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Android文本语音API开发教程

Android 7.0 提供了 TextToSpeech API，可以方便地实现将文本转化为语音的功能。借助于 TextToSpeech API，企业可以很容易地开发出自己的基于文本的语音播放应用程序。

TextToSpeechDemo 是一个使用 TextToSpeech API 进行文本语音播放的实例，修改自 Android SDK 自带的 Demo 实例，其运行效果如图 1 所示。点击 speak 按钮就可以将按钮下方显示的文本内容以语音方式播放出来。

文本语音播放
图 1  文本语音播放

其布局文件 text_to_speech.xml 的内容如下： 
  1. <?xml version="l.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     android:layout_width="match_parent"
  4.     android:layout_height="match_parent"
  5.     android:orientation="vertical">
  6.  
  7.     <Button
  8.         android:id="@+id/again_button"
  9.         android:layout_width="wrap_content"
  10.         android:layout_height="wrap_content"
  11.         android:enabled="false"
  12.         android:text="speak" />
  13.  
  14.     <TextView
  15.         android:id="@+id/textView1"
  16.         android:layout_width="wrap_content"
  17.         android:layout_height="wrap_content"
  18.         android:text="Large Text"
  19.         android:textAppearance="?android:attr/textAppearanceLarge" />
  20. </LinearLayout>
实例 TextToSpeechDemo 中 TextToSpeechActivity.java 的代码如下： 
  1. package introduction.android.texttospeechdemo;
  2.  
  3. import java.util.Locale;
  4. import java.util.Random;
  5.  
  6. import android.app.Activity;
  7. import android.os.Bundle;
  8. import android.speech.tts.TextToSpeech;
  9. import android.util.Log;
  10. import android.view.View;
  11. import android.widget.Button;
  12. import android.widget.TextView;
  13.  
  14. public class TextToSpeechActivity extends Activity implements TextToSpeech.OnInitListener {
  15.     private static final String TAG = "TextToSpeechDemo";
  16.     private TextToSpeech mTts;
  17.     private Button mAgainButton;
  18.     private TextView tv;
  19.  
  20.     @Override
  21.     public void onCreate(Bundle savedInstanceState) {
  22.         super.onCreate(savedInstanceState);
  23.         setContentView(R.layout.activity_text_to_speech);
  24.  
  25.         // Initialize text-to-speech. This is an asynchronous operation.
  26.         // The OnInitListener (second argument) is called after initialization completes.
  27.         mTts = new TextToSpeech(this, this// TextToSpeech.OnInitListener
  28.         );
  29.         tv = (TextView) this.findViewById(R.id.textView1);
  30.  
  31.         // The button is disabled in the layout.
  32.         // It will be enabled upon initialization of the TTS engine.
  33.         mAgainButton = (Button) findViewById(R.id.again_button);
  34.  
  35.         mAgainButton.setOnClickListener(new View.OnClickListener() {
  36.             public void onClick(View v) {
  37.                 sayHello();
  38.             }
  39.         });
  40.     }
  41.  
  42.     @Override
  43.     public void onDestroy() {
  44.         // Don't forget to shutdown!
  45.         if (mTts != null) {
  46.             mTts.stop();
  47.             mTts.shutdown();
  48.         }
  49.         super.onDestroy();
  50.     }
  51.  
  52.     // Implements TextToSpeech.OnInitListener.
  53.     public void onInit(int status) {
  54.         // status can be either TextToSpeech.SUCCESS or TextToSpeech.ERROR.
  55.         if (status == TextToSpeech.SUCCESS) {
  56.             // Set preferred language to US english.
  57.             // Note that a language may not be available, and the result will indicate this,
  58.             int result = mTts.setLanguage(Locale.US);
  59.             // Try this someday for some interesting results.
  60.             // int result mTts.setLanguage(Locale.FRANCE);
  61.             if (result == TextToSpeech.LANG_MISSING_DATA || result == TextToSpeech.LANG_NOT_SUPPORTED) {
  62.                 // Lanuage data is missing or the language is not supported.
  63.                 Log.e(TAG, "Language is not available.");
  64.             } else {
  65.                 // Check the documentation for other possible result codes.
  66.                 // For example, the language may be available for the locale,
  67.                 // but not for the specified country and variant.
  68.  
  69.                 // The TTS engine has been successfully initialized.
  70.                 // Allow the user to press the button for the app to speak again.
  71.                 mAgainButton.setEnabled(true);
  72.                 // Greet the user.
  73.                 sayHello();
  74.             }
  75.         } else {
  76.             // Initialization failed.
  77.             Log.e(TAG, "Could not initialize TextToSpeech.");
  78.         }
  79.     }
  80.  
  81.     private static final Random RANDOM = new Random();
  82.     private static final String[] HELLOS = {
  83.             "Hello",
  84.             "Congratulation",
  85.             "Greetings",
  86.             "How are you!",
  87.             "What's your name?",
  88.             "I am a good student!",
  89.             "Oh My God!"
  90.     };
  91.  
  92.     private void sayHello() {
  93.         // Select a random hello.
  94.         int helloLength = HELLOS.length;
  95.         String hello = HELLOS[RANDOM.nextInt(helloLength)];
  96.         mTts.speak(hello, TextToSpeech.QUEUE_FLUSH, // Drop all pending entries in the playback queue,
  97.                 null);
  98.         tv.setText(hello);
  99.     }
  100. }
在这段内码中： 
  1. private static final String[] HELLOS = {
  2.     "Hello",
  3.     "Congratulation",
  4.     "Greetings",
  5.     "How are you!",
  6.     "What's your name?",
  7.     "I am a good student!",
  8.     "Oh My God!"
  9. };
HELLOS 数组中存放了用于播放的文本，读者如果想播放自己的文本，只需要替换该数组内的字符串即可。

mTts = new TextToSpeech(this,this);

创建了 TextToSpeech 实例 mTts，该构造方法的第一个参数表示容纳该对象的容器，第二个参数表示实现文本语音回调接口 TextToSpeech.OnInitListener 的类，该接口提供一个 public void onInit(int status) 方法，用于对文本语音 API 进行初始化。

TextToSpeech 实例通过 speak 方法即可进行语音播放。本实例是以随机顺序播放 HELLOS 中的字符串的。

目前，该功能对英文支持较好，暂不支持中文文本播放。