我正在尝试使用我在应用中常用的字符串而不是文本来编写NDef消息。
示例：
@Override
public NdefMessage createNdefMessage(NfcEvent event) {
Time time = new Time();
time.setToNow();
String text = ("Beam me up!\n\n" +
"Beam Time: " + time.format("%H:%M:%S"));
NdefMessage msg = new NdefMessage(NdefRecord.createMime(
"application/com.nfc.linkingmanager.beam", text.getBytes())
/**
我想写下：
的值android:id="@+id/timeEdit
而不是：
Beam me up!\n\n" +
"Beam Time: " + time.format("%H:%M:%S"
VIEWCOUNTRY.JAVA（另一个能够引用我正在寻找的值的Java类：timeEdit）
public class ViewCountry extends Activity {
private long rowID;
private TextView nameTv;
private TextView capTv;
private TextView codeTv;
private TextView timeTv;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.view_country);
setUpViews();
Bundle extras = getIntent().getExtras();
rowID = extras.getLong(CountryList.ROW_ID);
}
private void setUpViews() {
nameTv = (TextView) findViewById(R.id.nameText);
capTv = (TextView) findViewById(R.id.capText);
timeTv = (TextView) findViewById(R.id.timeEdit);
codeTv = (TextView) findViewById(R.id.codeText);
}
@Override
protected void onResume()
{
super.onResume();
new LoadContacts().execute(rowID);
}
private class LoadContacts extends AsyncTask<Long, Object, Cursor>
{
DatabaseConnector dbConnector = new DatabaseConnector(ViewCountry.this);
@Override
protected Cursor doInBackground(Long... params)
{
dbConnector.open();
return dbConnector.getOneContact(params[0]);
}
@Override
protected void onPostExecute(Cursor result)
{
super.onPostExecute(result);
result.moveToFirst();
// get the column index for each data item
int nameIndex = result.getColumnIndex("name");
int capIndex = result.getColumnIndex("cap");
int codeIndex = result.getColumnIndex("code");
int timeIndex = result.getColumnIndex("time");
nameTv.setText(result.getString(nameIndex));
capTv.setText(result.getString(capIndex));
// timeTv.setText(result.getInt(timeIndex)); // <--- HERE WAS AN ERROR
timeTv.setText(result.getString(timeIndex)); // time was stored as Sting all the time
codeTv.setText(result.getString(codeIndex));
result.close();
dbConnector.close();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
super.onCreateOptionsMenu(menu);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.view_country_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case R.id.editItem:
Intent addEditContact =
new Intent(this, AddEditDevice.class);
addEditContact.putExtra(CountryList.ROW_ID, rowID);
addEditContact.putExtra("name", nameTv.getText());
addEditContact.putExtra("cap", capTv.getText());
addEditContact.putExtra("code", codeTv.getText());
startActivity(addEditContact);
return true;
case R.id.deleteItem:
deleteContact();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
private void deleteContact()
{
AlertDialog.Builder alert = new AlertDialog.Builder(ViewCountry.this);
alert.setTitle(R.string.confirmTitle);
alert.setMessage(R.string.confirmMessage);
alert.setPositiveButton(R.string.delete_btn,
new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int button)
{
final DatabaseConnector dbConnector =
new DatabaseConnector(ViewCountry.this);
AsyncTask<Long, Object, Object> deleteTask =
new AsyncTask<Long, Object, Object>()
{
@Override
protected Object doInBackground(Long... params)
{
dbConnector.deleteContact(params[0]);
return null;
}
@Override
protected void onPostExecute(Object result)
{
finish();
}
};
deleteTask.execute(new Long[] { rowID });
}
}
);
alert.setNegativeButton(R.string.cancel_btn, null).show();
}
}
答案 0 :(得分：0)
您没有在代码中显示使用此方法的位置，因此它可能比这更复杂，但一般来说：
public MyActivity extends Activity{
...
private final TextView tvTimeStamp; // <--- declare it, it's class level so is available to all methods of this class
...
@Override
public void onCreate(Bundle savedInstance){
super.onCreate(savedInstance);
...
setContentView(R.layout.my_activity_layout);
tvTimeStamp = (TextView)findViewById(R.id.timeEdit); // <---- get a reference to it
...
}
@Override
public NdefMessage createNdefMessage(NfcEvent event) {
Time time = new Time();
time.setToNow();
String text = ("Beam me up!\n\n" +
"Beam Time: " + time.format("%H:%M:%S"));
NdefMessage msg = new NdefMessage(NdefRecord.createMime(
tvTimeStamp.getText(), text.getBytes()) // <----- use it here!
}
}
要在另一个类中获取TextView的值，您可以使用以下技术：
一个：通过添加构造函数，将TextView的值传递给构建NFC消息的类，例如
public class MyNfcClass{
private String timeStamp;
public void MyNfcClass(String timeStamp){
this.timeStamp = timeStamp;
}
}
这样做的缺点是，如果TextView发生变化，您的NFC类将无法知道。
两个：定义一个接口。请参阅本教程http://www.tutorialspoint.com/java/java_interfaces.htm
三：当且仅当NFC类的生命周期等于或小于Activity的生命周期时，才将对TextView的引用传递给类。只有这样才能真正了解生命周期，并且您可以保证不会泄漏参考。如果你不明白这一点，那就认为它是verboten;）
四：如果Nfc类在另一个Activity中实例化，从另一个Activity（或活动链中的某个地方）开始，则传递用于启动Activity的Intent extras中的值。与选项1相同的缺点。
总之，选项2是首选。这是Java和Android的“方式”。
祝你好运。