onNewIntent 永远不会在片段中触发

Question

我在获取 onNewIntent 方法以在 Fragment 中工作时遇到问题。我已经尝试了一切，但似乎没有任何效果。我的项目在使用活动时运行良好，但是当我切换到片段时它停止工作。我的想法是我想制作标签，其中一个标签写入 NFC 标签，而其他标签将从 NFC 标签读取数据。这是我的片段代码（写标签）：

    public class Home extends Fragment {

    NfcAdapter nfcAdapter;
    Button writebtn;
    Tag tag;
    EditText txtName1, txtName2, txtName3;

    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);
        nfcAdapter = NfcAdapter.getDefaultAdapter(getContext());

         txtName1 = (EditText)view.findViewById(R.id.pName1);
         txtName2= (EditText)view.findViewById(R.id.pName2);
        txtName3= (EditText)view.findViewById(R.id.pName3);
        writebtn=(Button)view.findViewById(R.id.nfcWriteBtn);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View v= inflater.inflate(R.layout.home, container,false);
        return v;

    }


    @Override
    public void onResume() {
        super.onResume();

        if(nfcAdapter !=null){

            /* go to phone's nfc settings */
            if(!nfcAdapter.isEnabled()){
                showNfcSettings();
            }
            enableForegroundDispatchSystem();
        }

    }

    private void showNfcSettings() {
        Intent nfcSettingIntent = new Intent(Settings.ACTION_NFC_SETTINGS);
        startActivity(nfcSettingIntent);
    }

    @Override
    public void onPause() {
        super.onPause();

        disableForegroundDispatchSystem();
    }


    protected void onNewIntent(Intent intent) {
        System.out.print("I am here in Home");
        Log.d("my tag", "I am here now");
        Toast.makeText(getActivity(), "NfcIntent!", Toast.LENGTH_SHORT).show();
        if (intent.hasExtra(NfcAdapter.EXTRA_TAG)) {
       // if (nfcAdapter.ACTION_TAG_DISCOVERED.equals(intent.getAction())) {
            Toast.makeText(getActivity(), "NfcIntent!", Toast.LENGTH_SHORT).show();
            tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
            writebtn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    NdefMessage ndefMessage = createNdefMessage(txtName1.getText().toString(), txtName2.getText().toString(),txtName3.getText().toString());
                    writeNdefMessage(tag, ndefMessage);
                }
            });

        }

    }


    private void enableForegroundDispatchSystem() {

        Intent intent = new Intent(getActivity(), getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);

        PendingIntent pendingIntent = PendingIntent.getActivity(getContext(), 0, intent, 0);

        IntentFilter[] intentFilters = new IntentFilter[]{};

        nfcAdapter.enableForegroundDispatch(getActivity(), pendingIntent, intentFilters, null);
    }

    private void disableForegroundDispatchSystem() {
        nfcAdapter.disableForegroundDispatch(getActivity());
    }
    private void formatTag(Tag tag, NdefMessage ndefMessage) {
        try {

            NdefFormatable ndefFormatable = NdefFormatable.get(tag);

            if (ndefFormatable == null) {
                Toast.makeText(getContext(), "Tag is not ndef formatable!", Toast.LENGTH_SHORT).show();
            }

            else{
                ndefFormatable.connect();
                ndefFormatable.format(ndefMessage);
                ndefFormatable.close();
                Toast.makeText(getContext(), "Tag writen!", Toast.LENGTH_SHORT).show();
            }
        } catch (Exception e) {
            Log.e("formatTag", e.getMessage());
        }

    }

    private void writeNdefMessage(Tag tag, NdefMessage ndefMessage) {

        try {

            if (tag == null) {
                Toast.makeText(getContext(), "Tag object cannot be null", Toast.LENGTH_SHORT).show();
                return;
            }

            Ndef ndef = Ndef.get(tag);

            if (ndef == null) {
                // format tag with the ndef format and writes the message.
                formatTag(tag, ndefMessage);
            } else {
                ndef.connect();
                if (!ndef.isWritable()) {
                    Toast.makeText(getContext(), "Tag is not writable!", Toast.LENGTH_SHORT).show();

                    ndef.close();
                    return;
                }

                ndef.writeNdefMessage(ndefMessage);
                ndef.close();

                Toast.makeText(getContext(), "Tag writen!", Toast.LENGTH_SHORT).show();

            }

        } catch (Exception e) {
            Log.e("writeNdefMessage", e.getMessage());
        }

    }


    private NdefRecord createTextRecord(String content) {
        try {
            byte[] language;
            language = Locale.getDefault().getLanguage().getBytes("UTF-8");

            final byte[] text = content.getBytes("UTF-8");
            final int languageSize = language.length;
            final int textLength = text.length;
            final ByteArrayOutputStream payload = new ByteArrayOutputStream(1 + languageSize + textLength);

            payload.write((byte) (languageSize & 0x1F));
            payload.write(language, 0, languageSize);
            payload.write(text, 0, textLength);

            return new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT, new byte[0], payload.toByteArray());

