Android仿京东首页画轴效果

记得之前京东首页有一个效果,有一个画轴,然后可以滚动画轴,去打开画(不知道怎么去形容这个效果,就叫做画轴效果吧- -!),然后去做相关操作,刚开始看到这个效果,想法是动态的去改变一个ImageView的高度,基本效果也就出来了,不过滚动部分的内容,当时接触的也不是很多,只是看过一些大牛的博客,略微了解了一点,当时也忙着写项目,也就没去多想,前些天忽然想到这个效果,就想着实现一下,不过京东新版本好像去掉这个东西了,只能凭着自己的记忆来大概搞一下,也是对滑动这部分内容的一个小练习吧.

先看一下效果图:

一、需求分析

看到效果之后,先来分析一下:
首先是需要一个可以滑动的画轴,并且这个画轴需要一定的滑动空间,有滑动的效果,这个用Scroller帮助完成就可以了.
然后看一下画轴点击移动时候的背景图,是跟随画轴移动,动态改变高度的.这个用一个ImageView来搞定,设置ImageView的scaleType就可以了,不过这个地方有一些小问题,下面会说.

二、具体实现

简单分析完,来实现一下,先来做一下画轴.创建一个ScrollPaintView继承自RelativeLayout,因为需要一定的滑动空间,所以需要是一个ViewGroup.

ScrollPaintView的一些基本属性:

public class ScrollPaintView extends RelativeLayout {
 
 private static final String TAG = "ScrollPaintView";
 
 private final int DEFAULT_PAINT_SCROLL_HEIGHT = 25;
 
 private final int DEFAULT_SCROLL_SPEED = 1000;
 
 private final int DEFAULT_PARTITION_NODE = 150;
 
 private final int DEFAULT_PAINT_SCROLL_TXT_SIZE = 16;
 
 private Scroller mScroller;
 
 private ImageView mPaintScrollImageView;
 
 private TextView mPaintScrollTextView;
 
 private ImageView mPaintView;
 
 private Bitmap mPaintScrollBp;
 
 private int mPaintIvHeight;
 
 private String mPaintScrollTxt;
 
 private float mPaintScrollTxtSize;
 
 private int mPaintScrollTxtColor;
 
 private int mPaintStartHeight;
 
 private int mLastY;
 
 private int mScrollSpeed;
 
 private int partitionNode;
 
 private boolean isScrllerTop = false;
 
 private boolean isClick = false;
 
 private LayoutParams lpp;
 
 private int screenHeight;
 
 private int screenWidth;
 
 private ScrollPaintCompleteListener listener;
 
 private int lastScrollY;
 
 public ScrollPaintView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 // 获取属性
 TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ScrollPaintView);
 mPaintIvHeight = (int) ta.getDimension(R.styleable.ScrollPaintView_paintScrollHeight, TypedValue.applyDimension(
  TypedValue.COMPLEX_UNIT_DIP, DEFAULT_PAINT_SCROLL_HEIGHT, getResources().getDisplayMetrics()));
 mScrollSpeed = ta.getInteger(R.styleable.ScrollPaintView_scrollSpeed, DEFAULT_SCROLL_SPEED);
 partitionNode = ta.getInteger(R.styleable.ScrollPaintView_scrollPartitionNode, DEFAULT_PARTITION_NODE);
 mPaintScrollBp = drawableToBitamp(ta.getDrawable(R.styleable.ScrollPaintView_paintScrollSrc));
 mPaintScrollTxt = ta.getString(R.styleable.ScrollPaintView_paintScrollTxt);
 mPaintScrollTxtColor = ta.getColor(R.styleable.ScrollPaintView_paintScrollTxtColor, Color.BLACK);
 mPaintScrollTxtSize = px2sp(ta.getDimensionPixelSize(R.styleable.ScrollPaintView_paintScrollTxtSize, DEFAULT_PAINT_SCROLL_TXT_SIZE));
 ta.recycle();
 }
}

