Android provides an existing mechanism for accessing private files while controlling their access modes: Context.openFileOutput and Context.openFileInput. As a Source/Sink primer, here's a cool way to adapt between the two:
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| // Available under the MIT license, http://opensource.org/licenses/MIT | |
| /** | |
| * Adapt between Context's file input/output streams and Guava's sinks and sources. | |
| * | |
| * This supports file modes. | |
| * | |
| * Usage: | |
| * ByteSink sink = | |
| * new AndroidPrivateFileGuavaAdapter( | |
| * "foo", Context.MODE_PRIVATE, context).asByteSink(); | |
| */ | |
| public class AndroidPrivateFileGuavaAdapter { | |
| private final String mName; | |
| private final int mMode; | |
| private final Context mContext; | |
| public AndroidPrivateFileHelper(String name, int mode, Context context) { | |
| mName = name; | |
| mMode = mode; | |
| mContext = context.getApplicationContext(); | |
| } | |
| public ByteSink asByteSink() { | |
| return new ByteSink() { | |
| public OutputStream openStream() throws IOException { | |
| return mContext.openFileOutput(mName, mMode); | |
| } | |
| }; | |
| } | |
| public ByteSource asByteSource() { | |
| return new ByteSource() { | |
| public InputStream openStream() throws IOException { | |
| return mContext.openFileInput(mName); | |
| } | |
| }; | |
| } | |
| public CharSink asCharSink() { | |
| return asByteSink().asCharSink(Charsets.UTF_8); | |
| } | |
| public CharSource asCharSource() { | |
| return asByteSource().asCharSource(Charsets.UTF_8); | |
| } | |
| } |
The usage would look like this:
AndroidPrivateFileGuavaAdapter adapter =
new AndroidPrivateFileGuavaAdapter("filename", Context.MODE_PRIVATE, context);
// Read all text
String contents = adapter.asCharSource().read();
// Write some bytes
byte[] bytes = ...; // obtains bytes from somewhere
adapter.asByteSink().write(bytes);