Post ICS i.e. Android 4+, the overriding of the HomeButton has been removed for security reasons, to enable the user exit in case the application turns out to be a malware.
Here is article for blocking home button on devices below 4.0 - Overriding Home Button
Code Extract -
public class DisableHardButton extends Activity {
TextView mTextView;
ToggleButton mToggleButton;
boolean isLock=false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mTextView=(TextView) findViewById(R.id.tvInfo);
mToggleButton=(ToggleButton) findViewById(R.id.btnLock);
mToggleButton.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
isLock=isChecked;
onAttachedToWindow();
}
});
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
if ( (event.getKeyCode() == KeyEvent.KEYCODE_HOME) && isLock) {
mTextView.setText("KEYCODE_HOME");
return true;
} else {
return super.dispatchKeyEvent(event);
}
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if( (keyCode==KeyEvent.KEYCODE_BACK) && isLock) {
mTextView.setText("KEYCODE_BACK");
return true;
} else {
return super.onKeyDown(keyCode, event);
}
}
@Override
public void onAttachedToWindow() {
System.out.println("Onactivity attached :"+isLock);
if(isLock) {
this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
super.onAttachedToWindow();
} else {
this.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION);
super.onAttachedToWindow();
}
}
}
XML -
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/tvInfo"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Hi! This is the testing of override home button" />
<ToggleButton
android:id="@+id/btnLock"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textOff="UnLocked"
android:textOn="Locked" />
</LinearLayout>
Code for specifically blocking the back button -
@Override
public void onBackPressed() {
//Do nothing
}
and for older then API 5 use this:
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
//Do nothing
return true;
}
return super.onKeyDown(keyCode, event);
}