“java.io.FileNotFoundException(没有这样的文件或目录)”

我的项目中有一个类来上传图像并保存在我的数据库中,如果成功,则将其保存在本地。这可行,我可以将图像保存在我在我的 android 手机上创建的自定义文件夹中。

但是,在另一堂课中,我正在尝试以文本形式下载编码图像并使用我上面使用的方法将其保存在本地,但它不再起作用了。看来我无法创建文件夹。

我不明白它是如何在我的其他班级而不是在这个班级工作的

我尝试检查我的清单文件,看看我是否包含了所需的权限以及它们是否在正确的位置

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="buenaventura.dorothy.tbmgmtapp">

    <uses-sdk android:minSdkVersion="8" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/lungs"
        android:label="@string/app_name"
        android:networkSecurityConfig="@xml/network_security_config"
        tools:replace="android:icon">
...

[编辑]好的,我尝试删除文件路径中的空格以检查空格是否真的是导致问题的原因,但它仍然没有工作

File folder = new File(Environment.getExternalStoragePublicDirectory( Environment.DIRECTORY_DCIM) + File.separator + "TBSystem" + File.separator + patient_id + File.separator + "lab_result_" + sqlDateToString(result_date) + ".jpg");

另外,它怎么能在我的另一个有空格的班级上工作,而不是在这个班级上? :(

File folder = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_DCIM) + File.separator + "TB System" + File.separator + patient_id);

if (!folder.exists()) {
    folder.mkdirs();
}

folder = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_DCIM) + File.separator + "TB System" + File.separator + patient_id + File.separator + "lab_result_" + result_date + ".jpg");

byte[] decodedBytes = Base64.decode(encoded_image, 0);
Bitmap imageBitmap = BitmapFactory.decodeByteArray(decodedBytes, 0, decodedBytes.length);

try (
    FileOutputStream out = new FileOutputStream(folder)) {
    imageBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out); 
} catch (IOException e) {
    e.printStackTrace();
}

W/System.err: java.io.FileNotFoundException: /storage/emulated/0/DCIM/TB System/pat1/lab_result_2019-04-06.jpg (No such file or directory)
W/System.err:     at java.io.FileOutputStream.open0(Native Method)
        at java.io.FileOutputStream.open(FileOutputStream.java:308)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:238)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:180)
        at buenaventura.dorothy.tbmgmtapp.db_volley.VolleyDownloadRequest$1.onResponse(VolleyDownloadRequest.java:569)
        at buenaventura.dorothy.tbmgmtapp.db_volley.VolleyDownloadRequest$1.onResponse(VolleyDownloadRequest.java:103)
        at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:82)
        at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:29)
        at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:102)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:6981)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)

patient_id 和 result_date 只是字符串。 encoded_image 是一个 lontext

我需要能够将我下载的编码文本转换为位图并将其保存在我希望在 DCIM 中找到的自定义文件夹“TB System”中。应在 TB System 中创建另一个文件夹(即 pat1、pat2、pat3、...),并将图像保存在其中。

stack overflow "java.io.FileNotFoundException (No such file or directory)"
原文答案

答案:

作者头像

我看到您使用的路径在“TB”和“System”之间包含一个空格,这可能会导致问题。您的其他类是否也包含带空格的文件路径?如果没有,这可能是问题所在。

在处理文件路径中的空格时查看这个有助于处理的 other question 。答案从未得到批准,所以我不确定是否真的解决了这个问题,但他们提到了这段代码:

Uri uri = Uri.parse(paths);
File file = new File(uri.getPath());

Uri.parse 修复了路径中的所有空格/反斜杠/非法字符问题,并生成了一个“好”的 uri。

作者头像

您是否检查了读写权限。

READ_EXTERNAL_STORAGE 和 WRITE_EXTERNAL_STORAGE 必须以编程方式签入

用这个

    private boolean checkPermission(){
      if(ActivityCompat.checkSelfPermission(this, 
        Manifest.permission.READ_EXTERNAL_STORAGE) != 
        PackageManager.PERMISSION_GRANTED &&
            ActivityCompat.checkSelfPermission(this, 
        Manifest.permission.WRITE_EXTERNAL_STORAGE) != 
        PackageManager.PERMISSION_GRANTED){
        return false;
    }
    return true;
}

