仿ios辅助按钮效果(就是那个一直在桌面的...)

参考https://github.com/Sbingo/FreeRadioGroup
本文主要是根据自己的需求进行重新定义了一下,并且指出使用时的注意事项
demo下载链接：http://pan.baidu.com/s/1hrRoLla 密码：iuxi

效果图

使用时根布局使用FramLayout

布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="sbingo.demo.Main2Activity">

    <demo.kotlin.freelayout.FreeLayout
        android:id="@+id/group"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:autoBack="true"
        app:iconButton="@mipmap/open_door"
        app:millisInFuture="500"
        app:moveable="true" />
</FrameLayout>

控件代码

package demo.kotlin.freelayout;

import android.animation.ObjectAnimator;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.CountDownTimer;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.LinearLayout;

/**
 * Created by gjl on 2017/6/8.
 */

public class FreeLayout extends LinearLayout {

    /**
     * 倒计时过程中
     * 回调{@link CountDownTimer#onTick(long)}的间隔时间
     */
    private MyCountDownTimer countDownTimer;
    /**
     * 倒计时时间
     */
    private long millisInFuture;
    private long countDownInterval = 500;
    private boolean moveable, autoBack;
    private float toAlpha,
            startX, startY,
            currentX, currentY;
    private int iconButton,
            currentLeft, currentTop,
            screenWidth, screenHeight,
            parentWidth, parentHeight,
            viewWidth, viewHight,
            minLeftMargin, maxLeftMargin,
            minTopMargin, maxTopMargin,
            bottomDistance, rightDistance,
            leftPadding, topPadding;

    public FreeLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
        screenWidth = displayMetrics.widthPixels;
        screenHeight = displayMetrics.heightPixels - getStatusBarHeight();
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.free);
        millisInFuture = ta.getInt(R.styleable.free_millisInFuture, 3 * 1000);
        toAlpha = ta.getFloat(R.styleable.free_toAlpha, 0.2f);
        moveable = ta.getBoolean(R.styleable.free_moveable, false);
        autoBack = ta.getBoolean(R.styleable.free_autoBack, false);
        iconButton = ta.getResourceId(R.styleable.free_iconButton, -1);
        ta.recycle();
        //如果作为单一控件使用(没有子控件),手动添加一个子控件,并添加按钮图片
        //注:这里使用ImageButton,如果需要文字,建议使用CheckBox,RadioButton,否则会导致拖动失灵(希望知道原理的大神可以回复指点)
        if (getChildCount() == 0) {
            ImageButton imageButton = new ImageButton(context);
            imageButton.setBackgroundResource(iconButton);
            addView(imageButton);
        }
        countDownTimer = new MyCountDownTimer(millisInFuture, countDownInterval);
        countDownTimer.start();
        //设置默认位置
        post(new Runnable() {
            @Override
            public void run() {
                MarginLayoutParams layoutParams = (MarginLayoutParams) getLayoutParams();
                layoutParams.topMargin = screenHeight / 2 - getHeight();
                layoutParams.leftMargin = screenWidth - getWidth();
                setLayoutParams(layoutParams);
            }
        });
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        if (moveable) {
            ViewGroup parentView = ((ViewGroup) getParent());
            MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
            viewWidth = getRight() - getLeft();
            viewHight = getBottom() - getTop();
            parentWidth = parentView.getMeasuredWidth();
            parentHeight = parentView.getMeasuredHeight();
            minLeftMargin = lp.leftMargin;
            leftPadding = parentView.getPaddingLeft();
            rightDistance = lp.rightMargin + parentView.getPaddingRight();
            maxLeftMargin = parentWidth - rightDistance - viewWidth - leftPadding;
            minTopMargin = lp.topMargin;
            topPadding = parentView.getPaddingTop();
            bottomDistance = lp.bottomMargin + parentView.getPaddingBottom();
            maxTopMargin = parentHeight - bottomDistance - viewHight - topPadding;
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startX = ev.getRawX();
                startY = ev.getRawY();
                setAlpha(1f);
                countDownTimer.cancel();
                if (moveable) {
                    MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
                    currentX = ev.getRawX();
                    currentY = ev.getRawY();
                    currentLeft = lp.leftMargin;
                    currentTop = lp.topMargin;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (moveable) {
                    currentLeft += ev.getRawX() - currentX;
                    currentTop += ev.getRawY() - currentY;
                    //判断左边界
                    currentLeft = currentLeft < minLeftMargin ? minLeftMargin : currentLeft;
                    //判断右边界
                    currentLeft = (leftPadding + currentLeft + viewWidth + rightDistance) > parentWidth ? maxLeftMargin : currentLeft;
                    //判断上边界
                    currentTop = currentTop < minTopMargin ? minTopMargin : currentTop;
                    //判断下边界
                    currentTop = (topPadding + currentTop + viewHight + bottomDistance) > parentHeight ? maxTopMargin : currentTop;
                    MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
                    lp.leftMargin = currentLeft;
                    lp.topMargin = currentTop;
                    setLayoutParams(lp);
                    currentX = ev.getRawX();
                    currentY = ev.getRawY();
                }
                break;
            case MotionEvent.ACTION_UP:
                float endX = ev.getRawX();
                float endY = ev.getRawY();
                countDownTimer.start();
                if (moveable && autoBack) {
                    MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
                    int fromLeftMargin = lp.leftMargin;
                    if (getLeft() < (parentWidth - getLeft() - viewWidth)) {
                        lp.leftMargin = minLeftMargin;
                    } else {
                        lp.leftMargin = maxLeftMargin;
                    }
                    ObjectAnimator marginChange = ObjectAnimator.ofInt(new Wrapper(this), "leftMargin", fromLeftMargin, lp.leftMargin);
                    marginChange.setDuration(500);
                    marginChange.start();
                }
                //滑动距离比较小，当作点击事件处理
                if (Math.abs(startX - endX) < 1 && Math.abs(startY - endY) < 1 && mLister != null) {
                    mLister.onViewClick();
                }
                break;
            default:
        }
        return super.dispatchTouchEvent(ev);
    }

    /**
     * 点击事件
     */

    private OnViewClickListener mLister;

    public interface OnViewClickListener {
        void onViewClick();
    }

    public void setOnViewClickListener(OnViewClickListener listener) {
        this.mLister = listener;
    }

    /**
     * 包装类
     */
    class Wrapper {
        private ViewGroup mTarget;

        public Wrapper(ViewGroup mTarget) {
            this.mTarget = mTarget;
        }

        public int getLeftMargin() {
            MarginLayoutParams lp = (MarginLayoutParams) mTarget.getLayoutParams();
            return lp.leftMargin;
        }

        public void setLeftMargin(int leftMargin) {
            MarginLayoutParams lp = (MarginLayoutParams) mTarget.getLayoutParams();
            lp.leftMargin = leftMargin;
            mTarget.requestLayout();
        }
    }

    public class MyCountDownTimer extends CountDownTimer {

        public MyCountDownTimer(long millisInFuture, long countDownInterval) {
            super(millisInFuture, countDownInterval);
        }

        @Override
        public void onTick(long millisUntilFinished) {
        }

        @Override
        public void onFinish() {
            setAlpha(toAlpha);
        }
    }

    /**
     *   * 获取状态栏的高度
     *   * @return 状态栏高度
     *   
     */
    public int getStatusBarHeight() {
        int result = 0;
        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
        if (resourceId > 0) {
            result = getResources().getDimensionPixelSize(resourceId);
        }
        return result;
    }
}