菜鸟的日常搬运
Java代码如下：
1.自定义ScrollView
package com.example.asus.myapplication;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.TranslateAnimation;
import android.widget.ImageView;
import android.widget.ScrollView;
import android.widget.Scroller;
/**
* 阻尼效果的scrollview
*/
public class DampView extends ScrollView {
private static final int LEN = 0xc8;
private static final int DURATION = 500;
private static final int MAX_DY = 200;
private Scroller mScroller;
TouchTool tool;
int left, top;
float startX, startY, currentX, currentY;
int imageViewH;
int rootW, rootH;
ImageView imageView;
boolean scrollerType;
//移动因子, 是一个百分比, 比如手指移动了100px, 那么View就只移动50px
//目的是达到一个延迟的效果
private static final float MOVE_FACTOR = 0.5f;
//松开手指后, 界面回到正常位置需要的动画时间
private static final int ANIM_TIME = 100;
//ScrollView的子View， 也是ScrollView的唯一一个子View
private View contentView;
//手指按下时的Y值, 用于在移动时计算移动距离
//如果按下时不能上拉和下拉， 会在手指移动时更新为当前手指的Y值
private float startYs;
//用于记录正常的布局位置
private Rect originalRect = new Rect();
//手指按下时记录是否可以继续下拉
private boolean canPullDown = false;
//手指按下时记录是否可以继续上拉
private boolean canPullUp = false;
//在手指滑动的过程中记录是否移动了布局
private boolean isMoved = false;
public DampView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public DampView(Context context, AttributeSet attrs) {
super(context, attrs);
mScroller = new Scroller(context);
}
public DampView(Context context) {
super(context);
}
public void setImageView(ImageView imageView) {
this.imageView = imageView;
}
@Override
protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {
return 0;
}
private int[] li = new int[2];
private int[] li2 = new int[2];
private float lastLy;
private boolean startIsTop = true;
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
super.dispatchTouchEvent(event);
int action = event.getAction();
if (!mScroller.isFinished()) {
return super.onTouchEvent(event);
}
currentX = event.getX();
currentY = event.getY();
imageView.getLocationInWindow(li);
getLocationOnScreen(li2);
imageView.getTop();
if (contentView == null) {
return super.dispatchTouchEvent(event);
}
switch (action) {
case MotionEvent.ACTION_DOWN:
if (li[1] != li2[1]) {// 判断开始触摸时，imageview和窗口顶部对齐没
startIsTop = false;
}
left = imageView.getLeft();
top = imageView.getBottom();
rootW = getWidth();
rootH = getHeight();
imageViewH = imageView.getHeight();
startX = currentX;
startY = currentY;
tool = new TouchTool(imageView.getLeft(), imageView.getBottom(), imageView.getLeft(),
imageView.getBottom() + LEN);
//判断是否可以上拉和下拉
canPullDown = isCanPullDown();
canPullUp = false;
//记录按下时的Y值
startY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
if (!startIsTop && li[1] == li2[1]) {
startY = currentY;
startIsTop = true;
}
if (imageView.isShown() && imageView.getTop() >= 0) {
if (tool != null) {
int t = tool.getScrollY(currentY - startY);
if (!scrollerType && currentY < lastLy && imageView.getHeight() > imageViewH) {
scrollTo(0, 0);
imageView.getLocationInWindow(li);
getLocationOnScreen(li2);
android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
params.height = t;
imageView.setLayoutParams(params);
if (imageView.getHeight() == imageViewH && li[1] == li2[1]) {
scrollerType = true;
}
if (startIsTop && li[1] != li2[1]) {
startIsTop = false;
}
}
if (t >= top && t <= imageView.getBottom() + LEN && li[1] == li2[1] && currentY > lastLy) {
android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
params.height = t;
imageView.setLayoutParams(params);
}
}
scrollerType = false;
}
lastLy = currentY;
//在移动的过程中， 既没有滚动到可以上拉的程度， 也没有滚动到可以下拉的程度
if (!canPullDown && !canPullUp) {
startY = event.getY();
canPullDown = isCanPullDown();
