本文介紹了如何正確實(shí)現(xiàn)導(dǎo)航抽屜中頂部的后退按鈕？的處理方法，對(duì)大家解決問(wèn)題具有一定的參考價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)吧！
問(wèn)題描述
我目前正試圖在我的天氣應(yīng)用程序中添加導(dǎo)航抽屜，所以我看了一個(gè)YouTube
教程，并且能夠以我想要的方式實(shí)現(xiàn)它，直到我意識(shí)到
我看的教程沒(méi)有介紹如何實(shí)現(xiàn)向上/頂部后退
按鈕，所以事實(shí)上，我現(xiàn)在不能回到
打開(kāi)任何導(dǎo)航選項(xiàng)卡后的默認(rèn)片段。我搜索了幾個(gè)
網(wǎng)站和YouTube視頻尋找如何實(shí)現(xiàn)頂部Back的教程
按鈕，但沒(méi)看到/找不到。我也搜索了這個(gè)網(wǎng)站，仍然
在這里沒(méi)有發(fā)現(xiàn)有類(lèi)似問(wèn)題的人。請(qǐng)問(wèn)有誰(shuí)能幫忙嗎？
以下是我的應(yīng)用程序當(dāng)前狀態(tài)的屏幕截圖：https://i.stack.imgur.com/SeSjV.png但如果我打開(kāi)任何導(dǎo)航欄選項(xiàng)(即設(shè)置)并單擊”上一步”，我將無(wú)法返回到顯示天氣的默認(rèn)片段。它也沒(méi)有”上-后”按鈕。
當(dāng)前，單擊”上一步”僅退出應(yīng)用程序。
這是我嘗試過(guò)的唯一代碼，但不起作用：
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
int backStackCount = fragmentManager.getBackStackEntryCount();//check currently how many frags loaded
if (backStackCount > 0) {
fragmentManager.popBackStack(); //go back to previously loaded fragment
}
}
return super.onOptionsItemSelected(item);
}
它出現(xiàn)以下錯(cuò)誤：
錯(cuò)誤：找不到符號(hào)
int backStackCount=fragmentManager.getBackStackEntryCount()；//check當(dāng)前有多少
加載的碎片
這是我的活動(dòng)代碼：
public class HomeActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;
// Last update time, click sound, search button, search panel.
TextView timeField;
MediaPlayer player;
ImageView Search;
EditText textfield;
// For scheduling background image change(using constraint layout, start counting from dubai, down to statue of liberty.
ConstraintLayout constraintLayout;
public static int count = 0;
int[] drawable = new int[]{R.drawable.dubai, R.drawable.norway, R.drawable.eiffel_tower, R.drawable.hong_kong, R.drawable.statue_of_liberty,
R.drawable.beijing, R.drawable.chicago, R.drawable.colombia, R.drawable.vienna,R.drawable.tokyo};
Timer _t;
private WeatherDataViewModel viewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
// use home activity layout.
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Allow activity to make use of the toolbar
drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
viewModel = new ViewModelProvider(this).get(WeatherDataViewModel.class);
// Trigger action to open & close nevigation drawer
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar
, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
timeField = findViewById(R.id.textView9);
Search = findViewById(R.id.imageView4);
textfield = findViewById(R.id.textfield);
// find the id's of specific variables.
BottomNavigationView bottomNavigationView = findViewById(R.id.bottomNavigationView);
// host 3 fragments along with bottom navigation.
final NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragment);
assert navHostFragment != null;
final NavController navController = navHostFragment.getNavController();
NavigationUI.setupWithNavController(bottomNavigationView, navController);
// Make hourly & daily tab unusable
bottomNavigationView.setOnNavigationItemSelectedListener(item -> {
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack();
}
return false;
});
navController.addOnDestinationChangedListener((controller, destination, arguments) -> navController.popBackStack(destination.getId(), false));
// For scheduling background image change
constraintLayout = findViewById(R.id.layout);
constraintLayout.setBackgroundResource(R.drawable.dubai);
_t = new Timer();
_t.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
// run on ui thread
runOnUiThread(() -> {
if (count < drawable.length) {
constraintLayout.setBackgroundResource(drawable[count]);
count = (count + 1) % drawable.length;
}
});
}
}, 5000, 5000);
Search.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// make click sound when search button is clicked.
