安卓自定义view—Canvas实现手写板和涂鸦功能(可以返回上一步手写的内容)

int anim abc_fade_in 0x7f010000 int anim abc_fade_out 0x7f010001 int anim abc_grow_fade_in_from_bottom 0x7f010002 int anim abc_popup_enter 0x7f010003 int anim abc_popup_exit 0x7f010004 int anim abc_shrink_fade_out_from_bottom 0x7f010005 int anim abc_slide_in_bottom 0x7f010006 int anim abc_slide_in_top 0x7f010007 int anim abc_slide_out_bottom 0x7f010008 int anim abc_slide_out_top 0x7f010009 int anim abc_tooltip_enter 0x7f01000a int anim abc_tooltip_exit 0x7f01000b int anim btn_checkbox_to_checked_box_inner_merged_animation 0x7f01000c int anim btn_checkbox_to_checked_box_outer_merged_animation 0x7f01000d int anim btn_checkbox_to_checked_icon_null_animation 0x7f01000e int anim btn_checkbox_to_unchecked_box_inner_merged_animation 0x7f01000f int anim btn_checkbox_to_unchecked_check_path_merged_animation 0x7f010010 int anim btn_checkbox_to_unchecked_icon_null_animation 0x7f010011 int anim btn_radio_to_off_mtrl_dot_group_animation 0x7f010012 int anim btn_radio_to_off_mtrl_ring_outer_animation 0x7f010013 int anim btn_radio_to_off_mtrl_ring_outer_path_animation 0x7f010014 int anim btn_radio_to_on_mtrl_dot_group_animation 0x7f010015 int anim btn_radio_to_on_mtrl_ring_outer_animation 0x7f010016 int anim btn_radio_to_on_mtrl_ring_outer_path_animation 0x7f010017 int attr actionBarDivider 0x7f020000 int attr actionBarItemBackground 0x7f020001 int attr actionBarPopupTheme 0x7f020002 int attr actionBarSize 0x7f020003 int attr actionBarSplitStyle 0x7f020004 int attr actionBarStyle 0x7f020005 int attr actionBarTabBarStyle 0x7f020006 int attr actionBarTabStyle 0x7f020007 int attr actionBarTabTextStyle 0x7f020008 int attr actionBarTheme 0x7f020009 int attr actionBarWidgetTheme 0x7f02000a int attr actionButtonStyle 0x7f02000b int attr actionDropDownStyle 0x7f02000c int attr actionLayout 0x7f02000d int attr actionMenuTextAppearance 0x7f02000e int attr actionMenuTextColor 0x7f02000f int attr actionModeBackground 0x7f020010 int attr actionModeCloseButtonStyle 0x7f020011 int attr actionModeCloseDrawable 0x7f020012 int attr actionModeCopyDrawable 0x7f020013 int attr actionModeCutDrawable 0x7f020014 int attr actionModeFindDrawable 0x7f020015 int attr actionModePasteDrawable 0x7f020016 int attr actionModePopupWindowStyle 0x7f020017 int attr actionModeSelectAllDrawable 0x7f020018 int attr actionModeShareDrawable 0x7f020019 int attr actionModeSplitBackground 0x7f02001a int attr actionModeStyle 0x7f02001b int attr actionModeWebSearchDrawable 0x7f02001c int attr actionOverflowButtonStyle 0x7f02001d int attr actionOverflowMenuStyle 0x7f02001e int attr actionProviderClass 0x7f02001f int attr actionViewClass 0x7f020020 int attr activityChooserViewStyle 0x7f020021 int attr alertDialogButtonGroupStyle 0x7f020022 int attr alertDialogCenterButtons 0x7f020023 int attr alertDialogStyle 0x7f020024 int attr alertDialogTheme 0x7f020025 int attr allowStacking 0x7f020026 int attr alpha 0x7f020027 int attr alphabeticModifiers 0x7f020028 int attr altSrc 0x7f020029 int attr animate_relativeTo 0x7f02002a int attr applyMotionScene 0x7f02002b int attr arcMode 0x7f02002c int attr arrowHeadLength 0x7f02002d int attr arrowShaftLength 0x7f02002e int attr attributeName 0x7f02002f int attr autoCompleteTextViewStyle 0x7f020030 int attr autoSizeMaxTextSize 0x7f020031 int attr autoSizeMinTextSize 0x7f020032 int attr autoSizePresetSizes 0x7f020033 int attr autoSizeStepGranularity 0x7f020034 int attr autoSizeTextType 0x7f020035 int attr autoTransition 0x7f020036 int attr background 0x7f020037 int attr backgroundSplit 0x7f020038 int attr backgroundStacked 0x7f020039 int attr backgroundTint 0x7f02003a int attr backgroundTintMode 0x7f02003b int attr barLength 0x7f02003c int attr barrierAllowsGoneWidgets 0x7f02003d int attr barrierDirection 0x7f02003e int attr barrierMargin 0x7f02003f int attr borderlessButtonStyle 0x7f020040 int attr brightness 0x7f020041 int attr buttonBarButtonStyle 0x7f020042 int attr buttonBarNegativeButtonStyle 0x7f020043 int attr buttonBarNeutralButtonStyle 