2
我的任務描述： 我正在開發Android上的視頻播放器（API> = 17）。它必須與HLS和multicast視頻一起工作。另外，它必須支持多個音軌。從AVPacket提供字節數據的MediaCodec：輸出緩衝區問題
爲什麼我決定使用ffmpeg：
- 在某些設備上
MediaPlayer不支持multicast- 視頻 MediaExtractor不HLS工作（getTrackCount()返回0）- ffmpeg的作品用
HLS和multicast
我的想法： 我在一個循環中使用ffmpeg解串一個流。我使用videoStream->codec->extradata獲得CSD，然後正確配置MediaFormat。在每次迭代中，當我有新的視頻AVPacket可用時，我使用av_bitstream_filter_init到h264_mp4toannexb過濾它的緩衝區。然後我調用java方法onNewVideoData，其中我得到了AVPacket字節數組。我清除了可用的輸入緩衝區，然後填入新的數據。我也得到了pts。由於我有一個沒有開始的流，另外，我通過從以下所有pts'減去第一個AVPacket的pts'來計算新的pts''。第一個pts我分配給0.然後我打電話queueInputBuffer發送緩衝區到解碼器。
我使用兩個線程：一個用於獲取和提交數據到輸入緩衝區，另一個用於將其發送到Surface。
完整的播放器的C代碼：
#include <jni.h>
#include <android/log.h>
#include <stddef.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/buffer.h>
#define TAG "ffmpegPlayer"
struct
{
const char* url;
jint width;
jint height;
jfloat aspectRatio;
jint streamsCount;
AVFormatContext* formatContext;
AVStream* videoStream;
} context;
AVPacket packet;
AVBitStreamFilterContext* avBitStreamFilterContext;
JNIEXPORT jbyteArray JNICALL Java_com_example_app_FfmpegPlayer_getCsdNative(JNIEnv* env, jobject x)
{
jbyteArray arr = (*env)->NewByteArray(env, context.videoStream->codec->extradata_size);
(*env)->SetByteArrayRegion(env, arr, 0, context.videoStream->codec->extradata_size, (jbyte*)context.videoStream->codec->extradata);
return arr;
}
JNIEXPORT jint JNICALL Java_com_example_app_FfmpegPlayer_getWidthNative(JNIEnv* env, jobject x)
{
return context.width;
}
JNIEXPORT jint JNICALL Java_com_example_app_FfmpegPlayer_getHeightNative(JNIEnv* env, jobject x)
{
return context.height;
}
JNIEXPORT jfloat JNICALL Java_com_example_app_FfmpegPlayer_getAspectRatioNative(JNIEnv* env, jobject x)
{
return context.aspectRatio;
}
JNIEXPORT jfloat JNICALL Java_com_example_app_FfmpegPlayer_getStreamsCountNative(JNIEnv* env, jobject x)
{
return context.streamsCount;
}
JNIEXPORT jlong JNICALL Java_com_example_app_FfmpegPlayer_getPtsNative(JNIEnv* env, jobject obj)
{
return packet.pts * av_q2d(context.videoStream->time_base) * 1000000;
}
JNIEXPORT jboolean JNICALL Java_com_example_app_FfmpegPlayer_initNative(JNIEnv* env, jobject obj, const jstring u)
{
av_register_all();
avBitStreamFilterContext = av_bitstream_filter_init("h264_mp4toannexb");
const char* url = (*env)->GetStringUTFChars(env, u , NULL);
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Init: %s", url);
AVFormatContext* formatContext = NULL;
if (avformat_open_input(&formatContext, url, NULL, NULL) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Unable to open input");
return JNI_FALSE;
}
if (avformat_find_stream_info(formatContext, NULL) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Unable to find stream info");
return JNI_FALSE;
}
AVInputFormat * iformat = formatContext->iformat;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "format: %s", iformat->name);
context.streamsCount = formatContext->nb_streams;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Streams count: %d", formatContext->nb_streams);
int i = 0;
AVStream* videoStream = NULL;
AVDictionaryEntry* lang;
for (i = 0; i < formatContext->nb_streams; i++) {
int codecType = formatContext->streams[i]->codec->codec_type;
if (videoStream == NULL && codecType == AVMEDIA_TYPE_VIDEO) {
videoStream = formatContext->streams[i];
}
else if (codecType == AVMEDIA_TYPE_AUDIO) {