看一下创建画轴:

 
 private void makePaintScroll() {
 // 如果已经存在,则不再创建
 if (null != mPaintScrollImageView || null != mPaintScrollTextView) {
  return;
 }
 // 创建滚轴
 mPaintScrollImageView = new ImageView(getContext());
 LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
 lp.height = mPaintIvHeight;
 mPaintScrollImageView.setLayoutParams(lp);
 mPaintScrollImageView.setScaleType(ImageView.ScaleType.FIT_XY);
 mPaintScrollImageView.setImageBitmap(null == mPaintScrollBp ? makeDefaultScroll() : mPaintScrollBp);
 addView(mPaintScrollImageView);
 // 创建文字
 mPaintScrollTextView = new TextView(getContext());
 LayoutParams lpt = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
 lpt.height = mPaintIvHeight;
 mPaintScrollTextView.setLayoutParams(lpt);
 mPaintScrollTextView.setText(null == mPaintScrollTxt ? "" : mPaintScrollTxt);
 mPaintScrollTextView.setTextSize(mPaintScrollTxtSize);
 mPaintScrollTextView.setTextColor(mPaintScrollTxtColor);
 mPaintScrollTextView.setGravity(Gravity.CENTER);
 addView(mPaintScrollTextView);
 }
 
 private Bitmap makeDefaultScroll() {
 Bitmap defaultBp = Bitmap.createBitmap(screenWidth, mPaintIvHeight,
  Bitmap.Config.ARGB_8888);
 //填充颜色
 defaultBp.eraseColor(Color.parseColor("#FF0000"));
 return defaultBp;
 }

创建了一个画轴ImageView和一个文字TextView作为初始的画轴,如果没有传入画轴的图片,则默认去创建一个画轴.不难理解,接着去配合Scroller,让画轴滚动起来.

简单滚动:

 
 private void handleView() {
 // 初始化Scroller
 mScroller = new Scroller(getContext());
 // 画轴点击效果
 mPaintScrollImageView.setOnTouchListener(new OnTouchListener() {
  @Override
  public boolean onTouch(View view, MotionEvent event) {
  int x = (int) event.getRawX();
  int y = (int) event.getRawY();
  int action = event.getAction();
  switch (action) {
   case MotionEvent.ACTION_DOWN: 
   isClick = true;
   mLastY = y;
   if (!mScroller.isFinished()) { // 如果上次的调用没有执行完就取消。
    mScroller.abortAnimation();
   }
   return true;
   case MotionEvent.ACTION_MOVE: 
   // 移动的距离
   int dy = y - mLastY;
   mLastY = y;
   // 滑动
   scrollBy(0, -dy);
   return true;
   case MotionEvent.ACTION_UP:
   mScroller.startScroll(getScrollX(), getScrollY(), -getScrollX(), -getScrollY(), 1000);
   invalidate();
   return true;
  }
  return false;
  }
 });
 }
 
 @Override
 public void computeScroll() {
 if (mScroller.computeScrollOffset()) { // 计算新位置，并判断上一个滚动是否完成。 
  scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
  invalidate();
  }
 }

这样滑动处理就做完了,在布局中引用一下,看一下效果

activity_main:

 <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="#eeeeee"
 tools:context="com.example.junweiliu.scrollpaintdemo.MainActivity">
  <!--画轴控件-->
 <com.example.junweiliu.scrollpaintdemo.widget.ScrollPaintView
  android:id="@+id/spv_paint"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  app:paintScrollHeight="25dp"
  app:paintScrollSrc="@mipmap/paint_scroll_img"
  app:paintScrollTxt="拉我看看"
  app:paintScrollTxtColor="#FF000000"
  app:paintScrollTxtSize="16sp"
 >
 </com.example.junweiliu.scrollpaintdemo.widget.ScrollPaintView>
</RelativeLayout>

效果图:

滚动条基本能用了,接着来设置一个ImageView来配合使用下,先获取到一个ImageView,然后拖动画轴时,来动态改变ImageView的高度,在做这部分内容前,先来考虑下,因为需求需要的是图画整体不会变形,是一点一点拉开的感觉,就像是打开一幅画一样,那么用哪种scaleType能满足呢.试了好多种,来分别看一下:

相关代码:

提供一个设置ImageView的方法
在MotionEvent.ACTION_MOVE:中动态改变ImageView的高度
滑动时动态改变ImageView的高度

 
 public void setPaintView(ImageView paintView) {
 if (null == paintView) {
  Log.e(TAG, "设置的View为空");
  return;
 }
 mPaintView = paintView;
 }

MotionEvent.ACTION_MOVE:

 // 滑动处理 
 case MotionEvent.ACTION_MOVE: 
 ...
 // 动态改变高度
 if (Math.abs(getScrollY()) > 0) {
    lpp.height = mPaintStartHeight + Math.abs(getScrollY());
    mPaintView.setLayoutParams(lpp);
   }

滑动处理:

 
 @Override
 public void computeScroll() {
 if (mScroller.computeScrollOffset()) { // 计算新位置，并判断上一个滚动是否完成。
  // 请求处理点击事件,防止父控件滑动
  requestDisallowInterceptTouchEvent(true);
  scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
  // 重新设置显示的控件高度
  if (0 < Math.abs(mScroller.getCurrY())) {
  if (!isScrllerTop) {
   lpp.height = mPaintStartHeight + Math.abs(mScroller.getCurrY()) + mPaintIvHeight / 2;
  } else {
   lpp.height = mPaintStartHeight + Math.abs(mScroller.getCurrY()) - mPaintIvHeight / 2;
  }
  } else {
  lpp.height = mPaintStartHeight;
  }
  mPaintView.setLayoutParams(lpp);
  invalidate();
 }
}

设置不同scaleType效果,简单试几个效果:

fitXY:

centerCrop:

matrix:

观察一下,好像那个效果都不是很好,不过matrix拉开的效果和预期需要的是一样的,不过用matrix之后,就没有办法设置其他scaleType了,没办法把图片进行缩放了,这肿么办呢,其实很简单,只需要把显示的图片提前进行一下缩放就可以了.

处理图片相关:

 
 public void setPaintView(ImageView paintView) {
 if (null == paintView) {
  Log.e(TAG, "设置的View为空");
  return;
 }
 // 处理图片,对图片按照屏幕宽高比进行缩放
 Bitmap bp = drawableToBitamp(paintView.getDrawable());
 paintView.setImageBitmap(scaleBitmal(bp));
 // 设置缩放形式
 paintView.setScaleType(ImageView.ScaleType.MATRIX);
 mPaintView = paintView;
 }
 
 private Bitmap drawableToBitamp(Drawable drawable) {
 if (null == drawable) {
  return null;
 }
 if (drawable instanceof BitmapDrawable) {
  BitmapDrawable bd = (BitmapDrawable) drawable;
  return bd.getBitmap();
 }
 int w = drawable.getIntrinsicWidth();
 int h = drawable.getIntrinsicHeight();
 Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
 Canvas canvas = new Canvas(bitmap);
 drawable.setBounds(0, 0, w, h);
 drawable.draw(canvas);
 return bitmap;
 }
 
 private Bitmap scaleBitmal(Bitmap bp) {
 // 宽度比例
 float scaleW = (float) screenWidth / (float) bp.getWidth();
 // 高度比例
 float scaleH = (float) screenHeight / (float) bp.getHeight();
 // 矩阵,用于缩放图片
 Matrix matrix = new Matrix();
 matrix.postScale(scaleW, scaleH);
 // 缩放后的图片
 Bitmap scaleBp = Bitmap.createBitmap(bp, 0, 0, bp.getWidth(), bp.getHeight(), matrix, true);
 return scaleBp;
 }

看一下效果:

效果还不错,接下来就是做一下细节上的处理,设置一个临界点,让画轴向上或者向下滚动,设置边界点,让画轴不越界等等.还有一般都是在ScrollView中使用到这个效果,所以要去处理一下事件冲突,当然还有去重写一下onMeasure方法,不然会出现不显示的情况.(相信大家也遇到过ScrollView里边嵌套ListView导致ListView显示不全)这里就不再详细介绍了.直接贴下代码.

