Question

我到处寻找我的问题的答案，我确实找到了大量的答案，应该解决了我的问题，但我无法解决它。

我的目标是放一张128GB的SD卡并将文件写入其中（csv或文本）。我试图在microSD卡中打开文件或文件夹，但它没有创建它。也没有创建文件。我认为我得到的路径是：

Environment.getExternalStorageDirectory()

不是SD卡路径。

这是我的java代码：

package com.example.thermie.test2;

import android.Manifest;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.OutputStreamWriter;
import java.util.Date;

import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
import static android.os.Environment.DIRECTORY_DCIM;
import static android.os.Environment.getExternalStorageDirectory;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "";
    private static final int MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE = 1;

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



// Log used as debug
        try {
            boolean mExternalStorageAvailable = false;
            boolean mExternalStorageWriteable = false;


            String state = Environment.getExternalStorageState();

            if (Environment.MEDIA_MOUNTED.equals(state)) {
                // We can read and write the media
                mExternalStorageAvailable = mExternalStorageWriteable = true;
                Toast.makeText(MainActivity.this,
                        "Read and Write", Toast.LENGTH_LONG).show();
            } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
                // We can only read the media
                mExternalStorageAvailable = true;
                mExternalStorageWriteable = false;
                Toast.makeText(MainActivity.this,
                        "onlyread", Toast.LENGTH_LONG).show();
            } else {
                // Something else is wrong. It may be one of many other states, but all we need
                //  to know is we can neither read nor write
                mExternalStorageAvailable = mExternalStorageWriteable = false;
             Toast.makeText(MainActivity.this,
                        "cant writer", Toast.LENGTH_LONG).show();

            }
            String sdkS =  String.valueOf(android.os.Build.VERSION.SDK_INT);
            Toast.makeText(MainActivity.this,
            sdkS, Toast.LENGTH_LONG).show();


            String dir = Environment.getExternalStorageDirectory()+File.separator+"myDirectory";
            //create folder
            File folder = new File(dir); //folder name
            boolean result = folder.mkdirs();

            //create file
            File file = new File(dir, "filename.txt");

            if (result){
                Toast.makeText(MainActivity.this,
                        "True", Toast.LENGTH_LONG).show();

            }
            TextView textView = (TextView)findViewById(R.id.textView2);
            textView.setText(dir);
            Toast.makeText(MainActivity.this,
                    String.valueOf(state), Toast.LENGTH_LONG).show();
        } catch (Exception e) {
            Log.e(TAG, "Error opening Log.", e);
            Toast.makeText(MainActivity.this,
                    "not good", Toast.LENGTH_LONG).show();
        }

    }
}

我的目录是：/ storage / emulated / 0 / myDirectory 哪个不在我的SD卡中，它是没有任何访问权限的目录中的内部存储器。

我的结果：

boolean result = folder.mkdirs();

不是真的。所以没有文件夹打开，我也尝试过：

boolean result = folder.mkdir();

和我的Toasts说：

读写
23（API）
已安装（已安装）（

手机galaxy s5。 andorid version 6.0.1 Marshmallow。

这是我的表现：

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

    package="com.example.thermie.test2">


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

    <application

        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

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

</manifest>

希望它足够详细。谢谢大家。

Answer 1

我认为我从Environment.getExternalStorageDirectory()获得的路径不是SD卡路径

正确。

在getExternalFilesDirs()上使用Context方法。如果返回2 + File个对象，则第二个和后续对象将是可读取和写入的可移动存储上的位置，没有任何权限。

Answer 2

你试过用过吗？ Enviroment.getExternalStoragePublicDirectory()? 如上所述，您也可以使用 getExternalFilesDirs() 但是，在上下文中，这可能适用于某些设备。我指的是refer to here。

