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Java 如何在oncreate活动上设置NavigationDrawer的默认片段

java android

Java 如何在oncreate活动上设置NavigationDrawer的默认片段,java,android,navigation-drawer,material-design,Java,Android,Navigation Drawer,Material Design,我尝试了很多片段事务方式，但我的默认片段在打开navigationdrawer活动时没有启动 public class MainActivity extends AppCompatActivity{ private DrawerLayout drawerLayout; private NavigationView navigationView; private int mSelectedId; @Override protected void

我尝试了很多片段事务方式，但我的默认片段在打开navigationdrawer活动时没有启动

     public class MainActivity extends AppCompatActivity{
    private DrawerLayout drawerLayout;
    private NavigationView navigationView;
    private int mSelectedId;

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


        Toolbar toolbar = (Toolbar)findViewById(R.id.tool_bar);
        toolbar.setNavigationIcon(R.drawable.nav_icon);
        setSupportActionBar(toolbar);

        drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        navigationView = (NavigationView)findViewById(R.id.nvView);
        setupDrawerContent(navigationView);

        mSelectedId = R.id.home;
        selectDrawerItem(mSelectedId);



    }


    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem.getItemId());
                        return true;
                    }
                });
    }
//    @Override
//    public boolean onCreateOptionsMenu(Menu menu) {
//        // Inflate the menu; this adds items to the action bar if it is present.
//        getMenuInflater().inflate(R.menu.menu_main, menu);
//        return true;
//    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        switch (item.getItemId()) {
            case android.R.id.home:
                drawerLayout.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
    }

    public void selectDrawerItem(int mSelectedId) {
        // Create a new fragment and specify the planet to show based on
        // position
        Fragment fragment = null;

        Class fragmentClass;
        switch(mSelectedId) {
            case R.id.home:
                fragmentClass = Main.class;
                break;
            case R.id.orderhistory:
                fragmentClass = Order_history.class;
                break;
            case R.id.profile:
                fragmentClass = Profile.class;
                break;
            case R.id.contact:
                fragmentClass = Contact.class;
                break;
            case R.id.polices:
                fragmentClass = polices.class;
                break;
            default:
                fragmentClass = Main.class;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.flContent, fragment);
        fragmentTransaction.commit();

        // Highlight the selected item, update the title, and close the drawer
//        menuItem.setChecked(true);
//        setTitle(menuItem.getTitle());
        drawerLayout.closeDrawers();
    }
}
它仍然在启动时首先显示活动。一定要提出建议，这样我才能前进

Activity_main.xml

    <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout"
    tools:context="in.co.blogspot.mellow.mellow.MainActivity">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <include
        android:id= "@+id/tool_bar"
        layout= "@layout/tool_bar"></include>

    <FrameLayout
        android:id="@+id/flContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/flContent"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>
我想你可以修改一下你的代码

以这种方式更改方法selectDrawerItem
selectDrawerItem（int mSelectedId）
，这样您就可以接收菜单的id，而不是菜单，因此在onCreate（）方法中可以执行类似操作

主要活动

public class MainActivity extends AppCompatActivity {

    private DrawerLayout drawerLayout;
    private NavigationView navigationView;
    private int mSelectedId;

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

        drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        navigationView = (NavigationView)findViewById(R.id.nvView);
        setupDrawerContent(navigationView);

        mSelectedId = R.id.orderhistory;
        selectDrawerItem(mSelectedId);

    }


    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem.getItemId());
                        return true;
                    }
                });
    }
//    @Override
//    public boolean onCreateOptionsMenu(Menu menu) {
//        // Inflate the menu; this adds items to the action bar if it is present.
//        getMenuInflater().inflate(R.menu.menu_main, menu);
//        return true;
//    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        switch (item.getItemId()) {
            case android.R.id.home:
                drawerLayout.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
    }

    public void selectDrawerItem(int mSelectedId) {
        // Create a new fragment and specify the planet to show based on
        // position
        Fragment fragment = null;

        Class fragmentClass;
        switch(mSelectedId) {
            case R.id.home:
                fragmentClass = Main.class;
                break;
            case R.id.orderhistory:
                fragmentClass = Order_history.class;
                break;
            default:
                fragmentClass = Main.class;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.flContent, fragment);
        fragmentTransaction.commit();

        // Highlight the selected item, update the title, and close the drawer
//        menuItem.setChecked(true);
//        setTitle(menuItem.getTitle());
        drawerLayout.closeDrawers();
    }
}
activity_main.xml

    <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout"
    tools:context="in.co.blogspot.mellow.mellow.MainActivity">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <include
        android:id= "@+id/tool_bar"
        layout= "@layout/tool_bar"></include>

    <FrameLayout
        android:id="@+id/flContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/flContent"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>
fragment_order_history.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.enterprise.prueba.Order_history">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />

</FrameLayout>
fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="I'm a fragment"/>

</LinearLayout>
已编辑

这很奇怪，现在我用相同的代码创建了一个新项目，这是我在Oncreate（）中选择order history时的结果

我更新代码以显示所有文件

默认情况下不会调用selectDrawerItem方法。您需要更改流程才能正常工作。drawer_view.xml的内容是什么？其中是否定义了
R.id.home
。每一个碎片都运转良好。我的问题是，当屏幕启动时，它首先显示主活动布局。我需要在启动时显示主片段，而不是显示主活动布局@Terence@abhilnair代码的哪一部分是空的？注意菜单项和设置标题。我删除了这2行，这是我的错误。我解决了空指针问题并尝试了您的建议，但MainActivity仍在启动initially@abhilnair我用索尼xperia p-API16果冻豆作为我的测试设备，更新了我的答案，以显示更新后的codeam的结果。更新代码后，现在导航抽屉项目也无法打开。耶，谢谢，成功了。。实际上，我在主活动中添加了工具栏。现在我转移到每一个片段和它的工作良好。谢谢你的建议@JorgeCasariego 
public class Main extends Fragment {

    public Main() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, null);


        // Inflate the layout for this fragment
        return rootView;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="I'm a fragment"/>

</LinearLayout>