Usually we need to store large files such as audio, video, etc. on our mobile phones. We have learned to use File for storage before (using File operations for storage); considering that the mobile phone itself has a small storage space, we need to store files in SDcards. Today, we also learned how to use sdcards on Android;
First of all, if you want to use sdcard to store in the program, we must set the following permissions in the file:
Add the permissions to access SDCard in the following:
<!-- existSDCardCreate and delete files permissions --> <uses-permission android:name=".MOUNT_UNMOUNT_FILESYSTEMS"/> <!-- PastSDCardWrite data permissions --> <uses-permission android:name=".WRITE_EXTERNAL_STORAGE"/>
Then when we use SDcard for reading and writing, we will use several static methods below the Environment class.
1: getDataDirectory() gets the data directory in Android
2: getDownloadCacheDirectory() Get the downloaded cache directory
3: getExternalStorageDirectory() Gets the directory to external storage, generally refers to SDcard
4: getExternalStorageState() Gets the current status of external settings. Generally refers to SDcard.
For external settings in Android, we commonly use MEDIA_MOUNTED (SDcard exists and can be read and written) MEDIA_MOUNTED_READ_ONLY (SDcard exists and can only be read). Of course, there are other states that can be found in the document.
5: getRootDirectory() to get the Android Root path
6: isExternalStorageEmulated() Returns the Boolean value to determine whether the external settings are valid
7: isExternalStorageRemovable() Returns the Boolean value and determines whether the external settings can be removed
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:andro android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <EditText android: android:layout_width="fill_parent" android:layout_height="wrap_content" /> <Button android: android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Write with SDcard" /> <EditText android: android:layout_width="fill_parent" android:layout_height="wrap_content" /> <Button android: android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Use SDcard read operation" /> </LinearLayout>
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public class MainActivity extends AppCompatActivity {
private Button bt1, bt2;
private EditText et1, et2;
private static final String FILENAME = "temp_file.txt";
@Override
public void onCreate(Bundle savedInstanceState) {
(savedInstanceState);
setContentView(.activity_main);
bt1 = (Button) (.bt1);
bt2 = (Button) (.bt2);
et1 = (EditText) (.et1);
et2 = (EditText) (.et2);
(new MySetOnClickListener());
(new MySetOnClickListener());
}
private class MySetOnClickListener implements OnClickListener {
@Override
public void onClick(View v) {
File file = new File((),
FILENAME);
switch (()) {
case .bt1:// Write with SDcardif (().equals(
Environment.MEDIA_MOUNTED)) {
try {
FileOutputStream fos = new FileOutputStream(file);
(().toString().getBytes());
();
(, "Writing to the file successfully",
Toast.LENGTH_LONG).show();
} catch (Exception e) {
(, "Write to file failed",
Toast.LENGTH_SHORT).show();
}
} else {
// At this time, SDcard does not exist or cannot perform read and write operations.(,
"The SDcard does not exist or cannot perform read and write operations", Toast.LENGTH_SHORT).show();
}
break;
case .bt2:// Use SDcard to readif (().equals(
Environment.MEDIA_MOUNTED)) {
try {
FileInputStream inputStream = new FileInputStream(file);
byte[] b = new byte[()];
(b);
(new String(b));
(, "Reading the file successfully",
Toast.LENGTH_LONG).show();
} catch (Exception e) {
(, "Read failed",
Toast.LENGTH_SHORT).show();
}
} else {
// At this time, SDcard does not exist or cannot perform read and write operations.(,
"The SDcard does not exist or cannot perform read and write operations", Toast.LENGTH_SHORT).show();
}
break;
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in .
int id = ();
//noinspection SimplifiableIfStatement
if (id == .action_settings) {
return true;
}
return (item);
}
}
The above description introduces you to using SDcard to read files in Android, hoping it will be helpful to everyone!