如果是真的做你的工作

如果 false 调用此方法

private static final int MY_PERMISSION_REQUEST_CODE = 1001;

ActivityCompat.requestPermissions(this, new String[]{
                Manifest.permission.READ_EXTERNAL_STORAGE,
                Manifest.permission.WRITE_EXTERNAL_STORAGE
        }, MY_PERMISSION_REQUEST_CODE);

并添加此代码

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode){
        case MY_PERMISSION_REQUEST_CODE:
            if(grantResults.length > 0 && grantResults[0] == 
             PackageManager.PERMISSION_GRANTED)
                //Do your work
            break;
    }
}
作者头像

您的代码有问题,我已经测试了文件夹中空格的组合以及它正在工作的确切文件名。基于您的问题的工作代码片段如下,

图片下载成功快照

enter image description here

代码布局视图

enter image description here

构建.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.zackdawood.albummanager"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

字符串.xml

<resources>
    <string name="app_name">AlbumManager</string>
    <string name="write_button">Write Image</string>
    <string name="read_button">Read Image</string>
    <string name="request_access">Request Access</string>
</resources>

external_files.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="."/>
</paths>

network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="true">
    <domain includeSubdomains="true">maven.apache.org</domain>
    <domain includeSubdomains="true">upload.wikimedia.org</domain>
</domain-config>
</network-security-config>

GenericFileProvider.java

package com.zackdawood.albummanager;

import android.support.v4.content.FileProvider;

public class GenericFileProvider extends FileProvider {
}

文件下载器.java

package com.zackdawood.albummanager;

import android.util.Log;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class FileDownloader {

    private static final String TAG = "FileDownloader";

    private static final int MEGABYTE = 1024 * 1024;

    public static void downloadFile(String fileUrl, File directory) {
        try {
            Log.v(TAG, "downloadFile() invoked ");
            Log.v(TAG, "downloadFile() fileUrl " + fileUrl);
            Log.v(TAG, "downloadFile() directory " + directory);

            URL url = new URL(fileUrl);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.connect();

            InputStream inputStream = urlConnection.getInputStream();
            FileOutputStream fileOutputStream = new FileOutputStream(directory);
            int totalSize = urlConnection.getContentLength();

            byte[] buffer = new byte[MEGABYTE];
            int bufferLength = 0;
            while ((bufferLength = inputStream.read(buffer)) > 0) {
                fileOutputStream.write(buffer, 0, bufferLength);
            }
            fileOutputStream.close();
            Log.v(TAG, "downloadFile() completed ");

        } catch (FileNotFoundException e) {
            e.printStackTrace();
            Log.e(TAG, "downloadFile() error" + e.getMessage());
            Log.e(TAG, "downloadFile() error" + e.getStackTrace());
        } catch (MalformedURLException e) {
            e.printStackTrace();
            Log.e(TAG, "downloadFile() error" + e.getMessage());
            Log.e(TAG, "downloadFile() error" + e.getStackTrace());
        } catch (IOException e) {
            e.printStackTrace();
            Log.e(TAG, "downloadFile() error" + e.getMessage());
            Log.e(TAG, "downloadFile() error" + e.getStackTrace());
        }
    }
}

MainActivity.java

package com.zackdawood.albummanager;

import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private static final String[] PERMISSIONS = {android.Manifest.permission.READ_EXTERNAL_STORAGE,
            android.Manifest.permission.WRITE_EXTERNAL_STORAGE,
            android.Manifest.permission.INTERNET};

    private static boolean hasPermissions(Context context, String... permissions) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
            for (String permission : permissions) {
                if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
        }
        return true;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);
        Log.v(TAG, "onCreate() Method invoked ");
    }

    public void write(View view) {
        if (!hasPermissions(MainActivity.this, PERMISSIONS)) {