0x7f020044 int attr buttonBarPositiveButtonStyle 0x7f020045 int attr buttonBarStyle 0x7f020046 int attr buttonCompat 0x7f020047 int attr buttonGravity 0x7f020048 int attr buttonIconDimen 0x7f020049 int attr buttonPanelSideLayout 0x7f02004a int attr buttonStyle 0x7f02004b int attr buttonStyleSmall 0x7f02004c int attr buttonTint 0x7f02004d int attr buttonTintMode 0x7f02004e int attr chainUseRtl 0x7f02004f int attr checkboxStyle 0x7f020050 int attr checkedTextViewStyle 0x7f020051 int attr circleRadius 0x7f020052 int attr clickAction 0x7f020053 int attr closeIcon 0x7f020054 int attr closeItemLayout 0x7f020055 int attr collapseContentDescription 0x7f020056 int attr collapseIcon 0x7f020057 int attr color 0x7f020058 int attr colorAccent 0x7f020059 int attr colorBackgroundFloating 0x7f02005a int attr colorButtonNormal 0x7f02005b int attr colorControlActivated 0x7f02005c int attr colorControlHighlight 0x7f02005d int attr colorControlNormal 0x7f02005e int attr colorError 0x7f02005f int attr colorPrimary 0x7f020060 int attr colorPrimaryDark 0x7f020061 int attr colorSwitchThumbNormal 0x7f020062 int attr commitIcon 0x7f020063 int attr constraintSet 0x7f020064 int attr constraintSetEnd 0x7f020065 int attr constraintSetStart 0x7f020066 int attr constraint_referenced_ids 0x7f020067 int attr constraints 0x7f020068 int attr content 0x7f020069 int attr contentDescription 0x7f02006a int attr contentInsetEnd 0x7f02006b int attr contentInsetEndWithActions 0x7f02006c int attr contentInsetLeft 0x7f02006d int attr contentInsetRight 0x7f02006e int attr contentInsetStart 0x7f02006f int attr contentInsetStartWithNavigation 0x7f020070 int attr contrast 0x7f020071 int attr controlBackground 0x7f020072 int attr crossfade 0x7f020073 int attr currentState 0x7f020074 int attr curveFit 0x7f020075 int attr customBoolean 0x7f020076 int attr customColorDrawableValue 0x7f020077 int attr customColorValue 0x7f020078 int attr customDimension 0x7f020079 int attr customFloatValue 0x7f02007a int attr customIntegerValue 0x7f02007b int attr customNavigationLayout 0x7f02007c int attr customPixelDimension 0x7f02007d int attr customStringValue 0x7f02007e int attr defaultDuration 0x7f02007f int attr defaultQueryHint 0x7f020080 int attr defaultState 0x7f020081 int attr deltaPolarAngle 0x7f020082 int attr deltaPolarRadius 0x7f020083 int attr deriveConstraintsFrom 0x7f020084 int attr dialogCornerRadius 0x7f020085 int attr dialogPreferredPadding 0x7f020086 int attr dialogTheme 0x7f020087 int attr displayOptions 0x7f020088 int attr divider 0x7f020089 int attr dividerHorizontal 0x7f02008a int attr dividerPadding 0x7f02008b int attr dividerVertical 0x7f02008c int attr dragDirection 0x7f02008d int attr dragScale 0x7f02008e int attr dragThreshold 0x7f02008f int attr drawPath 0x7f020090 int attr drawableBottomCompat 0x7f020091 int attr drawableEndCompat 0x7f020092 int attr drawableLeftCompat 0x7f020093 int attr drawableRightCompat 0x7f020094 int attr drawableSize 0x7f020095 int attr drawableStartCompat 0x7f020096 int attr drawableTint 0x7f020097 int attr drawableTintMode 0x7f020098 int attr drawableTopCompat 0x7f020099 int attr drawerArrowStyle 0x7f02009a int attr dropDownListViewStyle 0x7f02009b int attr dropdownListPreferredItemHeight 0x7f02009c int attr duration 0x7f02009d int attr editTextBackground 0x7f02009e int attr editTextColor 0x7f02009f int attr editTextStyle 0x7f0200a0 int attr elevation 0x7f0200a1 int attr expandActivityOverflowButtonDrawable 0x7f0200a2 int attr firstBaselineToTopHeight 0x7f0200a3 int attr flow_firstHorizontalBias 0x7f0200a4 int attr flow_firstHorizontalStyle 0x7f0200a5 int attr flow_firstVerticalBias 0x7f0200a6 int attr flow_firstVerticalStyle 0x7f0200a7 int attr flow_horizontalAlign 0x7f0200a8 int attr flow_horizontalBias 0x7f0200a9 int attr flow_horizontalGap 0x7f0200aa int attr flow_horizontalStyle 0x7f0200ab int attr flow_lastHorizontalBias 0x7f0200ac int attr flow_lastHorizontalStyle 0x7f0200ad int attr flow_lastVerticalBias 0x7f0200ae int attr flow_lastVerticalS