平时，常常使用mac链接Ipad。把ipad当做mac的第二屏幕使用。不知道系统怎么了，突然就修改了ipad的分辨率。而且在设置中也无法进行修改。在网上查找了大量的解决办法，都是安装duet这个软件或者其他软件。但是安装这些软件都没有解决问题。于是我找到了这个博客：博客地址。我将给出更加具体的解决方案。
- 第一步：安装displayplacer
brew tap jakehilborn/jakehilborn && brew install displayplacer
- 第二步：查看mac上所有显示器的分辨率和已经选择的情况
displayplacer list
以下是输出：
Persistent screen id: 9337D70B-9BF9-6382-F8F2-1E7B5CBF95B6
Contextual screen id: 1803908288
Type: MacBook built in screen //这里表示说是Mac自己的显示器
Resolution: 1920x1080
Hertz: N/A
Color Depth: 8
Scaling:off
Origin: (0,0) - main display
Rotation: 0 - rotate internal screen example (may crash computer, but will be rotated after rebooting): `displayplacer "id:9337D70B-9BF9-6382-F8F2-1E7B5CBF95B6 degree:90"`
Resolutions for rotation 0:
mode 0: res:1920x1080 color_depth:4
mode 1: res:1920x1080 color_depth:8 <-- current mode
mode 2: res:640x480 color_depth:4
mode 3: res:640x480 color_depth:8
mode 4: res:800x600 color_depth:4
mode 5: res:800x600 color_depth:8
mode 6: res:1024x768 color_depth:4
mode 7: res:1024x768 color_depth:8
mode 8: res:1024x576 color_depth:4
mode 9: res:1024x576 color_depth:8
mode 10: res:1280x720 color_depth:4
mode 11: res:1280x720 color_depth:8
mode 12: res:1280x960 color_depth:4
mode 13: res:1280x960 color_depth:8
mode 14: res:1344x1008 color_depth:4
mode 15: res:1344x1008 color_depth:8
mode 16: res:1344x756 color_depth:4
mode 17: res:1344x756 color_depth:8
mode 18: res:1440x900 color_depth:4
mode 19: res:1440x900 color_depth:8
mode 20: res:1680x1050 color_depth:4
mode 21: res:1680x1050 color_depth:8
mode 22: res:1600x900 color_depth:4
mode 23: res:1600x900 color_depth:8
mode 24: res:1920x1200 color_depth:4
mode 25: res:1920x1200 color_depth:8
mode 26: res:2560x1440 color_depth:4
mode 27: res:2560x1440 color_depth:8
mode 28: res:2560x1600 color_depth:4
mode 29: res:2560x1600 color_depth:8
mode 30: res:960x540 color_depth:4 scaling:on
mode 31: res:960x540 color_depth:8 scaling:on
mode 32: res:720x450 color_depth:4 scaling:on
mode 33: res:720x450 color_depth:8 scaling:on
mode 34: res:840x525 color_depth:4 scaling:on
mode 35: res:840x525 color_depth:8 scaling:on
mode 36: res:800x450 color_depth:4 scaling:on
mode 37: res:800x450 color_depth:8 scaling:on
mode 38: res:960x600 color_depth:4 scaling:on
mode 39: res:960x600 color_depth:8 scaling:on
mode 40: res:1280x720 color_depth:4 scaling:on
mode 41: res:1280x720 color_depth:8 scaling:on
mode 42: res:1280x800 color_depth:4 scaling:on
mode 43: res:1280x800 color_depth:8 scaling:on
Persistent screen id: F6D36293-8397-08D5-FC5A-39F710C620CB
Contextual screen id: 188943829
Type: 27 inch external screen // 这里表示27寸外接显示器
Resolution: 1920x1080
Hertz: 60
Color Depth: 8
Scaling:off
Origin: (-1920,0)
Rotation: 0
