android里面的Handler简单解析

Posted 2022-12-12 轻烟散入五侯家

public class MainActivity extends AppCompatActivity 

    public static final int UPDATE_TEXT = 1;
    private TextView text;

    private Handler handler = new Handler(Looper.getMainLooper())
        public void handleMessage(Message msg)//handler接收到指令后分不同的情况对界面UI进行更新
            switch(msg.what)
                case UPDATE_TEXT:text.setText("Hello");
                break;
            default:
                  break;
            
        
    ;

        @Override
        protected void onCreate(Bundle savedInstanceState) 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            text = (TextView) findViewById(R.id.textView);

            findViewById(R.id.button).setOnClickListener(new View.OnClickListener() 
                @Override
                public void onClick(View v) 
                    new Thread(new Runnable() 
                        public void run()
                            Message message = new Message();
                            message.what = UPDATE_TEXT;
                            handler.sendMessage(message);//子线程只是通过message发送要执行修改界面UI的指令
                        
                    ).start();
                
            );