player = MediaPlayer.create(HomeActivity.this, R.raw.click);
player.start();
getWeatherData(textfield.getText().toString().trim());
// make use of some fragment's data
Fragment currentFragment = navHostFragment.getChildFragmentManager().getFragments().get(0);
if (currentFragment instanceof FirstFragment) {
FirstFragment firstFragment = (FirstFragment) currentFragment;
firstFragment.getWeatherData(textfield.getText().toString().trim());
} else if (currentFragment instanceof SecondFragment) {
SecondFragment secondFragment = (SecondFragment) currentFragment;
secondFragment.getWeatherData(textfield.getText().toString().trim());
} else if (currentFragment instanceof ThirdFragment) {
ThirdFragment thirdFragment = (ThirdFragment) currentFragment;
thirdFragment.getWeatherData(textfield.getText().toString().trim());
}
}
private void getWeatherData(String name) {
ApiInterface apiInterface = ApiClient.getClient().create(ApiInterface.class);
Call<Example> call = apiInterface.getWeatherData(name);
call.enqueue(new Callback<Example>() {
@Override
public void onResponse(@NonNull Call<Example> call, @NonNull Response<Example> response) {
try {
assert response.body() != null;
timeField.setVisibility(View.VISIBLE);
timeField.setText("First Updated:" + " " + response.body().getDt());
} catch (Exception e) {
timeField.setVisibility(View.GONE);
timeField.setText("First Updated: Unknown");
Log.e("TAG", "No City found");
Toast.makeText(HomeActivity.this, "No City found", Toast.LENGTH_SHORT).show();
}
}
@Override
public void onFailure(@NotNull Call<Example> call, @NotNull Throwable t) {
t.printStackTrace();
}
});
}
});
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.settings_id:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment,
new Settings()).commit();
break;
case R.id.ads_upgrade_id:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment,
new Upgrade()).commit();
break;
case R.id.privacy_policy_id:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment,
new Privacy_Policy()).commit();
break;
}
drawer.closeDrawer(GravityCompat.START);
return true;
}
@Override
public void onBackPressed() {
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
// Open/close drawer animation
}
}
推薦答案
if (item.getItemId() == android.R.id.home) {
int backStackCount = fragmentManager.getBackStackEntryCount();//check currently how many frags loaded
if (backStackCount > 0) {
fragmentManager.popBackStack(); //go back to previously loaded fragment
}
}
當(dāng)前，單擊”上一步”僅退出應(yīng)用程序。
使用popBackStack()將彈出使您的應(yīng)用程序存在的后棧，但您只需返回到默認(rèn)片段。
要解決此問(wèn)題，您需要更改抽屜漢堡按鈕的行為，以便有時(shí)可以使用它打開(kāi)抽屜的navView布局，有時(shí)可以使用它返回到默認(rèn)片段；后者是在您要添加頂部的后退按鈕時(shí)使用的。
如何實(shí)現(xiàn)導(dǎo)航抽屜的上/上后退按鈕
這需要訪(fǎng)問(wèn)使您能夠?qū)陕?tīng)器添加到漢堡點(diǎn)擊的setToolbarNavigationClickListener方法。
在這種情況下，您需要在onCreate()方法Add：
中根據(jù)需要返回到Home片段
toggle.setToolbarNavigationClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Enable the functionality of opening the side drawer, when the burger icon is clicked
toggle.setDrawerIndicatorEnabled(true); // Show the burger icon & enable the drawer funcionality
navController.navigate(R.id.home); // Back to default fragment (replace home with your default fragment id in the navGraph)
}
});
剩下的部分是在您想要轉(zhuǎn)到某個(gè)片段時(shí)顯示后退按鈕
并使用toggle.setDrawerIndicatorEnabled()啟用/禁用單擊主頁(yè)/漢堡圖標(biāo)時(shí)打開(kāi)/關(guān)閉抽屜的功能
navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
@Override
public void onDestinationChanged(@NonNull NavController controller, @NonNull NavDestination destination, @Nullable Bundle arguments) {
// Repeat this condition for all the Fragments that you want to show the back button
if (destination.getId() == R.id.settings_id) { // replace `settings_id` with your fragment id in the navGraph that you want to show the back button
// Disable the functionality of opening the side drawer, when the burger icon is clicked & show the UP button instead
toggle.setDrawerIndicatorEnabled(false);
}
}
});
這篇關(guān)于如何正確實(shí)現(xiàn)導(dǎo)航抽屜中頂部的后退按鈕？的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，