Resolutions for rotation 0:
mode 0: res:1920x1080 hz:60 color_depth:4
mode 1: res:1920x1080 hz:60 color_depth:8 <-- current mode // 这是目前的分辨率
mode 2: res:1280x720 hz:60 color_depth:4
mode 3: res:1280x720 hz:60 color_depth:8
mode 4: res:1920x1080 hz:50 color_depth:4
mode 5: res:1920x1080 hz:50 color_depth:8
mode 6: res:1280x720 hz:50 color_depth:4
mode 7: res:1280x720 hz:50 color_depth:8
mode 8: res:720x576 hz:50 color_depth:4
mode 9: res:720x576 hz:50 color_depth:8
mode 10: res:720x480 hz:60 color_depth:4
mode 11: res:720x480 hz:60 color_depth:8
mode 12: res:1920x1080 hz:72 color_depth:4
mode 13: res:1920x1080 hz:72 color_depth:8
mode 14: res:640x480 hz:60 color_depth:4
mode 15: res:640x480 hz:60 color_depth:8
mode 16: res:800x600 hz:60 color_depth:4
mode 17: res:800x600 hz:60 color_depth:8
mode 18: res:1024x768 hz:60 color_depth:4
mode 19: res:1024x768 hz:60 color_depth:8
mode 20: res:1024x576 hz:60 color_depth:4
mode 21: res:1024x576 hz:60 color_depth:8
mode 22: res:1280x960 hz:60 color_depth:4
mode 23: res:1280x960 hz:60 color_depth:8
mode 24: res:1344x1008 hz:60 color_depth:4
mode 25: res:1344x1008 hz:60 color_depth:8
mode 26: res:1344x756 hz:60 color_depth:4
mode 27: res:1344x756 hz:60 color_depth:8
mode 28: res:1440x900 hz:60 color_depth:4
mode 29: res:1440x900 hz:60 color_depth:8
mode 30: res:1680x1050 hz:60 color_depth:4
mode 31: res:1680x1050 hz:60 color_depth:8
mode 32: res:1600x900 hz:60 color_depth:4
mode 33: res:1600x900 hz:60 color_depth:8
mode 34: res:1920x1200 hz:60 color_depth:4
mode 35: res:1920x1200 hz:60 color_depth:8
mode 36: res:2560x1440 hz:60 color_depth:4
mode 37: res:2560x1440 hz:60 color_depth:8
mode 38: res:2560x1600 hz:60 color_depth:4
mode 39: res:2560x1600 hz:60 color_depth:8
mode 40: res:640x480 hz:50 color_depth:4
mode 41: res:640x480 hz:50 color_depth:8
mode 42: res:800x600 hz:50 color_depth:4
mode 43: res:800x600 hz:50 color_depth:8
mode 44: res:1024x768 hz:50 color_depth:4
mode 45: res:1024x768 hz:50 color_depth:8
mode 46: res:1024x576 hz:50 color_depth:4
mode 47: res:1024x576 hz:50 color_depth:8
mode 48: res:1280x960 hz:50 color_depth:4
mode 49: res:1280x960 hz:50 color_depth:8
mode 50: res:1344x1008 hz:50 color_depth:4
mode 51: res:1344x1008 hz:50 color_depth:8
mode 52: res:1344x756 hz:50 color_depth:4
mode 53: res:1344x756 hz:50 color_depth:8
mode 54: res:1440x900 hz:50 color_depth:4
mode 55: res:1440x900 hz:50 color_depth:8
mode 56: res:1680x1050 hz:50 color_depth:4
mode 57: res:1680x1050 hz:50 color_depth:8
mode 58: res:1600x900 hz:50 color_depth:4
mode 59: res:1600x900 hz:50 color_depth:8
mode 60: res:1920x1200 hz:50 color_depth:4
mode 61: res:1920x1200 hz:50 color_depth:8
mode 62: res:2560x1440 hz:50 color_depth:4
