1.ViewDragHelper介绍
效果图.gif
- 1.1创建
mViewDragHelper= ViewDragHelper.create(this, mDragHelperCallback);
1.2实现拖动
@Override
public boolean onTouchEvent(MotionEvent event) {
mViewDragHelper.processTouchEvent(event);
return true;
}
//拖动我们的子view
private ViewDragHelper.Callback mDragHelperCallback=new ViewDragHelper.Callback() {
@Override
public boolean tryCaptureView(@NonNull View child, int pointerId) {
//指定子view是否可以拖动
//代表都可以
return true;
}
@Override
public int clampViewPositionHorizontal(@NonNull View child, int left, int dx) {
//水平拖动移动的位置
return left;
}
@Override
public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
//垂直拖动移动的位置
return top;
}
};
2.效果分析实现
- 2.1 后面不能拖动
- 2.2 列表只能垂直拖动
- 2.3 垂直拖动的范围只能是后面菜单 View 的高度
获取控件的宽高一定是要在测量完毕之后才能去拿，也就是要在onMeasure()之后 - 2.4 手指松开的时候两者选其一，要么打开要么关闭
效果图.gif
public class VerticalDragListView extends FrameLayout {
//这是系统给我们写好的一个工具类
private ViewDragHelper mViewDragHelper;
private View mDragListView;
// 后面菜单的高度
private int mMenuHeight;
public VerticalDragListView(Context context) {
this(context, null);
}
public VerticalDragListView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public VerticalDragListView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mViewDragHelper = ViewDragHelper.create(this, mDragHelperCallback);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mViewDragHelper.processTouchEvent(event);
return true;
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
int childCount = getChildCount();
if (childCount != 2) {
throw new RuntimeException("VerticalDragListView只能包含两个子布局");
}
mDragListView = getChildAt(1);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if(changed){
View menuView = getChildAt(0);
mMenuHeight = menuView.getMeasuredHeight();
}
}
/**
* 拖动我们的子view
*/
private ViewDragHelper.Callback mDragHelperCallback = new ViewDragHelper.Callback() {
@Override
public boolean tryCaptureView(@NonNull View child, int pointerId) {
//指定子view是否可以拖动
//true代表都可以
// 2.1 后面不能拖动
return mDragListView == child;
}
// 2.2 列表只能垂直拖动
@Override
public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
// 2.3 垂直拖动的范围只能是后面菜单 View 的高度
if (top <= 0) {
top = 0;
}
if (top >= mMenuHeight) {
top = mMenuHeight;
}
return top;
}
// 2.4 手指松开的时候两者选其一，要么打开要么关闭
@Override
public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
Log.e("TAG", "yvel -> " + yvel + " mMenuHeight -> " + mMenuHeight);
Log.e("TAG", "top -> " + mDragListView.getTop());
if(releasedChild==mDragListView){
if(mDragListView.getTop()>mMenuHeight/2){
//打开
mViewDragHelper.settleCapturedViewAt(0,mMenuHeight);
}else{
mViewDragHelper.settleCapturedViewAt(0,0);
}
invalidate();
}
}
};
/**
* 响应滚动
*/
@Override
public void computeScroll() {
if(mViewDragHelper.continueSettling(true)){
invalidate();
}
}
}
将前面换成ListView分析事件的分发和拦截
效果分析.gif
主布局
<?xml version="1.0" encoding="utf-8"?>
<com.hbwj.a09_.VerticalDragListView 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">
<TextView
android:layout_width="match_parent"
android:layout_height="200dp"
android:background="@color/colorPrimary"
android:gravity="center"
android:text="后面" />
<!-- <TextView
android:layout_width="match_parent"
android:layout_height="200dp"
android:background="@color/colorAccent"
android:gravity="center"
android:text="前面" />-->
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFFFF" />
</com.hbwj.a09_.VerticalDragListView>
VerticalDragListView代码
public class VerticalDragListView extends FrameLayout {
//这是系统给我们写好的一个工具类
private ViewDragHelper mDragHelper;
private View mDragListView;
// 后面菜单的高度
private int mMenuHeight;
private boolean mMenuIsOpen;
public VerticalDragListView(Context context) {
this(context, null);
}
public VerticalDragListView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public VerticalDragListView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mDragHelper = ViewDragHelper.create(this, mDragHelperCallback);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mDragHelper.processTouchEvent(event);
return true;
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
int childCount = getChildCount();
if (childCount != 2) {
throw new RuntimeException("VerticalDragListView只能包含两个子布局");
}
mDragListView = getChildAt(1);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (changed) {
View menuView = getChildAt(0);
mMenuHeight = menuView.getMeasuredHeight();
}
}
/**
* 拖动我们的子view
*/
private ViewDragHelper.Callback mDragHelperCallback = new ViewDragHelper.Callback() {
@Override
public boolean tryCaptureView(@NonNull View child, int pointerId) {
//指定子view是否可以拖动
//true代表都可以
// 2.1 后面不能拖动
return mDragListView == child;
}
// 2.2 列表只能垂直拖动
@Override
public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
// 2.3 垂直拖动的范围只能是后面菜单 View 的高度
if (top <= 0) {
top = 0;
}
if (top >= mMenuHeight) {
top = mMenuHeight;
}
return top;
}
// 2.4 手指松开的时候两者选其一，要么打开要么关闭
@Override
public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
Log.e("TAG", "yvel -> " + yvel + " mMenuHeight -> " + mMenuHeight);
Log.e("TAG", "top -> " + mDragListView.getTop());
if (releasedChild == mDragListView) {
if (mDragListView.getTop() > mMenuHeight / 2) {
//打开
mDragHelper.settleCapturedViewAt(0, mMenuHeight);
mMenuIsOpen = true;
} else {
mDragHelper.settleCapturedViewAt(0, 0);
mMenuIsOpen = false;
}
invalidate();
}
}
};
// 现象就是ListView可以滑动，但是菜单滑动没有效果了
private float mDownY;
@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
// 菜单打开要拦截
if (mMenuIsOpen) {
return true;
}
//向下滑动拦截，不给listview处理
//父View拦截子View ，但是子 View 可以调这个方法
// requestDisallowInterceptTouchEvent 请求父View不要拦截，改变的其实就是 mGroupFlags 的值
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mDownY=event.getY();
mDragHelper.processTouchEvent(event);
break;
case MotionEvent.ACTION_MOVE:
float moveY = event.getY();
if((moveY-mDownY)>0&&!canChildScrollUp()){
// 向下滑动 && 滚动到了顶部，拦截不让ListView做处理
return true;
}
break;
default:
break;
}
return super.onInterceptTouchEvent(event);
}
/**
* 参看SwipeRefreshLayout源码的canChildScrollUp
* 判断View是否滚动到了最顶部,还能不能向上滚
*/
@SuppressLint("ObsoleteSdkInt")
public boolean canChildScrollUp() {
if (android.os.Build.VERSION.SDK_INT < 14) {
if (mDragListView instanceof AbsListView) {
final AbsListView absListView = (AbsListView) mDragListView;
return absListView.getChildCount() > 0
&& (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0)
.getTop() < absListView.getPaddingTop());
} else {
return ViewCompat.canScrollVertically(mDragListView, -1) || mDragListView.getScrollY() > 0;
}
} else {
return ViewCompat.canScrollVertically(mDragListView, -1);
}
}
/**
* 响应滚动
*/
@Override
public void computeScroll() {
if (mDragHelper.continueSettling(true)) {
invalidate();
}
}
}
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