lang = av_dict_get(formatContext->streams[i]->metadata, "language", NULL, 0);
if (lang != NULL) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Audio stream %d: %s", i, lang->value);
}
}
}
if (videoStream == NULL) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Unable to find video stream");
return JNI_FALSE;
}
context.videoStream = videoStream;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Video stream: %d", videoStream->index);
AVCodecContext *codecContext = formatContext->streams[videoStream->index]->codec;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "width: %d, height: %d", codecContext->width, codecContext->height);
context.width = codecContext->width;
context.height = codecContext->height;
AVRational aspectRatio = codecContext->sample_aspect_ratio;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "aspect ratio: %d/%d", aspectRatio.num, aspectRatio.den);
context.aspectRatio = aspectRatio.num/aspectRatio.den;
context.formatContext = formatContext;
return JNI_TRUE;
}
void filterPacket()
{
av_bitstream_filter_filter(avBitStreamFilterContext, context.videoStream->codec, NULL, &packet.data, &packet.size, packet.data, packet.size, packet.flags);
}
JNIEXPORT void JNICALL Java_com_example_app_FfmpegPlayer_startNative(JNIEnv* env, jobject obj)
{
jclass cl = (*env)->GetObjectClass(env, obj);
jmethodID updateMethodId = (*env)->GetMethodID(env, cl, "onNewVideoData", "()V");
while (av_read_frame(context.formatContext, &packet) >= 0) {
if (context.formatContext == NULL) {
return;
}
if (packet.stream_index == context.videoStream->index) {
filterPacket();
(*env)->CallVoidMethod(env, obj, updateMethodId);
}
}
}
JNIEXPORT jbyteArray JNICALL Java_com_example_app_FfmpegPlayer_getVideoDataNative(JNIEnv* env, jobject obj)
{
AVBufferRef *buf = packet.buf;
jbyteArray arr = (*env)->NewByteArray(env, buf->size);
(*env)->SetByteArrayRegion(env, arr, 0, buf->size, (jbyte*)buf->data);
return arr;
}
完整的Java代碼：
package com.example.app;
import android.media.MediaCodec;
import android.media.MediaFormat;
import android.view.Surface;
import java.nio.ByteBuffer;
public class FfmpegPlayer {
static {
System.loadLibrary("avutil-54");
System.loadLibrary("swscale-3");
System.loadLibrary("swresample-1");
System.loadLibrary("avcodec-56");
System.loadLibrary("avformat-56");
System.loadLibrary("avfilter-5");
System.loadLibrary("ffmpeg-player");
}
private native boolean initNative(String url);
private native boolean startNative();
private native int getWidthNative();
private native int getHeightNative();
private native float getAspectRatioNative();
private native byte[] getVideoDataNative();
private native long getPtsNative();
private native byte[] getCsdNative();
private String source;
private PlayerThread playerThread;
private int width;
private int height;
private MediaCodec decoder;
private ByteBuffer[] inputBuffers;
private Surface surface;
private long firstPtsTime;
public PlanetaPlayer(Surface surface) {
this.surface = surface;
}
public void setDataSource(String source) {
if (!initNative(source)) {
return;
}
width = getWidthNative();
height = getHeightNative();
MediaFormat format = MediaFormat.createVideoFormat("video/avc", width, height);
format.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, width * height);
format.setByteBuffer("csd-0", ByteBuffer.wrap(getCsdNative()));