Answer 3

使用此

 public static File getCacheDirectory(Context context, boolean preferExternal) {
    File appCacheDir = null;
    String externalStorageState;
    try {
        externalStorageState = Environment.getExternalStorageState();
    } catch (NullPointerException e) {
        externalStorageState = "";
    }
    if (preferExternal && MEDIA_MOUNTED.equals(externalStorageState)) {
        appCacheDir = getSecondaryExternalCacheDir(context);
    }

    if (appCacheDir == null) {
        appCacheDir = getPrimaryExternalCacheDir(context);
    }
    return appCacheDir;
}

private static File getSecondaryExternalCacheDir(Context context) {
    File dataDir = new File(new File(Environment.getExternalStorageDirectory(), "Android"), "data");
    File appCacheDir = new File(new File(dataDir, context.getPackageName()), "cache");
    if (!appCacheDir.exists()) {
        if (!appCacheDir.mkdirs()) {
            return null;
        }
    }
    return appCacheDir;
}

private static File getPrimaryExternalCacheDir(Context context) {
    File dataDir = new File(new File(context.getExternalFilesDir(null), "Android"), "data");
    File appCacheDir = new File(new File(dataDir, context.getPackageName()), "cache");
    if (!appCacheDir.exists()) {
        if (!appCacheDir.mkdirs()) {
            return null;
        }
    }
    return appCacheDir;
}

Answer 4

好这是我的草率代码，它在我的本地存储中写了一个txt文件。（xml文件相同）

package com.example.thermie.test2;


import android.Manifest;
import android.content.Context;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Date;

import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
import static android.R.attr.path;
import static android.os.Environment.DIRECTORY_DCIM;
import static android.os.Environment.getExternalStorageDirectory;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "";
    private static final int MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE = 1;
    private String filename = "natiFile.txt";
    private String filepath = "/storage/extSdCard";
    File myExternalFile;

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



// Log used as debug
        try {
            boolean mExternalStorageAvailable = false;
            boolean mExternalStorageWriteable = false;


            String state = Environment.getExternalStorageState();

            if (Environment.MEDIA_MOUNTED.equals(state)) {
                // We can read and write the media
                mExternalStorageAvailable = mExternalStorageWriteable = true;
                Toast.makeText(MainActivity.this,
                        "Read and Write", Toast.LENGTH_LONG).show();
            } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
                // We can only read the media
                mExternalStorageAvailable = true;
                mExternalStorageWriteable = false;
                Toast.makeText(MainActivity.this,
                        "onlyread", Toast.LENGTH_LONG).show();
            } else {
                // Something else is wrong. It may be one of many other states, but all we need
                //  to know is we can neither read nor write
                mExternalStorageAvailable = mExternalStorageWriteable = false;
             Toast.makeText(MainActivity.this,
                        "cant writer", Toast.LENGTH_LONG).show();

            }
            String sdkS =  String.valueOf(android.os.Build.VERSION.SDK_INT);
            Toast.makeText(MainActivity.this,
            sdkS, Toast.LENGTH_LONG).show();


            File dir = Environment.getExternalStoragePublicDirectory(DIRECTORY_DCIM);
            final File file = new File(dir, "config.txt");

            String secStore = System.getenv("SECONDARY_STORAGE");
            File f_secs = new File(secStore);


            myExternalFile = new File(getExternalFilesDir(filepath), filename);

            String data = "gdsg";
            try {
                FileOutputStream fos = new FileOutputStream(myExternalFile);
                fos.write(data.getBytes());
                fos.close();
                Toast.makeText(MainActivity.this,
                        "great", Toast.LENGTH_LONG).show();
            } catch (IOException e) {
                e.printStackTrace();
            }



            File folder = new File(f_secs.getAbsolutePath() + "/TollCulator/");
            boolean testing = folder.mkdirs();
            if (testing){
                Toast.makeText(MainActivity.this,
                        "True", Toast.LENGTH_LONG).show();

            }
            TextView textView = (TextView)findViewById(R.id.textView2);
            textView.setText(f_secs.getPath());
            Toast.makeText(MainActivity.this,
                    String.valueOf(state), Toast.LENGTH_LONG).show();
        } catch (Exception e) {
            Log.e(TAG, "Error opening Log.", e);
            Toast.makeText(MainActivity.this,
                    "not good", Toast.LENGTH_LONG).show();
        }

    }
}

在外部microSD卡中创建文件夹或文件

4 个答案: