一，两种方式捕捉

1，重写 onBackPressed方法

@Override

public void onBackPressed() {

super.onBackPressed();

}

2，重写onKeyDown方法

@Override

public boolean onKeyDown(intkeyCode,KeyEvent event) {

if(keyCode==KeyEvent.KEYCODE_BACK&&event.getAction()==KeyEvent.ACTION_DOWN){

}

}

二，再按一次退出程序

private longexitTime=0;

@Override

public booleanonKeyDown(intkeyCode,KeyEvent event) {

if(keyCode==KeyEvent.KEYCODE_BACK&&event.getAction()==KeyEvent.ACTION_DOWN){

if((System.currentTimeMillis()-exitTime)>2000){

Toast.makeText(this,"你真的要退出程序吗?,Toast.LENGTH_SHORT).show();

exitTime=System.currentTimeMillis();

}else{

finish();

}

return true;

}

return super.onKeyDown(keyCode,event);

}