LogUtils.log("CSD: ");
outputAsHex(getCsdNative());
try {
decoder = MediaCodec.createDecoderByType("video/avc");
decoder.configure(format, surface, null, 0);
decoder.start();
playerThread = new PlayerThread();
playerThread.start();
new OutputThread().run();
}
catch (Exception e) {
e.printStackTrace();
}
}
public void onNewVideoData() {
int index = decoder.dequeueInputBuffer(0);
if (index >= 0) {
byte[] data = getVideoDataNative();
ByteBuffer byteBuffer = decoder.getInputBuffers()[index];
byteBuffer.clear();
byteBuffer.put(data);
long pts = getPtsNative();
LogUtils.log("Input AVPacket pts: " + pts);
LogUtils.log("Input AVPacket data length: " + data.length);
LogUtils.log("Input AVPacket data: ");
outputAsHex(data);
if (firstPtsTime == 0) {
firstPtsTime = pts;
pts = 0;
}
else {
pts -= firstPtsTime;
}
decoder.queueInputBuffer(index, 0, data.length, pts, 0);
}
}
private void outputAsHex(byte[] data) {
String[] test = new String[data.length];
for (int i = 0; i < data.length; i++) {
test[i] = String.format("%02x", data[i]);
}
LogUtils.log(test);
}
private class PlayerThread extends Thread {
@Override
public void run() {
super.run();
startNative();
}
}
private class OutputThread extends Thread {
@Override
public void run() {
super.run();
MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
while (true) {
int index = decoder.dequeueOutputBuffer(info, 0);
if (index >= 0) {
ByteBuffer buffer = decoder.getOutputBuffers()[index];
buffer.position(info.offset);
buffer.limit(info.offset + info.size);
byte[] test = new byte[info.size];
for (int i = 0; i < info.size; i++) {
test[i] = buffer.get(i);
}
LogUtils.log("Output info: size=" + info.size + ", presentationTimeUs=" + info.presentationTimeUs + ",offset=" + info.offset + ",flags=" + info.flags);
LogUtils.log("Output data: ");
outputAsHex(test);
decoder.releaseOutputBuffer(index, true);
}
}
}
}
}
問題： 因爲我使用的TS文件與測試以下視頻流：
Codec: H264 - MPEG-4 AVC (part 10) (h264)
Resolution: 720x578
Frame rate: 25
Decoded format: Planar 4:2:0 YUV
的CSD如下：
[00, 00, 00, 01, 09, 10, 00, 00, 00, 01, 27, 4d, 40, 1e, 9a, 62, 01, 68, 48, b0, 44, 20, a0, a0, a8, 00, 00, 03, 00, 08, 00, 00, 03, 01, 94, a0, 00, 00, 00, 01, 28, ee, 3c, 80]
在不同設備上我有不同的結果。但我無法在Surface上顯示視頻。
輸入：
Input AVPacket pts: 351519222
Input AVPacket data length: 54941
Input AVPacket data: [00, 00, 00, 01, 09, 10, 00, 00, 00, 01, 27, 4d, 40, 1e, 9a, 62, 01, 68, 48, b0, 44, 20, a0, a0, a8, 00, 00, 03, 00, 08, 00, 00, 03, 01, 94, a0, 00, 00, 00, 01,...]
------------------------------------
Input AVPacket pts: 351539222
Input AVPacket data length: 9605
Input AVPacket data: [00, 00, 00, 01, 09, 30, 00, 00, 00, 01, 06, 01, 01, 24, 80, 00, 00, 00, 01, 21, e3, bd, da, e4, 46, c5, 8b, 6b, 7d, 07, 59, 23, 6f, 92, e9, fb, 3b, b9, 4d, f9,...]
------------------------------------
Input AVPacket pts: 351439222
Input AVPacket data length: 1985
Input AVPacket data: [00, 00, 00, 01, 09, 50, 00, 00, 00, 01, 06, 01, 01, 14, 80, 00, 00, 00, 01, 21, a8, f2, 74, 69, 14, 54, 4d, c5, 8b, e8, 42, 52, ac, 80, 53, b4, 4d, 24, 1f, 6c,...]
------------------------------------
Input AVPacket pts: 351459222
Input AVPacket data length: 2121
Input AVPacket data: [00, 00, 00, 01, 09, 50, 00, 00, 00, 01, 06, 01, 01, 24, 80, 00, 00, 00, 01, 21, a8, f3, 74, e9, 0b, 8b, 17, e8, 43, f8, 10, 88, ca, 2b, 11, 53, c8, 31, f0, 0b,...]
