Android开发中如何去掉app标题栏的实现

requestWindowFeature(Window.FEATURE_NO_TITLE);//这行代码必须写在setContentView()方法的前面

package com.wust.selfviewgroup;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
 
public class MainActivity extends Activity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE); //这个方法必须写在 setContentView 的前面，了解源码的同学应该知道其原因
        setContentView(R.layout.activity_main);
    }
}

<application android:theme="@android:style/Theme.NoTitleBar">

getSupportActionBar().hide();//这行代码必须写在setContentView()方法的后面

package com.wust.selfviewgroup;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.view.Window;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        getSupportActionBar().hide(); //这个方法要写在 setContentView() 之后
    }
}

<application android:theme="@style/Theme.AppCompat.NoActionBar">