Android簡單實作懸浮吸附的FloatingView

/**
 * @ProjectName: yqf-android
 * @Package: com.jao.pointsystem.weight
 * @ClassName: ScrollFloatinigButton
 * @Description: java類作用描述
 * @Author: OlderJiao
 * @CreateDate: 2020/3/24 10:47
 * @UpdateUser: 更新者：
 * @UpdateDate: 2020/3/24 10:47
 * @Version: 1.0
 */
@SuppressLint("AppCompatCustomView")
public class ScrollFloatinigButton extends FrameLayout {
    private static final String TAG = "ScrollFloatinigButton";
    private float mX;
    private float mY;
    private int mParentWidth;
    private int mParentHeight;
    private boolean mScrollEnable = true;
    private int mScrollLeft;
    private int mScrollTop;
    private int mRight;
    private int mScrollRight;
    private int mScrollBottom;
    private boolean hasScroll;
    boolean isScroll = false;
    private boolean isAdsorb = true;//是否自動吸附到兩邊

    public ScrollFloatinigButton(Context context) {
        this(context, null);
    }

    public ScrollFloatinigButton(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ScrollFloatinigButton(Context context, AttributeSet attrs, final int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ScrollFloatinigView);
        mScrollEnable = ta.getBoolean(R.styleable.ScrollFloatinigView_scrollEnable, true);
        ta.recycle();
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        //防止布局重置時重置ScrollFloatinigView的位置
        ViewParent parent = getParent();
        if (parent instanceof ViewGroup) {
            ((ViewGroup) getParent()).addOnLayoutChangeListener(new OnLayoutChangeListener() {
                @Override
                public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
                    if (hasScroll && mScrollRight != 0 && mScrollBottom != 0)
                        layout(mScrollLeft, mScrollTop, mScrollRight, mScrollBottom);
                }
            });
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if (getParent() instanceof ViewGroup) {
            mParentWidth = ((ViewGroup) getParent()).getWidth();
            mParentHeight = ((ViewGroup) getParent()).getHeight();
        }
        Log.i(TAG, "onSizeChanged: ");
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (!mScrollEnable) return super.onTouchEvent(ev);
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mX = ev.getX();
                mY = ev.getY();
                super.onTouchEvent(ev);
                return true;
            case MotionEvent.ACTION_MOVE:
                int scaledTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
                float x = ev.getX();
                float y = ev.getY();
                x = x - mX;
                y = y - mY;
                if (Math.abs(scaledTouchSlop) < Math.abs(x) || Math.abs(scaledTouchSlop) < Math.abs(y)) {
                    isScroll = true;
                }
                if (isScroll) {
                    mScrollLeft = (int) (getX() + x);
                    mScrollTop = (int) (getY() + y);
                    mScrollRight = (int) (getX() + getWidth() + x);
                    mScrollBottom = (int) (getY() + getHeight() + y);
                    //防止滑出父界面
                    if (mScrollLeft < 0 || mScrollRight > mParentWidth) {
                        mScrollLeft = (int) getX();
                        mScrollRight = (int) getX() + getWidth();
                    }
                    if (mScrollTop < 0 || mScrollBottom > mParentHeight) {
                        mScrollTop = (int) getY();
                        mScrollBottom = (int) getY() + getHeight();
                    }
                    layout(mScrollLeft, mScrollTop, mScrollRight, mScrollBottom);
                    hasScroll = true;
                    return true;
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                if (isScroll) {
                    isScroll = false;
                    setPressed(false);//重置點擊狀態
                    if (isAdsorb) {//判斷是否開啟吸附
                        //獲取螢屏中間值
                        int mind = getScreenWidth() / 2;
                        //獲取控制元件寬度的中間值
                        int viewWithMind = getWidth() / 2;
                        //手指抬起時 自動吸附到螢屏兩邊
                        if (mScrollLeft + viewWithMind > mind) {
                            mScrollRight = getScreenWidth();
                            mScrollLeft = getScreenWidth() - getWidth();
                        } else {
                            mScrollRight = getWidth();
                            mScrollLeft = 0;
                        }
                        layout(mScrollLeft, mScrollTop, mScrollRight, mScrollBottom);
                    }
                    return true;
                }
                break;
        }
        return super.onTouchEvent(ev);
    }

    public boolean isAdsorb() {
        return isAdsorb;
    }

    public void setAdsorb(boolean adsorb) {
        isAdsorb = adsorb;
    }

    /**
     * 得到螢屏寬度
     *
     * @return
     */
    private int getScreenWidth() {
        WindowManager windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics displayMetrics = new DisplayMetrics();
        windowManager.getDefaultDisplay().getMetrics(displayMetrics);
        return displayMetrics.widthPixels;
    }
}

布局代碼，參考一下控制元件就OK了

<androidx.constraintlayout.widget.ConstraintLayout 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=".ZoomActivity">

    <com.example.test.widget.ScrollFloatinigButton
        android:layout_width="100dp"
        android:layout_height="150dp"
        android:layout_marginRight="20dp"
        android:layout_marginBottom="50dp"
        android:background="@color/gray"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

自定義的屬性

<declare-styleable name="ScrollFloatinigView">
        <attr name="scrollEnable" format="boolean" />
    </declare-styleable>

有問題歡迎指正，共同學習，共同進步