... on and on
華碩Zenfone（Android的5.0。2）輸出線程（解碼，只有8個字節的數據的25個緩衝器奇怪的結果）後：
Output info: size=8, presentationTimeUs=-80001,offset=0,flags=0
Output data:
[01, 00, 00, 00, 90, c5, 99, ac]
---------------------------
Output info: size=8, presentationTimeUs=0,offset=0,flags=1
Output data:
[01, 00, 00, 00, 78, ea, 86, ac]
---------------------------
Output info: size=8, presentationTimeUs=720000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e8, 86, b6, ac]
---------------------------
Output info: size=8, presentationTimeUs=780000,offset=0,flags=1
Output data:
[01, 00, 00, 00, c0, cb, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=840000,offset=0,flags=0
Output data:
[01, 00, 00, 00, 80, 87, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=960000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, 3f, 8b, ac]
---------------------------
Output info: size=8, presentationTimeUs=1040000,offset=0,flags=1
Output data:
[01, 00, 00, 00, f8, 76, 85, ac]
---------------------------
Output info: size=8, presentationTimeUs=1180000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, 87, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=1260000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e8, b5, d2, ac]
---------------------------
Output info: size=8, presentationTimeUs=1800000,offset=0,flags=0
Output data:
[01, 00, 00, 00, 90, c5, 99, ac]
---------------------------
Output info: size=8, presentationTimeUs=1860000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, c0, 84, ac]
---------------------------
Output info: size=8, presentationTimeUs=2080000,offset=0,flags=1
Output data:
[01, 00, 00, 00, c0, cb, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=3440000,offset=0,flags=1
Output data:
[01, 00, 00, 00, 80, 87, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=3520000,offset=0,flags=0
Output data:
[01, 00, 00, 00, 78, ea, 86, ac]
---------------------------
Output info: size=8, presentationTimeUs=4160000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e8, 86, b6, ac]
---------------------------
Output info: size=8, presentationTimeUs=4300000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, 3f, 8b, ac]
---------------------------
Output info: size=8, presentationTimeUs=4400000,offset=0,flags=1
Output data:
[01, 00, 00, 00, 90, c5, 99, ac]
---------------------------
Output info: size=8, presentationTimeUs=4480000,offset=0,flags=1
Output data:
[01, 00, 00, 00, f8, 76, 85, ac]
---------------------------
Output info: size=8, presentationTimeUs=4680000,offset=0,flags=0
Output data:
[01, 00, 00, 00, c0, cb, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=4720000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, c0, 84, ac]
---------------------------
Output info: size=8, presentationTimeUs=4760000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e0, 87, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=4800000,offset=0,flags=0
Output data:
[01, 00, 00, 00, 58, 54, 83, ac]
---------------------------
Output info: size=8, presentationTimeUs=5040000,offset=0,flags=0
Output data:
[01, 00, 00, 00, e8, b5, d2, ac]
---------------------------
Output info: size=8, presentationTimeUs=5100000,offset=0,flags=1
Output data:
[01, 00, 00, 00, 80, 87, 93, ac]
---------------------------
Output info: size=8, presentationTimeUs=5320000,offset=0,flags=0
Output data:
[01, 00, 00, 00, 78, ea, 86, ac]
---------------------------
Output info: size=8, presentationTimeUs=5380000,offset=0,flags=1
Output data:
[01, 00, 00, 00, e8, 86, b6, ac]
其他華碩Zenfone日誌：
01-25 17:11:36.859 4851-4934/com.example.app I/OMXClient: Using client-side OMX mux.
01-25 17:11:36.865 317-1075/? I/OMX-VDEC-1080P: component_init: OMX.qcom.video.decoder.avc : fd=43
01-25 17:11:36.867 317-1075/? I/OMX-VDEC-1080P: Capabilities: driver_name = msm_vidc_driver, card = msm_vdec_8974, bus_info = , version = 1, capabilities = 4003000
01-25 17:11:36.881 317-1075/? I/OMX-VDEC-1080P: omx_vdec::component_init() success : fd=43
01-25 17:11:36.885 4851-4934/com.example.app I/ACodec: [OMX.qcom.video.decoder.avc] DRC Mode: Dynamic Buffer Mode
01-25 17:11:36.893 317-20612/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.933 317-12269/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.933 317-12269/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.935 317-5559/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.957 317-5559/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.957 4851-4934/com.example.app I/ExtendedCodec: Decoder will be in frame by frame mode
01-25 17:11:36.963 317-1075/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.963 317-1075/? E/C2DColorConvert: unknown format passed for luma alignment number
01-25 17:11:36.964 317-20612/? E/OMX-VDEC-1080P: Extension: OMX.google.android.index.describeColorFormat not implemented
01-25 17:11:37.072 317-20612/? E/OMX-VDEC-1080P: Extension: OMX.google.android.index.describeColorFormat not implemented
01-25 17:11:37.072 4851-4934/com.example.app W/ACodec: do not know color format 0x7fa30c04 = 2141391876
華碩的Nexus 7（的Android 6.0。 1）崩潰：
01-25 17:23:06.921 11602-11695/com.example.app I/OMXClient: Using client-side OMX mux.
