android app中用java实现将H264视频流保存到本地

以下是用Java在Android应用程序中将H264视频流保存到本地的示例代码：

首先，你需要创建一个类来处理视频编码和保存：

import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.os.Environment;

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

public class VideoEncoder {

    private static final String MIME_TYPE = "video/avc"; // H.264 Advanced Video Coding
    private static final int FRAME_RATE = 30; // 帧率
    private static final int I_FRAME_INTERVAL = 1; // I帧间隔（单位秒）
    private static final int BIT_RATE = 125000; // 比特率（单位bps）

    private MediaCodec mediaCodec;
    private MediaMuxer mediaMuxer;
    private int trackIndex;
    private boolean isMuxerStarted;

    public VideoEncoder() throws IOException {
        MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, 640, 480);
        format.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);
        format.setInteger(MediaFormat.KEY_FRAME_RATE, FRAME_RATE);
        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, I_FRAME_INTERVAL);
        format.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Flexible);
        mediaCodec = MediaCodec.createEncoderByType(MIME_TYPE);
        mediaCodec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mediaCodec.start();
        mediaMuxer = new MediaMuxer(Environment.getExternalStorageDirectory() + "/output.mp4", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
    }

    public void encode(byte[] data) {
        long presentationTimeUs = System.nanoTime() / 1000;
        ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
        int inputBufferIndex = mediaCodec.dequeueInputBuffer(-1);
        if (inputBufferIndex >= 0) {
            ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
            inputBuffer.clear();
            inputBuffer.put(data);
            mediaCodec.queueInputBuffer(inputBufferIndex, 0, data.length, presentationTimeUs, 0);
        }
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
        int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
        while (outputBufferIndex >= 0) {
            ByteBuffer outputBuffer = mediaCodec.getOutputBuffers()[outputBufferIndex];
            if (!isMuxerStarted) {
                MediaFormat outputFormat = mediaCodec.getOutputFormat();
                trackIndex = mediaMuxer.addTrack(outputFormat);
                mediaMuxer.start();
                isMuxerStarted = true;
            }
            mediaMuxer.writeSampleData(trackIndex, outputBuffer, bufferInfo);
            mediaCodec.releaseOutputBuffer(outputBufferIndex, false);
            outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
        }
    }

    public void release() {
        mediaCodec.stop();
        mediaCodec.release();
        mediaMuxer.stop();
        mediaMuxer.release();
    }
}

这个类使用MediaCodec API对视频进行编码，并使用MediaMuxer API将编码后的视频写入文件。

在你的Activity中，你可以使用Camera API或其他方法来捕获视频帧，并将它们传递给VideoEncoder对象进行编码和保存。以下是使用Camera API捕获视频帧并将它们传递给VideoEncoder对象的示例代码：

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import androidx.annotation.NonNull;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import java.io.IOException;

public class MainActivity extends Activity implements SurfaceHolder.Callback, Camera.PreviewCallback {

    private static final int CAMERA_PERMISSION_REQUEST_CODE = 100;
    private static final String TAG = "MainActivity";

    private Camera camera;
    private SurfaceView surfaceView;
    private SurfaceHolder surfaceHolder;
    private VideoEncoder videoEncoder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        surfaceView = findViewById(R.id.surfaceView);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        openCamera();
        try {
            videoEncoder = new VideoEncoder();
        } catch (IOException e) {
            Log.e(TAG, "Failed to create VideoEncoder", e);
        }
    }

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

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        releaseCamera();
        videoEncoder.release();
    }

    private void openCamera() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
        } else {
            camera = Camera.open();
            try {
                camera.setPreviewDisplay(surfaceHolder);
                camera.setPreviewCallback(this);
                Camera.Parameters parameters = camera.getParameters();
                Camera.Size size = parameters.getPreviewSize();
                int bufferSize = size.width * size.height * 3 / 2;
                camera.addCallbackBuffer(new byte[bufferSize]);
                camera.startPreview();
            } catch (IOException e) {
                Log.e(TAG, "Failed to start preview", e);
            }
        }
    }

    private void releaseCamera() {
        if (camera != null) {
            camera.stopPreview();
            camera.setPreviewCallback(null);
            camera.release();
            camera = null;
        }
    }

    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        if (videoEncoder != null) {
            videoEncoder.encode(data);
        }
        camera.addCallbackBuffer(data);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                openCamera();
            }
        }
    }
}

在这个示例中，MainActivity类使用SurfaceView来显示摄像头预览，并使用Camera API来捕获视频帧。当收到预览帧时，它将它们传递给VideoEncoder对象进行编码和保存。

请注意，这只是一个基本示例，你需要根据你的需求进行修改和扩展。