UiHandler.java revision 1ddcf0f2bf44d3c9db89112ef52510d9b2433ac4 
1/*
2 * Copyright (C) 2012 Google Inc.
3 * Licensed to The Android Open Source Project.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18package com.android.mail.ui;
19
20import android.app.Activity;
21import android.app.FragmentTransaction;
22import android.os.Handler;
23
24import com.android.mail.utils.LogUtils;
25
26import java.util.concurrent.atomic.AtomicInteger;
27
28/**
29 * A thin wrapper of {@link Handler} to run a callback in UI thread. Any callback posted to this
30 * handler is guarantee to run inside {@link Activity} life cycle. However, it can be dropped if the
31 * {@link Activity} has been stopped. This handler is safe to use with {@link FragmentTransaction}.
32 *
33 * @author phamm
34 */
35public class UiHandler {
36    private final Handler mHandler = new Handler();
37    private boolean mEnabled = true;
38    private final static String LOG_TAG = new LogUtils().getLogTag();
39
40    /** Number of {@link Runnable} in the queue. */
41    private AtomicInteger mCount = new AtomicInteger(0);
42
43    public void post(final Runnable r) {
44        if (mEnabled) {
45            mCount.incrementAndGet();
46            mHandler.post(new Runnable() {
47                @Override
48                public void run() {
49                    mCount.decrementAndGet();
50                    r.run();
51                }
52            });
53        } else {
54            LogUtils.d(LOG_TAG, "UiHandler is disabled in post(). Dropping Runnable.");
55        }
56    }
57
58    public void postDelayed(final Runnable r, long delayMillis) {
59        if (mEnabled) {
60            mCount.incrementAndGet();
61            mHandler.postDelayed(new Runnable() {
62                @Override
63                public void run() {
64                    mCount.decrementAndGet();
65                    r.run();
66                }
67            }, delayMillis);
68        } else {
69            LogUtils.d(LOG_TAG, "UiHandler is disabled in postDelayed(). Dropping Runnable.");
70        }
71    }
72
73    public void removeCallbacks(Runnable r) {
74        mHandler.removeCallbacks(r);
75    }
76
77    public void setEnabled(boolean enabled) {
78        mEnabled = enabled;
79        if (!mEnabled) {
80            int count = mCount.getAndSet(0);
81            if (count > 0) {
82                LogUtils.e(LOG_TAG, "Disable UiHandler. Dropping %d Runnables.", count);
83            }
84            mHandler.removeCallbacksAndMessages(null);
85        }
86    }
87
88    /**
89     * @return whether the {@link UiHandler} is enabled. It's safe to edit UI if the
90     *         {@link UiHandler} is enabled.
91     */
92    public boolean isEnabled() {
93        return mEnabled;
94    }
95}