1. Use threads in Android development

package cn.fc.androidthreadtest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView textView;

    public static final int UPDATE_TEXT = 1;

    public Handler handler = new Handler(){

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case UPDATE_TEXT:
                    textView.setText("nice to meet you 2222222222222");
                    break;
                default:
                    break;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView)findViewById(R.id.text);
        Button change_text = (Button)findViewById(R.id.change_text);
        change_text.setOnClickListener(this);
    }

    @Override
    public void onClick(View v){
        switch (v.getId()){
            case R.id.change_text:
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        // 在子线程种切换ui操作，会导致系统崩溃
//                        textView.setText("Nice to meet you");
                        Message message = new Message();
                        message.what = UPDATE_TEXT;
                        handler.sendMessage(message);
                    }
                }).start();
                break;
            default:
                break;
        }
    };
}

Need to pay attention to switching ui operations in the child thread, will cause the system to crash