- Dailer
String number = tv.getText().toString(); // get No from an edittext
Intent it = new Intent(Intent.ACTION_DIAL);
it.setData(Uri.parse("tel:"+number));
this.startActivity(it);
------- permission ------
<uses-permission android:name="android.permission.CALL_PHONE"/>
- SMS
String mNo = evMobileNo.getText().toString();
String content = evSMSContent.getText().toString();
SmsManager sm = SmsManager.getDefault();
ArrayList<String> text = sm.divideMessage(content); // just in case message is too long
for (String s : text) {
sm.sendTextMessage(mNo, null, s, null, null);
}
Toast.makeText(MainActivity.this, "sent success",
Toast.LENGTH_LONG).show();
------- permission ------
<uses-permission android:name="android.permission.SEND_SMS" />
- Save/Read File to/from memory card
public void savePrivateMode(String fileName, String fileContent)
throws Exception {
FileOutputStream out = context.openFileOutput(fileName,
Context.MODE_PRIVATE);
out.write(fileContent.getBytes());
out.close();
}
The mode is Context.MODE_PRIVATE, only the app who created the file is allowed to access the file, no one else is allowed to access it.
The file permission is -rw-rw----
If save the same file name again and again, the content will be overwrited.
And the location of this file is /data/data/<app package name>/files/<file name> in the memory card.
public void saveAppendMode(String fileName, String fileContent)
throws Exception {
FileOutputStream out = context.openFileOutput(fileName,
Context.MODE_APPEND);
out.write(fileContent.getBytes());
out.close();
}
The mode is Context.MODE_APPEND, only the app who created the file is allowed to access the file, no one else is allowed to access it.
The file permission is -rw-rw----
If save the same file name again and again, the content will be appended.
And the location of this file is /data/data/<app package name>/files/<file name> in the memory card.
FileInputStream input = context.openFileInput(fileName);
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = input.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
// omit i/o close() method
return new String(out.toByteArray());
}
This method is allowed to read file under /data/data/<app package name>/files/<file name> at the same app.
If another app needs to access this file in this app, the code is as follows,
public String read(String fileName) throws Exception {
String fn = "/data/data/<package name>/files/"+fileName;
File file = new File(fn);
// should NOT be context.openFileInput(fileName); it is for memory card
FileInputStream input = new FileInputStream(file);
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = input.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
// omit i/o close() method
return new String(out.toByteArray());
}
If the mode is Context.MODE_PRIVATE or Context.MODE_APPEND, cannot read file from external app, unless the external app set the mode as Context.MODE_WORLD_READABLE when saving the file.
If an app is open the file to be read/write for external apps, when save a file, the file mode need to set as Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE
- Save/Read File to/from SD card
if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
file location:
File file = new File(Environment.getExternalStorageDirectory(),fileName);
Enviroment.getExternalStorageDirectory() points to /mnt/sdcard for current android os, and points to /sdcard for very older os version.
- SharedPreferences
public void save(String color, int fontSize) {
SharedPreferences sf = context.getSharedPreferences("custprefer",
Context.MODE_PRIVATE);
Editor edit = sf.edit();
edit.putString("color", color);
edit.putInt("fontSize", fontSize);
edit.commit();
}
in the end, a new file custprefer.xml will be generated at folder /data/data/<package>/shared_prefs/custprefer.xml as follows,
<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
<int name="fontSize" value="12" />
<string name="color">red</string>
</map>
- SQLite
package com.example.dbdemo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBHelper extends SQLiteOpenHelper {
public DBHelper(Context context) {
super(context, "demo.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table person(pid integer primary key autoincrement,name varchar(20))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
From the constructor, set db version is 1, and db file name is demo.db, onCreate() will be triggered if demo.db does not exit.
This is a test class to trigger onCreate() method.
package com.example.dbdemo.test;
import com.example.dbdemo.DBHelper;
import android.test.AndroidTestCase;
public class DBHelperTester extends AndroidTestCase {
public void testDB() throws Exception {
DBHelper helper = new DBHelper(this.getContext());
helper.getWritableDatabase();
}
}
then the new demo.db file will be found in folder /data/data/<package>/databases/demo.db, use the tools sqlite expert to check the table is created successfully.
Now change above code to make the version to 2 in the constructor,and add some db changes in method onUpgrade() which will be triggered if db version changes
package com.example.dbdemo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBHelper extends SQLiteOpenHelper {
public DBHelper(Context context) {
super(context, "demo.db", null, 2);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table person(pid integer primary key autoincrement,name varchar(20))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("create table teacher(tid integer primary key autoincrement,name varchar(20))");
db.execSQL("alter table person add address varchar(20) null");
}
}
run above test method again, found a new table and a new field are created.
This is a simple class to insert a record
public class MyDbService {
private DBHelper dbHelper;
public MyDbService(DBHelper dbHelper) {
this.dbHelper = dbHelper;
}
public void save() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL("insert into person (name) values (?)",
new Object[] { "testuser" });
}
}
- TBC
