使用mediacodec播放的代码

以下是一个简单的使用MediaCodec进行视频解码和渲染的示例代码：

import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Surface;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    private static final String TAG = "MainActivity";

    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;
    private MediaExtractor mMediaExtractor;
    private MediaMuxer mMediaMuxer;
    private MediaCodec mMediaCodec;
    private int mTrackIndex;
    private boolean mIsEOS;
    private boolean mIsStarted;
    private long mStartTime;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mSurfaceView = (SurfaceView) findViewById(R.id.surface_view);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mMediaExtractor = new MediaExtractor();
        try {
            mMediaExtractor.setDataSource(Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator + "test.mp4");
        } catch (IOException e) {
            e.printStackTrace();
        }

        int trackCount = mMediaExtractor.getTrackCount();
        for (int i = 0; i < trackCount; i++) {
            MediaFormat format = mMediaExtractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("video/")) {
                mMediaExtractor.selectTrack(i);
                try {
                    mMediaCodec = MediaCodec.createDecoderByType(mime);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                mMediaCodec.configure(format, holder.getSurface(), null, 0);
                break;
            }
        }

        if (mMediaCodec == null) {
            return;
        }

        mMediaCodec.start();
        mIsStarted = true;
        mStartTime = System.currentTimeMillis();
        new Thread(new DecodeRunnable()).start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    private void release() {
        if (mMediaCodec != null) {
            mMediaCodec.stop();
            mMediaCodec.release();
            mMediaCodec = null;
        }

        if (mMediaExtractor != null) {
            mMediaExtractor.release();
            mMediaExtractor = null;
        }

        if (mMediaMuxer != null) {
            mMediaMuxer.stop();
            mMediaMuxer.release();
            mMediaMuxer = null;
        }
    }

    private class DecodeRunnable implements Runnable {

        @Override
        public void run() {
            ByteBuffer[] inputBuffers = mMediaCodec.getInputBuffers();
            ByteBuffer[] outputBuffers = mMediaCodec.getOutputBuffers();
            MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

            while (!mIsEOS) {
                int inputBufferIndex = mMediaCodec.dequeueInputBuffer(10000);
                if (inputBufferIndex >= 0) {
                    ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                    int sampleSize = mMediaExtractor.readSampleData(inputBuffer, 0);
                    if (sampleSize < 0) {
                        mMediaCodec.queueInputBuffer(inputBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                        mIsEOS = true;
                    } else {
                        long presentationTimeUs = mMediaExtractor.getSampleTime();
                        mMediaCodec.queueInputBuffer(inputBufferIndex, 0, sampleSize, presentationTimeUs, 0);
                        mMediaExtractor.advance();
                    }
                }

                int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 10000);
                switch (outputBufferIndex) {
                    case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                        outputBuffers = mMediaCodec.getOutputBuffers();
                        break;
                    case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                        MediaFormat newFormat = mMediaCodec.getOutputFormat();
                        mTrackIndex = mMediaMuxer.addTrack(newFormat);
                        mMediaMuxer.start();
                        break;
                    case MediaCodec.INFO_TRY_AGAIN_LATER:
                        break;
                    default:
                        if (!mIsStarted) {
                            mMediaCodec.releaseOutputBuffer(outputBufferIndex, false);
                            break;
                        }
                        ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                        mMediaMuxer.writeSampleData(mTrackIndex, outputBuffer, bufferInfo);
                        mMediaCodec.releaseOutputBuffer(outputBufferIndex, true);
                        break;
                }

                if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    break;
                }
            }

            release();
        }
    }
}

这段代码使用了MediaExtractor来获取视频的格式和轨道信息，使用MediaCodec来进行视频解码，使用SurfaceView来进行视频渲染。注意，这段代码还包括了将解码后的视频数据保存到本地的功能，但这个功能并不是本代码示例的重点。