webRTC（二十二）：android 錄屏保存

在錄屏基礎上使用MediaMuxer將錄屏保存爲視頻，詳細代碼如下：

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.hardware.display.DisplayManager;
import android.hardware.display.VirtualDisplay;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.media.projection.MediaProjection;
import android.media.projection.MediaProjectionManager;
import android.os.Bundle;
import android.os.Environment;
import android.util.DisplayMetrics;
import android.view.Surface;
import android.view.View;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicBoolean;

public class SaveScreenActivity extends AppCompatActivity {

    private static final int REQUEST_CODE = 102;
    private MediaProjectionManager projectionManager;
    private MediaProjection mediaProjection;
    private VirtualDisplay mVirtualDisplay;

    MediaCodec mediaCodec;
    MediaMuxer mediaMuxer;
    Surface surface;

    int width;
    int height;
    int dpi;
    private MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
    private int videoTrackIndex = -1;
    String filePath;
    private AtomicBoolean mQuit = new AtomicBoolean(false);

    @Override
    protected void onDestroy() {
        super.onDestroy();
        release();
    }

    private void release() {
        if (mediaCodec != null) {
            mediaCodec.stop();
            mediaCodec.release();
            mediaCodec = null;
        }
        if (mVirtualDisplay != null) {
            mVirtualDisplay.release();
            mVirtualDisplay = null;
        }
        if (mediaProjection != null) {
            mediaProjection.stop();
            mediaProjection = null;
        }
        if (mediaMuxer != null) {
            mediaMuxer.release();
            mediaMuxer = null;
        }
    }

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

        DisplayMetrics metric = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(metric);
        width = metric.widthPixels;
        height = metric.heightPixels;
        dpi = metric.densityDpi;
        File file = new File(Environment.getExternalStorageDirectory(),
                "record-" + width + "x" + height + "-" + System.currentTimeMillis() + ".mp4");
        filePath = file.getAbsolutePath();

        projectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);

        findViewById(R.id.stop).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mQuit.set(true);
                Toast.makeText(SaveScreenActivity.this, "Recorder stop", Toast.LENGTH_SHORT).show();
            }
        });
    }

    @Override
    public void onAttachedToWindow() {
        super.onAttachedToWindow();
        Intent captureIntent = projectionManager.createScreenCaptureIntent();
        startActivityForResult(captureIntent, REQUEST_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
            mediaProjection = projectionManager.getMediaProjection(resultCode, data);


            new Thread() {
                @Override
                public void run() {
                    try {
                        try {
                            prepareEncoder();
                            mediaMuxer = new MediaMuxer(filePath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                        mVirtualDisplay = createVirtualDisplay();
                        recordVirtualDisplay();

                    } finally {
                        release();
                    }
                }
            }.start();

            Toast.makeText(this, "Recorder is running...", Toast.LENGTH_SHORT).show();
            moveTaskToBack(true);
        }
    }


    /**
     * name: 是生成的VirtualDisplay實例的名稱；
     * width, height: 分別是生成實例的寬高，必須大於0；
     * dpi: 生成實例的像素密度，必須大於0，一般都取1；
     * surface: 這個比較重要，是你生成的VirtualDisplay的載體，
     * 我的理解是，VirtualDisplay的內容是一幀幀的屏幕截圖（所以你看到是有寬高，像素密度等設置），
     * 所以MediaProjection獲取到的其實是一幀幀的圖，然後通過          surface（surface你可以理解成是android的一個畫布，
     * 默認它會以每秒60幀來刷新，這裏我們不再展開細說），來順序播放這些圖片，形成視頻。
     *
     * @return
     */
    private VirtualDisplay createVirtualDisplay() {
        return mediaProjection.createVirtualDisplay("RecordScreen",
                width, height, dpi,
                DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,
                surface, null /*Callbacks*/, null /*Handler*/);
    }

    private void prepareEncoder() throws IOException {
        MediaFormat format = MediaFormat.createVideoFormat("video/avc", width, height);
        format.setInteger(MediaFormat.KEY_COLOR_FORMAT,
                MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
        format.setInteger(MediaFormat.KEY_BIT_RATE, 6000000);
        format.setInteger(MediaFormat.KEY_FRAME_RATE, 30);
        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 10);

        mediaCodec = MediaCodec.createEncoderByType("video/avc");
        mediaCodec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        surface = mediaCodec.createInputSurface();
        mediaCodec.start();
    }


    private void recordVirtualDisplay() {
        while (!mQuit.get()) {
            int index = mediaCodec.dequeueOutputBuffer(bufferInfo, 10000);
            if (index == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                resetOutputFormat();
            } else if (index >= 0) {
                encodeToVideoTrack(index);
                mediaCodec.releaseOutputBuffer(index, false);
            }
        }
    }
    private void encodeToVideoTrack(int index) {
        ByteBuffer encodedData = mediaCodec.getOutputBuffer(index);

        if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
            bufferInfo.size = 0;
        }
        if (bufferInfo.size == 0) {
            encodedData = null;
        }
        if (encodedData != null) {
            encodedData.position(bufferInfo.offset);
            encodedData.limit(bufferInfo.offset + bufferInfo.size);
            mediaMuxer.writeSampleData(videoTrackIndex, encodedData, bufferInfo);
        }
    }

    private void resetOutputFormat() {
        MediaFormat newFormat = mediaCodec.getOutputFormat();
        videoTrackIndex = mediaMuxer.addTrack(newFormat);
        mediaMuxer.start();
    }
}

    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.camera.autofocus" />
    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />