Java 从一个片段传递到另一个片段

我在这里尝试创建一个菜单，它在单击时从一个片段传递到另一个片段。当我按下菜单中的特定项目（活动）时，活动退出，故障消失

    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();// this line has the problem

这是我的完整日志：

在 android.support.v4.app.backbackbackrecord.doAddOp（backbackbackrecord.java:414） 在 android.support.v4.app.BackStackRecord.replace（BackStackRecord.java:449） 在 android.support.v4.app.BackStackRecord.replace（BackStackRecord.java:441） atbr.examplozingintegration.MainActivity.selectDrawerItem（MainActivity.java:84 atbr.examplozingintegration.MainActivity$1.onNavigationItemSelected（MainActivity.java:50） 在 android.support.design.widget.NavigationView$1.onMenuItemSelected（NavigationView.java:150） 在 android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected（MenuBuilder.java:811） 在 android.support.v7.view.menu.menuitemmpl.invoke（menuitemmpl.java:152） 在 android.support.v7.view.menu.MenuBuilder.performitemation（MenuBuilder.java:958） 在 android.support.design.internal.NavigationMenuPresenter$1.onClick（NavigationMenuPresenter.java:308） 在android.view.view.performClick上（view.java:4439） 在android.view.view$PerformClick.run（view.java:18395） 位于android.os.Handler.handleCallback（Handler.java:725） 位于android.os.Handler.dispatchMessage（Handler.java:92） 位于android.os.Looper.loop（Looper.java:176） 位于android.app.ActivityThread.main（ActivityThread.java:5319） 位于java.lang.reflect.Method.Invokenactive（本机方法） 位于java.lang.reflect.Method.invoke（Method.java:511） 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:1102） 位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:869） 在dalvik.system.NativeStart.main（本机方法）

MainActivity.java

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        txResult = (TextView) findViewById(R.id.txResult);
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        nvDrawer = (NavigationView) findViewById (R.id.nvView);
        setupDrawerContent(nvDrawer);}



    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

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

        Class fragmentClass;
        switch(menuItem.getItemId()) {
            case R.id.nav_first_fragment:
                fragmentClass = MainActivity.class;
                break;
            case R.id.nav_second_fragment:
                fragmentClass = SecondActivity.class;
                break;
            case R.id.nav_third_fragment:
                fragmentClass = ThirdActivity.class;
                break;
            default:
                fragmentClass = MainActivity.class;
        }

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

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawer.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

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

 private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

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

        Class fragmentClass;
        switch(menuItem.getItemId()) {
            case R.id.nav_first_fragment:
                fragmentClass = MainActivity.class;
                break;
            case R.id.nav_second_fragment:
                fragmentClass = SecondActivity.class;
                break;
            case R.id.nav_third_fragment:
                fragmentClass = ThirdActivity.class;
                break;
            default:
                fragmentClass = SecondActivity.class;
        }

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

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawer.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

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

SecondActivity.java

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        txResult = (TextView) findViewById(R.id.txResult);
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        nvDrawer = (NavigationView) findViewById (R.id.nvView);
        setupDrawerContent(nvDrawer);}



    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

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

        Class fragmentClass;
        switch(menuItem.getItemId()) {
            case R.id.nav_first_fragment:
                fragmentClass = MainActivity.class;
                break;
            case R.id.nav_second_fragment:
                fragmentClass = SecondActivity.class;
                break;
            case R.id.nav_third_fragment:
                fragmentClass = ThirdActivity.class;
                break;
            default:
                fragmentClass = MainActivity.class;
        }

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

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawer.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

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

 private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

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

        Class fragmentClass;
        switch(menuItem.getItemId()) {
            case R.id.nav_first_fragment:
                fragmentClass = MainActivity.class;
                break;
            case R.id.nav_second_fragment:
                fragmentClass = SecondActivity.class;
                break;
            case R.id.nav_third_fragment:
                fragmentClass = ThirdActivity.class;
                break;
            default:
                fragmentClass = SecondActivity.class;
        }

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

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawer.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

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

---

您的问题不清楚，因为您没有发布完整的类代码，以及您遇到的错误

据我所知，当选择导航抽屉中的项目时，您希望更改片段。类似于Gmail应用程序，当用户从收件箱文件夹移动到已发送文件夹或任何其他文件夹时

如果您正尝试执行相同的操作，则需要执行一个活动，即插入片段。选择导航抽屉中的项目后，应根据导航抽屉中选择的选项将当前片段替换为新片段

检查以下两个链接，这将给你整个想法

链接1：

链接2:

调用

remove（Fragment）

，然后调用

add（int，Fragment，String）

以实际替换片段。因此，在您的情况下，可能会出现容器视图中没有片段，因此您正在调用

remove（null）

。因此，请检查是否必须添加或替换片段

您可以检查容器视图中是否有任何片段，并相应地继续：

 FragmentManager fragmentManager = getSupportFragmentManager();
 android.support.v4.app.Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.flContent);
 if(currentFragment==null){ 
    fragmentManager.beginTransaction().add(R.id.flContent, fragment).commit();
 }else{
   fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
 }

---

希望这能解决您的问题。

您在logcat中有任何错误吗？请发布。这是logcat错误：致命异常：main java.lang.nullpointerException请在您的问题中发布完整的日志cat。添加了完整的logcat@rohit5k2哪一行是第84行？错误在MainActivity.java:84什么是flContainer？它在代码中：我想你的

FrameLayout

的id是你添加片段的地方。它是第一行的一个打字错误。已编辑。它无法解决fragmentManager#。很抱歉，如果我发布愚蠢的问题，这是我第一次编程Android。这不是一个愚蠢的问题打开。选中“编辑”。