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我需要从相机捕获视频并将其保存到存储卡，我正在使用谷歌教程，但调用时仍然出现错误

mRecorder.setCamera(mCamera); // 4.b.1 step from tutorial

我尝试将其放入try并查看异常

try {
    mRecorder.setCamera(mCamera);
} catch(Exception e) {
    Log.d("MyVideoRecord", "Error setting the camera: " + e.getMessage());
    System.out.println("CameraPreview::record() - setCamera() thrown an exception");
    System.out.println("Exception: "+e.getMessage());
    System.out.println("Exception: "+e.getLocalizedMessage());
    System.out.println("Exception: "+e.toString());
    e.printStackTrace();

    return false;
}

LogCat 输出

D/MyVideoRecord(2681): Error setting the camera: null
I/System.out(2681): CameraPreview::record() - setCamera() thrown an exception
I/System.out(2681): Exception: null
I/System.out(2681): Exception: null
I/System.out(2681): Exception: java.lang.NullPointerException
W/System.err(2681): java.lang.NullPointerException
W/System.err(2681):     at com.example.myvideorecord.CameraPreview.record(CameraPreview.java:101)
W/System.err(2681):     at com.example.myvideorecord.MainActivity.onOptionsItemSelected(MainActivity.java:104)
W/System.err(2681):     at android.app.Activity.onMenuItemSelected(Activity.java:2502)
W/System.err(2681):     at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:969)
W/System.err(2681):     at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
W/System.err(2681):     at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
W/System.err(2681):     at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
W/System.err(2681):     at com.android.internal.view.menu.IconMenuView.invokeItem(IconMenuView.java:468)
W/System.err(2681):     at com.android.internal.view.menu.IconMenuItemView.performClick(IconMenuItemView.java:126)
W/System.err(2681):     at android.view.View$PerformClick.run(View.java:14263)
W/System.err(2681):     at android.os.Handler.handleCallback(Handler.java:605)
W/System.err(2681):     at android.os.Handler.dispatchMessage(Handler.java:92)
W/System.err(2681):     at android.os.Looper.loop(Looper.java:137)
W/System.err(2681):     at android.app.ActivityThread.main(ActivityThread.java:4441)
W/System.err(2681):     at java.lang.reflect.Method.invokeNative(Native Method)
W/System.err(2681):     at java.lang.reflect.Method.invoke(Method.java:511)
W/System.err(2681):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
W/System.err(2681):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
W/System.err(2681):     at dalvik.system.NativeStart.main(Native Method)
D/dalvikvm(2681): Debugger has detached; object registry had 425 entries

看起来mCamera指针从日志中为空，但我不认为是这种情况，因为我之前已经解锁了 mCamera而没有错误。我查看了文档，但没有任何关于setCamera()返回错误或抛出异常的消息。我在清单中设置了CAMERA,WRITE_EXTERNAL_STORAGE和权限。RECORD_AUDIO我不知道是什么可能导致问题或如何追踪它。有人可以帮我吗？

非常感谢 ！:)

这是我的所有代码：

CameraPreview.java

我已经实现record()（这就是发生错误的地方）和stopRecord()方法。其余文件来自谷歌教程。

package com.example.myvideorecord;

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

import android.content.Context;
import android.hardware.Camera;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

//http://developer.android.com/guide/topics/media/camera.html#capture-video
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
        private SurfaceHolder mHolder;
        private Camera mCamera;
        private boolean recording;
        private MediaRecorder mRecorder;

        public CameraPreview(Context context, Camera camera) {
            super(context);
            System.out.println("CameraPreview() - Started");
            mCamera = camera;
            recording = false;

            // 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);

            System.out.println("CameraPreview() - Ended");
        }

        public void surfaceCreated(SurfaceHolder holder) {
            System.out.println("CameraPreview::surfaceCreated() - Started");
            // 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("MyVideoRecord", "Error setting camera preview: " + e.getMessage());
            }

            System.out.println("CameraPreview::surfaceCreated() - Ended");
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            System.out.println("CameraPreview::surfaceDestroyed()");
            // empty. Take care of releasing the Camera preview in your activity.
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
            System.out.println("CameraPreview::surfaceChanged() - Started");

            // 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("MyVideoRecord", "Error starting camera preview: " + e.getMessage());
            }

            System.out.println("CameraPreview::surfaceChanged() - Ended");
        }


        public boolean record()
        {
            // if already recording, return
            if( recording ) return false;

            // We are recording
            recording = true;
            // log start of the method
            System.out.println("CameraPreview::record() - Method start");

