Android 不使用现有的应用程序录制视频

我创建了一个使用外部摄像头应用程序录制视频的应用程序。有人告诉我，有一种方法可以让你的应用程序通过打电话给摄像机来录制视频。我被困了几天，看是否有人愿意帮忙。这是我的密码

import java.io.File;
import java.sql.Date;
import java.text.SimpleDateFormat;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;



public class ActivityRecord extends Activity{
    private MediaRecorder recorder;
    private String OUTPUT_FILE;


    private Uri fileUri;
    //public static final int MEDIA_TYPE_VIDEO = 2;
    static final int REQUEST_VIDEO_CAPTURE = 1;
    private static final int CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE = 200;
    public static ActivityRecord ActivityContext =null; 
    public static TextView output;
    Intent takeVideoIntent;


    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)
        }
        return c; // returns null if camera is unavailable
    }

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

        ActivityContext = this;

        Button buttonRecording = (Button)findViewById(R.id.recordButton);
       // output = (TextView)findViewById(R.id.videoView);

        buttonRecording.setOnClickListener(new Button.OnClickListener(){

            @Override
            public void onClick(View arg0) {

                // create new Intentwith with Standard Intent action that can be
                // sent to have the camera application capture an video and return it. 
                Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
                if (takeVideoIntent.resolveActivity(getPackageManager()) != null) {
                    startActivityForResult(takeVideoIntent, REQUEST_VIDEO_CAPTURE);
                }

                // create a file to save the video
                fileUri = getOutputMediaFileUri(REQUEST_VIDEO_CAPTURE); 

                // set the image file name  
                intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);  

                // set the video image quality to high
                intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1); 

                // start the Video Capture Intent
                startActivityForResult(intent, CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE);

            }});


    }


        // Check that the SDCard is mounted
        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
                  Environment.DIRECTORY_PICTURES), "MyCameraVideo");
       public static final int MEDIA_TYPE_IMAGE = 1;
        public static final int MEDIA_TYPE_VIDEO1 = 2;

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

        /** Create a File for saving an image or video */
        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("20140129_HHmmss").format(new Date(type));
            File mediaFile;
            if (type == MEDIA_TYPE_IMAGE){
                mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "IMG_"+ timeStamp + ".jpg");
            } else if(type == REQUEST_VIDEO_CAPTURE) {
                mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "VID_"+ timeStamp + ".mp4");
            } else {
                return null;
            }

            return mediaFile;
        }
}

我想从iside应用程序录制视频，但不使用手机附带的摄像头应用程序。下面是我的错误

---

在您的

按钮记录
上单击（…）
方法，您创建了一个名为
Intent
的
Intent
，但随后尝试使用
takeVideoIntent
，您在
活动中声明了该方法，但从未初始化。这就是为什么会出现
NullPointerException

Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
if (takeVideoIntent.resolveActivity(getPackageManager()) != null) {
    startActivityForResult(takeVideoIntent, REQUEST_VIDEO_CAPTURE);
}

你有什么问题/你看到了什么错误/你的问题是什么？那么你的问题是什么？您遇到了什么错误？我的问题是如何在不使用内置摄像头应用程序的情况下调用和使用摄像头