我m trying to encrypt a file from my SD card but i have some exception. How can i make sdcard read/write ? I已经在我的设备上的模拟器终端中尝试了一些linux命令，但是它们没有用。
这是我的例外
07-21 19:03:12.453 31541-31541/encryption.nikola.com.test W/System.err﹕ java.io.FileNotFoundException: /encrypt.txt: open failed: EROFS (Read-only file system)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:458)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:128)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:117)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at encryption.nikola.com.test.Crypto.encryptor(Crypto.java:39)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at encryption.nikola.com.test.MainActivity.onActivityResult(MainActivity.java:60)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.Activity.dispatchActivityResult(Activity.java:5467)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.deliverResults(ActivityThread.java:3380)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2784)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2826)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.access$800(ActivityThread.java:139)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:102)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.os.Looper.loop(Looper.java:136)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5103)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515)
07-21 19:03:12.463 31541-31541/encryption.nikola.com.test W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:788)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:604)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ at dalvik.system.NativeStart.main(Native Method)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ Caused by: libcore.io.ErrnoException: open failed: EROFS (Read-only file system)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ at libcore.io.Posix.open(Native Method)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
07-21 19:03:12.473 31541-31541/encryption.nikola.com.test W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:442)
在这里，我将向您展示应用程序的代码
public class MainActivity extends Activity {
final int ACTIVITY_CHOOSE_FILE = 1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btn = (Button) this.findViewById(R.id.btnActivity1);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent chooseFile;
Intent intent;
chooseFile = new Intent(Intent.ACTION_GET_CONTENT);
chooseFile.setType("file/*");
intent = Intent.createChooser(chooseFile, "Choose a file");
startActivityForResult(intent, ACTIVITY_CHOOSE_FILE);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
String filePath = null;
switch(requestCode) {
case ACTIVITY_CHOOSE_FILE: {
if (resultCode == RESULT_OK){
Uri uri = data.getData();
filePath = uri.getPath();
}
}
}
Crypto crypto = new Crypto();
crypto.encryptor(filePath);
}
}
这是加密类
public class Crypto {
public void encryptor(String inputFilePath) {
FileOutputStream fos = null;
File file = new File(inputFilePath);
String keyString = "140405PX_0.$88";
String algorithm = "DESede";
try {
FileInputStream fileInputStream = new FileInputStream(file);
byte[] fileByteArray = new byte[fileInputStream.available()];
fileInputStream.read(fileByteArray);
for (byte b : fileByteArray) {
System.out.println(b);
}
SecretKey secretKey = getKey(keyString);
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new CipherOutputStream(new FileOutputStream("encrypt.txt"), cipher));
objectOutputStream.writeObject(fileByteArray);
objectOutputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public static SecretKey getKey(String message) throws Exception {
String messageToUpperCase = message.toUpperCase();
byte[] digestOfPassword = messageToUpperCase.getBytes();
byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
SecretKey key = new SecretKeySpec(keyBytes, "DESede");
return key;
}
的Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="encryption.nikola.com.test" >
<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/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>