handler更新ui线程的基本用法

1.因为费时操作要放子线程，更新UI要放UI线程（主线程），所以子线程和主线程通信，通信的话要用到handler这个东西。

这里讲的比较简单，举2个例子说明

2.使用post的是handler ,使用message的是handler2

public class MainActivity extends AppCompatActivity {
 
    private TextView textView;
    private Handler handler = new Handler();
 
    private Handler handler2=new Handler(){
        @Override
        public void handleMessage(Message msg) {
                switch (msg.what){
                    case 1:
                        textView.setText(msg.obj.toString());
                }
        }
    };
 
    Button button;
    private static final String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        textView =findViewById(R.id.textview);
 
        new Thread(){
            @Override
            public void run() {
                Message message = new Message();
                //区分标志
                message.what=1;
                //传参到ui线程
                message.obj=123123;
                handler2.sendMessage(message);
            }
        }.start();
 
        new Thread(){
            @Override
            public void run() {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        textView.setText("fjidfjiijisdf");
                    }
                });
            }
        }.start();
    }
 
}

3. 实例化handler在其他线程的时候要下面这样写

 private Handler handler = new Handler(Looper.getMainLooper());