Android Camera App预览问题

Question

我想问一些有关以下问题的建议。 我目前正在为Android使用摄像头应用程序，但遇到问题。 我使用了官方的android开发网站作为指导，并且该程序运行正常，除了当我第一次单击捕获按钮时，预览冻结并保持这种状态。 现在，这不会导致应用程序停止运行，因为冻结后，我仍然可以单击该按钮并拍照。 我知道这一点，因为如果我检查保存位置，拍摄的照片就在那里。

因此，总而言之，我希望我的程序即使在拍照后也能连续显示预览。 任何帮助，将不胜感激！

我的代码：

我的主要活动：

package com.camera123.cr;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.app.SearchManager.OnCancelListener;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.ShutterCallback;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.FrameLayout;

public class Camera123 extends Activity{
    /** Called when the activity is first created. */
private Camera mCamera;
    private cameraPreview mPreview;
    private MediaRecorder mMediaRecorder;
    private boolean isRecording = false;
    private Button captureButton;
    FrameLayout preview;



    public static final int MEDIA_TYPE_IMAGE = 1;
    public static final int MEDIA_TYPE_VIDEO = 2;



    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Create an instance of Camera
        mCamera = getCameraInstance();

        // Create our Preview view and set it as the content of our activity.
        mPreview = new cameraPreview(this, mCamera);

        captureButton = (Button) findViewById(R.id.button_capture);
        preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);



        captureButton.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        // get an image from the camera

                        mCamera.takePicture(null, null, mPicture);



                    }
                }
            );


    }





    /** A safe way to get an instance of the Camera object. */
    public static Camera getCameraInstance(){
        Camera c = null;
        try {
        c = Camera.open(); // attempt to get a Camera instance
        if (c != null){
            Camera.Parameters params = c.getParameters();
            c.setParameters(params);
        }
    }
    catch (Exception e){
        Log.d("DEBUG", "Camera did not open");
        // Camera is not available (in use or does not exist)
    }
        return c; // returns null if camera is unavailable
    }

    private PictureCallback mPicture = new PictureCallback() {

        @Override
        public void onPictureTaken(byte[] data, Camera camera) {

            File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
            if (pictureFile == null){
                Log.d("DEBUG", "Error creating media file, check storage permissions: " /*+
                    e.getMessage()*/);
                return;
            }

            try {
                FileOutputStream fos = new FileOutputStream(pictureFile);
                fos.write(data);
                fos.close();
            } catch (FileNotFoundException e) {
                Log.d("DEBUG", "File not found: " + e.getMessage());
            } catch (IOException e) {
                Log.d("DEBUG", "Error accessing file: " + e.getMessage());
            }
        }
    };



    /** Create a file Uri for saving an image or video */
    private static Uri getOutputMediaFileUri(int type){
          return Uri.fromFile(getOutputMediaFile(type));
    }

    private static File getOutputMediaFile(int type){
        // To be safe, you should check that the SDCard is mounted
        // using Environment.getExternalStorageState() before doing this.

        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
                  Environment.DIRECTORY_PICTURES), "MyCameraApp");
        // This location works best if you want the created images to be shared
        // between applications and persist after your app has been uninstalled.

        // Create the storage directory if it does not exist
        if (! mediaStorageDir.exists()){
            if (! mediaStorageDir.mkdirs()){
                Log.d("MyCameraApp", "failed to create directory");
                return null;
            }
        }

        // Create a media file name
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        File mediaFile;
        if (type == MEDIA_TYPE_IMAGE){
            mediaFile = new File(mediaStorageDir.getPath() + File.separator +
            "IMG_"+ timeStamp + ".jpg");
        } else if(type == MEDIA_TYPE_VIDEO) {
            mediaFile = new File(mediaStorageDir.getPath() + File.separator +
            "VID_"+ timeStamp + ".mp4");
        } else {
            return null;
        }

        return mediaFile;
    }



    private void releaseCamera(){
        if (mCamera != null){
            isRecording = false;
            mCamera.stopPreview();
        mCamera.setPreviewCallback(null);
            mCamera.release();        // release the camera for other applications
            mCamera = null;
        }
    }


}    

我的预览班：

package com.camera123.cr;

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;

public class cameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public cameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d("DEBUG", "Error setting camera preview: " + e.getMessage());
        }


    }

    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null){
          // preview surface does not exist
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d("DEBUG", "Error starting camera preview: " + e.getMessage());
        }
    }
}

我的main.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
  <FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    />

  <Button
    android:id="@+id/button_capture"
    android:text="Capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    />
</LinearLayout>

而我的清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.camera123.cr"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" />

    <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_VIDEO" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".Camera123"
            android:label="@string/app_name" 

            android:screenOrientation="landscape">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

我认为记录不充分，但是拍摄照片实际上会停止预览。 地点：

mCamera.startPreview();

在PictureCallback的onPictureTaken（）方法中，以在捕获完成后重新启动它。