java - 无需按钮即可在 Activity 开始时播放文本到语音

Question

我在我的应用程序中使用文本转语音，并且我已经能够让它在我的所有按钮上正常工作。但是，当我尝试在启动 Activity 中使用文本转语音时，应用程序崩溃了。这是一个空指针异常，所以我知道我只是错误地编码了它。为了澄清我想要它做什么。我希望它在泼水 Activity 期间说话。当启动 Activity hibernate 时，我希望它再次说话，告诉用户它已完成加载。我已经为启动 Activity 包含了 java。

public class mainj extends Activity implements OnInitListener {

    private TextToSpeech myTTS;
    // status check code
    private int MY_DATA_CHECK_CODE = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.loadscreen);
        Thread logoTimer = new Thread() {
            public void run() {
                try {
                    try {
                        sleep(5000);
                        speakWords("loading");
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

                    Intent menuIntent = new Intent("android.intent.action.MENU");
                    startActivity(menuIntent);

                    Intent checkTTSIntent = new Intent();
                    checkTTSIntent
                            .setAction(TextToSpeech.Engine.ACTION_CHECK_TTS_DATA);
                    startActivityForResult(checkTTSIntent, MY_DATA_CHECK_CODE);
                }

                finally {
                    finish();
                }
            }

        };
        logoTimer.start();
    }

    // speak the user text
    private void speakWords(String speech) {

        // speak straight away
        myTTS.speak(speech, TextToSpeech.QUEUE_FLUSH, null);
    }

    // act on result of TTS data check
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        if (requestCode == MY_DATA_CHECK_CODE) {
            if (resultCode == TextToSpeech.Engine.CHECK_VOICE_DATA_PASS) {
                // the user has the necessary data - create the TTS
                myTTS = new TextToSpeech(this, this);
            } else {
                // no data - install it now
                Intent installTTSIntent = new Intent();
                installTTSIntent
                        .setAction(TextToSpeech.Engine.ACTION_INSTALL_TTS_DATA);
                startActivity(installTTSIntent);
            }
        }
    }

    // setup TTS
    public void onInit(int initStatus) {

        // check for successful instantiation
        if (initStatus == TextToSpeech.SUCCESS) {
            if (myTTS.isLanguageAvailable(Locale.US) == TextToSpeech.LANG_AVAILABLE)
                myTTS.setLanguage(Locale.US);
        } else if (initStatus == TextToSpeech.ERROR) {
            Toast.makeText(this, "Sorry! Text To Speech failed...",
                    Toast.LENGTH_LONG).show();
        }
    }

}

Answer 1

在你 sleep 后，你就在线程的开头调用speakWords。调用 myTTS.speak。此时查看您的代码，myTTS 似乎尚未初始化并且为 null，因此会因 NPE 而崩溃。

这段代码应该可以防止 NPE，但是如果 TTS 引擎的初始化时间太长，那么您将不会看到“正在加载”。另外，我猜测 5 秒(顺便说一句，这是一个非常长的时间) sleep 是为了让它初始化？

public class mainj extends Activity implements OnInitListener {

private TextToSpeech myTTS;
// status check code
private int MY_DATA_CHECK_CODE = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.loadscreen);
    Intent checkTTSIntent = new Intent();
    checkTTSIntent
         .setAction(TextToSpeech.Engine.ACTION_CHECK_TTS_DATA);
    startActivityForResult(checkTTSIntent, MY_DATA_CHECK_CODE);
    Thread logoTimer = new Thread() {
        public void run() {
            try {
                try {
                    sleep(5000);
                    speakWords("loading");
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                Intent menuIntent = new Intent("android.intent.action.MENU");
                startActivity(menuIntent);

            }

            finally {
                finish();
            }
        }

    };
    logoTimer.start();
}

// speak the user text
private void speakWords(String speech) {

    // speak straight away
   if(myTTS != null)
   {
        myTTS.speak(speech, TextToSpeech.QUEUE_FLUSH, null);
   }
}

// act on result of TTS data check
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

    if (requestCode == MY_DATA_CHECK_CODE) {
        if (resultCode == TextToSpeech.Engine.CHECK_VOICE_DATA_PASS) {
            // the user has the necessary data - create the TTS
            myTTS = new TextToSpeech(this, this);
        } else {
            // no data - install it now
            Intent installTTSIntent = new Intent();
            installTTSIntent
                    .setAction(TextToSpeech.Engine.ACTION_INSTALL_TTS_DATA);
            startActivity(installTTSIntent);
        }
    }
}

// setup TTS
public void onInit(int initStatus) {

    // check for successful instantiation
    if (initStatus == TextToSpeech.SUCCESS) {
        if (myTTS.isLanguageAvailable(Locale.US) == TextToSpeech.LANG_AVAILABLE)
            myTTS.setLanguage(Locale.US);
    } else if (initStatus == TextToSpeech.ERROR) {
        Toast.makeText(this, "Sorry! Text To Speech failed...",
                Toast.LENGTH_LONG).show();
    }
}

}