Java 碎片赢了'；隐藏

我有一个导航栏，当按下按钮时应该隐藏起来，但什么也没发生

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
private TextView mavisTxt;
private Button testBtn;
private Fragment navigationBar;


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

}

private void initVariables() {
    navigationBar = new HeaderNav();
    mavisTxt = (TextView)findViewById(R.id.mavisTxt);
    testBtn = (Button)findViewById(R.id.testBtn);


    testBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
                FragmentManager fm = getSupportFragmentManager();
                fm.beginTransaction()
                        .hide(navigationBar)
                        .commit();
                mavisTxt.setText("navbar is hidden");
        }
    });

}
}

这是片段的java文件

public class HeaderNav extends Fragment {
    private static Button homeBtn, optionsBtn, connectionBtn, micBtn, aboutBtn;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.navbar, container, false);

        homeBtn = (Button)view.findViewById(R.id.homeBtn);
        optionsBtn = (Button)view.findViewById(R.id.optionsBtn);
        connectionBtn = (Button)view.findViewById(R.id.micBtn);
        micBtn = (Button)view.findViewById(R.id.homeBtn);
        aboutBtn = (Button)view.findViewById(R.id.aboutBtn);

        return view;
    }
}

以及主活动xml中的片段标记：

<fragment
        android:id="@+id/navigationBar"
        android:name="com.example.egi.mavisme.HeaderNav"
        android:layout_width="fill_parent"
        android:layout_height="60dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:layout="@layout/navbar" />

这是我现在的代码：

public class MainActivity extends AppCompatActivity {
    private TextView mavisTxt;
    private Button testBtn;
    private HeaderNav navigationBar;

    private FragmentManager fm;
    private FragmentTransaction ft;


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

    }

    private void initVariables() {
        fm = getSupportFragmentManager();
        ft = fm.beginTransaction();
        navigationBar = (HeaderNav)fm.findFragmentById(R.id.navigationBar);

        mavisTxt = (TextView)findViewById(R.id.mavisTxt);
        testBtn = (Button)findViewById(R.id.testBtn);


        testBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                    ft.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out);
                    ft.hide(navigationBar)
                    .commit();
                    if(navigationBar.isHidden()) {mavisTxt.setText("navbar is hidden");}
            }
        });

    }
}

---

这里有一些事情需要注意-

使用

操作栏/工具栏

，这不是iOS

你必须先添加一个片段

您正在使用show调用，而不是隐藏它

testBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
                FragmentManager fm = getSupportFragmentManager();
                fm.beginTransaction()
                        .**show**(navigationBar)
                        .commit();
                mavisTxt.setText("navbar is hidden");
        }
    });

---

使用

replace

方法，而不是

show

我正试图隐藏该导航条检查此项查看此项您无法隐藏在xml中创建的片段。应该是这样的。hide（）进行了更正，但仍然不起作用。首先添加一个片段是什么意思？我已经创造了碎片，不是吗？

testBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
                FragmentManager fm = getSupportFragmentManager();
                fm.beginTransaction()
                        .**show**(navigationBar)
                        .commit();
                mavisTxt.setText("navbar is hidden");
        }
    });