三、完整代码

MainActivity:

package com.example.junweiliu.scrollpaintdemo;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.example.junweiliu.scrollpaintdemo.widget.ScrollPaintView;
public class MainActivity extends AppCompatActivity {
  private static final String TAG = "MainActivity";
  
  private ImageView mPaintIv;
  
  private ScrollPaintView mScrollPaintView;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initView();
  }
  
  private void initView() {
    mPaintIv = (ImageView) findViewById(R.id.iv_paint);
    mScrollPaintView = (ScrollPaintView) findViewById(R.id.spv_paint);
    mScrollPaintView.setPaintView(mPaintIv);
    mPaintIv.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        Toast.makeText(MainActivity.this, "功夫!", Toast.LENGTH_SHORT).show();
      }
    });
    mScrollPaintView.setScrollPaintCompleteListener(new ScrollPaintView.ScrollPaintCompleteListener() {
      @Override
      public void onScrollTouch(TextView tv) {
        mPaintIv.setVisibility(View.VISIBLE);
      }
      @Override
      public void onScrollTop(TextView tv) {
//        Log.e(TAG, "收缩了");
        tv.setText("拉我看看");
        if (View.VISIBLE == mPaintIv.getVisibility()) {
          mPaintIv.setVisibility(View.GONE);
        }
      }
      @Override
      public void onScrollBottom(TextView tv) {
//        Log.e(TAG, "展开了");
        tv.setText("到底了");
        Intent intent = new Intent(MainActivity.this, DetailActivity.class);
        startActivity(intent);
        // 延迟800毫秒重置位置
        new Handler(new Handler.Callback() {
          @Override
          public boolean handleMessage(Message message) {
            mScrollPaintView.replaceScroll();
            return false;
          }
        }).sendEmptyMessageDelayed(0, 600);
      }
      @Override
      public void onScrollMove(TextView tv) {
//        Log.e(TAG, "移动了");
        tv.setText("请上下拖动");
      }
    });
  }
}

ScrollPaintView:

package com.example.junweiliu.scrollpaintdemo.widget;
import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.Scroller;
import android.widget.TextView;
import com.example.junweiliu.scrollpaintdemo.R;

public class ScrollPaintView extends RelativeLayout {
  
  private static final String TAG = "ScrollPaintView";
  
  private final int DEFAULT_PAINT_SCROLL_HEIGHT = 25;
  
  private final int DEFAULT_SCROLL_SPEED = 1000;
  
  private final int DEFAULT_PARTITION_NODE = 150;
  
  private final int DEFAULT_PAINT_SCROLL_TXT_SIZE = 16;
  
  private Scroller mScroller;
  
  private ImageView mPaintScrollImageView;
  
  private TextView mPaintScrollTextView;
  
  private ImageView mPaintView;
  
  private Bitmap mPaintScrollBp;
  
  private int mPaintIvHeight;
  
  private String mPaintScrollTxt;
  
  private float mPaintScrollTxtSize;
  
  private int mPaintScrollTxtColor;
  
  private int mPaintStartHeight;
  
  private int mLastY;
  
  private int mScrollSpeed;
  
  private int partitionNode;
  
  private boolean isScrllerTop = false;
  
  private boolean isClick = false;
  
  private LayoutParams lpp;
  
  private int screenHeight;
  
  private int screenWidth;
  
  private ScrollPaintCompleteListener listener;
  
  private int lastScrollY;
  
  public interface ScrollPaintCompleteListener {
    
    public void onScrollTouch(TextView tv);
    
    public void onScrollTop(TextView tv);
    
    public void onScrollBottom(TextView tv);
    
