在 Android 中使用工具栏实现正确的后退导航和主页按钮处理

Question

我在同一 activity 中使用单个 activity 和多个片段（附有屏幕截图）来提供无缝导航。但是在实现了最新的工具栏和导航视图之后，似乎很难处理导航和主页按钮。我遇到以下问题。

管理左上角的 Hamburger/Back 按钮。将图标和功能切换到菜单和后退导航。
- 页面标题 - 每当片段被推入和弹出时更改页面标题。

我尝试了几种方法，例如覆盖 onBackPressed()、setHomeAsUpIndicator、手动弹出片段。早些时候我使用 ActionBarDrawer 切换来处理这个但它现在以某种方式失败了。我检查了 google 个样本，他们似乎在大多数地方使用单独的活动。

谁能指导我如何实现正确的后退导航来处理内部片段和页面标题中的 NavigationView、后退按钮？我正在使用 AppCompatActivity、android.app.Fragment、NavigationView 和 Toolbar.

Answer 1

将其添加到您调用片段的 MainActivity 中。 getBackStackEntryCount() Return number of fragments in the back stack. where the fragment on the bottom of the stack has index 0. popBackStack() 将最上面的 Fragment 弹出后栈

 @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == android.R.id.home) {
            if (getSupportFragmentManager().getBackStackEntryCount() == 1) {
                getSupportFragmentManager().popBackStack();
            } else {
                super.onBackPressed();
            }
        }
        return true;
    }

然后在你想要返回的 Fragment 中使用这个函数

  @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            getActivity().onBackPressed();
        }
        return true;
    }

Answer 2

"Page title - Changing the page titles whenever a fragment in pushed and popped"

删除片段时，有方法isRemoving()。这有助于改回标题。

@Override
public void onStop() {
    super.onStop();
    if (isRemoving()) {
        // Change your title here
    }
}

"functionality to Menu and Back nav"

建议：我们必须依赖默认的android导航系统。如果我们对片段使用 addToBackStack()，理论上我们根本不需要重写 onBackPressed()。

"App does not redefine the expected function of a system icon (such as the Back button)."
"App supports standard system Back button navigation and does not make use of any custom, on-screen "“后退按钮”提示。

核心应用质量：https://developer.android.com/distribute/essentials/quality/core.html

"Managing the Hamburger/Back button at left top"

我建议使用 activity 而不是 'MainActivityDetailFragment' 以避免并发症。

Answer 3

尝试这样的事情：

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

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    if (getSupportActionBar()!=null) {
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    drawer = (DrawerLayout) findViewById(R.id.drawer_layout);

    final ActionBarDrawerToggle drawerToggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(drawerToggle);
    drawerToggle.syncState();

    final View.OnClickListener originalToolbarListener = drawerToggle.getToolbarNavigationClickListener();

    final View.OnClickListener navigationBackPressListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            getFragmentManager().popBackStack();
        }
    };

    getFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            if (getFragmentManager().getBackStackEntryCount() > 0) {
                drawerToggle.setDrawerIndicatorEnabled(false);
                drawerToggle.setToolbarNavigationClickListener(navigationBackPressListener);
            } else {
                drawerToggle.setDrawerIndicatorEnabled(true);
                drawerToggle.setToolbarNavigationClickListener(originalToolbarListener);
            }
        }
    });

    // Though below steps are not related but I have included to show drawer close on Navigation Item click. 

    navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(MenuItem item) {
            int id = item.getItemId();
            /**
             * handle item clicks using id
             */
            drawer.closeDrawer(GravityCompat.START);
            return true;
        }
    });
}

处理抽屉状态onBackPressed:

@Override
public void onBackPressed() {
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

要在返回时重新加载之前的 fragment，请始终将片段事务添加到返回堆栈，如下所示：

FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
SomeFragment fragmentToBeLoaded = new SomeFragment();
fragmentTransaction.replace(R.id.fragment_container, fragmentToBeLoaded,
                fragmentToBeLoaded.getName());
fragmentTransaction.addToBackStack(fragmentToBeLoaded.getName());
fragmentTransaction.commit();

要动态更改页面标题，您可以从每个 Fragments onStart 或 onResume 方法中调用它：

@Override
public void onStart() {
   super.onStart();
   getActivity().setTitle("Title for fragment");
}

