近日看到了ViewDragHelper这个工具，觉得对视图拖拽来说可以提供很大的帮助，特此写下一个小例子mark一下。
package com.fly.xwx.viewgroupsection.widget;
import android.content.Context;
import android.graphics.Point;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by Mr.Xu on 2016/8/9 0009.
*/
public class DraggerHelperView extends ViewGroup {
GridView gridView;
//默认间距
private static final int DEFAULT_COLUMS_PADDING = 20;
//列数
private int mColums = 3;
private static final String TAG = DraggerHelperView.class.getSimpleName();
private ViewDragHelper mDragger;
public DraggerHelperView(Context context, AttributeSet attrs) {
super(context, attrs);
mDragger = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {
@Override
public boolean tryCaptureView(View child, int pointerId) {
return true;
}
/**
* clampViewPositionHorizontal,clampViewPositionVertical
* 可以在该方法中对child移动的边界进行控制，
* left , top 分别为即将移动到的位置，
* 比如横向的情况下，
* 我希望只在ViewGroup的内部移动，
* 即：paddingleft<=滑动范围<=ViewGroup.
* getWidth()-paddingright-child.getWidth。
*/
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
int leftBound = getPaddingLeft();
int rightBound = getWidth() - child.getWidth() - leftBound;
int newLeft = Math.min(Math.max(left, leftBound), rightBound);
return newLeft;
}
@Override
public int clampViewPositionVertical(View child, int top, int dy) {
int topBound = getPaddingTop();
int bottomBound = getHeight() - child.getHeight() - topBound;
int newTop = Math.min(Math.max(top, topBound), bottomBound);
return newTop;
}
@Override
public int getViewHorizontalDragRange(View child) {
return getMeasuredWidth() - child.getMeasuredWidth();
}
@Override
public int getViewVerticalDragRange(View child) {
return getMeasuredHeight() - child.getMeasuredHeight();
}
@Override
public void onViewReleased(View releasedChild, float xvel, float yvel) {
//从childView 的 TAG 中取出原始坐标
Point position = (Point) releasedChild.getTag();
mDragger.settleCapturedViewAt(position.x, position.y);
invalidate();
}
});
}
public int getmColums() {
return mColums;
}
public void setmColums(int mColums) {
if (mColums > getChildCount() || mColums == 0)
throw new IllegalArgumentException("input data illegal");
this.mColums = mColums;
requestLayout();
}
@Override
public void computeScroll() {
if (mDragger.continueSettling(true)) {
invalidate();
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return mDragger.shouldInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mDragger.processTouchEvent(event);
return false;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int measuredWidth = MeasureSpec.getSize(widthMeasureSpec);
int measuredHeight = MeasureSpec.getSize(heightMeasureSpec);
int measuredModeW = MeasureSpec.getMode(widthMeasureSpec);
int measuredModeH = MeasureSpec.getMode(heightMeasureSpec);
int cCount = getChildCount();
Log.e(TAG, "measuredWidth=" + measuredWidth + "measuredHeight=" + measuredHeight);
switch (measuredModeW) {
case MeasureSpec.EXACTLY:
Log.e(TAG, "EXACTLY=W");
break;
case MeasureSpec.AT_MOST:
Log.e(TAG, "AT_MOST=W");
break;
case MeasureSpec.UNSPECIFIED:
Log.e(TAG, "UNSPECIFIED=W");
break;
}
switch (measuredModeH) {
case MeasureSpec.EXACTLY:
Log.e(TAG, "EXACTLY=H");
break;
case MeasureSpec.AT_MOST:
Log.e(TAG, "AT_MOST=H");
break;
case MeasureSpec.UNSPECIFIED:
Log.e(TAG, "UNSPECIFIED=H");
break;
}
//自动排序
// for (int i = 0; i < cCount; i++) {
// View childView = getChildAt(i);
// measureChild(childView, widthMeasureSpec, heightMeasureSpec);
// widgetWidth = childView.getPaddingLeft() +
// childView.getMeasuredWidth() + childView.getPaddingRight();
//
// if (width + widgetWidth + DEFAULT_COLUMS_PADDING > measuredWidth) {
// mColums = i;
// break;
// }
// width += widgetWidth + DEFAULT_COLUMS_PADDING;
// }
int height = 0;
int width = 0;
int widgetHeight = 0;
int widgetWidth = 0;
int maxWidth = 0;
for (int i = 0; i < cCount; i++) {
View childView = getChildAt(i);
measureChild(childView, widthMeasureSpec, heightMeasureSpec);
Log.e(TAG, "childWidth=" + childView.getMeasuredHeight());
widgetHeight = childView.getMeasuredHeight() + asd childView.getPaddingTop() + childView.getPaddingBottom();
widgetWidth = childView.getPaddingLeft() +
childView.getMeasuredWidth() + childView.getPaddingRight();
if (i % mColums == 0) {
height += widgetHeight + DEFAULT_COLUMS_PADDING;
maxWidth = Math.max(maxWidth, width);
Log.e(TAG, "maxWidth=" + maxWidth);
width = widgetWidth + DEFAULT_COLUMS_PADDING;
} else {
width += widgetWidth + DEFAULT_COLUMS_PADDING;
}
}
height += DEFAULT_COLUMS_PADDING;
width = maxWidth + DEFAULT_COLUMS_PADDING;
Log.e(TAG, "parentWidth=" + width + "/parentHeight=" + height);
setMeasuredDimension((measuredModeW == MeasureSpec.EXACTLY) ? measuredWidth : width,
(measuredModeH == MeasureSpec.EXACTLY) ? measuredHeight : height);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int cCount = getChildCount();
//最后使用的l t r b
int layoutLeft = 0;
int layoutRight = 0;
int layoutTop = 0;
int layoutBottom = 0;
//下一个子视图的l
int lineLeft = 0;
//下一行子视图的t
int lineTop = DEFAULT_COLUMS_PADDING;
//子视图具体所占大小
int widgetHeight = 0;
int widgetWidth = 0;
for (int i = 0; i < cCount; i++) {
View childView = getChildAt(i);
widgetHeight = childView.getMeasuredHeight() + childView.getPaddingTop() + childView.getPaddingBottom();
widgetWidth = childView.getPaddingLeft() +
childView.getMeasuredWidth() + childView.getPaddingRight();
if (i % mColums == 0) {
//左边
lineLeft = 0;
//累加一下行高
layoutTop += lineTop;
layoutLeft = DEFAULT_COLUMS_PADDING;
} else {
//右边
layoutLeft = DEFAULT_COLUMS_PADDING + lineLeft;
}
layoutRight = layoutLeft + widgetWidth;
lineTop = Math.max(lineTop, widgetHeight + DEFAULT_COLUMS_PADDING);
lineLeft = layoutRight;
layoutBottom = layoutTop + widgetHeight;
childView.setTag(new Point(layoutLeft, layoutTop));
childView.layout(layoutLeft, layoutTop, layoutRight, layoutBottom);
}
}
}
不好意思之前忘了贴出用法了，写的比较懒还没有写上自定义属性所以暂时只需要这样就可以了
通过实例方法setmColums()可以即时改变排列:
public void setmColums(int mColums) {
if (mColums > getChildCount() || mColums == 0)
throw new IllegalArgumentException("input data illegal");
this.mColums = mColums;
requestLayout();
}