Question

我的项目中有一个类可以上传图像并将其保存在数据库中，如果成功，则可以将其保存在本地。这行得通，我可以将图像保存在我在Android手机上创建的自定义文件夹中。

但是，在另一个类中，我试图以文本形式下载编码的图像，并使用我上面使用的方法将其保存在本地，但是它不再起作用。看来我无法创建文件夹。

我不了解它如何在我的其他班级上发挥作用，而不是在本课程中

我尝试检查清单文件，看看是否包含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">
...

[EDIT]好吧，我尝试删除文件路径中的空格，以检查空格是否确实是导致问题的原因，并且仍然无法正常工作

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

此外，它如何在我的其他带有空格的类上而不是在这个空格上起作用？：（

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。 encode_image是一个文字

我需要能够将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。应当在TB System内创建另一个文件夹（即pat1，pat2，pat3，...），并将图像保存在其中。

Answer 1

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

查看此other question有助于处理文件路径中的空格。答案从未获得批准，所以我不确定是否确实解决了问题，但是他们提到了以下代码段：

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

Uri.parse解决了所有空白/反斜杠/非法字符问题在路径上产生一个“好”的uri。

Answer 2

您是否正在检查读写权限。

READ_EXTERNAL_STORAGE和WRITE_EXTERNAL_STORAGE必须以编程方式签入

使用此

    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，请做您的工作

如果为假，则调用此方法

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;
    }
}

Answer 3

您的代码中有问题，我已经使用文件夹中的空格测试了组合，并且还使用了确切的文件名进行了测试。根据您的问题运行的代码段如下，

图像下载成功快照

代码布局视图

build.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'
}

strings.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 {
}

FileDownloader.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

读取图像输出

“ java.io.FileNotFoundException（无此类文件或目录）”

3 个答案: