实现方法一：自定义View
可随意拖动拖拽的View，限制拖动范围是父布局中；
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.ImageView;public class DragActionButton extends ImageView {private int parentHeight;private int parentWidth;private int lastX;private int lastY;private ViewGroup parent;public DragActionButton(Context context) {super(context);}public DragActionButton(Context context, AttributeSet attrs) {super(context, attrs);}public DragActionButton(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}@Overridepublic boolean onTouchEvent(MotionEvent event) {int rawX = (int) event.getRawX();int rawY = (int) event.getRawY();switch (event.getAction() & MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN:getParent().requestDisallowInterceptTouchEvent(true);lastX = rawX;lastY = rawY;if (getParent() != null) {parent = (ViewGroup) getParent();parentHeight = parent.getHeight();parentWidth = parent.getWidth();}break;case MotionEvent.ACTION_MOVE:if (parentHeight <= 0.2 || parentWidth <= 0.2) {break;}int dx = rawX - lastX;int dy = rawY - lastY;//这里修复一些华为手机无法触发点击事件int distance = (int) Math.sqrt(dx * dx + dy * dy);if (distance == 0) {break;}float x = getX() + dx;float y = getY() + dy;//检测是否到达边缘 左上右下x = x < 0 ? 0 : x + getWidth() > parentWidth ? parentWidth - getWidth() : x;y = y < 0 ? 0 : y + getHeight() > parentHeight ? parentHeight - getHeight() : y;setX(x);setY(y);lastX = rawX;lastY = rawY;Log.i("ACTION_MOVE", "getX=" + getX() + ";getY=" + getY() + ";parentWidth=" + parentWidth+ ";parentHeight=" + parentHeight);break;case MotionEvent.ACTION_UP:case MotionEvent.ACTION_CANCEL:this.setAlpha(1.0f);Log.i("ACTION_UP", "getX=" + getX() + ";getY=" + getY());break;}return true;}}下面是可以左右吸边的效果；
import android.animation.ObjectAnimator;
import android.content.Context;
import android.os.Handler;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;
import android.widget.Toast;import androidx.annotation.Nullable;public class DragFloatActionButton extends ImageView {private int parentHeight;private int parentWidth;Handler handler = new Handler();Runnable runnable = new Runnable() {@Overridepublic void run() {setAlpha(0.3f);}};private int lastX;private int lastY;private ViewGroup parent;public DragFloatActionButton(Context context) {super(context);}public DragFloatActionButton(Context context, AttributeSet attrs) {super(context, attrs);}public DragFloatActionButton(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}private int downX;private int downY;private long downTime;@Overridepublic boolean onTouchEvent(MotionEvent event) {int rawX = (int) event.getRawX();int rawY = (int) event.getRawY();switch (event.getAction() & MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN:this.setAlpha(0.9f);getParent().requestDisallowInterceptTouchEvent(true);lastX = rawX;lastY = rawY;downX = rawX;downY = rawY;downTime = System.currentTimeMillis();if (getParent() != null) {parent = (ViewGroup) getParent();parentHeight = parent.getHeight();parentWidth = parent.getWidth();}break;case MotionEvent.ACTION_MOVE:if (parentHeight <= 0.2 || parentWidth <= 0.2) {break;}this.setAlpha(0.9f);int dx = rawX - lastX;int dy = rawY - lastY;//这里修复一些华为手机无法触发点击事件int distance = (int) Math.sqrt(dx * dx + dy * dy);if (distance == 0) {break;}float x = getX() + dx;float y = getY() + dy;//检测是否到达边缘 左上右下x = x < 0 ? 0 : x + getWidth() > parentWidth ? parentWidth - getWidth() : x;y = y < 0 ? 0 : y + getHeight() > parentHeight ? parentHeight - getHeight() : y;setX(x);setY(y);lastX = rawX;lastY = rawY;Log.i("ACTION_MOVE", "getX=" + getX() + ";getY=" + getY() + ";parentWidth=" + parentWidth+ ";parentHeight=" + parentHeight);break;case MotionEvent.ACTION_UP:moveHide(rawX);if(onClickListener != null&& Math.abs(downX - rawX) < 10&& Math.abs(downY - rawY) < 10&& System.currentTimeMillis() - downTime < 1000){Log.i("ACTION_UP", "触发点击事件 ");onClickListener.onClick(this);}break;}return true;}OnClickListener onClickListener;@Overridepublic void setOnClickListener(@Nullable OnClickListener l) {onClickListener = l;}private void moveHide(int rawX) {if (rawX >= parentWidth / 2) {//靠右吸附animate().setInterpolator(new DecelerateInterpolator()).setDuration(500).xBy(parentWidth - getWidth() - getX()).start();myRunable();} else {//靠左吸附ObjectAnimator oa = ObjectAnimator.ofFloat(this, "x", getX(), 0);oa.setInterpolator(new DecelerateInterpolator());oa.setDuration(500);oa.start();myRunable();}}private void myRunable() {handler.removeCallbacks(runnable);handler.postDelayed(runnable, 2000);}实现方法二：自定义ViewGroup
使用ViewDragHelper实现：
ViewDragHelper is a utility class for writing custom ViewGroups. It offers a number of useful operations and state tracking for allowing a user to drag and reposition views within their parent ViewGroup.
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RelativeLayout;import androidx.customview.widget.ViewDragHelper;public class DragViewGroup extends RelativeLayout {private ViewDragHelper mDragger;private View mDragView;public DragViewGroup(Context context, AttributeSet attrs) {super(context, attrs);this.setGravity(Gravity.CENTER);mDragger = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {@Overridepublic boolean tryCaptureView(View child, int pointerId) {return true;}@Overridepublic int clampViewPositionHorizontal(View child, int left, int dx) {final int leftBound = getPaddingLeft();final int rightBound = getWidth() - mDragView.getWidth();final int newLeft = Math.min(Math.max(left, leftBound), rightBound);return newLeft;}@Overridepublic int clampViewPositionVertical(View child, int top, int dy) {final int topBound = getPaddingTop();final int bottomBound = getHeight() - mDragView.getHeight();final int newTop = Math.min(Math.max(top, topBound), bottomBound);return newTop;}//手指释放的时候回调@Overridepublic void onViewReleased(View releasedChild, float xvel, float yvel) {Log.i("onViewReleased", "view: x :"+mDragView.getX() +"y:"+mDragView.getY()+"\nviewgroup: w: "+getWidth() + "h : "+getHeight());}});}@Overridepublic boolean onInterceptTouchEvent(MotionEvent event) {return mDragger.shouldInterceptTouchEvent(event);}@Overridepublic boolean onTouchEvent(MotionEvent event) {mDragger.processTouchEvent(event);return true;}@Overrideprotected void onFinishInflate() {super.onFinishInflate();mDragView = getChildAt(0);}
}
)
