从设备中选择文件时，我使用这个fileutils类：
public class FileUtils {
private FileUtils() {
}
private static final String TAG = "FileUtils";
private static final boolean DEBUG = false;
private static boolean isExternalStorageDocument(Uri uri) {
return "com.android.externalstorage.documents".equals(uri.getAuthority());
}
private static boolean isDownloadsDocument(Uri uri) {
return "com.android.providers.downloads.documents".equals(uri.getAuthority());
}
private static boolean isMediaDocument(Uri uri) {
return "com.android.providers.media.documents".equals(uri.getAuthority());
}
private static boolean isGooglePhotosUri(Uri uri) {
return "com.google.android.apps.photos.content".equals(uri.getAuthority());
}
private static String getDataColumn(Context context, Uri uri, String selection,
String[] selectionArgs) {
Cursor cursor = null;
final String column = "_data";
final String[] projection = {
column
};
try {
cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs,
null);
if (cursor != null && cursor.moveToFirst()) {
if (DEBUG)
DatabaseUtils.dumpCursor(cursor);
final int column_index = cursor.getColumnIndexOrThrow(column);
return cursor.getString(column_index);
}
} finally {
if (cursor != null)
cursor.close();
}
return null;
}
@RequiresApi(api = Build.VERSION_CODES.KITKAT)
public static String getPath(final Context context, final Uri uri) {
if (DEBUG)
Log.d(TAG + " File -",
"Authority: " + uri.getAuthority() +
", Fragment: " + uri.getFragment() +
", Port: " + uri.getPort() +
", Query: " + uri.getQuery() +
", Scheme: " + uri.getScheme() +
", Host: " + uri.getHost() +
", Segments: " + uri.getPathSegments().toString()
);
final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
// DocumentProvider
if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
//// ExternalStorageProvider
if (isExternalStorageDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
// This is for checking Main Memory
if ("primary".equalsIgnoreCase(type)) {
if (split.length > 1) {
return Environment.getExternalStorageDirectory() + "/" + split[1];
} else {
return Environment.getExternalStorageDirectory() + "/";
}
// This is for checking SD Card
} else {
return "storage" + "/" + docId.replace(":", "/");
}
}
// DownloadsProvider
else if (isDownloadsDocument(uri)) {
final String id = DocumentsContract.getDocumentId(uri);
if (id.startsWith("raw:")) {
String[] data = new String[2];
data[0] = id.replaceFirst("raw:", "");
data[1] = null;
return data[0];
}
final Uri contentUri = ContentUris.withAppendedId(
Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));
return getDataColumn(context, contentUri, null, null);
}
// MediaProvider
else if (isMediaDocument(uri)) {
final String docId = DocumentsContract.getDocumentId(uri);
final String[] split = docId.split(":");
final String type = split[0];
Uri contentUri = null;
if ("image".equals(type)) {
contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
} else if ("video".equals(type)) {
contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
} else if ("audio".equals(type)) {
contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
}
final String selection = "_id=?";
final String[] selectionArgs = new String[]{
split[1]
};
return getDataColumn(context, contentUri, selection, selectionArgs);
}
}
// MediaStore (and general)
else if ("content".equalsIgnoreCase(uri.getScheme())) {
// Return the remote address
if (isGooglePhotosUri(uri))
return uri.getLastPathSegment();
return getDataColumn(context, uri, null, null);
}
// File
else if ("file".equalsIgnoreCase(uri.getScheme())) {
return uri.getPath();
}
return null;
}
我在onActivityResult中这样称呼这个类：
String sourcePath = FileUtils.getPath(this, data.getData());
出于某种原因，我得到了以下崩溃：
Caused by java.lang.IllegalArgumentException: Unknown URI: content://downloads/public_downloads/230
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:165)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
at android.content.ContentProviderProxy.query(ContentProviderNative.java:418)
at android.content.ContentResolver.query(ContentResolver.java:760)
at android.content.ContentResolver.query(ContentResolver.java:710)
at android.content.ContentResolver.query(ContentResolver.java:668)
at com.HBiSoft.ProGolf.Utils.FileUtils.getDataColumn(FileUtils.java:50)
at com.HBiSoft.ProGolf.Utils.FileUtils.getPath(FileUtils.java:116)
at com.HBiSoft.ProGolf.MainActivity.onActivityResult(MainActivity.java:652)
at android.app.Activity.dispatchActivityResult(Activity.java:7638)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4515)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4563)
at android.app.ActivityThread.-wrap21(Unknown Source)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1779)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:7000)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:441)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
只有在从下载文件夹中选择文件时才会发生崩溃。
有人能帮我解决这个问题吗？
我创建了一个gist来解决这个问题，这里是链接。
重要
当你从Google Drive或Dropbox中选择一个文件时，你会得到以下错误：
Caused by java.lang.IllegalArgumentException: column '_data' does not exist
