Android 使用 getExternalFilesDir 保存图片不一致

Question

在我的应用程序中，我尝试拍照、保存并使用从 Android Developers tutorial

获得的代码将其添加到 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");
        }
    }
}

有时此代码会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。

这是成功捕获图像的 logcat 输出，其中图像出现在 ImageView

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

这里是 logcat 图像捕获失败的输出，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

这似乎是随机工作，并且 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。我还在清单文件中添加了 WRITE_EXTERNAL_STORAGE 权限。

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

我也知道我可以使用图片中的缩略图，但我想要完整尺寸的图片，因为稍后我会将它添加到 class。

有人知道出了什么问题吗？

Answer 1

当您的应用程序处于后台时，您的进程正在终止。这对于 Android 来说是正常的，尽管您在这里可能出乎意料。您需要在保存的实例状态 Bundle.

中保持 EXTRA_OUTPUT

另请注意 since file: Uri values are being banned，您应该考虑改用 FileProvider。

This sample app 证明了这两件事。不可否认，代码比较复杂：

/***
 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();
      }
    }
  }
}

关于你的问题，我将我的输出位置保存在 Bundle 中的 onSaveInstanceState() 中，如果我有一个 Bundle 则在 onCreate() 中再次使用它正在恢复中。

Android 使用 getExternalFilesDir 保存图片不一致

Android inconsistent picture saving with getExternalFilesDir

java

camera

android

image