如何处理从jni到AudioTrack的呼叫而不会崩溃？

Question

我试图从jni回调中写入AudioTrack，但收到信号7（SIGBUS），错误地址00000000。

我已经看了看Wolf3D例如，对于odroid，他们似乎使用android.os.Handler发布一个Runnable将在正确的线程上下文做一个更新。我也尝试了AttachCurrentThread，但是在这种情况下我也失败了。

即使我将其包装在线程中，然后将其发布到处理程序中，它也可以在从构造函数运行时播放声音。当我通过jni的回调执行“相同”操作时，它将失败。我认为我正在违反一些规则，但是我无法弄清楚它们是什么。到目前为止，我还没有在SO上找到答案。

所以我想知道是否有人知道该怎么做。

编辑：下面回答。

以下代码说明了该问题。

Java：

package com.example.jniaudiotrack;

import android.app.Activity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;

public class JniAudioTrackActivity extends Activity {
    AudioTrack mAudioTrack;
    byte[] mArr;
    public static final Handler mHandler = new Handler();

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mArr = new byte[2048];
        for (int i = 0; i < 2048; i++) {
            mArr[i] = (byte) (Math.sin(i) * 128);
        }

        mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                11025,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_8BIT,
                2048,
                AudioTrack.MODE_STREAM);
        mAudioTrack.play();

        new Thread(new Runnable() {
            public void run() {
                mHandler.post(new Runnable() {
                    public void run() {
                        mAudioTrack.write(mArr, 0, 2048);
                        Log.i(TAG, "*** Handler from constructor ***");
                    }
                });
            }
        }).start();

        new Thread(new Runnable() {
            public void run() {
                audioFunc();
            }
        }).start();
    }

    public native void audioFunc();

    @SuppressWarnings("unused")
    private void audioCB() {
        mHandler.post(new Runnable() {
            public void run() {
                mAudioTrack.write(mArr, 0, 2048);
                Log.i(TAG, "*** audioCB called ***");
            }
        });
    }

    private static final String TAG = "JniAudioTrackActivity";

    static {
        System.loadLibrary("jni_audiotrack");
    }
}

cpp：

#include <jni.h>

extern "C" {
    JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj);
}

JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj)
{
    JNIEnv* jniEnv;
    JavaVM* vm;
    env->GetJavaVM(&vm);
    vm->AttachCurrentThread(&jniEnv, 0);

    jclass cls = env->GetObjectClass(obj);
    jmethodID audioCBID = env->GetMethodID(cls, "audioCB", "()V");

    if (!audioCBID) {
        return;
    }

    env->CallVoidMethod(cls, audioCBID);
}

跟踪代码段：

I/DEBUG   ( 1653): pid: 9811, tid: 9811  >>> com.example.jniaudiotrack <<<
I/DEBUG   ( 1653): signal 7 (SIGBUS), fault addr 00000000
I/DEBUG   ( 1653):  r0 00000800  r1 00000026  r2 00000001  r3 00000000
I/DEBUG   ( 1653):  r4 42385726  r5 41049e54  r6 bee25570  r7 ad00e540
I/DEBUG   ( 1653):  r8 000040f8  r9 41048200  10 41049e44  fp 00000000
I/DEBUG   ( 1653):  ip 000000f8  sp bee25530  lr ad02dbb5  pc ad012358  cpsr 20000010
I/DEBUG   ( 1653):          #00  pc 00012358  /system/lib/libdvm.so

Answer 1

似乎出现了内存问题。
使mAudioTrack和mArr静态可解决该问题。
我向回调发送了错误的对象。请参阅fadden的评论。我已经删除了对AttachCurrentThread的调用，因为在这种情况下它没有任何区别。

Java：

package com.example.jniaudiotrack;

import android.app.Activity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;

public class JniAudioTrackActivity extends Activity {
    public AudioTrack mAudioTrack;
    public byte[] mArr;
    public static Handler mHandler = new Handler();

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mArr = new byte[2048];
        for (int i = 0; i < 2048; i++) {
            mArr[i] = (byte) (Math.sin(i) * 128);
        }

        mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                    11025,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_8BIT,
                    2048,
                    AudioTrack.MODE_STREAM);
        mAudioTrack.play();

        new Thread(new Runnable() {
            public void run() {
                audioFunc();
            }
        }).start();
    }

    public native void audioFunc();

    @SuppressWarnings("unused")
    private void audioCB() {
        mHandler.post(new Runnable() {
            public void run() {
                mAudioTrack.write(mArr, 0, 2048);
                Log.i(TAG, "*** audioCB called ***");
            }
        });
    }

    private static final String TAG = "JniAudioTrackActivity";

    static {
        System.loadLibrary("jni_audiotrack");
    }
}

Cpp：

#include <jni.h>

extern "C" {
    JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj);
}

JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj)
{
    jclass cls = env->GetObjectClass(obj);
    jmethodID audioCBID = env->GetMethodID(cls, "audioCB", "()V");

    if (!audioCBID) {
        return;
    }

    env->CallVoidMethod(obj, audioCBID);
}