    public void onScrollMove(TextView tv);
  }
  public ScrollPaintView(Context context) {
    this(context, null);
  }
  public ScrollPaintView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }
  public ScrollPaintView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    // 获取属性
    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ScrollPaintView);
    mPaintIvHeight = (int) ta.getDimension(R.styleable.ScrollPaintView_paintScrollHeight, TypedValue.applyDimension(
        TypedValue.COMPLEX_UNIT_DIP, DEFAULT_PAINT_SCROLL_HEIGHT, getResources().getDisplayMetrics()));
    mScrollSpeed = ta.getInteger(R.styleable.ScrollPaintView_scrollSpeed, DEFAULT_SCROLL_SPEED);
    partitionNode = ta.getInteger(R.styleable.ScrollPaintView_scrollPartitionNode, DEFAULT_PARTITION_NODE);
    mPaintScrollBp = drawableToBitamp(ta.getDrawable(R.styleable.ScrollPaintView_paintScrollSrc));
    mPaintScrollTxt = ta.getString(R.styleable.ScrollPaintView_paintScrollTxt);
    mPaintScrollTxtColor = ta.getColor(R.styleable.ScrollPaintView_paintScrollTxtColor, Color.BLACK);
    mPaintScrollTxtSize = px2sp(ta.getDimensionPixelSize(R.styleable.ScrollPaintView_paintScrollTxtSize, DEFAULT_PAINT_SCROLL_TXT_SIZE));
    ta.recycle();
    init();
    makePaintScroll();
    handleView();
  }
  
  public void setPaintView(ImageView paintView) {
    if (null == paintView) {
      Log.e(TAG, "设置的View为空");
      return;
    }
    // 处理图片,对图片按照屏幕宽高比进行缩放
    Bitmap bp = drawableToBitamp(paintView.getDrawable());
    paintView.setImageBitmap(scaleBitmal(bp));
    // 设置缩放形式
    paintView.setScaleType(ImageView.ScaleType.MATRIX);
    mPaintView = paintView;
  }
  
  public void setScrollPaintCompleteListener(ScrollPaintCompleteListener listener) {
    if (null != listener) {
      this.listener = listener;
    }
  }
  
  private void init() {
    mScroller = new Scroller(getContext());
    lpp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    // 获取屏幕信息
    DisplayMetrics displayMetrics = new DisplayMetrics();
    ((Activity) getContext()).getWindowManager().getDefaultDisplay()
        .getMetrics(displayMetrics);
    // 屏幕高度
    screenHeight = displayMetrics.heightPixels;
    // 屏幕宽度
    screenWidth = displayMetrics.widthPixels;
  }
  
  private void makePaintScroll() {
    // 如果已经存在,则不再创建
    if (null != mPaintScrollImageView || null != mPaintScrollTextView) {
      return;
    }
    // 创建滚轴
    mPaintScrollImageView = new ImageView(getContext());
    LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    lp.height = mPaintIvHeight;
    mPaintScrollImageView.setLayoutParams(lp);
    mPaintScrollImageView.setScaleType(ImageView.ScaleType.FIT_XY);
    mPaintScrollImageView.setImageBitmap(null == mPaintScrollBp ? makeDefaultScroll() : mPaintScrollBp);
    addView(mPaintScrollImageView);
    // 创建文字
    mPaintScrollTextView = new TextView(getContext());
    LayoutParams lpt = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    lpt.height = mPaintIvHeight;
    mPaintScrollTextView.setLayoutParams(lpt);
    mPaintScrollTextView.setText(null == mPaintScrollTxt ? "" : mPaintScrollTxt);
    mPaintScrollTextView.setTextSize(mPaintScrollTxtSize);
    mPaintScrollTextView.setTextColor(mPaintScrollTxtColor);
    mPaintScrollTextView.setGravity(Gravity.CENTER);
    addView(mPaintScrollTextView);
  }
  