mode 63: res:2560x1440 hz:50 color_depth:8
mode 64: res:2560x1600 hz:50 color_depth:4
mode 65: res:2560x1600 hz:50 color_depth:8
mode 66: res:640x480 hz:72 color_depth:4
mode 67: res:640x480 hz:72 color_depth:8
mode 68: res:800x600 hz:72 color_depth:4
mode 69: res:800x600 hz:72 color_depth:8
mode 70: res:1024x768 hz:72 color_depth:4
mode 71: res:1024x768 hz:72 color_depth:8
mode 72: res:1024x576 hz:72 color_depth:4
mode 73: res:1024x576 hz:72 color_depth:8
mode 74: res:1280x720 hz:72 color_depth:4
mode 75: res:1280x720 hz:72 color_depth:8
mode 76: res:1280x960 hz:72 color_depth:4
mode 77: res:1280x960 hz:72 color_depth:8
mode 78: res:1344x1008 hz:72 color_depth:4
mode 79: res:1344x1008 hz:72 color_depth:8
mode 80: res:1344x756 hz:72 color_depth:4
mode 81: res:1344x756 hz:72 color_depth:8
mode 82: res:1440x900 hz:72 color_depth:4
mode 83: res:1440x900 hz:72 color_depth:8
mode 84: res:1680x1050 hz:72 color_depth:4
mode 85: res:1680x1050 hz:72 color_depth:8
mode 86: res:1600x900 hz:72 color_depth:4
mode 87: res:1600x900 hz:72 color_depth:8
mode 88: res:1920x1200 hz:72 color_depth:4
mode 89: res:1920x1200 hz:72 color_depth:8
mode 90: res:2560x1440 hz:72 color_depth:4
mode 91: res:2560x1440 hz:72 color_depth:8
mode 92: res:2560x1600 hz:72 color_depth:4
mode 93: res:2560x1600 hz:72 color_depth:8
mode 94: res:960x540 hz:60 color_depth:4 scaling:on
mode 95: res:960x540 hz:60 color_depth:8 scaling:on
mode 96: res:960x540 hz:50 color_depth:4 scaling:on
mode 97: res:960x540 hz:50 color_depth:8 scaling:on
mode 98: res:960x540 hz:72 color_depth:4 scaling:on
mode 99: res:960x540 hz:72 color_depth:8 scaling:on
mode 100: res:720x450 hz:60 color_depth:4 scaling:on
mode 101: res:720x450 hz:60 color_depth:8 scaling:on
mode 102: res:840x525 hz:60 color_depth:4 scaling:on
mode 103: res:840x525 hz:60 color_depth:8 scaling:on
mode 104: res:800x450 hz:60 color_depth:4 scaling:on
mode 105: res:800x450 hz:60 color_depth:8 scaling:on
mode 106: res:960x600 hz:60 color_depth:4 scaling:on
mode 107: res:960x600 hz:60 color_depth:8 scaling:on
mode 108: res:1280x720 hz:60 color_depth:4 scaling:on
mode 109: res:1280x720 hz:60 color_depth:8 scaling:on
mode 110: res:1280x800 hz:60 color_depth:4 scaling:on
mode 111: res:1280x800 hz:60 color_depth:8 scaling:on
mode 112: res:720x450 hz:50 color_depth:4 scaling:on
mode 113: res:720x450 hz:50 color_depth:8 scaling:on
mode 114: res:840x525 hz:50 color_depth:4 scaling:on
mode 115: res:840x525 hz:50 color_depth:8 scaling:on
mode 116: res:800x450 hz:50 color_depth:4 scaling:on
mode 117: res:800x450 hz:50 color_depth:8 scaling:on
mode 118: res:960x600 hz:50 color_depth:4 scaling:on
mode 119: res:960x600 hz:50 color_depth:8 scaling:on