01-25 17:23:06.952 11602-11694/com.example.app I/MediaCodec: [OMX.qcom.video.decoder.avc] setting surface generation to 11880449
01-25 17:23:06.954 194-194/? E/OMX-VDEC-1080P: Extension: OMX.google.android.index.storeANWBufferInMetadata not implemented
01-25 17:23:06.954 194-194/? E/OMX-VDEC-1080P: Extension: OMX.google.android.index.storeMetaDataInBuffers not implemented
01-25 17:23:06.954 194-194/? E/OMXNodeInstance: getExtensionIndex(45:qcom.decoder.avc, OMX.google.android.index.storeMetaDataInBuffers) ERROR: NotImplemented(0x80001006)
01-25 17:23:06.954 11602-11695/com.example.app E/ACodec: [OMX.qcom.video.decoder.avc] storeMetaDataInBuffers failed w/ err -2147483648
01-25 17:23:06.963 11602-11695/com.example.app D/SurfaceUtils: set up nativeWindow 0xa0b7a108 for 720x576, color 0x7fa30c03, rotation 0, usage 0x42002900
01-25 17:23:06.967 194-604/? E/OMX-VDEC-1080P: GET_MV_BUFFER_SIZE returned: Size: 122880 and alignment: 8192
01-25 17:23:07.203 11602-11695/com.example.app W/AHierarchicalStateMachine: Warning message AMessage(what = 'omxI') = {
int32_t type = 0
int32_t event = 2130706432
int32_t data1 = 1
int32_t data2 = 0
} unhandled in root state.
01-25 17:23:07.232 11602-11695/com.example.app D/SurfaceUtils: set up nativeWindow 0xa0b7a108 for 720x576, color 0x7fa30c03, rotation 0, usage 0x42002900
01-25 17:23:07.241 194-194/? E/OMX-VDEC-1080P: GET_MV_BUFFER_SIZE returned: Size: 122880 and alignment: 8192
01-25 17:23:07.242 194-194/? E/OMX-VDEC-1080P: Insufficient sized buffer given for playback, expected 671744, got 663552
01-25 17:23:07.242 194-194/? E/OMXNodeInstance: useBuffer(45:qcom.decoder.avc, Output:1 [email protected]) ERROR: BadParameter(0x80001005)
01-25 17:23:07.243 11602-11695/com.example.app E/ACodec: registering GraphicBuffer 0 with OMX IL component failed: -2147483648
01-25 17:23:07.243 11602-11695/com.example.app E/ACodec: Failed to allocate output port buffers after port reconfiguration: (-2147483648)
01-25 17:23:07.243 11602-11695/com.example.app E/ACodec: signalError(omxError 0x80001001, internalError -2147483648)
01-25 17:23:07.243 11602-11694/com.example.app E/MediaCodec: Codec reported err 0x80001001, actionCode 0, while in state 6
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: java.lang.IllegalStateException
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at android.media.MediaCodec.native_dequeueOutputBuffer(Native Method)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at android.media.MediaCodec.dequeueOutputBuffer(MediaCodec.java:2379)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at com.example.app.FfmpegPlayer$OutputThread.run(FfmpegPlayer.java:122)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at com.example.app.FfmpegPlayer.setDataSource(FfmpegPlayer.java:66)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at com.example.app.activities.TestActivity$2.surfaceCreated(TestActivity.java:151)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at android.view.SurfaceView.updateWindow(SurfaceView.java:583)
01-25 17:23:07.245 11602-11602/com.example.app W/System.err: at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:177)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2055)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.Choreographer.doCallbacks(Choreographer.java:670)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.Choreographer.doFrame(Choreographer.java:606)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.os.Handler.handleCallback(Handler.java:739)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.os.Handler.dispatchMessage(Handler.java:95)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.os.Looper.loop(Looper.java:148)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5417)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at java.lang.reflect.Method.invoke(Native Method)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
01-25 17:23:07.246 11602-11602/com.example.app W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
另一個設備總是有空輸出緩衝區，思想索引aren> = 0;
我在做什麼錯？