android studio 55[2]线程更新UI handler 2

    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Hello World!"        android:id="@+id/mTxtShowTest"        app:layout_constraintBottom_toBottomOf="parent"        app:layout_constraintLeft_toLeftOf="parent"        app:layout_constraintRight_toRightOf="parent"        app:layout_constraintTop_toTopOf="parent" />    <Button        android:id="@+id/mBtn1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Button"        tools:layout_editor_absoluteX="174dp"        tools:layout_editor_absoluteY="470dp" />主代码：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 {    TextView mTxtShowTest;    Button mBtn1, mBtn2, mBtn3;    // 2、在主线程中创建自定义Handler（mHandler）的实例    private mHandler mhandler = new mHandler();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mTxtShowTest = (TextView) findViewById(R.id.mTxtShowTest);        mBtn1 = (Button) findViewById(R.id.mBtn1);        mBtn1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                new Thread(new Runnable() {                    @Override                    public void run() {                        // 3、创建所需消息对象                        Message msg = Message.obtain();                        msg.what = 1;                        //4、发送消息                        mhandler.sendMessage(msg);                    }                    // 5、开启线程                }).start();            }        });    }    //1、自定义Handler子类，继承Handler，重写handleMessage()方法    class mHandler extends Handler {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            //执行的UI操作            if (msg.what==1){                mTxtShowTest.setText("匿名内部类方法");            }        }    }}
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