mode 120: res:1280x720 hz:50 color_depth:4 scaling:on
mode 121: res:1280x720 hz:50 color_depth:8 scaling:on
mode 122: res:1280x800 hz:50 color_depth:4 scaling:on
mode 123: res:1280x800 hz:50 color_depth:8 scaling:on
mode 124: res:720x450 hz:72 color_depth:4 scaling:on
mode 125: res:720x450 hz:72 color_depth:8 scaling:on
mode 126: res:840x525 hz:72 color_depth:4 scaling:on
mode 127: res:840x525 hz:72 color_depth:8 scaling:on
mode 128: res:800x450 hz:72 color_depth:4 scaling:on
mode 129: res:800x450 hz:72 color_depth:8 scaling:on
mode 130: res:960x600 hz:72 color_depth:4 scaling:on
mode 131: res:960x600 hz:72 color_depth:8 scaling:on
mode 132: res:1280x720 hz:72 color_depth:4 scaling:on
mode 133: res:1280x720 hz:72 color_depth:8 scaling:on
mode 134: res:1280x800 hz:72 color_depth:4 scaling:on
mode 135: res:1280x800 hz:72 color_depth:8 scaling:on
Persistent screen id: 6161706C-6950-6164-0000-053900000000 // 其实Ipad的id是不会变的
Contextual screen id: 4128834
Type: 41 inch external screen // 这里其实是Ipad的显示器
Resolution: 2560x1440
Hertz: 60
Color Depth: 4
Scaling:off
Origin: (-1188,1080)
Rotation: 0
Resolutions for rotation 0:
mode 0: res:1x1 hz:60 color_depth:4
mode 1: res:1366x1024 hz:60 color_depth:4 scaling:on
mode 2: res:1366x1024 hz:60 color_depth:4
mode 3: res:2560x1440 hz:60 color_depth:4 <-- current mode // 可以看出，目前的Ipad的扩展分辨率是不正常的
mode 4: res:2560x1600 hz:60 color_depth:4
mode 5: res:3840x2160 hz:60 color_depth:4
mode 6: res:4096x2160 hz:60 color_depth:4
mode 7: res:4096x2304 hz:60 color_depth:4
mode 8: res:5120x2880 hz:60 color_depth:4
mode 9: res:6016x3384 hz:60 color_depth:4
mode 10: res:1024x640 hz:60 color_depth:4 scaling:on
mode 11: res:1152x720 hz:60 color_depth:4 scaling:on
mode 12: res:1152x800 hz:60 color_depth:4 scaling:on
mode 13: res:1440x900 hz:60 color_depth:4 scaling:on
mode 14: res:1680x1050 hz:60 color_depth:4 scaling:on
mode 15: res:1920x1200 hz:60 color_depth:4 scaling:on
mode 16: res:1504x846 hz:60 color_depth:4 scaling:on
mode 17: res:1920x1080 hz:60 color_depth:4 scaling:on
mode 18: res:2048x1152 hz:60 color_depth:4 scaling:on
mode 19: res:2304x1296 hz:60 color_depth:4 scaling:on
mode 20: res:2560x1440 hz:60 color_depth:4 scaling:on
mode 21: res:3008x1692 hz:60 color_depth:4 scaling:on
mode 22: res:3360x1890 hz:60 color_depth:4 scaling:on
mode 23: res:3840x2160 hz:60 color_depth:4 scaling:on
mode 24: res:4096x2160 hz:60 color_depth:4 scaling:on
可以从上面的输出可知，Ipad外接屏的id为6161706C-6950-6164-0000-053900000000， 当前的分辨率是**res:2560x1440 。
然后通过网络查找得Ipad pro（12.9）本身的分辨率是：2732*2048。所以，我选择的是es:1366x1024的分辨率。大家需要根据自己的具体情况来选择不同的分辨率
displayplacer "id:6161706C-6950-6164-0000-053900000000 res:1366x1024 origin:(-1440,0) degree:0"