The document provides a tutorial on developing an Android application that intercepts incoming calls using the TelephonyManager and PhoneStateListener. It includes code snippets for managing call states and integrating UI components such as buttons and text views. Additionally, it mentions required permissions and offers references to the author's background and online resources.

1. Develop on Android
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Lesson : Telephony, calls

2. Telephony, the calls
• In this lesson, you will learn to intercept incoming calls.
• For this, you will learn to use the telephony manager
TelephonyManager.

3. Telephony, the calls
• You have to use the telephony manager with getSystemService.
TelephonyManager telephonyManager =
(TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
• Register a listener PhoneStateListener.
MyPhoneStateListener myPhoneStateListener = new MyPhoneStateListener();
telephonyManager.listen(myPhoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);

4. Telephony, the calls
• Manage the events (ringing, hang up, …) in the method
onCallStateChanged().
public class MyPhoneStateListener extends PhoneStateListener {
public void onCallStateChanged(int state, String incomingNumber) {
super.onCallStateChanged(state, incomingNumber);
switch(state) {
case TelephonyManager.CALL_STATE_IDLE: break;
case TelephonyManager.CALL_STATE_RINGING: break;
case TelephonyManager.CALL_STATE_OFFHOOK: break;
}
}
}

5. Telephony, the calls
• When the application is interrupted (onPause() called), unregister the listening with
the event LISTEN_NONE.
public void onPause() {
telephonyManager.listen(myPhoneStateListener, PhoneStateListener.LISTEN_NONE);
}
• When the application is resumed (onResume() called), re-register the listening with
the event LISTEN_CALL_STATE.
public void onResume() {
telephonyManager.listen(myPhoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);
}

6. Layout main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<Button
android:id="@+id/btnCall"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="doClick"
android:text="Call" />
<TextView
android:id="@+id/tv_log"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</LinearLayout>

7. File Main.java
public class Main extends Activity {
TextView tv_log = null;
TelephonyManager telephonyManager = null;
MyPhoneStateListener myPhoneStateListener = null;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv_log = (TextView)findViewById(R.id.tv_log);
Button btnCall = (Button)findViewById (R.id.btnCall);
btnCall.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("tel:010101"));
startActivity(intent);
}
});

8. File Main.java
telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
myPhoneStateListener = new MyPhoneStateListener();
}
public void onResume() {
super.onResume();
telephonyManager.listen(myPhoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);
}
public void onPause() {
super.onPause();
telephonyManager.listen(myPhoneStateListener, PhoneStateListener.LISTEN_NONE);
}

9. File Main.java
public class MyPhoneStateListener extends PhoneStateListener {
public void onCallStateChanged(int state, String incomingNumber) {
super.onCallStateChanged(state, incomingNumber);
switch(state) {
case TelephonyManager.CALL_STATE_IDLE:
tv_log.setText("Call state idle : " + incomingNumber); break;
case TelephonyManager.CALL_STATE_RINGING:
tv_log.setText("Call state ringing : " + incomingNumber); break;
case TelephonyManager.CALL_STATE_OFFHOOK:
tv_log.setText("Call state Offhook : " + incomingNumber); break;
default:
tv_log.setText("Call state other : " + incomingNumber); break;
}
}
}
}

10. Project AndroidManifest.xml
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>

11. Test on your mobile
Telephony_Calls

12. Follow me on my channel PengYooTV …
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Who am I ?
Bruno Delb (www.delb.cn),
Author of the first french book of development of Java mobile application (2002),
Consultant, project manager and developer of social & mobile applications,
let’s talk about your needs ...
And on Weibo :
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