(Service)异步消息处理：Message、Handler

布局文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.hzx.androidthreadtest.MainActivity">

    <Button
        android:id="@+id/btn_change_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Change Text"/>
    <TextView
        android:id="@+id/show_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Hello world"
        android:textSize="25sp"/>

</RelativeLayout>

Activity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    public static final  int UPDATE_TEXT  = 1;
    private TextView text;
    private int put_count  = 0;

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

        text = (TextView)findViewById(R.id.show_text);
        //Button btn_change_text = (Button)findViewById(R.id.btn_change_text);
        //btn_change_text.setOnClickListener((View.OnClickListener) MainActivity.this);

        findViewById(R.id.btn_change_text).setOnClickListener((View.OnClickListener) this);

        handler = new MyHandler();
    }

    public void onClick(View v){
        Message message = new Message();
        message.what = UPDATE_TEXT;
        handler.sendMessage(message);
        Log.d("123","点击");
    }

    class MyHandler extends Handler{
        public void handleMessage(Message msg){
            switch (msg.what){
                case UPDATE_TEXT:
                    //在这里可以进行UI操作
                    put_count++;
                    text.setText("Nice to meet you! count:"+put_count);
                    break;
            }
        }
    }

}

效果

image.png