        } catch (UnsupportedEncodingException e) {
            Log.e("createTextRecord", e.getMessage());
        }
        return null;
    }
    private NdefMessage createNdefMessage(String content, String content2, String content3) {

        NdefRecord ndefRecord = createTextRecord(content);
        NdefRecord ndefRecord2 = createTextRecord(content2);
        NdefRecord ndefRecord3 = createTextRecord(content3);

        NdefMessage ndefMessage = new NdefMessage(new NdefRecord[]{ndefRecord, ndefRecord2, ndefRecord3});

        return ndefMessage;
    }

}

在包含选项卡的 Activity 中，我创建了这个方法：

 public class DosisHome extends AppCompatActivity {

    protected DrawerLayout mDrawerLayout;
    private ActionBarDrawerToggle mtoggle;
    NfcAdapter nfcAdapter;
    private Toolbar mtoolbar;
    Fragment fragment;
    private TextView mName;
    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;
    private NavigationView mNavigationView;

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

        mtoolbar = (Toolbar) findViewById(R.id.nav_action);
        setSupportActionBar(mtoolbar);
        mNavigationView= (NavigationView)findViewById(R.id.nav_view);
        mDrawerLayout = findViewById(R.id.drawer_layout);
        mtoggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
        mDrawerLayout.addDrawerListener(mtoggle);
        mtoggle.syncState();
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));

        tabLayout.setupWithViewPager(mViewPager);
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                switch (tab.getPosition())
                {
                    case 0:
                        mViewPager.setCurrentItem(0);
                        mtoolbar.setTitle("Home");
                        break;

                    case 1:
                        mViewPager.setCurrentItem(1);
                        mtoolbar.setTitle("Write");
                        break;

                    case 2:
                        mViewPager.setCurrentItem(2);
                        mtoolbar.setTitle("Read");
                        break;

                    case 3:
                        mViewPager.setCurrentItem(3);
                        mtoolbar.setTitle("Others");
                        break;

                    case 4:
                        mViewPager.setCurrentItem(4);
                        mtoolbar.setTitle("Alarm");
                        break;


                    default:
                        mViewPager.setCurrentItem(tab.getPosition());
                        mtoolbar.setTitle("Home APP");
                        break;
                }

            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

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

        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                // set item as selected to persist highlight
                menuItem.setChecked(true);

                switch (menuItem.getItemId()){

                    case R.id.nav_write:
                        mViewPager.setCurrentItem(0);
                        mDrawerLayout.closeDrawers();
                        mtoolbar.setTitle("Write");
                        break;

                    case R.id.nav_read:
                        mViewPager.setCurrentItem(1);
                        mDrawerLayout.closeDrawers();
                        mtoolbar.setTitle("Read");
                        break;

                    case R.id.nav_other:
                        mViewPager.setCurrentItem(2);
                        mDrawerLayout.closeDrawers();
                        mtoolbar.setTitle("Others");
                        break;

                    case R.id.nav_alarm:
                        mViewPager.setCurrentItem(3);
                        mDrawerLayout.closeDrawers();
                        mtoolbar.setTitle("Alarm");
                        break;

                    case R.id.nav_logout:
                        FirebaseAuth.getInstance().signOut();
                        finish();
                        startActivity(new Intent(getApplicationContext(),Login.class));

                }


                // close drawer when item is tapped
                mDrawerLayout.closeDrawers();
                return true;
            }
        });

        mDrawerLayout.addDrawerListener(
                new DrawerLayout.DrawerListener() {
                    @Override
                    public void onDrawerSlide(View drawerView, float slideOffset) {
                        // Respond when the drawer's position changes
                    }

                    @Override
                    public void onDrawerOpened(View drawerView) {
                        // Respond when the drawer is opened
                    }

                    @Override
                    public void onDrawerClosed(View drawerView) {
                        // Respond when the drawer is closed
                    }

                    @Override
                    public void onDrawerStateChanged(int newState) {
                        // Respond when the drawer motion state changes
                    }
                }
        );

    }

    @Override
    public void onNewIntent(Intent intent) {
        setIntent(intent);
        super.onNewIntent(intent);
        Toast.makeText(this, "I am in TabsHome", Toast.LENGTH_SHORT).show();
        System.out.print("I am here in TabsHome");
        Log.d("my tag", "I am here");
        // Notify fragment about the new intent

       if(fragment instanceof Home){
           Log.d("my tag", "I am here");
           Home hm = (Home) fragment;
           hm.onNewIntent(intent);
        }

    }







    @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_dosis_home, 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.


        if(mtoggle.onOptionsItemSelected(item)){
            return true;
        }
        //noinspection SimplifiableIfStatement
        if (item.getItemId()== R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position){

                case 0:
                    Home home= new Home();
                    return home;
                case 1:
                    Writer write = new Writer();
                    return write;

                case 2:
                    Reader read= new Reader();
                    return read;

                case 3:
                    Others other= new Others();
                    return other;

                case 4:
                    Alarm alarm= new Alarm();
                    return alarm;