注意：我考虑了标准布局声明，因此我没有包含任何布局。

Answer 4

对于您的 Activity 和 Fragment。

，通过某种责任分工来说明要容易得多

问题 1：管理左上角的 Hamburger/Back 按钮。将图标和功能切换到菜单和返回导航。

从图中可以看出，解决方案应该由 Activity 封装，看起来像这样：

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    private ActionBarDrawerToggle mDrawerToggle;
    private DrawerLayout mDrawer;
    private ActionBar mActionBar;

    private boolean mToolBarNavigationListenerIsRegistered = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        mActionBar = getSupportActionBar();

        mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerToggle = new ActionBarDrawerToggle(this, mDrawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        mDrawer.addDrawerListener(mDrawerToggle);
        mDrawerToggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        // On orientation change savedInstanceState will not be null.
        // Use this to show hamburger or up icon based on fragment back stack.
        if(savedInstanceState != null){
            resolveUpButtonWithFragmentStack();
        } else {
            // You probably want to add your ListFragment here.
        }
    }

    @Override
    public void onBackPressed() {

        if (mDrawer.isDrawerOpen(GravityCompat.START)) {
            mDrawer.closeDrawer(GravityCompat.START);

        } else {
            int backStackCount = getSupportFragmentManager().getBackStackEntryCount();

            if (backStackCount >= 1) {
                getSupportFragmentManager().popBackStack();
                // Change to hamburger icon if at bottom of stack
                if(backStackCount == 1){
                    showUpButton(false);
                }
            } else {
                super.onBackPressed();
            }
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.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.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;

        } else if (id == android.R.id.home) {
            // Home/Up logic handled by onBackPressed implementation
            onBackPressed();
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        // Navigation drawer item selection logic goes here

        mDrawer.closeDrawer(GravityCompat.START);
        return true;
    }

    private void replaceFragment() {
        /**
        * Your fragment replacement logic goes here
        * e.g.
        * FragmentTransaction ft = getFragmentManager().beginTransaction();
        * String tag = "MyFragment";
        * ft.replace(R.id.content, MyFragment.newInstance(tag), tag).addToBackStack(null).commit();
        */

        // The part that changes the hamburger icon to the up icon
        showUpButton(true);
    }

    private void resolveUpButtonWithFragmentStack() {
        showUpButton(getSupportFragmentManager().getBackStackEntryCount() > 0);
    }

    private void showUpButton(boolean show) {
        // To keep states of ActionBar and ActionBarDrawerToggle synchronized,
        // when you enable on one, you disable on the other.
        // And as you may notice, the order for this operation is disable first, then enable - VERY VERY IMPORTANT.
        if(show) {
            // Remove hamburger
            mDrawerToggle.setDrawerIndicatorEnabled(false);
            // Show back button
            mActionBar.setDisplayHomeAsUpEnabled(true);
            // when DrawerToggle is disabled i.e. setDrawerIndicatorEnabled(false), navigation icon
            // clicks are disabled i.e. the UP button will not work.
            // We need to add a listener, as in below, so DrawerToggle will forward
            // click events to this listener.
            if(!mToolBarNavigationListenerIsRegistered) {
                mDrawerToggle.setToolbarNavigationClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        onBackPressed();
                    }
                });

                mToolBarNavigationListenerIsRegistered = true;
            }

        } else {
            // Remove back button
            mActionBar.setDisplayHomeAsUpEnabled(false);
            // Show hamburger
            mDrawerToggle.setDrawerIndicatorEnabled(true);
            // Remove the/any drawer toggle listener 
            mDrawerToggle.setToolbarNavigationClickListener(null);
            mToolBarNavigationListenerIsRegistered = false;
        }

        // So, one may think "Hmm why not simplify to:
        // .....
        // getSupportActionBar().setDisplayHomeAsUpEnabled(enable);
        // mDrawer.setDrawerIndicatorEnabled(!enable);
        // ......
        // To re-iterate, the order in which you enable and disable views IS important #dontSimplify.
    }
}

问题 2：页面标题 - 每次推送和弹出片段时更改页面标题。

基本上，这可以在 onStart 中为每个 Fragment 处理，即您的 ListFragment、DetailsFragment 和 CommentsFragment 看起来像这样：

@Override
public void onStart() {
    super.onStart();
    // where mText is the title you want on your toolbar/actionBar
    getActivity().setTitle(mText);
}

在您的片段 onCreate 中也可能值得 setRetainInstance(true)。

Answer 5

好的，经过大量测试终于成功设置好了导航。我需要和你完全一样，唯一的区别是我使用的是 v4 片段，但我认为这不会改变这里的任何东西。

我不使用 ActionBarDrawerToggle，因为来自 Google 的最新示例不再使用此组件。

下面的解决方案也适用于深度导航：parent activity --> fragment --> fragment etc.