            Log.v(TAG, "download() Method DON'T HAVE PERMISSIONS ");

            Toast t = Toast.makeText(getApplicationContext(), "You don't have write access !", Toast.LENGTH_LONG);
            t.show();

        } else {

            new DownloadFile().execute("https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Adler.jpg/547px-Adler.jpg", "lab_result_2019-04-06.jpg");

        }
    }

    public void read(View view) {
        if (!hasPermissions(MainActivity.this, PERMISSIONS)) {

            Log.v(TAG, "download() Method DON'T HAVE PERMISSIONS ");

            Toast t = Toast.makeText(getApplicationContext(), "You don't have read access !", Toast.LENGTH_LONG);
            t.show();

        } else {

            File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);

            File directory = new File(folder + "/TB System");
            File imgFile = new File(directory, "lab_result_2019-04-06.jpg");

            Log.v(TAG, "view() Method imgfile " + imgFile.getAbsolutePath());

            Uri path = FileProvider.getUriForFile(this, BuildConfig.APPLICATION_ID + ".fileprovider", imgFile);

            Log.v(TAG, "view() Method path " + path);

            Intent imageIntent = new Intent(Intent.ACTION_VIEW);
            imageIntent.setDataAndType(path, "image/*");
            imageIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            imageIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

            try {
                startActivity(imageIntent);
            } catch (ActivityNotFoundException e) {
                Toast.makeText(MainActivity.this, "No Application available to view Image", Toast.LENGTH_SHORT).show();
            }

        }
    }

    public void request(View view) {
        ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);

    }

    private class DownloadFile extends AsyncTask<String, Void, Void> {

        @Override
        protected Void doInBackground(String... strings) {
            Log.v(TAG, "doInBackground() Method invoked ");

            String fileUrl = strings[0];   // -> http://maven.apache.org/maven-1.x/maven.pdf
            String fileName = strings[1];  // -> maven.pdf
            File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);

            File directory = new File(folder + "/TB System");
            if (!directory.exists()) {
                directory.mkdir();
                Log.v(TAG, "doInBackground() Method Directory Created ");

            }

            File imgFile = new File(directory, fileName);
            Log.v(TAG, "doInBackground() imgFile invoked " + imgFile.getAbsolutePath());
            Log.v(TAG, "doInBackground() imgFile invoked " + imgFile.getAbsoluteFile());

            try {
                imgFile.createNewFile();
                Log.v(TAG, "doInBackground() file created" + imgFile);

            } catch (IOException e) {
                e.printStackTrace();
                Log.e(TAG, "doInBackground() error" + e.getMessage());
                Log.e(TAG, "doInBackground() error" + e.getStackTrace());

            }
            FileDownloader.downloadFile(fileUrl, imgFile);
            Log.v(TAG, "doInBackground() file download completed");

            return null;
        }
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="395dp"
        android:layout_height="715dp"
        android:orientation="vertical"
        tools:layout_editor_absoluteX="8dp"
        tools:layout_editor_absoluteY="8dp">

        <Button
            android:id="@+id/button2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/write_button"
            android:onClick="write"/>

        <Button
            android:id="@+id/button3"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/read_button"
            android:onClick="read"/>

        <Button
            android:id="@+id/button4"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/request_access"
            android:onClick="request"/>
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zackdawood.albummanager">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:networkSecurityConfig="@xml/network_security_config">
        <provider
            android:name=".GenericFileProvider"
            android:authorities="${applicationId}.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/external_files"/>
        </provider>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

应用启动器屏幕

enter image description here

读取图像输出

enter image description here

作者头像

在访问或写入文件之前,请创建其父文件和文件本身,以确保安全。在这种情况下...就在 try catch 块之前,或者至少在 FileOutputStream 行之前,通过 if (!folder.exists()) folder.createNewFile(); 创建文件

您需要存储权限(READ-WRITE EXTERNAL STORAGE)才能在应用程序的数据目录之外创建文件

这可能会有所帮助