阅读NFC标签和返回按钮

Question

我的问题是关于后退按钮和后台堆栈，我有一个阅读nfc标签的应用程序，所以我先启动Activity A，然后进入活动B，在manifest中声明SingleTop。 我将手机标记为标签，它读取标签，此时一切正常。

如果我按后退按钮，它可以追溯到活动B，而不是去活性的，然后如果我按了后退按钮它再次进入到活动A.

像这样：

A-> B->阅读标签 - > B->按下后退按钮 - > B->按下后退按钮 - > A->按下后退按钮 - >关闭应用程序。

，我想是这样的：

A-> B->阅读Tags-> B->按返回按钮 - > A->按后退按钮 - >关闭应用程序。

我只想要B的一个实例。 我试过单个任务，但问题是我点击了应用程序图标，并且活动b已启动，但读取标记的意图被保留。

public class B extends Activity { 
private static final String KINVEY_KEY = YOUR_APP_KEY; 
private static final String KINVEY_SECRET_KEY = 'YOUR_APP_SECRET_KEY'; 

private KCSClient kinveyClient; 
private NfcAdapter mNfcAdapter; 

private Button mEnableWriteButton; 
private EditText mTextField; 
private ProgressBar mProgressBar; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_tags); 

    mTextField = (EditText) findViewById(R.id.text_field); 

    mProgressBar = (ProgressBar) findViewById(R.id.progress_bar); 
    mProgressBar.setVisibility(View.GONE); 

    mEnableWriteButton = (Button) findViewById(R.id.enable_write_button); 
    mEnableWriteButton.setOnClickListener(new OnClickListener() { 

     @Override 
     public void onClick(View v) { 
      setTagWriteReady(!isWriteReady); 
      mProgressBar.setVisibility(isWriteReady ? View.VISIBLE : View.GONE); 
     } 
    }); 

    mNfcAdapter = NfcAdapter.getDefaultAdapter(this); 
    if (mNfcAdapter == null) { 
     Toast.makeText(this, 'Sorry, NFC is not available on this device', Toast.LENGTH_SHORT).show(); 
     finish(); 
    } 

    // Initialize Kinvey 
    KinveySettings settings = new KinveySettings(KINVEY_KEY, KINVEY_SECRET_KEY); 
    kinveyClient = KCSClient.getInstance(this.getApplicationContext(), settings); 
} 

private boolean isWriteReady = false; 

public void setTagWriteReady(boolean isWriteReady) { 
    this.isWriteReady = isWriteReady; 
    if (isWriteReady) { 
     IntentFilter[] writeTagFilters = new IntentFilter[] { new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED) }; 
     mNfcAdapter.enableForegroundDispatch(TagsActivity.this, NfcUtils.getPendingIntent(TagsActivity.this), 
       writeTagFilters, null); 
    } else { 
     // Disable dispatch if not writing tags 
     mNfcAdapter.disableForegroundDispatch(TagsActivity.this); 
    } 
    mProgressBar.setVisibility(isWriteReady ? View.VISIBLE : View.GONE); 
} 

@Override 
public void onNewIntent(Intent intent) { 
    // onResume gets called after this to handle the intent 
    setIntent(intent); 
} 

@Override 
public void onResume() { 
    super.onResume(); 
    if (isWriteReady && NfcAdapter.ACTION_TAG_DISCOVERED.equals(getIntent().getAction())) { 
     processWriteIntent(getIntent()); 
    } else if (!isWriteReady 
      && (NfcAdapter.ACTION_TAG_DISCOVERED.equals(getIntent().getAction()) || NfcAdapter.ACTION_NDEF_DISCOVERED 
        .equals(getIntent().getAction()))) { 
     processReadIntent(getIntent()); 
    } 
} 

private static final String MIME_TYPE = 'application/com.tapped.nfc.tag'; 


public void processWriteIntent(Intent intent) { 
    if (isWriteReady && NfcAdapter.ACTION_TAG_DISCOVERED.equals(getIntent().getAction())) { 

     Tag detectedTag = getIntent().getParcelableExtra(NfcAdapter.EXTRA_TAG); 

     String tagWriteMessage = mTextField.getText().toString(); 
     byte[] payload = new String(tagWriteMessage).getBytes(); 

     if (detectedTag != null && NfcUtils.writeTag(
       NfcUtils.createMessage(MIME_TYPE, payload), detectedTag)) { 

      Toast.makeText(this, "Wrote '" + tagWriteMessage + "' to a tag!", 
        Toast.LENGTH_LONG).show(); 
      setTagWriteReady(false); 
     } else { 
      Toast.makeText(this, "Write failed. Please try again.", Toast.LENGTH_LONG).show(); 
     } 
    } 
} 

public void processReadIntent(Intent intent) { 
    List<NdefMessage> intentMessages = NfcUtils.getMessagesFromIntent(intent); 
    List<String> payloadStrings = new ArrayList<String>(intentMessages.size()); 

    for (NdefMessage message : intentMessages) { 
     for (NdefRecord record : message.getRecords()) { 
      byte[] payload = record.getPayload(); 
      String payloadString = new String(payload); 

      if (!TextUtils.isEmpty(payloadString)) 
       payloadStrings.add(payloadString); 
     } 
    } 

    if (!payloadStrings.isEmpty()) { 
     String content = TextUtils.join(",", payloadStrings); 
     Toast.makeText(TagsActivity.this, "Read from tag: " + content, 
       Toast.LENGTH_LONG).show(); 
     saveTag(content); 
    } 
} 

private void saveTag(String tagMessage){ 
    TagReadEntity tag = new TagReadEntity(UUID.randomUUID().toString(), 
      tagMessage, System.currentTimeMillis()); 

    kinveyClient.mappeddata("tags").save(tag, new ScalarCallback<TagReadEntity>() { 

     @Override 
     public void onSuccess(TagReadEntity tag) { 
      Log.i("NFC Demo", "Saved tag!"); 
     } 

     @Override 
     public void onFailure(Throwable e) { 
      Log.e("NFC Demo", "Error saving tag", e); 
     } 
    }); 
} 
} 

和清单：

<activity 
     android:name=".TagsActivity" 
     android:label="@string/title_activity_tags" 
     android:launchMode="singleTop" 
     android:screenOrientation="portrait" > 
     <intent-filter> 
      <action android:name="android.nfc.action.NDEF_DISCOVERED" /> 

      <category android:name="android.intent.category.DEFAULT" /> 

      <data android:mimeType="application/com.tapped.nfc.tag" /> 
     </intent-filter> 
     <intent-filter> 
      <action android:name="android.nfc.action.TAG_DISCOVERED" /> 

      <category android:name="android.intent.category.DEFAULT" /> 

      <data android:mimeType="application/com.tapped.nfc.tag" /> 
     </intent-filter> 
    </activity> 

Answer 1

香港专业教育学院申报的任务，因为singletask，似乎现在的工作。

android:launchMode="singleTask" 

香港专业教育学院尝试非标准和每次香港专业教育学院读一个NFC标签，一个新的活动被创造了，如果读10个标签，我需要TI按后退按钮9times。 之后，我尝试了singleTop，现在我从A到B，然后无论我读了多少次标签，都只有2个B的实例，所以我需要按回来一次去活动B，然后再回来关闭应用程序。