            //mCamera.stopPreview();
            mCamera.unlock();


            // 
            // !!! THIS IS WHERE ERROR OCCURS !!!
            //
            //
            try {
                mRecorder.setCamera(mCamera);
            } catch(Exception e) {
                Log.d("MyVideoRecord", "Error setting the camera: " + e.getMessage());
                System.out.println("CameraPreview::record() - setCamera() thrown an exception");
                System.out.println("Exception: "+e.getMessage());
                System.out.println("Exception: "+e.getLocalizedMessage());
                System.out.println("Exception: "+e.toString());
                e.printStackTrace();

                return false;
            }

            // Set media recorder properties            
            mRecorder.setAudioSamplingRate(MediaRecorder.AudioSource.CAMCORDER);
            mRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
            mRecorder.setProfile( CamcorderProfile.get( CamcorderProfile.QUALITY_LOW ) );
            //mRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString());
            mRecorder.setOutputFile("/sdcard/MVR_video");

            // probably not needed
            //mRecorder.setPreviewDisplay());

            // Prepare media recorder
            try {
                mRecorder.prepare();
            } catch (Exception e) {
                Log.d("MyVideoRecord", "Error preparing media recorder: " + e.getMessage());
                System.out.println("CameraPreview::record() - prepare() thrown an exception");

                return false;
            }

            mRecorder.start();

            System.out.println("CameraPreview::record() - Method returning TRUE");
            return true;
        }

        public void stopRecord() {
            System.out.println("CameraPreview::stopRecord() - Method start");

            if(recording)
            {
                mRecorder.stop();
                mRecorder.release();
                mCamera.lock();
            }
        }    
    }

MainActivity.java

package com.example.myvideorecord;

import android.app.Activity;
import android.content.SharedPreferences;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.FrameLayout;

// http://developer.android.com/reference/android/app/Activity.html
public class MainActivity extends Activity {
    private Camera mCamera;
    private CameraPreview mPreview;
    private Camera.Parameters parameters;
    private FrameLayout preview;
    private SharedPreferences preferences;

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

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

        // Get parameters of camera (not neccessary now)
        parameters = getCameraParameters(mCamera);
        parameters.getFocusMode();

        // get preview reference
        preview = (FrameLayout) findViewById(R.id.camera_preview);

        mPreview = new CameraPreview(this, mCamera);

        preferences = getPreferences(MODE_PRIVATE);
    }

    @Override
    public void onStart() {
        super.onStart();

        // Create our Preview view and set it as the content of our activity.        

        System.out.println("MainActivity::onCreate() - adding view to preview");
        preview.addView(mPreview);
        System.out.println("MainActivity::onCreate() - view added");
    }
    @Override
    public void onStop() {
        super.onStop();     
        System.out.println("MainActivity::onStop() - Method start");

        // here shoud go something like
        // preview.stop
        preview.removeView(mPreview);
        mPreview.stopRecord();
    }

    @Override
    public void onPause() {
        super.onPause();

        // Save all needed information
        //preferences.edit();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        System.out.println("MainActivity::onDestroy() - Method start");

        mCamera.stopPreview();
        releaseCameraInstance(mCamera);
    } 



    /*
     * 
     *  MENU 
     * 
     * */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        System.out.println("MainActivity::onCreateOptionsMenu() - Method start");

        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        System.out.println("MainActivity::onOptionsItemSelected() - Method start");

        // Handle item selection
        switch (item.getItemId()) {
            case R.id.menu_settings:
                return true;
            case R.id.menu_quit:
                this.finish();
                return true;
            case R.id.menu_record:
                mPreview.record();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }



    /*
     * 
     *  Camera handling
     * 
     * */
    /** 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
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
            System.out.println("getCameraInstance() - excepction");
        }

        System.out.println("getCameraInstance() - returning camera");
        return c; // returns null if camera is unavailable
    }

    public static Camera.Parameters getCameraParameters(Camera c)
    {
        System.out.println("getCameraParameters() - getting parameters of camera");
        Camera.Parameters par;
        par = c.getParameters();

        System.out.println("getCameraParameters() - returning parameters of camera");
        return par;
    }

    /* release camera object and log it */
    public static void releaseCameraInstance(Camera c){
        System.out.println("releaseCameraInstance() - camera released");
        c.release();
    }
}
4

1 回答 1

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你mRecorder是空的，因为你从来没有初始化它。在构造函数中初始化它以及相机和其他东西；）

mRecorder = new MediaRecorder();
于 2012-12-04T19:59:47.147 回答