Android重写返回键处理事件 4000

@Override
public void onBackPressed() {
Dialog dialog = new AlertDialog.Builder(this).setTitle("信息提示")
.setMessage("确定要退出系统吗?")
.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNeutralButton("取消", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
return;
}
}).create();
dialog.show();
}