单一职责原则 (Single Responsibility Principle)开/闭原则 (Open-Close Principle)Li...

package com.jy.day15installapkmorethreaddownload; import android.content...

package com.jy.day15installapkmorethreaddownload; import android.content...

package com.jy.day15installapkmorethreaddownload; import android.app.Act...

package com.jy.day15installapkmorethreaddownload; import java.util.concu...