Question

我有一个实现MainActivity的活动（TextToSpeech）并且运作正常。当一个按钮的onClick被调用时，它会说出EditText中输入的内容。

MainActivity：

public class MainActivity extends AppCompatActivity implements TextToSpeech.OnInitListener{

    private TextToSpeech engine;
    private EditText text;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        text = (EditText) findViewById(R.id.text);
        engine = new TextToSpeech(this, this);

        Intent i=getIntent();
        Bundle b=i.getExtras();
        word=b.getString("word");
        speakText2(word);
    }

    // speakText is called by onClick button
    public void speakText(View v) {
        String textContents = text.getText().toString();
        engine.speak(textContents, TextToSpeech.QUEUE_FLUSH, null, null);
    }

    public void speakText2(String textContents) {
        engine.speak(textContents, TextToSpeech.QUEUE_ADD, null, null);
    }

    @Override
    public void onInit(int i) {
        if (i == TextToSpeech.SUCCESS) {
            //Setting speech Language
            engine.setLanguage(Locale.ENGLISH);
            engine.setPitch(1);
        }
    }
}

现在，我想从另一个活动中调用MainActivity并传递一个字符串来说出来。我试过了：

MainActivity mainactivity = new MainActivity();
String word;
word = "speak";
mainactivity.speakText2(word); // Error

但是，得到错误：

Caused by: 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
at MainActivity.speakText2(TTSEngine.java:53)

我尝试使用其他活动的意图：

Intent intent = new Intent(this, MainActivity.class);
intent.putExtra("word", word);
startActivity(intent);

但是，得到错误：

I/TextToSpeech: Sucessfully bound to com.google.android.tts
W/TextToSpeech: speak failed: not bound to TTS engine
W/TextToSpeech: speak failed: not bound to TTS engine
W/TextToSpeech: speak failed: not bound to TTS engine
I/TextToSpeech: Connected to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
I/TextToSpeech: Set up connection to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}

我尝试在我想要使用它的活动中实现TextToSpeech。但是，它在第一次调用speakText2并且给出错误时不起作用：

W/TextToSpeech: speak failed: not bound to TTS engine
I/TextToSpeech: Connected to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
I/TextToSpeech: Set up connection to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}

其余时间它完美运作。知道如何解决这个问题吗？

Answer 1

在onInit完成后，你只能让引擎说话，所以在onInit（）中执行以下操作：

if（status == TextToSpeech.SUCCESS）{ speakText2（字）;

}

Answer 2

您必须使用Intent来启动Activity。见https://developer.android.com/training/basics/firstapp/starting-activity.html

当您手动创建Activity实例时，未调用onCreate方法（以及任何其他生命周期方法） - 这就是您获取NPE访问engine属性的原因 - 它没有初始化。

如何从其他活动调用TextToSpeech活动？

2 个答案: