android View 跟随手指移动的7种方式

###View 跟随手指移动的7种方式

. layout方法

底层还是1 系统封装好的偏移方法。

MarginlayoutParams LayoutParams 的leftMargin topmargin

scrollTo scrollBy

Scroller

属性动画（后边详细讲）

support包中的ViewDragHelper

1.layout方法

2.offsetLeftAndRight(offsetX); offsetTopAndBottom(offsetY);

// 视图坐标方式
@Override
public boolean onTouchEvent(MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// 记录触摸点坐标
lastX = x;
lastY = y;
break;
case MotionEvent.ACTION_MOVE:
// 计算偏移量
int offsetX = x - lastX;
int offsetY = y - lastY;
// 在当前left、top、right、bottom的基础上加上偏移量
layout(getLeft() + offsetX,
getTop() + offsetY,
getRight() + offsetX,
getBottom() + offsetY);
//                        offsetLeftAndRight(offsetX);
//                        offsetTopAndBottom(offsetY);
break;
}
return true;
}

3.LayoutParams

case MotionEvent.ACTION_MOVE:
// 计算偏移量
int offsetX = x - lastX;
int offsetY = y - lastY;
ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) getLayoutParams();
//                LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) getLayoutParams();
layoutParams.leftMargin = getLeft() + offsetX;

4000
layoutParams.topMargin = getTop() + offsetY;
setLayoutParams(layoutParams);
break;

scrollBy

case MotionEvent.ACTION_MOVE:
int offsetX = x - lastX;
int offsetY = y - lastY;
((View) getParent()).scrollBy(-offsetX, -offsetY);
break;

scroller

private void ininView(Context context) {
setBackgroundColor(Color.BLUE);
// 第一步 初始化Scroller
mScroller = new Scroller(context);
}

//第二步 此方法为模板代码
@Override
public void computeScroll() {
super.computeScroll();
// 判断Scroller是否执行完毕
if (mScroller.computeScrollOffset()) {
((View) getParent()).scrollTo(
mScroller.getCurrX(),
mScroller.getCurrY());
// 通过重绘来不断调用computeScroll
invalidate();
}
}

@Override
public boolean onTouchEvent(MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
lastX = (int) event.getX();
lastY = (int) event.getY();
break;
case MotionEvent.ACTION_MOVE:
int offsetX = x - lastX;
int offsetY = y - lastY;
((View) getParent()).scrollBy(-offsetX, -offsetY);
break;
case MotionEvent.ACTION_UP:
// 手指离开时，执行滑动过程
View viewGroup = ((View) getParent());
//第三部 启动scroller
mScroller.startScroll(
viewGroup.getScrollX(),//当前view的左上角相对于母视图的左上角的X轴偏移量
viewGroup.getScrollY(),//开始的x y
-viewGroup.getScrollX(),
-viewGroup.getScrollY());//滑动的distanceXY
invalidate();
break;
}
return true;
}

ViewDragHelper

public class DragViewGroup extends FrameLayout {

private ViewDragHelper mViewDragHelper;
private View mMenuView, mMainView;
private int mWidth;

public DragViewGroup(Context context) {
super(context);
initView();
}

public DragViewGroup(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}

public DragViewGroup(Context context,
AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView();
}

@Override
protected void onFinishInflate() {
super.onFinishInflate();
mMenuView = getChildAt(0);
mMainView = getChildAt(1);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mWidth = mMenuView.getMeasuredWidth();
}

@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return mViewDragHelper.shouldInterceptTouchEvent(ev);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
//将触摸事件传递给ViewDragHelper,此操作必不可少
mViewDragHelper.processTouchEvent(event);
return true;
}

private void initView() {
mViewDragHelper = ViewDragHelper.create(this, callback);
}

private ViewDragHelper.Callback callback =
new ViewDragHelper.Callback() {

// 何时开始检测触摸事件
@Override
public boolean tryCaptureView(View child, int pointerId) {
//如果当前触摸的child是mMainView时开始检测
return mMainView == child;
}

// 触摸到View后回调
@Override
public void onViewCaptured(View capturedChild,
int activePointerId) {
super.onViewCaptured(capturedChild, activePointerId);
}

// 当拖拽状态改变，比如idle，dragging
@Override
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
}

// 当位置改变的时候调用,常用与滑动时更改scale等
@Override
public void onViewPositionChanged(View changedView,
int left, int top, int dx, int dy) {
super.onViewPositionChanged(changedView, left, top, dx, dy);
}

// 处理垂直滑动
@Override
public int clampViewPositionVertical(View child, int top, int dy) {
return 0;
}

// 处理水平滑动
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
return left;
}

// 拖动结束后调用
@Override
public void onViewReleased(View releasedChild, float xvel, float yvel) {
super.onViewReleased(releasedChild, xvel, yvel);
//手指抬起后缓慢移动到指定位置
if (mMainView.getLeft() < 500) {
//关闭菜单
//相当于Scroller的startScroll方法
mViewDragHelper.smoothSlideViewTo(mMainView, 0, 0);
ViewCompat.postInvalidateOnAnimation(DragViewGroup.this);
} else {
//打开菜单
mViewDragHelper.smoothSlideViewTo(mMainView, 300, 0);
ViewCompat.postInvalidateOnAnimation(DragViewGroup.this);
}
}
};

@Override
public void computeScroll() {
if (mViewDragHelper.continueSettling(true)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
}

<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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">

<com.imooc.dragviewtest.DragViewGroup
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/view">

<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_blue_light">

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Menu" />
</FrameLayout>

<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_orange_dark">

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Main" />
</FrameLayout>
</com.imooc.dragviewtest.DragViewGroup>
</RelativeLayout>