            }
            return null;
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 5;
        }
        /*to set text instead of icons*/
        public CharSequence getPageTitle(int position){

            return null;
        }
    }
}

我的带有标签的 Activity 的 AndroidManifest ：

   <activity android:name=".TabsHome"
        android:windowSoftInputMode="adjustPan"
        android:screenOrientation="portrait"
        android:launchMode="singleTop">

        <intent-filter>
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.LAUNCHER" />
            <action android:name="android.nfc.action.TAG_DISCOVERED" />
            <action android:name="android.nfc.action.NDEF_DISCOVERED" />


            <data android:mimeType="text/plain" />
        </intent-filter>

        <meta-data
            android:name="android.nfc.action.TECH_DISCOVERED"
            android:resource="@xml/nfc_tech_filter" />
    </activity>

我用解决方案研究了类似的问题，但似乎没有一个适用于我的实现。我在这里做错了什么？

Answer 1

我不确定你们是否解决了这个问题。但是，我试图做同样的事情，有一个 NFC 片段来读取标签，对我来说，问题是当我将意图移动到 onNewIntent 开始工作的活动时，意图没有在片段中的正确时间初始化，并且从那里我将意图发送到要处理的片段。不确定这是否仍然有用，如果有更好的方法可以随意分享，因为如果可能的话，我希望片段完全独立于活动。

Answer 2

在活动中这样做：

    override fun onNewIntent(intent: Intent) {
        super.onNewIntent(intent)
        setIntent(intent)//This will be used in NFCCardFragment
    }

在activity中调用setIntent时，在fragment中调用onResume方法automatically！

所以你可以像这样从中获得意图：

    override fun onResume() {
        super.onResume()
        nfcAdapter?.let { adapter ->
            if (adapter.isEnabled)
                adapter.enableForegroundDispatch(
                    requireActivity(),
                    nfcPendingIntent,
                    nfcFilters,
                    nfcTechLists
                )
        }

        //this part is the point
        requireActivity().intent?.let {
        //Do whatever you want!
            resolveNFCIntent(it)
        }
    }

Answer 3

onNewIntent 属于 Activity，因此您不能直接在片段中使用它。您可以做的是在数据到达 onNewIntent 时将数据从您的 Activity 传递给您的片段，前提是您有对片段的引用。

@Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
List<Fragment> allFragments = getSupportFragmentManager().getFragments();
Fragment fragment;
    for (Fragment fragment : allFragments) {
        if (fragment instanceof Home) {
            Home frgHome = (Home) fragment;
            frgHome.onNewIntent(intent);
        }
    }
}

Answer 4

您的问题是，您的 fragment 变量永远不会初始化，因此 fragment instanceof Home 条件永远不会起作用。

您希望将 newIntent 数据传递给位于ViewPager 中的Home 片段作为第一页（即第0 个索引）。所以你可以让你的SectionsPagerAdapter通过getItem(int position)方法给你Home片段。但是，如果您查看 getItem() 方法的实现，您总是会返回片段的新实例

case 0:
    Home home= new Home();
    return home;

因此，如果您调用mSectionAdapater.getItem()，它将为您提供另一个 Home Fragment 实例，而不是当前正在显示的实例。所以你需要先在你的SectionsPagerAdapter 中做一些更改，我在下面显示。

用这个改变你的SectionsPagerAdapter：

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private List<Fragment> mFragments = new ArrayList<>();

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        mFragments.add(new Home());
        mFragments.add(new Writer());
        mFragments.add(new Reader());
        mFragments.add(new Others());
        mFragments.add(new Alarm());
    }

    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return mFragments.size();
    }

    /*to set text instead of icons*/
    public CharSequence getPageTitle(int position) {

        return null;
    }
}

现在，在 Activity 中更改 onNewIntent() 方法：

@Override
public void onNewIntent(Intent intent) {
    setIntent(intent);
    super.onNewIntent(intent);
    Toast.makeText(this, "I am in TabsHome", Toast.LENGTH_SHORT).show();
    System.out.print("I am here in TabsHome");
    Log.d("my tag", "I am here");
    // Notify fragment about the new intent

    Fragment fragment = mSectionsPagerAdapter.getItem(0);

    if(fragment instanceof Home){
       Log.d("my tag", "I am here");
       Home hm = (Home) fragment;
       hm.onNewIntent(intent);
    }

}

Answer 5

你能做的就是使用一个接口。

在您的 Activity 中使用：

private interfaceName listener;

public void setNewIntentListner(Fragment fragmentName) {
    listener =  fragmentName;
}

 @Override
protected void onNewIntent(Intent intent) {
    if(listener != null){
    listener.newIntent(intent);
    }

    return;
}

界面：

public interface InterfaceName{
    void newIntent(Intent intent);
}

终于在你的片段中：

public class fragmentName extends Fragment implements interfaceName{

    private MainActivity mainActivity;

    @Override
    public void onStart() {
        super.onStart();
        mainActiviyt = (MainActivity)getActivity();
        mainActivity.setNewIntentListner(this);

    }
    @Override
    public void newIntent(Intent intent) {
    // here you have your intent in your fragment 
    }

}