片段中唯一需要更改的是更改标题：

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

    getActivity().setTitle(R.string.targets);
}

在parentActivityonCreate方法中，我初始化如下：

    mNavigationView = (NavigationView) findViewById(R.id.navigation_view);
    setupDrawerContent(mNavigationView);

    final Toolbar toolbar = (Toolbar) findViewById(R.id.drawer_toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_menu_24);// Set the hamburger icon
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);// Set home button pressable

    // Handle the changes on the actionbar
    getSupportFragmentManager().addOnBackStackChangedListener(
            new FragmentManager.OnBackStackChangedListener() {
                public void onBackStackChanged() {
                    // When no more fragments to remove, we display back the hamburger icon and the original activity title
                    if (getSupportFragmentManager().getBackStackEntryCount() <= 0) {
                        getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_menu_24);
                        setTitle(R.string.app_name);
                    }
                    // Else displays the back arrow
                    else {
                        getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_arrow_back_24);
                    }
                }
            });

下面是处理主页按钮上的操作的代码：

@Override
public boolean onOptionsItemSelected(MenuItem item){
    // Close the soft keyboard right away
    Tools.setSoftKeyboardVisible(mViewPager, false);

    switch (item.getItemId()) {
        case android.R.id.home:

            // When no more fragments to remove, open the navigation drawer
            if (getSupportFragmentManager().getBackStackEntryCount() <= 0) {
                mDrawerLayout.openDrawer(GravityCompat.START);
            }
            // Removes the latest fragment
            else {
                getSupportFragmentManager().popBackStack();
            }

            return true;
    }
    return super.onOptionsItemSelected(item);
}

最后是处理后按动作的代码：

@Override
public void onBackPressed() {
    // When no more fragments to remove, closes the activity
    if (getSupportFragmentManager().getBackStackEntryCount() <= 0) {
        super.onBackPressed();
    }
    // Else removes the latest fragment
    else {
        getSupportFragmentManager().popBackStack();
    }
}

注意：我正在使用 AppCompatActivity、NavigationView 和主题 Theme.AppCompat.Light.NoActionBar。

Answer 6

tl;博士

看这个： https://youtu.be/ANpBWIT3vlU

克隆这个： https://github.com/shredderskelton/androidtemplate.

这是一个非常普遍的问题，我已经通过创建一种模板项目克服了这个问题，每当我开始一个新的 Android 项目时都会使用它。这个想法是将处理后退按钮、'hamburger' 指示器和片段管理的逻辑尽可能多地抽象为可重用的 classes:

首先创建一个 BaseActivity 和 BaseFragment class。这是您要访问尽可能多的可重用代码的地方。

让我们从您的 BaseActivity 开始

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    fragmentManager = getSupportFragmentManager();
    fragmentHandler = new AddFragmentHandler(fragmentManager);
    fragmentManager.addOnBackStackChangedListener(backStackListener);
}

FragmentManager是拥有后台栈的关键，所以你需要从这里监听后台栈的变化。 AddFramentHandler 有点 class 我精心设计，以便更容易地从 Fragments 添加 Fragments。稍后会详细介绍。

@Override
public void onBackPressed() {
    if (sendBackPressToDrawer()) {
        //the drawer consumed the backpress
        return;
    }

    if (sendBackPressToFragmentOnTop()) {
        // fragment on top consumed the back press
        return;
    }

    //let the android system handle the back press, usually by popping the fragment
    super.onBackPressed();

    //close the activity if back is pressed on the root fragment
    if (fragmentManager.getBackStackEntryCount() == 0) {
        finish();
    }
}

onBackPressed 是大部分魔法发生的地方。您会注意到方法的纯文本格式。我是 Clean Code 的超级粉丝 - 如果您需要写注释，那么您的代码就不干净了。基本上，当您不确定为什么按下后退按钮没有按您期望的方式发生时，您确实需要有一个可以运行的中心位置。这个方法就是那个地方。

private void syncDrawerToggleState() {
    ActionBarDrawerToggle drawerToggle = getDrawerToggle();
    if (getDrawerToggle() == null) {
        return;
    }
    if (fragmentManager.getBackStackEntryCount() > 1) {
        drawerToggle.setDrawerIndicatorEnabled(false);
        drawerToggle.setToolbarNavigationClickListener(navigationBackPressListener); //pop backstack
    } else {
        drawerToggle.setDrawerIndicatorEnabled(true);
        drawerToggle.setToolbarNavigationClickListener(drawerToggle.getToolbarNavigationClickListener()); //open nav menu drawer
    }
}

这是BaseActivity的另一个关键部分。基本上，此方法会检查您是否位于根片段并相应地设置指示器。请注意，它会根据返回堆栈中的片段数量更改侦听器。

然后是BaseFragment：

@Override
public void onResume() {
    super.onResume();
    getActivity().setTitle(getTitle());
}

protected abstract String getTitle();

上面的代码显示了片段如何处理标题。

在 Android 中使用工具栏实现正确的后退导航和主页按钮处理

Implementing proper back navigation and home button handling using Toolbar in Android

android

android-fragments

navigation-drawer

android-navigationview

"Page title - Changing the page titles whenever a fragment in pushed and popped"

"functionality to Menu and Back nav"

"Managing the Hamburger/Back button at left top"