点击另一个NFC设备后，无法进入onNewIntent

Question

主要问题是，当我用其他NFC启用的手机(NFC是ON)点击我的手机时，我们无法去onNewIntent()。在除主要意图之外的任何情况下，我都无法访问newintent。NDEF、TECH、TAG三种滤镜我都试过了。

package com.example.nfctry;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.os.Bundle;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.view.Menu;
import android.widget.Toast;
public class MainActivity extends Activity {
NfcAdapter adapter;
PendingIntent pendingIntent;
IntentFilter writeTagFilters[];
boolean writeMode;
Tag myTag;
Context ctx;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ctx = this;
    adapter = NfcAdapter.getDefaultAdapter(this);
    pendingIntent = PendingIntent.getActivity(this,0,new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);
    IntentFilter tagDetected = new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED);
    tagDetected.addCategory(Intent.CATEGORY_DEFAULT);
    writeTagFilters = new IntentFilter[] {tagDetected};
    onNewIntent(getIntent());

}
@Override
protected void onNewIntent(Intent intent)
{
    Toast.makeText(this,""+intent.getAction(), Toast.LENGTH_LONG).show();
    super.onNewIntent(intent);
    // getIntent() should always return the most recent
    if(NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction()))
    {
        myTag= intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
        Toast.makeText(this,"DETECTED muahhhhh"  + myTag.toString(), Toast.LENGTH_LONG).show();
    }

}

@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;
}
}

在android mainfest中我也添加了intentfilters

 <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.nfctry"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
    android:minSdkVersion="15"
    android:targetSdkVersion="17" />
<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.nfctry.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
        <action android:name="android.nfc.action.NDEF_DISCOVERED" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.nfc.action.TECH_DISCOVERED" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.nfc.action.TAG_DISCOVERED" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
        <meta-data
        android:name="android.nfc.action.TECH_DISCOVERED"
        android:resource="@xml/nfc_tech_filter" />
    </activity>
</application>

Answer 1

这与您使用的TAG过滤器无关。只有当使用launchMode: singleTop或singleTask调用intent时，您的onNewIntent才会被调用，当然，当您自己调用它时。当你的应用程序在前面时，它不会捕捉到NDEF/TECH/TAG发现。你需要使用ForegroundDispatching来捕捉当前应用程序中的标签发现事件。

当您的ForegroundDispatch捕获事件并且您在PendingIntent中使用PendingIntent.getActivity和标志FLAG_ACTIVITY_SINGLE_TOP时，它将调用onNewIntent。

你应该在onResume:

中启用ForegroundDispatch

@Override
public void onResume()
{
    super.onResume();
    PendingIntent pendingIntent     = PendingIntent.getActivity(this,0,new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);     
    IntentFilter[] intentFilters    = { new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED) };      
    adapter.enableForegroundDispatch(   this,
            pendingIntent, 
            intentFilters,
            new String[][]{
            new String[]{"android.nfc.tech.NfcA"}
        });     
}

并在onPause中禁用它:

@Override
public void onPause() {
    super.onPause();
    if (adapter != null) 
    {
        try {
            adapter.disableForegroundDispatch(this);
        } 
        catch (NullPointerException e) {
        }
    }
}  

要在当前代码中使用ForegroundDispatch捕获TAG事件，它将像这样:

public class MainActivity extends Activity {
    NfcAdapter adapter;
    PendingIntent pendingIntent;
    IntentFilter writeTagFilters[];
    boolean writeMode;
    Tag myTag;
    Context ctx;    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ctx = this;
        adapter = NfcAdapter.getDefaultAdapter(this);
        onNewIntent(this.getIntent());      
    }

    @Override
    public void onNewIntent(Intent data) 
    {
        Toast.makeText(this,""+intent.getAction(), Toast.LENGTH_LONG).show();
        super.onNewIntent(intent);
        // getIntent() should always return the most recent
        if(NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction()))
        {
            myTag= intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
            Toast.makeText(this,"DETECTED muahhhhh"  + myTag.toString(), Toast.LENGTH_LONG).show();
        }
    }   
    @Override
    public void onResume()
    {
        super.onResume();
        PendingIntent pendingIntent     = PendingIntent.getActivity(this,0,new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);     
        IntentFilter[] intentFilters    = { new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED) };      
        adapter.enableForegroundDispatch(   this,
                pendingIntent, 
                intentFilters,
                new String[][]{
                new String[]{"android.nfc.tech.NfcA"}
            });     
    }
    @Override
    public void onPause() {
        super.onPause();
        if (adapter != null) 
        {
            try {
                adapter.disableForegroundDispatch(this);
            } 
            catch (NullPointerException e) {
            }
        }
    }    
    @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;
    }
}

还要注意，你应该在你的清单中添加NFC用户权限。