Java 在Android中前后切换自定义摄像头

我想在代码中添加一个切换摄像头按钮。 这是代码。 我不明白我该怎么做。 请提出一些方法

先谢谢你

CameraDemo.java

public class CameraDemo extends Activity {
    private static final String TAG = "CameraDemo";
    Camera camera;
    Preview preview;
    Button buttonClick,switchCam;
    int which=0;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);


        switchCam=(Button)findViewById(R.id.switchcam);
        preview = new Preview(this);
        ((RelativeLayout) findViewById(R.id.preview)).addView(preview);

        buttonClick = (Button) findViewById(R.id.buttonClick);
        buttonClick.setOnClickListener( new OnClickListener() {
            public void onClick(View v) {
                preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback);

                AlertDialog.Builder alertDialog = new AlertDialog.Builder(CameraDemo.this);

                // Setting Dialog Title
                alertDialog.setTitle("Confirm");

                // Setting Dialog Message
                alertDialog.setMessage("Are You Done ?");

                // Setting Icon to Dialog
                alertDialog.setIcon(R.drawable.doneimg);

                // Setting Positive "Yes" Button
                alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog,int which) {

                        AlertDialog.Builder alertDialog = new AlertDialog.Builder(CameraDemo.this);

                        // Setting Dialog Title
                        alertDialog.setTitle("Confirm Student");

                        // Setting Dialog Message
                        alertDialog.setMessage("Are you a Student?");

                        // Setting Icon to Dialog
                        alertDialog.setIcon(R.drawable.student);

                        // Setting Positive "Yes" Button
                        alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int which) {

                                // Write your code here to invoke YES event
                                Intent i = new Intent(getApplicationContext(),
                                        ScanId.class);
                                startActivity(i);
                                finish();
                            }
                        });

                        // Setting Negative "NO" Button
                        alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int which) {
                                // Write your code here to invoke NO event
                                Toast.makeText(getApplicationContext(), "Sorry, Only Students Allowed", Toast.LENGTH_SHORT).show();
                                dialog.cancel();
                            }
                        });

                        // Showing Alert Message
                        alertDialog.show();
                    }
                });

                // Setting Negative "NO" Button
                alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // Write your code here to invoke NO event
                        Toast.makeText(getApplicationContext(), "Sorry, Only Students Allowed", Toast.LENGTH_SHORT).show();
                        dialog.cancel();
                    }
                });

                // Showing Alert Message
                alertDialog.show();

            }
        });
        Log.d(TAG, "onCreate'd");



    }


    ShutterCallback shutterCallback = new ShutterCallback() {
        public void onShutter() {
            Log.d(TAG, "onShutter'd");
        }
    };

    /** Handles data for raw picture */
    PictureCallback rawCallback = new PictureCallback() {
        public void onPictureTaken(byte[] data, Camera camera) {
            Log.d(TAG, "onPictureTaken - raw");
        }
    };

    /** Handles data for jpeg picture */
    PictureCallback jpegCallback = new PictureCallback() {
        public void onPictureTaken(byte[] data, Camera camera) {
            FileOutputStream outStream = null;
            long time = 0;
            try {
                // write to local sandbox file system
//                outStream = CameraDemo.this.openFileOutput(String.format("%d.jpg", System.currentTimeMillis()), 0);
                // Or write to sdcard
                time =  System.currentTimeMillis();
                outStream = new FileOutputStream(String.format("/sdcard/%d.jpg",time));
                outStream.write(data);
                outStream.close();
                Log.d(TAG, "onPictureTaken - wrote bytes: " + data.length);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {



            }
            Log.d(TAG, "onPictureTaken - jpeg");
        }
    };

}

nextjava文件>>Preview.Java

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;


class Preview extends SurfaceView implements SurfaceHolder.Callback {
    private static final String TAG = "Preview";

    SurfaceHolder mHolder;
    public Camera camera;
    int which=0;


    Preview(Context context) {
        super(context);

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, acquire the camera and tell it where
        // to draw.
        camera = Camera.open();
        try {
            camera.setPreviewDisplay(holder);
            camera.setDisplayOrientation(90);


            camera.setPreviewCallback(new PreviewCallback() {

                public void onPreviewFrame(byte[] data, Camera arg1) {
                    FileOutputStream outStream = null;
                    try {
                        outStream = new FileOutputStream(String.format("/sdcard/%d.jpg", System.currentTimeMillis()));
                        outStream.write(data);
                        outStream.close();
                        Log.d(TAG, "onPreviewFrame - wrote bytes: " + data.length);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                    }
                    Preview.this.invalidate();
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // Surface will be destroyed when we return, so stop the preview.
        // Because the CameraDevice object is not a shared resource, it's very
        // important to release it when the activity is paused.
        camera.stopPreview();
        camera = null;
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // Now that the size is known, set up the camera parameters and begin
        // the preview.
        Camera.Parameters parameters = camera.getParameters();
//        parameters.setPreviewSize(w, h);
        camera.setParameters(parameters);
        camera.startPreview();
    }





    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);
        Paint p= new Paint(Color.RED);
        Log.d(TAG,"draw");
        canvas.drawText("PREVIEW", canvas.getWidth()/2, canvas.getHeight()/2, p );
    }
}

XML文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:id="@+id/layout">

    <RelativeLayout android:id="@+id/preview"
        android:layout_weight="1" android:layout_width="fill_parent"
        android:layout_height="match_parent">


        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="New Button"
            android:id="@+id/switchcam"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="170dp" />
    </RelativeLayout>



    <Button android:layout_width="80dp"
        android:layout_height="80dp"
        android:id="@+id/buttonClick"
        android:text=""
        android:layout_gravity="center_horizontal|bottom"
        android:layout_marginBottom="50dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:background="@drawable/circlebutton"
         />

    <Button
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:id="@+id/gallery"
        android:background="@drawable/grid"
        android:layout_marginBottom="50dp"
        android:layout_marginLeft="60dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />


</RelativeLayout>

只需使用方法重新打开相机即可

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你好，乔迪，谢谢你的回复。我一按按钮就这么做了。。但当我点击按钮时，应用程序正在崩溃。我该怎么办？你调试了吗？？你犯了什么错误？？你必须让我们知道stacktrace和确切的错误，crash对我来说没什么。。。如果需要进一步信息，请更新您的问题。请注意，引用的代码是错误的。Camera.open（）使用的整数索引不是Camera.CameraInfo类中的常量之一。

//swap the id of the camera to be used
if(currentCameraId == Camera.CameraInfo.CAMERA_FACING_BACK){
    currentCameraId = Camera.CameraInfo.CAMERA_FACING_FRONT;
}
else {
    currentCameraId = Camera.CameraInfo.CAMERA_FACING_BACK;
}
camera = Camera.open(currentCameraId);