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    if (null != mPaintView && getTop() + mPaintIvHeight != mPaintView.getHeight()) {
      // 重新设置图画高度
      mPaintStartHeight = getTop() + mPaintIvHeight / 2;
      lpp.height = mPaintStartHeight;
      mPaintView.setLayoutParams(lpp);
    }
    // 测量状态栏高度
    Rect frame = new Rect();
    ((Activity) getContext()).getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
    int statusBarHeight = frame.top;
    // 高度为屏幕高度减去状态栏高度和top的高度
    setMeasuredDimension(screenWidth, screenHeight - getTop() - statusBarHeight);
  }
  
  private void handleView() {
    mPaintScrollImageView.setOnTouchListener(new OnTouchListener() {
      @Override
      public boolean onTouch(View view, MotionEvent event) {
        if (null == mPaintView) {
          Log.e(TAG, "设置的View为空");
          return true;
        }
        // 获取点击的XY坐标
        int x = (int) event.getRawX();
        int y = (int) event.getRawY();
        int action = event.getAction();
        switch (action) {
          case MotionEvent.ACTION_DOWN: {
            // 请求处理点击事件
            requestDisallowInterceptTouchEvent(true);
            isClick = true;
            mLastY = y;
            if (!mScroller.isFinished()) { // 如果上次的调用没有执行完就取消。
              mScroller.abortAnimation();
            }
            if (null != listener) {
              listener.onScrollTouch(mPaintScrollTextView);
            }
            return true;
          }
          case MotionEvent.ACTION_MOVE: {
            // 移动的距离
            int dy = y - mLastY;
            mLastY = y;
            // 滑动
            scrollBy(0, -dy);
            // 如果是向上滑动并且是在初始位置,则不去做处理
            if (getScrollY() >= 0 && dy <= 0) {
              lpp.height = mPaintStartHeight;
              mPaintView.setLayoutParams(lpp);
              scrollTo(0, 0);
              return true;
            }
            // 如果是向下滑动并且超过屏幕高度,则不去处理
            if (Math.abs(getScrollY()) >= getHeight() - mPaintIvHeight && dy >= 0) {
              lpp.height = mPaintStartHeight + getHeight() - mPaintIvHeight;
              mPaintView.setLayoutParams(lpp);
              scrollTo(0, -(getHeight() - mPaintIvHeight));
              return true;
            }
            // 滚动回调
            if (null != listener) {
              listener.onScrollMove(mPaintScrollTextView);
            }
            // 重新设置显示的控件高度
            if (Math.abs(getScrollY()) > 0) {
              lpp.height = mPaintStartHeight + Math.abs(getScrollY());
              mPaintView.setLayoutParams(lpp);
            }
            return true;
          }
          case MotionEvent.ACTION_UP:
            // 恢复事件处理
            requestDisallowInterceptTouchEvent(false);
            isClick = false;
            // 没有发生移动
            if (getScrollY() >= 0) {
              if (null != listener) {
                listener.onScrollTop(mPaintScrollTextView);
              }
              return true;
            }
            if (-getScrollY() < partitionNode) {  // 如果小于临界值,则返回起始坐标
              // XY都从滑动的距离回去，最后一个参数是多少毫秒内执行完这个动作。
              isScrllerTop = true;
              mScroller.startScroll(getScrollX(), getScrollY(), -getScrollX(), -getScrollY(), mScrollSpeed);
            } else {  // 如果大于临界值,则展开
              isScrllerTop = false;
              mScroller.startScroll(getScrollX(), getScrollY(), -getScrollX(), -(getHeight() - (-getScrollY()) - mPaintIvHeight), mScrollSpeed);
            }
            invalidate();
            return true;
        }
        return false;
      }
    });
  }
  
