[英]read and write files to removable sd card
如何在Android中讀取和寫入可移動SD卡的文件?
我想將Android Id存儲在文本文件中。 應在外部SD卡上創建文本文件。
碼:
PackageManager m = getPackageManager();
String s = getPackageName();
PackageInfo p = m.getPackageInfo(s, 0);
s = p.applicationInfo.dataDir;
File myFile = new File(s + "/MyDoople.txt");
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append(TxtS.getText());
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),"Text Updated",Toast.LENGTH_SHORT).show();
第二是
File sdCard = new File("file:///mnt/external_sd/");
File myFile = new File(sdCard, "test.txt");
FileWriter writer = new FileWriter(myFile);
writer.append(TESTSTRING);
writer.flush();
writer.close();
試試下面的內容。 使用Environment.getExternalStorageDirectory()來獲取路徑
File dir =new File(android.os.Environment.getExternalStorageDirectory(),"MyFolder");
if(!dir.exists())
{
dir.mkdirs();
}
String filename= "MyDoople.txt";
try
{
File f = new File(dir+File.separator+filename);
FileOutputStream fOut = new FileOutputStream(f);
OutputStreamWriter myOutWriter = new OutputStreamWriter(
fOut);
myOutWriter.append("Mytest");
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),
"Text Updated",
Toast.LENGTH_SHORT).show();
}
catch(Exception e)
{
e.printStackTrace();
}
更新:
try
{
FileWriter fileWritter = new FileWriter(f,true);
BufferedWriter bufferWritter = new BufferedWriter(fileWritter);
bufferWritter.write("Mydata");
bufferWritter.close();
}
catch(Exception e)
{
e.printStackTrace();
}
當我用文本文件查看器打開時,我的設備上的結果。
編輯:
以下是hackish,而不是推薦的方式。
在我的設備(三星Galaxy s3)中,我的內部手機內存名為sdCard0和我的外部extSdcard。 此Environment.getExternalStorageDirectory()將提供內部內存的路徑。 在這種情況下,您可以使用以下內容獲取外部存儲器的路徑。
String externalpath = new String();
String internalpath = new String();
public void getExternalMounts() {
Runtime runtime = Runtime.getRuntime();
try
{
Process proc = runtime.exec("mount");
InputStream is = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
String line;
BufferedReader br = new BufferedReader(isr);
while ((line = br.readLine()) != null) {
if (line.contains("secure")) continue;
if (line.contains("asec")) continue;
if (line.contains("fat")) {//external card
String columns[] = line.split(" ");
if (columns != null && columns.length > 1) {
externalpath = externalpath.concat("*" + columns[1] + "\n");
}
}
else if (line.contains("fuse")) {//internal storage
String columns[] = line.split(" ");
if (columns != null && columns.length > 1) {
internalpath = internalpath.concat(columns[1] + "\n");
}
}
}
}
catch(Exception e)
{
e.printStackTrace();
}
System.out.println("Path of sd card external............"+externalpath);
System.out.println("Path of internal memory............"+internalpath);
}
也許你忘了這些權限。
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
package com.example.writeinsdcard;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import android.os.Environment;
import android.util.Log;
import android.widget.TextView;
public class MainActivity extends Activity {
private static final String TAG = "Sdcard";
private TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_main);
tv = (TextView) findViewById(R.id.TextView01);
checkExternalMedia();
writeToSDFile();
readRaw();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/** Method to check whether external media available and writable. This is adapted from
http://developer.android.com/guide/topics/data/data-storage.html#filesExternal */
private void checkExternalMedia(){
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
// Can read and write the media
mExternalStorageAvailable = mExternalStorageWriteable = true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
// Can only read the media
mExternalStorageAvailable = true;
mExternalStorageWriteable = false;
} else {
// Can't read or write
mExternalStorageAvailable = mExternalStorageWriteable = false;
}
tv.append("\n\nExternal Media: readable="
+mExternalStorageAvailable+" writable="+mExternalStorageWriteable);
}
/** Method to write ascii text characters to file on SD card. Note that you must add a
WRITE_EXTERNAL_STORAGE permission to the manifest file or this method will throw
a FileNotFound Exception because you won't have write permission. */
private void writeToSDFile(){
// Find the root of the external storage.
// See http://developer.android.com/guide/topics/data/data-storage.html#filesExternal
File root = android.os.Environment.getExternalStorageDirectory();
tv.append("\nExternal file system root: "+root);
File dir = new File (root.getAbsolutePath() + "/download");
dir.mkdirs();
File file = new File(dir, "myData.txt");
try {
FileOutputStream f = new FileOutputStream(file);
PrintWriter pw = new PrintWriter(f);
pw.println("Howdy do to you.");
pw.println("Here is a second line.");
pw.flush();
pw.close();
f.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
Log.i(TAG, "File not found. Did you" +
" add a WRITE_EXTERNAL_STORAGE permission to the manifest?");
} catch (IOException e) {
e.printStackTrace();
}
tv.append("\n\nFile written to:\n"+file);
}
/** Method to read in a text file placed in the res/raw directory of the application. The
method reads in all lines of the file sequentially. */
private void readRaw(){
tv.append("\n\nData read from res/raw/textfile.txt:\n");
InputStream is = this.getResources().openRawResource(R.raw.textfile);
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr, 8192); // 2nd arg is buffer size
// More efficient (less readable) implementation of above is the composite expression
/*BufferedReader br = new BufferedReader(new InputStreamReader(
this.getResources().openRawResource(R.raw.textfile)), 8192);*/
try {
String test;
while (true){
test = br.readLine();
// readLine() returns null if no more lines in the file
if(test == null) break;
tv.append("\n"+" "+test);
}
isr.close();
is.close();
br.close();
} catch (IOException e) {
e.printStackTrace();
}
tv.append("\n\nThat is all");
}
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.writesdcard"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<!--permission to write external storage -->
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.writesdcard.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>
private static String getExternalStoragePath(Context mContext) {
StorageManager mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);
Class<?> storageVolumeClazz = null;
try {
storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
Method getPath = storageVolumeClazz.getMethod("getPath");
Method isRemovable = storageVolumeClazz.getMethod("isRemovable");
Object result = getVolumeList.invoke(mStorageManager);
final int length = Array.getLength(result);
for (int i = 0; i < length; i++) {
Object storageVolumeElement = Array.get(result, i);
String path = (String) getPath.invoke(storageVolumeElement);
boolean removable = (Boolean) isRemovable.invoke(storageVolumeElement);
if (removable == true) {
return path;
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
並輸入此代碼。
如果SD卡可用,它將返回SD卡路徑
然后你可以使用那條路徑。
String sdCardPath = getExternalStoragePath(context);
File Path1 = new File(sdCardPath + "NewFolder");
if (!Path1.exists()) {
Path1.mkdir();
}
File file = new File(Path1, "test.txt");
我的問題解決了。 我直接使用路徑“/ mnt / external_sd / .. Path of File。”。
但它只適用於我的設備
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