Question

我对Android开发完全陌生，必须编写一个简单的应用程序来读取大学的nfc标签（使用nexus s）。

我的问题是，当nexus发现一个标签时，我的应用程序没有列在“选择一个动作”-popup中。目的是使用前缀调度方法读取标签，如http://developer.android.com/guide/topics/nfc/index.html中所述和 http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/nfc/ForegroundDispatch.html

我认为清单中缺少一些东西，但我不知道是什么。这是清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.iforge.android.nfc"
>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.NFC" />
<uses-permission android:name="android.permission.CALL_PHONE" />
<application
    android:icon="@drawable/icon"
    android:label="@string/app_name"
>
<activity android:name=".simulator.FakeTagsActivity"
    android:theme="@android:style/Theme.NoTitleBar">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>

</activity>

    <activity android:name="TagViewer"
        android:theme="@android:style/Theme.NoTitleBar"
    >
        <intent-filter>
            <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
            <data android:mimeType="mime/type" />
        </intent-filter>

        <intent-filter>
            <action android:name="android.nfc.action.TECH_DISCOVERED"/>

        </intent-filter>

        <intent-filter>
            <action android:name="android.nfc.action.TAG_DISCOVERED"/>
        </intent-filter>
    </activity>
</application>
<uses-sdk android:minSdkVersion="10" />
<uses-feature android:name="android.hardware.nfc" android:required="true" />

这是发现标记时应该调用的活动的代码（它是从android NFCDemo以及ForegroundDispatch示例构建的）：

public class TagViewer extends Activity 
{

WebView webView;
private NfcAdapter mAdapter;
private PendingIntent mPendingIntent;
private IntentFilter[] mFilters;
private String[][] mTechLists;

@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    mAdapter = NfcAdapter.getDefaultAdapter(this);
    mPendingIntent = PendingIntent.getActivity(
            this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);

    IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
    try {
        ndef.addDataType("*/*");    /* Handles all MIME based dispatches. 
                                       You should specify only the ones that you need. */
    }
    catch (MalformedMimeTypeException e) {
        throw new RuntimeException("fail", e);
    }

    mFilters = new IntentFilter[] {
            ndef,
    };

    mTechLists = new String[][] { new String[] { NfcF.class.getName() } };


    setContentView(R.layout.tag_viewer);
    webView = (WebView) findViewById(R.id.webView1);
    webView.getSettings().setJavaScriptEnabled(true); 
    webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(false);
    webView.getSettings().setPluginsEnabled(false);
    webView.getSettings().setSupportMultipleWindows(false);
    webView.getSettings().setSupportZoom(false);
    webView.setVerticalScrollBarEnabled(false);
    webView.setHorizontalScrollBarEnabled(false);

    resolveIntent(getIntent());
}

@Override
public void onResume() {
    super.onResume();
    mAdapter.enableForegroundDispatch(this, mPendingIntent, mFilters, mTechLists);
}

@Override
public void onPause() {
    super.onPause();
    mAdapter.disableForegroundDispatch(this);
}

void resolveIntent(Intent intent) 
{
    // Parse the intent
    String action = intent.getAction();
    if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action)) 
    {
        // When a tag is discovered we send it to the service to be save. We
        // include a PendingIntent for the service to call back onto. This
        // will cause this activity to be restarted with onNewIntent(). At
        // that time we read it from the database and view it.
        Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
        NdefMessage[] msgs;
        if (rawMsgs != null) 
        {
            msgs = new NdefMessage[rawMsgs.length];
            for (int i = 0; i < rawMsgs.length; i++) 
            {
                msgs[i] = (NdefMessage) rawMsgs[i];
            }
        } 
        else 
        {
            // Unknown tag type
            byte[] empty = new byte[] {};
            NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN, empty, empty, empty);
            NdefMessage msg = new NdefMessage(new NdefRecord[] {record});
            msgs = new NdefMessage[] {msg};
        }
        // Setup the web-view
        setUpWebView(msgs);
    } 
    else 
    {
        Log.e("ViewTag", "Unknown intent " + intent);
        finish();
        return;
    }
}

void setUpWebView(NdefMessage[] msgs) 
{
    if (msgs == null || msgs.length == 0) return;

    String urlToLoad = MessageParser.parseMessage(msgs[0]);
    if(!urlToLoad.matches("")) webView.loadUrl(urlToLoad);

}

@Override
public void onNewIntent(Intent intent) 
{
    setIntent(intent);
    resolveIntent(intent);
    Log.i("Foreground dispatch", "Discovered tag with intent: " + intent);
}
}

