我正在创建一个有词汇表的应用程序，当用户点击某个项目时，应该使用文字转语音来说明该词。
我想出了如何初始化它并从MainActivity调用该方法，但它似乎不适用于任何其他类。
我是Android开发的新手，也是编码的新手，所以如果有无用的线或没有正确编写，你可以指向我，所以我可以删除/修复。
提前致谢！
public class MainActivity extends ActionBarActivity
implements NavigationDrawerFragment.NavigationDrawerCallbacks, TextToSpeech.OnInitListener/*, TextToSpeech.OnUtteranceCompletedListener*/{ //The 2nd and 3rd implements are part of a test
//private Speaker speaker;
TextToSpeech tts;
public boolean ready = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // this is the original one
tts = new TextToSpeech(this, this);
//tts.setLanguage(Locale.US);
//these methods below are for TTS
@Override
public void onInit(int status) { //for TTS
if (status == TextToSpeech.SUCCESS) {
// Change this to match your
// locale
tts.setLanguage(Locale.US);
ready = true;
} else {
ready = false;
}
}
@Override
protected void onDestroy() { //for TTS
super.onDestroy();
}
public void textToSpeech(String text){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
ttsGreater21(text);
} else {
ttsUnder20(text);
}
}
@SuppressWarnings("deprecation")
private void ttsUnder20(String text) {
HashMap<String, String> map = new HashMap<>();
map.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, "MessageId");
tts.speak(text, TextToSpeech.QUEUE_FLUSH, map);
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private void ttsGreater21(String text) {
String utteranceId=this.hashCode() + "";
tts.speak(text, TextToSpeech.QUEUE_FLUSH, null, utteranceId);
//tts.speak(text, TextToSpeech.QUEUE_FLUSH, null, null);
}
public void ttsExample(View y) {
Button myButton = (Button) y;
textToSpeech("Random joke");
}
}
这是我用来在另一个类中调用它的方法，我确定问题在这里，因为我不知道如何使它工作，我尝试了各种不同的方法。
MainActivity mainActivity = new MainActivity();
mainActivity.textToSpeech(clickedVocab); //<--here
这是列表所在的完整类（以及上面的2行）：
public class VocabularyFragment extends Fragment implements View.OnClickListener {
//initialize vocab list
private ArrayList<String> vocabsList;
private ArrayAdapter<String> itemsAdapter;
private ListView vocabListView;
private String clickedVocab;
private View rootview;
private Speaker speaker;
private final int CHECK_CODE = 0x1;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootview = inflater.inflate(R.layout.fragment_vocab_list,container, false); //this works!
initialVocabList(rootview);
Button b = (Button) rootview.findViewById(R.id.BtnAddVocab);
b.setOnClickListener(this);
return rootview;
}
void initialVocabList(View view) {
// ADD HERE
vocabListView = (ListView)view.findViewById(R.id.vocabList);
//vocabsList = new ArrayList<String>();
//retrieve from SharedPreferences
TinyDB tinydb = new TinyDB(getActivity());
vocabsList = tinydb.getListString("vocabs");
//itemsAdapter = new ArrayAdapter<String>(this, R.layout.vocab_notes_item, items);
itemsAdapter = new ArrayAdapter<String>(getActivity(), R.layout.vocab_notes_item, vocabsList);
vocabListView.setAdapter(itemsAdapter);
// Setup remove listener method call
setupListViewListener();
// Setup Onclick method call
setOnClickListener();
}
private void setupListViewListener() {
vocabListView.setOnItemLongClickListener(
new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapter,
View item, int pos, long id) {
// Remove the item within array at position
/* createDelVocDialog();
if (confirmDelete){ //if boolean is true
items.remove(pos);
}*/
noteDeletedToast(vocabsList.get(pos));
vocabsList.remove(pos);
// Refresh the adapter
itemsAdapter.notifyDataSetChanged();
// Return true consumes the long click event (marks it handled)
return true;
}
});
}
private void setOnClickListener() {
vocabListView.setOnItemClickListener(
new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapter,
View view, int pos, long id) {
//System.out.println("entrei"); //anderson's test "dividir para conquistar"
Context context = view.getContext();
clickedVocab = vocabsList.get(pos);
MainActivity mainActivity = new MainActivity();
mainActivity.textToSpeech(clickedVocab); //<-- HERE!
Toast.makeText(context, "Item: " + clickedVocab, Toast.LENGTH_SHORT).show();
}
});
}
private void noteDeletedToast (String note) {
Toast.makeText(getActivity(), "Vocab note deleted: " + note , Toast.LENGTH_SHORT).show();
}
private void onAddVocab(View v) {
EditText vocabTextBox = (EditText) v.findViewById(R.id.edTextVocab);
if (vocabTextBox.getText().toString().equals("")) { //Check if the EditText is not empty
Toast.makeText(getActivity(), "You forgot to write in the box!", Toast.LENGTH_SHORT).show();
return;
} else {
String itemText = vocabTextBox.getText().toString();
itemsAdapter.add(itemText.trim()); //This also performs "trim" on text
vocabTextBox.setText("");
Toast.makeText(getActivity(), "Note added", Toast.LENGTH_SHORT).show();
//save to SharedPreferences
TinyDB tinydb = new TinyDB(getActivity());
tinydb.putListString("vocabs", vocabsList);
}
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.BtnAddVocab:
onAddVocab(rootview);
break;
}
}
}
最后，这是错误消息：
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.speech.tts.TextToSpeech.speak(java.lang.CharSequence, int, android.os.Bundle, java.lang.String)' on a null object reference
感谢任何帮助=）