What exactly IntentService is? check this link to find out more about IntentService and Service in Android.
In this sample app I used the IntentService to perform a reading operation in the background Service. First, user will choose a text file from the android storages, and then the file will be sent to the IntentService to be read (reading operation is executed in the background service). When the task or operation is complete, the content of the file will be shown as a final result through a TextView on UI thread and the IntentService will stop itself.
The sample app was built using eclipse, java 1.7, and can run on Android 2.1 Eclair (API 7) - Android 4.4 KitKat (API 19).
Note:
- > The sample app uses a support library (android-support-v7-appcompat), see how to set up a support library on eclipse.
- > The sample app needs a third-party app to select a text file from the android storages, such as a File Manager.
Download: IntentServiceSample.zip (source), IntentServiceSample.apk (Apk).
src/com.me.intentservicesample/MainActivity.java
package com.me.intentservicesample;
import java.net.URISyntaxException;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity {
private static final int REQ_CODE = 0;
//private ResponseReciever mResponseReciever = new ResponseReciever();
private BroadcastReceiver reciever = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
Bundle bundle = intent.getExtras();
if (bundle != null) {
String data = bundle.getString(Services.DATA);
int status = bundle.getInt(Services.STATUS);
if (status == RESULT_OK) {
//MainActivity mainActivity = new MainActivity();
Toast.makeText(MainActivity.this, "Finished",
Toast.LENGTH_LONG).show();
updateTextView(data);
}
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
protected void onResume() {
super.onResume();
IntentFilter intentFilter = new IntentFilter(Services.ACTION_BROADCAST);
//intentFilter.addDataScheme("text/plain");
LocalBroadcastManager.getInstance(MainActivity.this).registerReceiver(
reciever, intentFilter);
}
@Override
protected void onPause() {
super.onPause();
LocalBroadcastManager.getInstance(MainActivity.this)
.unregisterReceiver(reciever);
}
/**
private class ResponseReciever extends BroadcastReceiver {
@Override
public void onReceive(Context ctx, Intent intent) {
// TODO Auto-generated method stub
Bundle bundle = intent.getExtras();
if (bundle != null) {
String data = bundle.getString(Services.DATA);
int status = bundle.getInt(Services.STATUS);
if (status == RESULT_OK) {
//MainActivity mainActivity = new MainActivity();
Toast.makeText(MainActivity.this, "Finished",
Toast.LENGTH_LONG).show();
//mainActivity.updateTextView(data);
}
}
}
}
*/
protected void updateTextView(String data) {
TextView tv = (TextView) findViewById(R.id.textView);
tv.setText(data.toString());
}
/** called when button "Open a File" clicked */
public void openFile(View v) {
// use implicit Intent to open a file
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("*/.txt");
intent.addCategory(Intent.CATEGORY_OPENABLE);
try {
startActivityForResult(
Intent.createChooser(intent, "Select a file txt"), REQ_CODE);
} catch (android.content.ActivityNotFoundException ex) {
Toast.makeText(getBaseContext(), "You a need a File Manager",
Toast.LENGTH_LONG).show();
ex.printStackTrace();
}
}
@Override
protected void onActivityResult(int reqCode, int resultCode, Intent data) {
// check activity result base on reqCode
// reqCode must be same as REQ_CODE
switch (reqCode) {
case REQ_CODE:
if (resultCode == RESULT_OK) {
// get Uri data from intent
Uri uri = data.getData();
String path = null;
try {
// convert Uri to file path (String)
path = getPath(getBaseContext(), uri);
// send the file path to Service
this.sendToService(path);
} catch (URISyntaxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
/** called to start the Service */
private void sendToService(String s) {
// create an explicit Intent for the Service
Intent intentService = new Intent(MainActivity.this, Services.class);
intentService.putExtra(Services.PATH, s);
startService(intentService);
}
public static String getPath(Context context, Uri uri)
throws URISyntaxException {
if ("content".equalsIgnoreCase(uri.getScheme())) {
String[] projection = { "_data" };
Cursor cursor = null;
try {
cursor = context.getContentResolver().query(uri, projection,
null, null, null);
int column_index = cursor.getColumnIndexOrThrow("_data");
if (cursor.moveToFirst()) {
return cursor.getString(column_index);
}
} catch (Exception e) {
e.printStackTrace();
}
} else if ("file".equalsIgnoreCase(uri.getScheme())) {
return uri.getPath();
}
return null;
}
@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;
}
@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 AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}
src/com.me.intentservicesample/Services.java
package com.me.intentservicesample;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import android.app.Activity;
import android.app.IntentService;
import android.content.Intent;
import android.support.v4.content.LocalBroadcastManager;
public class Services extends IntentService {
private static int mStatus = Activity.RESULT_CANCELED;
public static final String PATH = "com.me.intentservicesample.PATH";
public static final String ACTION_BROADCAST = "com.me.intentservicesample.BROADCAST";
public static final String STATUS = "com.me.intentservicesample.STATUS";
public static final String DATA = "com.me.intentservicesample.DATA";
public Services() {
super("Services");
// TODO Auto-generated constructor stub
}
@Override
protected void onHandleIntent(Intent intent) {
// TODO Auto-generated method stub
// get data from incoming intent
String filePath = intent.getStringExtra(PATH);
String fileContent = this.readFile(filePath);
if (fileContent != null) {
// report the work status to registered components
publishResult(mStatus, fileContent);
}
}
private void publishResult(int status, String data) {
Intent localIntent = new Intent(Services.ACTION_BROADCAST);
localIntent.putExtra(Services.STATUS, status);
localIntent.putExtra(Services.DATA, data);
LocalBroadcastManager.getInstance(Services.this).sendBroadcast(
localIntent);
}
/** read the incoming file to get the file content as String */
private String readFile(String path) {
File file = new File(path);
int i, j = 0;
byte[] data = new byte[(int) file.length()];
String string = null;
InputStream in = null;
try {
in = new BufferedInputStream(new FileInputStream(file));
while ((i = in.read()) != -1) {
data[j++] = (byte) i;
}
string = byteToString(data).toString();
mStatus = Activity.RESULT_OK;
return string;
} catch (FileNotFoundException ex) {
ex.printStackTrace();
} catch (IOException ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return string;
}
/** called to cast byte array to String */
private static String byteToString(byte[] b) {
char[] c = new char[b.length];
StringBuilder sb = new StringBuilder();
for (int i = 0; i < c.length; i++) {
c[i] = (char) b[i];
sb.append(c[i]);
}
return sb.toString();
}
}
res/layout/activity_main.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.me.intentservicesample.MainActivity"
tools:ignore="MergeRootFrame" />
res/layout/fragment_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.me.intentservicesample.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:onClick="openFile"
android:text="Open a File" />
<LinearLayout
android:id="@+id/linear"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/button"
android:orientation="vertical" >
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="10dp"
android:singleLine="false"
android:text="@string/hello_world" />
</LinearLayout>
</RelativeLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.me.intentservicesample"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="7"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<service
android:name="com.me.intentservicesample.Services"
android:exported="false" >
</service>
<activity
android:name="com.me.intentservicesample.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>
When you launch the sample app:
When the button "Open a File" was clicked:
After completing the operation, show the final result to the user:
Source: Android Developer (Background Service).
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