要解决此问题，您实际上必须为您尝试选择的文件制作一个临时副本。
首先，你必须检查content://uri是否来自Google Drive，你可以通过以下操作来完成：
public boolean isGoogleDrive(Uri uri) {
return String.valueOf(uri).toLowerCase().contains("com.google.android.apps");
}
如果是来自Google Drive的文件，则返回true。如果是，我将调用AsyncTask，如下所示：
//The data.getData() below refers to the uri you get in onActivityResult
if (isGoogleDrive(data.getData())) {
DownloadAsyncTask asyntask = new DownloadAsyncTask(data.getData(), this);
asyntask.execute();
asyntask.callback = this;
}
在AsyncTask中，我们将使用Uri打开InputStream，并获取字节数据，我们将用它来复制文件。
以下是AsyncTask类(我添加了注释以使其更易于理解)：
class DownloadAsyncTask extends AsyncTask<Uri, Void, String> {
private Uri mUri;
CallBackTask callback;
Context mContext;
private AlertDialog mdialog;
DownloadAsyncTask(Uri uri, Context context) {
this.mUri = uri;
mContext = context;
}
// In the onPreExecute() I'm displaying a custom dialog, this is not necessary, but recommended for when the user selects a large file
@Override
protected void onPreExecute() {
final AlertDialog.Builder mPro = new AlertDialog.Builder(new ContextThemeWrapper(mContext, R.style.myDialog));
@SuppressLint("InflateParams")
//Get reference to dialog layout
final View mPView = LayoutInflater.from(mContext).inflate(R.layout.dialog, null);
//Get reference to dialog title
final TextView title = mPView.findViewById(R.id.txtTitle);
//Get reference to dialog description
final TextView desc = mPView.findViewById(R.id.txtDesc);
//Set title text
title.setText("Please wait..");
//Set description text
desc.setText("Drive files needs to be imported, this might take some time depending on the file size.");
mPro.setView(mPView);
mdialog = mPro.create();
mdialog.show();
}
@RequiresApi(api = Build.VERSION_CODES.KITKAT)
@Override
protected String doInBackground(Uri... params) {
//This will be the file we will use (the one that will be copied)
File file = null;
try {
//Create a temporary folder where the copy will be saved to
File temp_folder = mContext.getExternalFilesDir("TempFolder");
//Use ContentResolver to get the name of the original name
//Create a cursor and pass the Uri to it
Cursor cursor = mContext.getContentResolver().query(mUri, null, null, null, null);
//Check that the cursor is not null
assert cursor != null;
int nameIndex = cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME);
cursor.moveToFirst();
//Get the file name
String filename = cursor.getString(nameIndex);
//Close the cursor
cursor.close();
//open a InputStream by passing it the Uri
//We have to do this in a try/catch
InputStream is = null;
try {
is = mContext.getContentResolver().openInputStream(mUri);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
//We now have a folder and a file name, now we can create a file
file = new File(temp_folder + "/" + filename);
//We can now use a BufferedInputStream to pass the InputStream we opened above to it
BufferedInputStream bis = new BufferedInputStream(is);
//We will write the byte data to the FileOutputStream, but we first have to create it
FileOutputStream fos = new FileOutputStream(file);
byte data[] = new byte[1024];
long total = 0;
int count;
//Below we will read all the byte data and write it to the FileOutputStream
while ((count = bis.read(data)) != -1) {
total += count;
fos.write(data, 0, count);
}
//The FileOutputStream is done and the file is created and we can clean and close it
fos.flush();
fos.close();
} catch (IOException e) {
Log.e("IOException = ", String.valueOf(e));
}
//Finally we can pass the path of the file we have copied
return file.getAbsolutePath();
}
protected void onPostExecute(String result) {
//We are done and can cancel the dialog
if (mdialog != null && mdialog.isShowing()) {
mdialog.cancel();
}
//I'm using a callback to let my Activity know that the AsyncTask is done. I pass the path along.
callback.getResultFromAsynTask(result);
}
}
你会看到，在上面的onPostExecute()中，我有callback.getResultFromAsynTask(result);。正如我在评论中提到的，我正在使用一个回调方法让"活动"知道我已经完成了，并将路径传递给回调。
在您的活动中，您必须实现回调，如下所示：
public class MainActivity extends AppCompatActivity implements CallBackTask {
CCD_ 11将看起来像这样：
interface CallBackTask {
void getResultFromAsynTask(String result);
}
现在您必须在Activity中实现它，才能在Activity:中获得结果
@Override
public void getResultFromAsynTask(String result) {
// Do what you need with the result like starting your new Activity and passing the path
final Intent intent = new Intent();
intent.setClass(MainActivity.this, Player.class);
intent.putExtra("path", result);
startActivity(intent);
}
GREAT，您现在有一个临时复制的File://(而不是content://)中的Uri。但是，在处理完文件后不要忘记删除该文件，否则您的应用程序大小将不断增大。
下面，我将删除我们之前创建的TempFolder，我将在ActivitiesonBackPressed中执行此操作(这也应该在onDestroy()中执行)：
@Override
public void onBackPressed() {
super.onBackPressed();
File dir = getBaseContext().getExternalFilesDir("TempFolder");
deleteRecursive(dir);
}
void deleteRecursive(File fileOrDirectory) {
if (fileOrDirectory.isDirectory())
for (File child : fileOrDirectory.listFiles())
deleteRecursive(child);
fileOrDirectory.delete();
}
这本书读得很多，但。。。通过这种方式，您将永远不会遇到任何content://Uri的问题。