Android相机应用程序崩溃

Question

我正在尝试将此YouTube相机教程http://www.youtube.com/watch?v=OMP6LHKEZOA中的代码与来自此处http://developer.android.com/training/basics/data-storage/files.html的一些代码合并，以将图像保存到SD卡。成功将图像保存到文件后，以下代码崩溃。如何让它不崩溃并返回主布局？

package com.example.test2;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
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.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity {
    ImageView iv;
    private Uri fileUri;

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

    iv=(ImageView)findViewById(R.id.imageView);
    Button btn = (Button)findViewById(R.id.takePhoto);
    btn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
            fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE); // create a file to save the image
            intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri); // set the image file name
            startActivityForResult(intent, 0);

        }
    });   
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    if(requestCode ==0)
    {
        Bitmap theImage = (Bitmap) data.getExtras().get("data");
        iv.setImageBitmap(theImage);
    }
}

//Uri fileUri = null;

public static final int MEDIA_TYPE_IMAGE = 1;

/** 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("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile;
    if (type == MEDIA_TYPE_IMAGE){
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
        "IMG_"+ timeStamp + ".jpg");
    } else {
        return null;
    }

    return mediaFile;
}
}