4/17学习总结：handler

package com.example.kaoyanpai.ui.home;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;

import com.example.kaoyanpai.DBService;
import com.example.kaoyanpai.R;
import com.example.kaoyanpai.school;

import java.util.List;

public class HomeFragment extends Fragment {

    private HomeViewModel homeViewModel;
    private Button button;
    private EditText editText;
    private TextView textView;
    @SuppressLint("HandlerLeak")
    private Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
            Log.i("789","789");
            switch (msg.what){
                case 0x11:
                    String s = (String) msg.obj;
                    textView.setText(s);
                    Log.i("message","123");
                    break;
                case 0x12:
                    String ss = (String) msg.obj;
                    textView.setText(ss);
                    break;
            }

        }
    };
    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        homeViewModel =
                ViewModelProviders.of(this).get(HomeViewModel.class);
        View root = inflater.inflate(R.layout.fragment_home, container, false);
        final TextView textView = root.findViewById(R.id.text_home);
        homeViewModel.getText().observe(this, new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {
                textView.setText(s);
            }
        });
        onStart(root);
        return root;

    }


    protected void onStart(View v){
          button=(Button)v.findViewById(R.id.button3);
          editText=(EditText)v.findViewById(R.id.schoolname);
          textView=(TextView)v.findViewById(R.id.show);
          button.setOnClickListener(new View.OnClickListener(){

              @Override
              public void onClick(View v) {
                  //创建一个线程
                  new Thread(new Runnable() {
                      @Override
                      public void run() {
                          Looper.prepare();
                  
                          Message message=handler.obtainMessage();
                          message.what=0x11;
                          message.obj="chenggong";
                          handler.sendMessage(message);
                      }
                  }).start();
              }
          });
    }

}