如果有人知道在使用 MediaRecorder 时如何在前后摄像头之间切换。我为此功能定义了一个按钮，但不知道如何定义 onclickListener。

总 Activity 如下:

import java.io.File;
import java.io.IOException;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.hardware.Camera;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.view.SurfaceHolder.Callback;
import android.view.View.OnClickListener;
import android.widget.Button;

public class Test_cameraActivity extends Activity implements Callback {

    // Camera variables to fiddle with video preview.
    // private Camera cam;
    // Viewholders etc
    private SurfaceHolder recordViewHolder;
    private SurfaceView recordSurface;
    private int width, height;
    // Button
    private Button recordBut;
    private Button switchBut;
    private Button libraryBut;

    private final static String DIRECTORY = "/hdrecorder"; // Directory where
                                                            // the film is
                                                            // stored
    private final static String recordFileName = "/hdtestfile.mp4"; 
    private final static String saveFileName = "/hdsavefile.mp4"; 
    private MyMediaRecorder recorder = null;
    private final static String LOG_TAG = "HD Recorder";
    private String filePath;

    // Activity overrides
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // *******************************************
        // fullscreen mode
        // *******************************************
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        // *******************************************

        setContentView(R.layout.main);

        File dir = new File(Environment.getExternalStorageDirectory()
                + DIRECTORY);
        if (!dir.exists()) {
            if (dir.mkdir()) {
                Log.v(LOG_TAG, "Created directory");
            } else {
                Log.v(LOG_TAG, "Failed to create Directory");
            }
        }

        File videoFile = new File(Environment.getExternalStorageDirectory()
                + DIRECTORY + recordFileName);

        if (!videoFile.exists()) {
            videoFile.delete(); // Reset recording
        }

        filePath = videoFile.getAbsolutePath();
        Log.v(LOG_TAG, "PATH:" + filePath);
        Log.v(LOG_TAG, "PATH:" + filePath);

        recordSurface = (SurfaceView) findViewById(R.id.videoSurface);
        recordBut = (Button) findViewById(R.id.RecordBut);
        recordBut.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (recorder.getState() != MyMediaRecorder.RECORDING) {
                    startRecord();
                } else {
                    stopRecord();
                    recorder.release();
                    moveRecordFileToSave();
                    if (recorder == null) {
                        Log.v(LOG_TAG, "Recorder is null");
                    }
                    Log.v(LOG_TAG, "Value of recorder:" + recorder);
                    createRecorder();
                    initiateRecorder(recordViewHolder, width, height);
                }
            }
        });

        switchBut = (Button) findViewById(R.id.SwitchBut);
        switchBut.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {


            }
        });

        libraryBut = (Button) findViewById(R.id.LibraryBut);
        libraryBut.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Test_cameraActivity.this,
                        FileExplorer.class);
                Test_cameraActivity.this.startActivity(intent);
            }
        });

        recordViewHolder = recordSurface.getHolder();
        recordViewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        recordViewHolder.addCallback(this);
        // setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
        createRecorder();

    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.v(LOG_TAG, "OnStart");
        if (recorder != null) {
            if (recorder.getState() == MyMediaRecorder.RELEASED) {
                createRecorder();
            }
        }
        Log.v(LOG_TAG, "SurfaceView create initiated. OnStart Done");

    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.v(LOG_TAG, "onStop received");
        forceStopRecorder();
    }

    // General Helpers.
    private void createRecorder() {
        recorder = new MyMediaRecorder();
    }

    private void startRecord() {
        if (recorder.getState() != MyMediaRecorder.PREPARED) {
            Log.e(LOG_TAG, "Not recordable yet");
            return;
        }
        recorder.start();
        Log.v(LOG_TAG, "Recording started");
        recordBut.setText("Stop Record");
    }

    private void stopRecord() {
        Log.v(LOG_TAG, "Stop of recorder");
        if (recorder.getState() == MyMediaRecorder.RECORDING) {
            recorder.stop();
        }
        recorder.reset();
        recordBut.setText("Record");
    }

    private void initiateRecorder(SurfaceHolder holder, int width, int height) {
        Log.v(LOG_TAG, "H: " + height + " W:" + width);
        if (recorder.getState() != MyMediaRecorder.INITIAL) {
            Log.v(LOG_TAG, "Dude - not existing MediaRecorder - quitting");
            return;
        }
        recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        recorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
        recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        recorder.setOutputFile(this.filePath);
        recorder.setVideoEncoder(MediaRecorder.VideoEncoder.MPEG_4_SP);
        recorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);
        recorder.setVideoSize(width, height);
        recorder.setVideoFrameRate(24);
        recorder.setPreviewDisplay(holder.getSurface());

        Log.d(LOG_TAG, "Preview restarted");
        try {
            recorder.prepare();
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // isPrepared = true;
    }

    private void forceStopRecorder() {
        Log.v(LOG_TAG, "Force release of recorder");
        if (recorder.getState() != MyMediaRecorder.RELEASED) {
            stopRecord();
            recorder.release();
        }
    }

    private void moveRecordFileToSave() {
        File source = new File(filePath);
        File dest = new File(Environment.getExternalStorageDirectory()
                + DIRECTORY + saveFileName);
        if (dest.exists()) {
            Log.v(LOG_TAG, "Delete old save file");
            dest.delete();
        }
        source.renameTo(dest);
    }

    // ***** Implementing Callback ********/
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        recordViewHolder = holder;
        this.width = width;
        this.height = height;
        if (recorder.getState() == MyMediaRecorder.RECORDING) {
            stopRecord();
        }

        if (recorder.getState() == MyMediaRecorder.PREPARED) {
            recorder.reset();
        }
        initiateRecorder(holder, width, height);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        Log.v(LOG_TAG, "Surface is created: Path to use" + filePath);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        Log.v(LOG_TAG, "Surface is Destroyed");
        forceStopRecorder();
    }

}

最佳答案

我有一些东西可能也有帮助，为了跳转到另一个摄像头，请按照以下方法操作:

public void flipit() {
    //myCamera is the Camera object
    if (Camera.getNumberOfCameras()>=2) {
        myCamera.stopPreview();
        myCamera.release();
        //"which" is just an integer flag
        switch (which) {
        case 0:
            myCamera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
            which = 1;
            break;
        case 1:
            myCamera = Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK);
            which = 0;
            break;
        }
        try {
            myCamera.setPreviewDisplay(mHolder);
            //"this" is a SurfaceView which implements SurfaceHolder.Callback,
            //as found in the code examples
            myCamera.setPreviewCallback(this);
            myCamera.startPreview();
        } catch (IOException exception) {
            myCamera.release();
            myCamera = null;
        }
    }
}

现在...为了魔术，不要从主线程调用此方法。相反，这个方法必须从一个单独的线程启动，我的代码是这样做的:

        //btn is a Button that the user clicks on
    btn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            //onClick is invoked from main thread
            //kick-off a different Thread to handle this call
            Thread t = new Thread() {
                public void run() {
                    //myViewer is the SurfaceView object which uses
                    //the camera
                    myViewer.flipit();
                }
            };
            t.start();
        }
    });

我已经在 Android 4.1.1 上对此进行了测试，因此我认为它可能适合您。 (或者直到谷歌决定打破相机打开/关闭/释放/解锁/重新连接/surfaceholder/onPause/onResume/etc..？的工作方式)

关于android - 使用MediaRecorder android时如何在前后摄像头之间切换，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7471025/