使用getExternalFilesDir保存Android不一致的图片

时间：2016-05-04 22:24:34

标签： java android image camera

在我的应用中，我正在尝试拍照，保存并使用我从Android Developers tutorial

获取的代码将其添加到ImageView 
private static final int REQUEST_IMAGE_CAPTURE = 1;
private String lastImagePath;

//Create temporary image file using getExternalFilesDir()
private File createImageFile() throws IOException{
    String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String imageFileName = "JPEG_" + timestamp + "_";
    File storageDir = getActivity().getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(imageFileName, ".jpg", storageDir);
    lastImagePath = image.getAbsolutePath();
    return image;
}

//Start picture intent and save to file
private void takePicture(){
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    File photoFile = null;
    if(takePictureIntent.resolveActivity(getActivity().getPackageManager())!= null){
        try{
            photoFile = createImageFile();
        }catch (IOException e){
            Log.e(TAG, "Error Creating image file");
            e.printStackTrace();
        }
        if (photoFile !=null){
            Log.e(TAG, photoFile.getAbsolutePath());
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));
            startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
        }
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data){
    super.onActivityResult(requestCode, resultCode, data);
    if(requestCode == REQUEST_IMAGE_CAPTURE && resultCode == Activity.RESULT_OK){

        //Ensure the path has been set
        if(lastImagePath !=null){
            Log.e(TAG, "LastImagePath: " + lastImagePath);

            //DEBUG:see if it actually created the file
            File file = new File(lastImagePath);
            if(file.exists()){
                Log.e(TAG, "File exists");
            }

            //Decode file
            Bitmap image = BitmapFactory.decodeFile(lastImagePath);

            //DEBUG: see if image is null
            if(image == null){
                Log.e(TAG, "Image is null");
            }else{
                Log.e(TAG, "Image is not null");
            }

            //convert full sized image to thumbnail and add it to imageView
            Bitmap thumbnail = ThumbnailUtils.extractThumbnail(image, 200, 200);
            image1.setImageBitmap(thumbnail);
        }else{
            Log.e(TAG, "lastImagePath is null");
        }
    }
}

有时此代码按预期工作并拍摄图像，保存图像，将其加载回程序并将其添加到图像视图中。但其他时候，它根本不起作用，似乎无法拍摄图像。

以下是成功捕获图像的logcat输出，其中图像显示在ImageView

中 
05-04 17:27:49.218 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: /storage/emulated/0/Android/data/com.noah.stickynotes_clientside/files/Pictures/JPEG_20160504_172748_-1847663626.jpg
05-04 17:28:03.886 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: LastImagePath: /storage/emulated/0/Android/data/com.noah.stickynotes_clientside/files/Pictures/JPEG_20160504_172748_-1847663626.jpg
05-04 17:28:04.359 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: File exists
05-04 17:28:04.825 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: Image is not null

这是失败的图像捕获的logcat输出，其中ImageView中没有图像

05-04 17:29:00.070 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: /storage/emulated/0/Android/data/com.noah.stickynotes_clientside/files/Pictures/JPEG_20160504_172900_-1359930406.jpg
05-04 17:29:06.581 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: LastImagePath: /storage/emulated/0/Android/data/com.noah.stickynotes_clientside/files/Pictures/JPEG_20160504_172900_-1359930406.jpg
05-04 17:29:06.583 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: File exists
05-04 17:29:06.583 4964-4964/com.noah.stickynotes_clientside E/SUBMIT_FRAGMENT: Image is null

这似乎随机工作，80％的时间都失败了。我正在使用getExternalFilesDir，因为我希望照片对应用程序是私有的。我还将WRITE_EXTERNAL_STORAGE权限添加到我的Manifest文件中。

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

我也明白我可以使用图片中的缩略图，但我希望拥有完整尺寸的图片，因为我稍后会将它添加到一个类中。

任何人都有任何关于什么出错的想法？​​

1 个答案:

答案 0 :(得分：2)

当您的应用在后台时，您的流程正在终止。这对于Android来说是正常的，尽管你可能不会在这里期待它。您需要在保存的实例状态EXTRA_OUTPUT中保留Bundle。

另请注意since file: Uri values are being banned，您应该考虑切换到使用FileProvider。

This sample app演示了这两件事。不可否认，代码更复杂：

/***
 Copyright (c) 2008-2016 CommonsWare, LLC
 Licensed under the Apache License, Version 2.0 (the "License"); you may not
 use this file except in compliance with the License. You may obtain a copy
 of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless required
 by applicable law or agreed to in writing, software distributed under the
 License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
 OF ANY KIND, either express or implied. See the License for the specific
 language governing permissions and limitations under the License.

 From _The Busy Coder's Guide to Android Development_
 https://commonsware.com/Android
 */

package com.commonsware.android.camcon;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v4.content.FileProvider;
import java.io.File;
import java.util.List;

public class CameraContentDemoActivity extends Activity {
  private static final String EXTRA_FILENAME=
    "com.commonsware.android.camcon.EXTRA_FILENAME";
  private static final String FILENAME="CameraContentDemo.jpeg";
  private static final int CONTENT_REQUEST=1337;
  private static final String AUTHORITY=
    BuildConfig.APPLICATION_ID+".provider";
  private static final String PHOTOS="photos";
  private File output=null;
  private Uri outputUri=null;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Intent i=new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

    if (savedInstanceState==null) {
      output=new File(new File(getFilesDir(), PHOTOS), FILENAME);

      if (output.exists()) {
        output.delete();
      }
      else {
        output.getParentFile().mkdirs();
      }
    }
    else {
      output=(File)savedInstanceState.getSerializable(EXTRA_FILENAME);
    }

    outputUri=FileProvider.getUriForFile(this, AUTHORITY, output);

    if (savedInstanceState==null) {
      i.putExtra(MediaStore.EXTRA_OUTPUT, outputUri);

      if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.LOLLIPOP) {
        i.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
      }
      else {
        List<ResolveInfo> resInfoList=
          getPackageManager()
            .queryIntentActivities(i, PackageManager.MATCH_DEFAULT_ONLY);

        for (ResolveInfo resolveInfo : resInfoList) {
          String packageName = resolveInfo.activityInfo.packageName;
          grantUriPermission(packageName, outputUri,
            Intent.FLAG_GRANT_WRITE_URI_PERMISSION |
              Intent.FLAG_GRANT_READ_URI_PERMISSION);
        }
      }

      startActivityForResult(i, CONTENT_REQUEST);
    }
  }

  @Override
  protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    outState.putSerializable(EXTRA_FILENAME, output);
  }

  @Override
  protected void onActivityResult(int requestCode, int resultCode,
                                  Intent data) {
    if (requestCode == CONTENT_REQUEST) {
      if (resultCode == RESULT_OK) {
        Intent i=new Intent(Intent.ACTION_VIEW);

        i.setDataAndType(outputUri, "image/jpeg");
        i.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        startActivity(i);
        finish();
      }
    }
  }
}

关于您的问题，我将输出位置保存在Bundle的{​​{1}}中并在onSaveInstanceState()中再次使用它，如果我有onCreate()的话恢复。

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