Android example source code file (SecureView.java)

This example Android source code file (SecureView.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

activity, android, app, application, button, motionevent, onclicklistener, ontouchlistener, override, secureviewoverlay, string, toast, ui, view, widget

The SecureView.java Android example source code

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.view;

import com.example.android.apis.R;

import android.app.Activity;
import android.app.AlertDialog;
import android.os.Bundle;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.Toast;


/**
 * This activity demonstrates two different ways in which views can be made more secure to
 * touch spoofing attacks by leveraging framework features.
 *
 * The activity presents 3 buttons that obtensibly perform a risky security critical
 * function.  Under ordinary circumstances, the user would never click on these buttons
 * or would at least think long and hard about it.  However, a carefully crafted toast can
 * overlay the contents of the activity in such a way as to make the user believe the buttons
 * are innocuous.  Since the toast cannot receive input, the touches are passed down to the
 * activity potentially yielding an effect other than what the user intended.
 *
 * To simulate the spoofing risk, this activity pops up a specially crafted overlay as
 * a toast layed out so as to cover the buttons and part of the descriptive text.
 * For the purposes of this demonstration, pretend that the overlay was actually popped
 * up by a malicious application published by the International Cabal of Evil Penguins.
 *
 * The 3 buttons are set up as follows:
 *
 * 1. The "unsecured button" does not apply any touch filtering of any kind.
 *    When the toast appears, this button remains clickable as usual which creates an
 *    opportunity for spoofing to occur.
 *
 * 2. The "built-in secured button" leverages the android:filterTouchesWhenObscured view
 *    attribute to ask the framework to filter out touches when the window is obscured.
 *    When the toast appears, the button does not receive the touch and appears to be inoperable.
 *
 * 3. The "custom secured button" adds a touch listener to the button which intercepts the
 *    touch event and checks whether the window is obscured.  If so, it warns the user and
 *    drops the touch event.  This example is intended to demonstrate how a view can
 *    perform its own filtering and provide additional feedback by examining the {@MotionEvent}
 *    flags to determine whether the window is obscured.  Here we use a touch listener but
 *    a custom view subclass could perform the filtering by overriding
 *    {@link View#onFilterTouchEventForSecurity(MotionEvent)}.
 *
 * Refer to the comments on {@View} for more information about view security.
 */
public class SecureView extends Activity {
    private int mClickCount;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.secure_view);

        Button toastButton = (Button) findViewById(R.id.secure_view_toast_button);
        toastButton.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                showOverlay();
            }
        });

        Button unsecureButton = (Button) findViewById(R.id.secure_view_unsecure_button);
        setClickedAction(unsecureButton);

        Button builtinSecureButton = (Button) findViewById(R.id.secure_view_builtin_secure_button);
        setClickedAction(builtinSecureButton);

        Button customSecureButton = (Button) findViewById(R.id.secure_view_custom_secure_button);
        setClickedAction(customSecureButton);
        setTouchFilter(customSecureButton);
    }

    private void showOverlay() {
        // Generate a toast view with a special layout that will position itself right
        // on top of this view's interesting widgets.  Sneaky huh?
        SecureViewOverlay overlay = (SecureViewOverlay)
                getLayoutInflater().inflate(R.layout.secure_view_overlay, null);
        overlay.setActivityToSpoof(this);

        Toast toast = new Toast(getApplicationContext());
        toast.setGravity(Gravity.FILL, 0, 0);
        toast.setView(overlay);
        toast.show();
    }

    private void setClickedAction(Button button) {
        button.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                String[] messages = getResources().getStringArray(R.array.secure_view_clicked);
                String message = messages[mClickCount++ % messages.length];

                new AlertDialog.Builder(SecureView.this)
                    .setTitle(R.string.secure_view_action_dialog_title)
                    .setMessage(message)
                    .setNeutralButton(getResources().getString(
                            R.string.secure_view_action_dialog_dismiss), null)
                    .show();
            }
        });
    }

    private void setTouchFilter(Button button) {
        button.setOnTouchListener(new OnTouchListener() {
            public boolean onTouch(View v, MotionEvent event) {
                if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != 0) {
                    if (event.getAction() == MotionEvent.ACTION_UP) {
                        new AlertDialog.Builder(SecureView.this)
                            .setTitle(R.string.secure_view_caught_dialog_title)
                            .setMessage(R.string.secure_view_caught_dialog_message)
                            .setNeutralButton(getResources().getString(
                                    R.string.secure_view_caught_dialog_dismiss), null)
                            .show();
                    }
                    // Return true to prevent the button from processing the touch.
                    return true;
                }
                return false;
            }
        });
    }
}