参考自--> Android群英传
项目地址-->书中自定义 view 汇总：https://github.com/FishInWater-1999/DesighViewText
确定 ViewGroup 的高度，并生成 Scroller 对象
代码语言：javascript复制 private void initView(Context context) {
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics dm = new DisplayMetrics();
wm.getDefaultDisplay().getMetrics(dm);
mScreenHeight = dm.heightPixels;
mScroller = new Scroller(context);
}确定子 View 的位置
代码语言：javascript复制 @Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int childCount = getChildCount();
// 设置 ViewGroup 的高度
MarginLayoutParams mlp = (MarginLayoutParams) getLayoutParams();
mlp.height = mScreenHeight * childCount;
setLayoutParams(mlp);
for (int i = 0 ; i < childCount ; i ){
View child = getChildAt(i);
if (child.getVisibility() != View.GONE){
child.layout(1, i * mScreenHeight,
r, (i 1) * mScreenHeight);
}
}
}粘性实现滑动
代码语言：javascript复制 @Override
public boolean onTouchEvent(MotionEvent event) {
int y = (int)event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
mLastY = y;
mStart = getScrollY();
break;
case MotionEvent.ACTION_MOVE:
if (!mScroller.isFinished()){
mScroller.abortAnimation();
}
int dy = mLastY - y;
if (getScrollY() < 0){
dy = 0;
}
if (getScrollY() > getHeight() - mScreenHeight){
dy = 0;
}
scrollBy(0, dy);
mLastY = y;
break;
case MotionEvent.ACTION_UP:
mEnd = getScrollY();
int dScrollY = mEnd - mStart;
if (dScrollY > 0){
if (dScrollY < mScreenHeight / 3){
mScroller.startScroll(
0 , getScrollY(),
0, -dScrollY
);
}else {
mScroller.startScroll(
0, getScrollY(),
0, mScreenHeight - dScrollY
);
}
}else {
if (-dScrollY < mScreenHeight / 3){
mScroller.startScroll(
0, getScrollY(),
0, -dScrollY
);
}else {
mScroller.startScroll(
0, getScrollY(),
0, -mScreenHeight - dScrollY
);
}
}
break;
}
postInvalidate();
return true;
}完整代码如下：
代码语言：javascript复制/**
* 定义 ViewGroup 实现类似：ScrollView 的功能
*/
public class ViewGroup_3_7 extends ViewGroup {
/*
数据成员
*/
private int mScreenHeight = 0;
private int childCount = 0;
private int mLastY = 0;
private int mStart = 0;
private int mEnd = 0;
private Scroller mScroller ;
/*
构造方法
*/
public ViewGroup_3_7(Context context) {
this(context, null);
}
public ViewGroup_3_7(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ViewGroup_3_7(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView(context);
}
/*
确定 ViewGroup 的高度
*/
private void initView(Context context) {
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics dm = new DisplayMetrics();
wm.getDefaultDisplay().getMetrics(dm);
mScreenHeight = dm.heightPixels;
mScroller = new Scroller(context);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int count = getChildCount();
for ( int i = 0 ; i < count ; i ){
View childViews = getChildAt(i);
measureChild(childViews, widthMeasureSpec, heightMeasureSpec);
}
}
/*
确定子 View 的位置
*/
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int childCount = getChildCount();
// 设置 ViewGroup 的高度
MarginLayoutParams mlp = (MarginLayoutParams) getLayoutParams();
mlp.height = mScreenHeight * childCount;
setLayoutParams(mlp);
for (int i = 0 ; i < childCount ; i ){
View child = getChildAt(i);
if (child.getVisibility() != View.GONE){
child.layout(1, i * mScreenHeight,
r, (i 1) * mScreenHeight);
}
}
}
/*
粘性实现滑动
*/
@Override
public boolean onTouchEvent(MotionEvent event) {
int y = (int)event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
mLastY = y;
mStart = getScrollY();
break;
case MotionEvent.ACTION_MOVE:
if (!mScroller.isFinished()){
mScroller.abortAnimation();
}
int dy = mLastY - y;
if (getScrollY() < 0){
dy = 0;
}
if (getScrollY() > getHeight() - mScreenHeight){
dy = 0;
}
scrollBy(0, dy);
mLastY = y;
break;
case MotionEvent.ACTION_UP:
mEnd = getScrollY();
int dScrollY = mEnd - mStart;
if (dScrollY > 0){
if (dScrollY < mScreenHeight / 3){
mScroller.startScroll(
0 , getScrollY(),
0, -dScrollY
);
}else {
mScroller.startScroll(
0, getScrollY(),
0, mScreenHeight - dScrollY
);
}
}else {
if (-dScrollY < mScreenHeight / 3){
mScroller.startScroll(
0, getScrollY(),
0, -dScrollY
);
}else {
mScroller.startScroll(
0, getScrollY(),
0, -mScreenHeight - dScrollY
);
}
}
break;
}
postInvalidate();
return true;
}
/*
*/
@Override
public void computeScroll() {
super.computeScroll();
if (mScroller.computeScrollOffset()){
scrollTo(0, mScroller.getCurrY());
postInvalidate();
}
}
}