我尝试了很多，但没有任何作用。如果有人能告诉我我错过了什么会很棒。我没时间了： - （

请

感谢

Answer 1

您的清单文件需要在单独的技术过滤器xml中处理技术发现的意图，如下所示：

<intent-filter>
       <action android:name="android.intent.action.MAIN" />
       <category android:name="android.intent.category.LAUNCHER" />
     </intent-filter>
     <intent-filter>
        <action android:name="android.nfc.action.TECH_DISCOVERED"/>
            </intent-filter>
            <meta-data android:name="android.nfc.action.TECH_DISCOVERED"
                               android:resource="@xml/nfc_tech_filter" />
            <intent-filter>
                <action android:name="android.nfc.action.TAG_DISCOVERED"/>
            </intent-filter>

然后你的res / xml / nfc_tech_filter.xml必须像这样处理你想要的nfc技术：

<resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
    <tech-list>
        <tech>android.nfc.tech.MifareUltralight</tech>
        <tech>android.nfc.tech.Ndef</tech>
        <tech>android.nfc.tech.NfcA</tech>
    </tech-list>
    <tech-list>
        <tech>android.nfc.tech.MifareClassic</tech>
        <tech>android.nfc.tech.Ndef</tech>
        <tech>android.nfc.tech.NfcA</tech>
    </tech-list>
</resources>

每个技术节点都像一个AND，而技术列表节点就像和OR一样。我建议您首先使用NFC标签阅读器等工具扫描您的标签，以便了解您的技术人员。

然后在java代码中，您可以启用/禁用您的前台调度系统，就像其他已经技术的网站一样，我设置了与xml中相同的技术，如下所示：

private void setUpForegroundDispatchSystem()
    {
        this.nfcAdapter = NfcAdapter.getDefaultAdapter(this);

        this.pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);

        IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
        try {
            ndef.addDataType("*/*");    /* Handles all MIME based dispatches. 
                                           You should specify only the ones that you need. */
          ndef.addDataScheme("http");
        }
        catch (MalformedMimeTypeException e) {
            throw new RuntimeException("fail", e);
        }
        this.intentFiltersArray = new IntentFilter[] {ndef};
        this.techListsArray = new String[][] { new String[] { MifareUltralight.class.getName(), Ndef.class.getName(), NfcA.class.getName()},
                                               new String[] { MifareClassic.class.getName(), Ndef.class.getName(), NfcA.class.getName()}};

    }

您必须在“暂停”和“恢复”方法中启用和禁用此功能。希望这些信息对您有所帮助。

Answer 2

前台调度明确要求使用已正确配置的Activity：看起来您不能使用AndroidManifest.xml中设置的IntentFilter进行前台调度（您的应用必须实际位于前台），即跑步）。以下代码似乎正常工作（我刚刚测试过）以防您仍然感兴趣（ACTION_TAG_DISCOVERED就是我正在观看的内容）：

private NfcAdapter mAdapter;
    private PendingIntent pendingIntent;
    private IntentFilter[] mFilters;
    private String[][] mTechLists;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.main);

        mAdapter = NfcAdapter.getDefaultAdapter(this);
        pendingIntent = PendingIntent.getActivity(
          this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);

     // Setup an intent filter for all MIME based dispatches
        IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
        try {
            ndef.addDataType("*/*");
        } catch (MalformedMimeTypeException e) {
            throw new RuntimeException("fail", e);
        }
        IntentFilter td = new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED);
        mFilters = new IntentFilter[] {
                ndef, td
        };

        // Setup a tech list for all NfcF tags
        mTechLists = new String[][] { new String[] { 
                NfcV.class.getName(),
                NfcF.class.getName(),
                NfcA.class.getName(),
                NfcB.class.getName()
            } };
    }

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

        mAdapter.enableForegroundDispatch(this, pendingIntent, mFilters, mTechLists);
    }

    @Override
    public void onPause()
    {
        super.onPause();
        mAdapter.disableForegroundDispatch(this);
    }

    @Override
    public void onNewIntent(Intent intent){
        // fetch the tag from the intent
        Tag t = (Tag)intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
        String tlist = getTechList(t);
        android.util.Log.v("NFC", "Discovered tag ["+tlist+"]["+t+"] with intent: " + intent);
        android.util.Log.v("NFC", "{"+t+"}");
}

Answer 3

intent-filter元素中缺少类别元素？参见

Android NFC: can we use intent filter with mime type? (android 2.3.3)

您也可以尝试在代码中完全不使用IntentFilter。

Answer 4

如果启动Activity并注册foregroudn dispatch，您所要做的就是为ACTION_TAG_DISCOVERED注册一个intent过滤器 - 这是最低过滤器并匹配所有发现的标签。如果您想要更具体，您可以为标签技术或包含ndef的标签注册意图过滤器。

但是如果你想通过点击标签从主屏幕启动你的应用程序，你可以采取不同的方式。我成功地将mime消息放到标签上，并将mime类型注册到我的活动中。另一种方法是将URL放到标签上，然后注册一个算法过滤器，用于计算方案和主机。对于哑剧，这就是你需要的：

要进行此匹配，标记需要具有带有mime的NDEF mime消息，如上所述。

Android NFC前台调度问题

4 个答案: