eclipse错误 The connection to adb is down,

运行android程序控制台输出

    [2012-07-18 16:18:26 - ]The connection to adb is down, and a severe error has occured.
    [2012-07-18 16:18:26 - ] You must restart adb and Eclipse.
    [2012-07-18 16:18:26 - ] Please ensure that adb is correctlylocated at 'D:\java\sdk\platform-tools\adb.exe' and can be executed.

点击Devices(Window-Show View-Other-Android-Devices)中的倒三角，选择Reset adb

或cmd跳到sdk tools文件路径下 
adb kill-server 
然后再adb start-server 

方法1.cmd中adb kill-server，然后adb -startserver 
方法2.方法1不管用，那么在任务管理器中杀死adb.exe，然后重启Eclipse。 
方法3.方法1和2都不管用，那么查看最后一句报错中：platform-tools中是否有adb.exe