當手機沒有連接PC時，手機log緩沖區仍然會保存指定大小的最新log，連接pc，通過adb logcat 仍然可以拿出來
如何查看log緩緩區的大小？
通過adb logcat -g 可以查看
C:\Users\zh>adb logcat -g
main: ring buffer is 64Kb (62Kb consumed), max entry is 5120b, max payload is 4068b
system: ring buffer is 64Kb (63Kb consumed), max entry is 5120b, max payload is 4068b
crash: ring buffer is 64Kb (1Kb consumed), max entry is 5120b, max payload is 4068b
C:\Users\zh>adb logcat -g
main: ring buffer is 256Kb (67Kb consumed), max entry is 5120b, max payload is 4068b
system: ring buffer is 256Kb (60Kb consumed), max entry is 5120b, max payload is 4068b
crash: ring buffer is 256Kb (1Kb consumed), max entry is 5120b, max payload is 4068b
C:\Users\zh>adb logcat -g
main: ring buffer is 1Mb (73Kb consumed), max entry is 5120b, max payload is 4068b
system: ring buffer is 1Mb (60Kb consumed), max entry is 5120b, max payload is 4068b
crash: ring buffer is 1Mb (1Kb consumed), max entry is 5120b, max payload is 4068b
上面的 64Kb、256Kb、1Mb 大小是可以指定的，指定路徑：
Settings --- Developer options --- Logger buffer sizes，彈出一個對話框，選擇設置即可
或通過命令行設置log緩存區大小：
adb logcat -G 10M
將緩沖區的log打印到屏幕並退出，使用 adb logcat -d 命令
adb logcat -d > log.txt