Android-- 仿淘宝商品详情 (继续拖动查看详情) 及标题栏渐变

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原文链接: blog.csdn.net

绪论

最近一直比较忙,也没抽出时间来写博客,也不得不说是自己犯了懒癌,人要是一懒就什么事都不想做了,如果不能坚持下来的话,那么估计就废了,��。最近自己攒了好多东西,接下来的时间我会慢慢都分享出来的。好了废话不多说了,下面我们开始正题:
今天要分享的是淘宝的详情页,之前在淘宝上买东西的时候看到淘宝的详情页效果比较不错,所以今天就来仿一下它的效果吧,可能没有淘宝的好,希望见谅啊。

效果图

先上效果图:

这是淘宝的:
这里写图片描述
我自己做的:
这里写图片描述
怎么样效果还差不多吧?GIF图效果看的不太清楚,见谅。
下面我们来看看怎么实现的吧

实现

首先我们分析淘宝布局的界面难点大致就下面3个部分:
*标题栏渐变,文字渐变隐藏
*透明通知栏(支持到4.4)
*继续拖动查看详情,Scrollview有一个弹性的效果
前两点我之前都已经实现过了,这里就不做过多介绍了,不清楚的小伙伴可以看我之前的文章:
Android带你解析ScrollView–仿QQ空间标题栏渐变
下面我们主要介绍一下Scrollview继续拖动查看详情有一个弹性动画的效果:
仔细分析这个效果我们知道上面的布局可以滑动,当滑动到下面的布局时候同时下面的布局依然可以滑动,所以我们自定义一个View来包含两个Scrollview,上面一个下面一个;然后监听Scrollview滑动到底部添加动画效果让其滑动到下面的Scrollview,当下面的Scrollview滑动到顶部的时候再添加一个向上的动画让其滑动到上面的Scrollview。
具体的可以看一下代码,注释已经很详细了:

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.widget.RelativeLayout;
import android.widget.ScrollView;

import java.util.Timer;
import java.util.TimerTask;

/**
 * 包含两个ScrollView的容器
 *
 */
public class ScrollViewContainer extends RelativeLayout {

    /**
     * 自动上滑
     */
    public static final int AUTO_UP = 0;
    /**
     * 自动下滑
     */
    public static final int AUTO_DOWN = 1;
    /**
     * 动画完成
     */
    public static final int DONE = 2;
    /**
     * 动画速度
     */
    public static final float SPEED = 8.5f;

    private boolean isMeasured = false;

    /**
     * 用于计算手滑动的速度
     */
    private VelocityTracker vt;

    private int mViewHeight;
    private int mViewWidth;

    private View topView;
    private View bottomView;

    private boolean canPullDown;
    private boolean canPullUp;
    private int state = DONE;

    /**
     * 记录当前展示的是哪个view,0是topView,1是bottomView
     */
    private int mCurrentViewIndex = 0;
    /**
     * 手滑动距离,这个是控制布局的主要变量
     */
    private float mMoveLen;
    private MyTimer mTimer;
    private float mLastY;
    /**
     * 用于控制是否变动布局的另一个条件,mEvents==0时布局可以拖拽了,mEvents==-1时可以舍弃将要到来的第一个move事件,
     * 这点是去除多点拖动剧变的关键
     */
    private int mEvents;
    boolean isTuninginterface=true;
    private Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            if (mMoveLen != 0) {
                if (state == AUTO_UP) {
                    mMoveLen -= SPEED;
                    if (mMoveLen <= -mViewHeight) {
                        mMoveLen = -mViewHeight;
                        state = DONE;
                        mCurrentViewIndex = 1;
                        if(isTuninginterface){
                            isTuninginterface=false;
                        }
                    }
                } else if (state == AUTO_DOWN) {
                    mMoveLen += SPEED;
                    if (mMoveLen >= 0) {
                        mMoveLen = 0;
                        state = DONE;
                        mCurrentViewIndex = 0;
                    }
                } else {
                    mTimer.cancel();
                }
            }
            requestLayout();
        }

    };

    public ScrollViewContainer(Context context) {
        super(context);
        init();
    }

    public ScrollViewContainer(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public ScrollViewContainer(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        mTimer = new MyTimer(handler);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                if (vt == null)
                    vt = VelocityTracker.obtain();
                else
                    vt.clear();
                mLastY = ev.getY();
                System.out.println("---ACTION_DOWN-mLastY------"+ev.getY());
                vt.addMovement(ev);
                mEvents = 0;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
            case MotionEvent.ACTION_POINTER_UP:
                
                mEvents = -1;
                break;
            case MotionEvent.ACTION_MOVE:
                vt.addMovement(ev);
                if (canPullUp && mCurrentViewIndex == 0 && mEvents == 0) {
                    mMoveLen += (ev.getY() - mLastY);
                    
                    if (mMoveLen > 0) {
                        mMoveLen = 0;
                        mCurrentViewIndex = 0;
                    } else if (mMoveLen < -mViewHeight) {
                        mMoveLen = -mViewHeight;
                        mCurrentViewIndex = 1;
                        if(isTuninginterface){
                            isTuninginterface=false;
                        }
                    }
                    if (mMoveLen < -8) {
                        
