static final String TAG = "SliderLayout";    private Scroller mScroller;    private int totalNum = 8;    private int index = 0;    private ImageView mSlider;    private GestureDetector detector;    private Drawable mSliderImage;    public SliderLayout(Context context) {        this(context, null);    }    public SliderLayout(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public SliderLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.SliderLayout);        mSliderImage = array.getDrawable(R.styleable.SliderLayout_slider_pic);        if (mSliderImage == null) {            mSliderImage = context.getResources().getDrawable(R.drawable.slider);        }        array.recycle();        init(context);    }    public int getIndex() {        return index;    }    public void setIndex(int index) {        if (this.index != index && index < totalNum && index >= 0) {            if (getOrientation() == HORIZONTAL){                horizontalScroll(index);            }else {                verticalScroll(index);            }            this.index = index;        }    }    //水平滑动    private void horizontalScroll(int index) {        int dx = (this.index - index) * (getWidth() / totalNum);//计算偏移量        if (mScroller.computeScrollOffset()) {            mScroller.abortAnimation();        }        mScroller.startScroll(mScroller.getFinalX(), 0, dx, 0);//开始移动        invalidate();    }    //垂直滑动    private void verticalScroll(int index) {        int dy = (this.index - index) * (getHeight() / totalNum);//计算偏移量        if (mScroller.computeScrollOffset()) {            mScroller.abortAnimation();        }        mScroller.startScroll(0, mScroller.getFinalY(), 0, dy);//开始移动        invalidate();    }    public int getTotalNum() {        return totalNum;    }    public void setTotalNum(int totalNum) {        if (this.totalNum != totalNum && totalNum > 0) {            this.totalNum = totalNum;            if (index >= totalNum) {                index = totalNum - 1;            }            resetSlider();        }    }    private void init(Context context) {        detector = new GestureDetector(context, mOnGestureListener);        mScroller = new Scroller(context, new DecelerateInterpolator());        mSlider = new ImageView(context);        mSlider.setImageDrawable(mSliderImage);        addView(mSlider, ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        super.onLayout(changed, l, t, r, b);        if (changed) {            resetSlider();        }    }    /**     * 重新设置滑块     */    private void resetSlider() {        if (getOrientation() == HORIZONTAL) {            resetHorizontalSlider();        }else {            resetVerticalSlider();        }    }    private void resetVerticalSlider() {        int scrollY = getScrollY();        int height = getHeight();        LayoutParams params = (LayoutParams) mSlider.getLayoutParams();        params.height = height / totalNum;//重新设置滑块的大小        params.width = ViewGroup.LayoutParams.MATCH_PARENT;        mSlider.setLayoutParams(params);        int dy = -height / totalNum * index - scrollY;//计算滑块需要移动的位置，上 + ，下 - ；        if (mScroller.computeScrollOffset()) {            mScroller.abortAnimation();//如果Scroller没有结束就结束动画        }        mScroller.startScroll(0, mScroller.getFinalY(), 0, dy);//开始滑动        invalidate();//必须要加上，不然没有滑动    }    private void resetHorizontalSlider() {        int scrollX = getScrollX();        int width = getWidth();        LayoutParams params = (LayoutParams) mSlider.getLayoutParams();        params.width = width / totalNum;//重新设置滑块的大小        params.height = ViewGroup.LayoutParams.MATCH_PARENT;        mSlider.setLayoutParams(params);        int dx = -width / totalNum * index - scrollX;//计算滑块需要移动的位置，左 + ，右 - ；        if (mScroller.computeScrollOffset()) {            mScroller.abortAnimation();//如果Scroller没有结束就结束动画        }        mScroller.startScroll(mScroller.getFinalX(), 0, dx, 0);//开始滑动        invalidate();//必须要加上，不然没有滑动    }    @Override    public void computeScroll() {        if (mScroller.computeScrollOffset()) {            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());            postInvalidate();        }    }    @Override    public boolean onTouchEvent(MotionEvent event) {        detector.onTouchEvent(event);        return true;    }    private GestureDetector.SimpleOnGestureListener mOnGestureListener = new GestureDetector.SimpleOnGestureListener() {        @Override        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {            float dx = e1.getX() - e2.getX();            if (Math.abs(velocityX) < 1000 && Math.abs(velocityY) < 500 && Math.abs(dx) < 100) {                onSingleTapConfirmed(e2);            }            return true;        }        @Override        public boolean onSingleTapConfirmed(MotionEvent e) {            if (getOrientation() == HORIZONTAL) {                float x = e.getX();                float childW = getWidth() / totalNum;                int column = (int) (x / childW);                Log.i(TAG, "onSingleTapConfirmed: column " + column);                setIndex(column);            }else{                float y = e.getY();                float childH = getHeight() / totalNum;                int row = (int) (y / childH);                Log.i(TAG, "onSingleTapConfirmed: row " + row);                setIndex(row);            }            return true;        }    };}

应用

<com.yyw.scrollerdemo.SliderLayout       android:id="@+id/slider"       android:background="@drawable/slider_bg"       android:orientation="horizontal"       android:layout_width="match_parent"       app:slider_pic="@drawable/slider"       android:layout_height="50dp"/>

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