  @Override
  public void computeScroll() {
    if (mScroller.computeScrollOffset()) { // 计算新位置，并判断上一个滚动是否完成。
      // 请求处理点击事件,防止父控件滑动
      requestDisallowInterceptTouchEvent(true);
      scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
      // 重新设置显示的控件高度
      if (0 < Math.abs(mScroller.getCurrY())) {
        if (!isScrllerTop) {
          lpp.height = mPaintStartHeight + Math.abs(mScroller.getCurrY()) + mPaintIvHeight / 2;
        } else {
          lpp.height = mPaintStartHeight + Math.abs(mScroller.getCurrY()) - mPaintIvHeight / 2;
        }
      } else {
        lpp.height = mPaintStartHeight;
      }
      mPaintView.setLayoutParams(lpp);
      invalidate();
    } else {
      // 重新设置画图高度,防止高度异常
      if (mPaintView.getHeight() > mPaintStartHeight + Math.abs(mScroller.getCurrY()) && !isScrllerTop && mScroller.getStartY() > 0) {
        lpp.height = mPaintStartHeight + Math.abs(mScroller.getCurrY());
        mPaintView.setLayoutParams(lpp);
      }
    }
    // 防止多次调用
    if (lastScrollY != mScroller.getCurrY()) {
      // 收缩完成
      if (mScroller.getCurrY() >= 0 && !isClick) {
        if (null != listener) {
          listener.onScrollTop(mPaintScrollTextView);
        }
      }
      // 展开完成
      if (-mScroller.getCurrY() >= getHeight() - mPaintIvHeight && !isClick) {
        if (null != listener) {
          listener.onScrollBottom(mPaintScrollTextView);
        }
      }
      lastScrollY = mScroller.getCurrY();
    }
  }
  
  public void replaceScroll() {
    // 重置信息
    scrollTo(0, 0);
    mScroller.setFinalY(0);
    lastScrollY = 0;
    lpp.height = mPaintStartHeight;
    mPaintView.setLayoutParams(lpp);
    if (null != listener) {
      listener.onScrollTop(mPaintScrollTextView);
    }
  }
  
  private Bitmap drawableToBitamp(Drawable drawable) {
    if (null == drawable) {
      return null;
    }
    if (drawable instanceof BitmapDrawable) {
      BitmapDrawable bd = (BitmapDrawable) drawable;
      return bd.getBitmap();
    }
    int w = drawable.getIntrinsicWidth();
    int h = drawable.getIntrinsicHeight();
    Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, w, h);
    drawable.draw(canvas);
    return bitmap;
  }
  
  private Bitmap scaleBitmal(Bitmap bp) {
    // 宽度比例
    float scaleW = (float) screenWidth / (float) bp.getWidth();
    // 高度比例
    float scaleH = (float) screenHeight / (float) bp.getHeight();
    // 矩阵,用于缩放图片
    Matrix matrix = new Matrix();
    matrix.postScale(scaleW, scaleH);
    // 缩放后的图片
    Bitmap scaleBp = Bitmap.createBitmap(bp, 0, 0, bp.getWidth(), bp.getHeight(), matrix, true);
    return scaleBp;
  }
  
  private Bitmap makeDefaultScroll() {
    Bitmap defaultBp = Bitmap.createBitmap(screenWidth, mPaintIvHeight,
        Bitmap.Config.ARGB_8888);
    //填充颜色
    defaultBp.eraseColor(Color.parseColor("#FF0000"));
    return defaultBp;
  }
  
  public int px2sp(float pxValue) {
    final float fontScale = getContext().getResources().getDisplayMetrics().scaledDensity;
    return (int) (pxValue / fontScale + 0.5f);
  }
}