                        ev.setAction(MotionEvent.ACTION_CANCEL);
                    }
                } else if (canPullDown && mCurrentViewIndex == 1 && mEvents == 0) {
                    mMoveLen += (ev.getY() - mLastY);
                    
                    if (mMoveLen < -mViewHeight) {
                        mMoveLen = -mViewHeight;
                        mCurrentViewIndex = 1;
                    } else if (mMoveLen > 0) {
                        mMoveLen = 0;
                        mCurrentViewIndex = 0;
                    }
                    if (mMoveLen > 8 - mViewHeight) {
                        
                        ev.setAction(MotionEvent.ACTION_CANCEL);
                    }
                } else
                    mEvents++;
                mLastY = ev.getY();
                
                requestLayout();
                break;
            case MotionEvent.ACTION_UP:
                mLastY = ev.getY();
                vt.addMovement(ev);
                
                vt.computeCurrentVelocity(700);
                
                float mYV = vt.getYVelocity();
                if (mMoveLen == 0 || mMoveLen == -mViewHeight)
                    break;
                if (Math.abs(mYV) < 500) {
                    
                    if (mMoveLen <= -mViewHeight / 2) {
                        state = AUTO_UP;
                    } else if (mMoveLen > -mViewHeight / 2) {
                        state = AUTO_DOWN;
                    }
                } else {
                    
                    if (mYV < 0)
                        state = AUTO_UP;
                    else
                        state = AUTO_DOWN;
                }
                mTimer.schedule(2);
                try {
                    vt.recycle();
                    vt=null;
                } catch (Exception e) {
                    e.printStackTrace();
                }
                break;

        }
        super.dispatchTouchEvent(ev);
        return true;
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        topView.layout(0, (int) mMoveLen, mViewWidth,
                topView.getMeasuredHeight() + (int) mMoveLen);
        bottomView.layout(0, topView.getMeasuredHeight() + (int) mMoveLen,
                mViewWidth, topView.getMeasuredHeight() + (int) mMoveLen
                        + bottomView.getMeasuredHeight());
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (!isMeasured) {
            isMeasured = true;
            mViewHeight = getMeasuredHeight();
            mViewWidth = getMeasuredWidth();
            System.out.println("======onMeasure====mViewHeight======"+mViewHeight);
            System.out.println("======onMeasure====mViewWidth======"+mViewWidth);
            topView = getChildAt(0);
            bottomView = getChildAt(1);
            bottomView.setOnTouchListener(bottomViewTouchListener);
            topView.setOnTouchListener(topViewTouchListener);
        }
    }

    private OnTouchListener topViewTouchListener = new OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            ScrollView sv = (ScrollView) v;
            Log.i("------getScrollY------", sv.getScrollY()+"");
            Log.i("------getMeasuredHeight---getChildAt---", sv.getChildAt(0).getMeasuredHeight()+"");
            Log.i("------getMeasuredHeight---sv---", sv.getMeasuredHeight()+"");
            if (sv.getScrollY() == (sv.getChildAt(0).getMeasuredHeight() - sv
                    .getMeasuredHeight()) && mCurrentViewIndex == 0)
                canPullUp = true;
            else
                canPullUp = false;
            return false;
        }
    };
    private OnTouchListener bottomViewTouchListener = new OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            ScrollView sv = (ScrollView) v;
            if (sv.getScrollY() == 0 && mCurrentViewIndex == 1)
                canPullDown = true;
            else
                canPullDown = false;
            return false;
        }
    };

    class MyTimer {
        private Handler handler;
        private Timer timer;
        private MyTask mTask;

        public MyTimer(Handler handler) {
            this.handler = handler;
            timer = new Timer();
        }

        public void schedule(long period) {
            if (mTask != null) {
                mTask.cancel();
                mTask = null;
            }
            mTask = new MyTask(handler);
            timer.schedule(mTask, 0, period);
        }

        public void cancel() {
            if (mTask != null) {
                mTask.cancel();
                mTask = null;
            }
        }

        class MyTask extends TimerTask {
            private Handler handler;

            public MyTask(Handler handler) {
                this.handler = handler;
            }

            @Override
            public void run() {
                handler.obtainMessage().sendToTarget();
            }

        }
    }
}

最后我们在xml布局里面最外层用这个ScrollviewContainer包裹着两个Scrollview分别为上面的布局和下面的布局就可以了,当然因为我们上面的布局还涉及到标题栏渐变,所以上面的Scrollview要自定义滑动监听,上面提到的文章里面有详细介绍。好了今天就到这里,有时间我会把代码整理出来放到我的Github上的。