java - 尝试使用文字转语音大声朗读短信时出现 NullPointerException

Question

当我尝试将文本转为语音以在到达时说出短信文本时，我遇到了一个Exception，它给了我一个NullPointerException，我似乎可以弄清楚是它想让我做或错误到底在哪里。我的问题可能是什么？

错误日志

java.lang.RuntimeException: Unable to start receiver com.fegeley.handsfreetexting.TTS: java.lang.NullPointerException
        at android.app.ActivityThread.handleReceiver(ActivityThread.java:2677)
        at android.app.ActivityThread.access$1800(ActivityThread.java:170)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1380)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:146)
        at android.app.ActivityThread.main(ActivityThread.java:5635)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at com.fegeley.handsfreetexting.TTS.speakText(TTS.java:52)
        at com.fegeley.handsfreetexting.TTS.onReceive(TTS.java:74)
        at android.app.ActivityThread.handleReceiver(ActivityThread.java:2669)
        at android.app.ActivityThread.access$1800(ActivityThread.java:170)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1380)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:146)
        at android.app.ActivityThread.main(ActivityThread.java:5635)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
        at dalvik.system.NativeStart.main(Native Method)

MainActivity.java

package com.fegeley.handsfreetexting;

import android.media.AudioManager;
import android.speech.tts.TextToSpeech;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.SmsMessage;
import android.view.View;
import android.widget.Toast;

import java.util.HashMap;
import java.util.Locale;


public class MainActivity extends ActionBarActivity {

TTS tts;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tts = new TTS();
    tts.giveContext(this);
}

@Override
public void onPause(){
    tts.onPause();
    super.onPause();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

TTS.java

package com.fegeley.handsfreetexting;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.AudioManager;
import android.os.Bundle;
import android.speech.tts.TextToSpeech;
import android.telephony.SmsMessage;

import java.util.HashMap;
import java.util.Locale;

/**
 * Created by Kayne on 1/14/2015.
 */
public class TTS extends BroadcastReceiver {

private static Context context;
TextToSpeech tts;

public TTS(){
}

public static void giveContext(Context con){
    context = con;
}

protected void onCreate(Bundle savedInstanceState){
    tts = new TextToSpeech(context,
            new TextToSpeech.OnInitListener() {
                @Override
                public void onInit(int status) {
                    if(status != TextToSpeech.ERROR){
                        tts.setLanguage(Locale.US);
                    }
                }
            });
}

public void onPause(){
    if(tts !=null){
        tts.stop();
        tts.shutdown();
    }
}

public void speakText(String toSpeak){
    HashMap<String, String> hash = new HashMap<String,String>();
    hash.put(TextToSpeech.Engine.KEY_PARAM_STREAM,
            String.valueOf(AudioManager.STREAM_NOTIFICATION));
    tts.speak(toSpeak, TextToSpeech.QUEUE_FLUSH, hash);
}

@Override
public void onReceive(Context context, Intent intent) {
    //---get the SMS message passed in---
    Bundle bundle = intent.getExtras();
    SmsMessage[] msgs = null;
    String str = "";
    //if (bundle != null)
    //{
        //---retrieve the SMS message received---
        Object[] pdus = (Object[]) bundle.get("pdus");
        msgs = new SmsMessage[pdus.length];
        for (int i=0; i<msgs.length; i++){
            msgs[i] = SmsMessage.createFromPdu((byte[]) pdus[i]);
            str += "SMS from " + msgs[i].getOriginatingAddress();
            str += " :";
            str += msgs[i].getMessageBody().toString();
            str += "\n";
        //}
        //---display the new SMS message---
        speakText(str);
    }
}
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.fegeley.handsfreetexting" >

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:screenOrientation="portrait" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <receiver android:name="com.fegeley.handsfreetexting.TTS">
        <intent-filter>
            <action android:name="android.provider.Telephony.SMS_RECEIVED"/>
        </intent-filter>
    </receiver>
</application>

<uses-permission android:name="android.permission.READ_SMS"/>
<uses-permission android:name="android.permission.RECEIVE_SMS"/>
<uses-permission android:name="android.permission.READ_CONTACTS"/>

</manifest>

Answer 1

第 52 行的“tts”对象为 NULL。

您似乎在 BroadcastReceiver 的“onCreate()”中对其进行了初始化。

protected void onCreate(Bundle savedInstanceState){
    tts = new TextToSpeech(context,
            new TextToSpeech.OnInitListener()

请注意 BroadcastReceiver 类没有任何 onCreate() Activity 风格的回调方法。

我猜你假设系统会调用 BroadcastReceiver 类的 onCreate()。对于 BroadcastReceiver 而言，情况并非如此。

您可以在 onReceive() 中初始化“tts”对象，如下所示:

public void onReceive(Context context1, Intent intent) {
    //---get the SMS message passed in---

    tts = new TextToSpeech(context,
            new TextToSpeech.OnInitListener() {
                @Override
                public void onInit(int status) {
                    if(status != TextToSpeech.ERROR){
                        tts.setLanguage(Locale.US);
                    }
                }
            });

此外，更改 MainActivity.java

中的以下行

删除:tts.giveContext(this); 添加:TTS.giveContext(getApplicationContext());

此更改是为了防止ReceiverCallNotAllowedException