小编Pra*_*eep的帖子

我有2个表A(id,Name),B(id,fid,Name),其中A.id = B.fid,我的要求是我想删除B中的行,只要A中的行删除

这是我试过的查询,但它给了我B附近的错误..

Create Trigger Delete_B_trigger After Delete on A For each row Begin Delete from B where fid = id; End

我写了一个小应用程序,它每3秒更改一次应用程序背景.我使用Handler和Runnable对象来实现这一点.它工作正常.这是我的代码:

  public class MainActivity extends Activity {

        private RelativeLayout backgroundLayout;
        private int count;
        private Handler hand = new Handler();

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            Button clickMe = (Button) findViewById(R.id.btn);

            backgroundLayout = (RelativeLayout) findViewById(R.id.background);

            clickMe.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {

                    count = 0;

                    hand.postDelayed(changeBGThread, 3000);

                }
            });

        }

private Runnable changeBGThread = new Runnable() {

        @Override
        public void run() {

            if(count == 3){
                count = 0;
            }

            switch (count) {
            case 0:
                backgroundLayout.setBackgroundColor(getResources().getColor(android.R.color.black));
                count++;
                break; …

我有2个活动A和B ..当我从B返回到A onRestart()时,A启动B,然后调用onStart()方法.我的问题是在onRestart() - > onStart()时,活动A中的所有视图都重绘了吗？