canPullUp = false;
break;
}
//计算手指移动的距离
float nowY = event.getY();
int deltaY = (int) (nowY - startY);
//是否应该移动布局
boolean shouldMove =
(canPullDown && deltaY > 0) //可以下拉， 并且手指向下移动
|| (canPullUp && deltaY < 0) //可以上拉， 并且手指向上移动
|| (canPullUp && canPullDown); //既可以上拉也可以下拉（这种情况出现在ScrollView包裹的控件比ScrollView还小）
if (shouldMove) {
//计算偏移量
int offset = (int) (deltaY * MOVE_FACTOR);
//随着手指的移动而移动布局
contentView.layout(originalRect.left, originalRect.top + offset,
originalRect.right, originalRect.bottom + offset);
isMoved = true; //记录移动了布局
}
break;
case MotionEvent.ACTION_UP:
if (!isMoved) break; //如果没有移动布局， 则跳过执行
// 开启动画
if (li[1] == li2[1]) {
scrollerType = true;
mScroller.startScroll(imageView.getLeft(), imageView.getBottom(), 0 - imageView.getLeft(),
imageViewH - imageView.getBottom(), DURATION);
}
TranslateAnimation anim = new TranslateAnimation(0, 0, contentView.getTop(),
originalRect.top);
anim.setDuration(ANIM_TIME);
anim.setInterpolator(new AccelerateDecelerateInterpolator());
// 设置回到正常的布局位置
contentView.startAnimation(anim);
contentView.layout(originalRect.left, originalRect.top,
originalRect.right, originalRect.bottom);
invalidate();
startIsTop = true;
//将标志位设回false
canPullDown = false;
canPullUp = false;
isMoved = false;
break;
}
return true;
}
@Override
public void computeScroll() {
super.computeScroll();
if (mScroller.computeScrollOffset()) {
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
imageView.layout(0, 0, x + imageView.getWidth(), y);
invalidate();
if (!mScroller.isFinished() && scrollerType && y > MAX_DY) {
android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
params.height = y;
imageView.setLayoutParams(params);
}
}
}
public class TouchTool {
private int startX, startY;
public TouchTool(int startX, int startY, int endX, int endY) {
super();
this.startX = startX;
this.startY = startY;
}
public int getScrollX(float dx) {
int xx = (int) (startX + dx / 2.5F);
return xx;
}
public int getScrollY(float dy) {
int yy = (int) (startY + dy / 2.5F);
return yy;
}
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
if (getChildCount() > 0) {
contentView = getChildAt(0);
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if (contentView == null) {
return;
}
//ScrollView中的唯一子控件的位置信息, 这个位置信息在整个控件的生命周期中保持不变
originalRect.set(contentView.getLeft(), contentView.getTop(), contentView
.getRight(), contentView.getBottom());
}
//判断是否滚动到顶部
private boolean isCanPullDown() {
return getScrollY() == 0 ||
contentView.getHeight() < getHeight() + getScrollY();
}
//判断是否滚动到底部
private boolean isCanPullUp() {
return contentView.getHeight() <= getHeight() + getScrollY();
}
}2.MainActivity主文件
public class MainActivity extends AppCompatActivity {
DampView dampView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dampView = findViewById(R.id.dv);
dampView.setImageView((ImageView) findViewById(R.id.search_src_text));
}布局文件
注意*：dampview只能有一个Child,当然子Child里面可以随便排列布局
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.asus.myapplication.MainActivity">
<ImageView
android:scaleType="centerCrop"
android:id="@+id/search_src_text"
android:src="@mipmap/ic_bg"
android:layout_width="match_parent"
android:layout_height="200dp" />
<com.example.asus.myapplication.DampView
android:id="@+id/dv"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_marginTop="50dp"
android:gravity="center"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:gravity="center"
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/text"
android:layout_gravity="center" />
</LinearLayout>
</RelativeLayout>
</com.example.asus.myapplication.DampView>
</RelativeLayout>效果图：