activity_main:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#eeeeee"
    tools:context="com.example.junweiliu.scrollpaintdemo.MainActivity">
  <ScrollView
      android:layout_width="match_parent"
      android:layout_height="match_parent">
    <RelativeLayout android:layout_width="match_parent"
            android:layout_height="match_parent">
      <!--头部图片部分-->
      <ImageView
          android:id="@+id/iv_banner"
          android:layout_width="match_parent"
          android:layout_height="200dp"
          android:scaleType="fitXY"
          android:src="@mipmap/show_banner"/>
      <!--中间内容部分-->
      <LinearLayout
          android:id="@+id/ll_first"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_below="@+id/iv_banner"
          android:layout_marginTop="20dp"
          android:orientation="horizontal"
          android:padding="16dp">
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_a"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="艺术片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_b"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="怀旧片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_c"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="科幻片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_d"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="动画片"
              android:textColor="#666666"/>
        </LinearLayout>
      </LinearLayout>
      <LinearLayout
          android:id="@+id/ll_sencond"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_below="@+id/ll_first"
          android:layout_marginTop="20dp"
          android:orientation="horizontal"
          android:padding="16dp">
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_a"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="艺术片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_b"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="怀旧片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_c"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="科幻片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_d"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="动画片"
              android:textColor="#666666"/>
        </LinearLayout>
      </LinearLayout>
      <LinearLayout
          android:id="@+id/ll_threeth"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_below="@+id/ll_sencond"
          android:layout_marginTop="20dp"
          android:orientation="horizontal"
          android:padding="16dp">
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_a"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="艺术片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_b"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="怀旧片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_c"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="科幻片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_d"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="动画片"
              android:textColor="#666666"/>
        </LinearLayout>
      </LinearLayout>
      <LinearLayout
          android:id="@+id/ll_fourth"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_below="@+id/ll_threeth"
          android:layout_marginTop="20dp"
          android:orientation="horizontal"
          android:padding="16dp">
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_a"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="艺术片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_b"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="怀旧片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginRight="16dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_c"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="科幻片"
              android:textColor="#666666"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:orientation="vertical">
          <ImageView
              android:layout_width="80dp"
              android:layout_height="120dp"
              android:scaleType="fitXY"
              android:src="@mipmap/movie_playbill_d"/>
          <TextView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_marginTop="10dp"
              android:gravity="center"
              android:text="动画片"
              android:textColor="#666666"/>
        </LinearLayout>
      </LinearLayout>
      <!--需要显示的图-->
      <ImageView
          android:id="@+id/iv_paint"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:scaleType="matrix"
          android:src="@mipmap/show_img"
          android:visibility="gone"/>
      <!--画轴控件-->
      <com.example.junweiliu.scrollpaintdemo.widget.ScrollPaintView
          android:id="@+id/spv_paint"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_below="@+id/iv_banner"
          app:paintScrollHeight="25dp"
          app:paintScrollSrc="@mipmap/paint_scroll_img"
          app:paintScrollTxt="拉我看看"
          app:paintScrollTxtColor="#FF000000"
          app:paintScrollTxtSize="16sp"
      >
      </com.example.junweiliu.scrollpaintdemo.widget.ScrollPaintView>
    </RelativeLayout>
  </ScrollView>
</RelativeLayout>

attr:

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <!--画轴的高度-->
  <attr name="paintScrollHeight" format="dimension"/>
  <!--画轴的图片-->
  <attr name="paintScrollSrc" format="reference"/>
  <!--画轴文字-->
  <attr name="paintScrollTxt" format="string"/>
  <!--画轴文字颜色-->
  <attr name="paintScrollTxtColor" format="color"/>
  <!--画轴文字大小-->
  <attr name="paintScrollTxtSize" format="dimension"/>
  <!--滚动速度-->
  <attr name="scrollSpeed" format="integer"/>
  <!--分割节点-->
  <attr name="scrollPartitionNode" format="integer"/>
  <declare-styleable name="ScrollPaintView">
    <attr name="paintScrollHeight"/>
    <attr name="paintScrollSrc"/>
    <attr name="paintScrollTxt"/>
    <attr name="paintScrollTxtColor"/>
    <attr name="paintScrollTxtSize"/>
    <attr name="scrollSpeed"/>
    <attr name="scrollPartitionNode"/>
  </declare-styleable>
</resources>

四、问题

滚动的时间不宜设置太短,因为动态设置ImageView高度时可能出现绘制速度赶不上滚动的速度,会出现错位,当然时间设置太短,也看不到这种滑动的效果了.暂时想到的做法就是这样,应该还会有更好的方法.

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