Android必会小功能总结

1.获取屏幕尺寸、密度等信息。
    1)最常用的方法：
        WindowManager windowManager = getWindowManager();   
        Display display = windowManager.getDefaultDisplay();   
        int w = display.getWidth();   
        int h = display.getHeight();
    2)用DisplayMetrics来获得参数：
        DisplayMetrics displayMetrics = new DisplayMetrics() ;
        displayMetrics = getResources().getDisplayMetrics();
        int width = display.getWidth();
        int height = display.getHeight();
        int densityDpi = displayMetrics.densityDpi;
    但是，需要注意的是，在一个低密度的小屏手机上，仅靠上面的代码是不能获取正确的尺寸的。比如说，一部240x320像素的低密度手机，如果运行上述代 码，获取到的屏幕尺寸是320x427。因此，研究之后发现，若没有设定多分辨率支持的话，Android系统会将240x320的低密度（120）尺寸 转换为中等密度（160）对应的尺寸，这样的话就大大影响了程序的编码。所以，需要在工程的AndroidManifest.xml文件中，加入 supports-screens节点，具体的内容如下：
        <supports-screens
            android:smallScreens="true"
            android:normalScreens="true"
            android:largeScreens="true"
            android:xlargeScreens="true"
            android:resizeable="true"
            android:anyDensity="true" />
    这样的话，当前的Android程序就支持了多种分辨率，那么就可以得到正确的物理尺寸了。
px与dip转换公式：
 pixs =dips * (densityDpi/160). 
 dips=(pixs*160)/densityDpi


dp与px转换的方法
 public static int dip2px(Context context, float dipValue){
 　　final float scale = context.getResources().getDisplayMetrics().density;
 　　return (int)(dipValue * scale +0.5f);
　　}

　　public static int px2dip(Context context, float pxValue){
 　　final float scale = context.getResource().getDisplayMetrics().density;
 　　return (int)(pxValue / scale +0.5f);
　　}

2.users-permission的总结：

在编写Android程序时经常会忘记添加权限，下面是网上收集的关于Android uses-permission的资料，方便查找~

android.permission.ACCESS_CHECKIN_PROPERTIES
允 许读写访问”properties”表在checkin数据库中，改值可以修改上传( Allows read/write access to the “properties” table in the checkin database, to change values that get uploaded)

android.permission.ACCESS_COARSE_LOCATION
允许一个程序访问CellID或WiFi热点来获取粗略的位置(Allows an application to access coarse (e.g., Cell-ID, WiFi) location)

android.permission.ACCESS_FINE_LOCATION
允许一个程序访问精良位置(如GPS) (Allows an application to access fine (e.g., GPS) location)

android.permission.ACCESS_LOCATION_EXTRA_COMMANDS
允许应用程序访问额外的位置提供命令(Allows an application to access extra location provider commands)

android.permission.ACCESS_MOCK_LOCATION
允许程序创建模拟位置提供用于测试(Allows an application to create mock location providers for testing)

android.permission.ACCESS_NETWORK_STATE
允许程序访问有关GSM网络信息(Allows applications to access information about networks)

android.permission.ACCESS_SURFACE_FLINGER
允许程序使用SurfaceFlinger底层特性(Allows an application to use SurfaceFlinger’s low level features)

android.permission.ACCESS_WIFI_STATE
允许程序访问Wi-Fi网络状态信息(Allows applications to access information about Wi-Fi networks)

android.permission.ADD_SYSTEM_SERVICE
允许程序发布系统级服务(Allows an application to publish system-level services).

android.permission.BATTERY_STATS
允许程序更新手机电池统计信息(Allows an application to update the collected battery statistics)

android.permission.BLUETOOTH
允许程序连接到已配对的蓝牙设备(Allows applications to connect to paired bluetooth devices)

android.permission.BLUETOOTH_ADMIN
允许程序发现和配对蓝牙设备(Allows applications to discover and pair bluetooth devices)

android.permission.BRICK
请求能够禁用设备(非常危险)(Required to be able to disable the device (very *erous!).)

android.permission.BROADCAST_PACKAGE_REMOVED
允许程序广播一个提示消息在一个应用程序包已经移除后(Allows an application to broadcast a notification that an application

package has been removed)

android.permission.BROADCAST_STICKY
允许一个程序广播常用intents(Allows an application to broadcast sticky intents)

android.permission.CALL_PHONE
允 许一个程序初始化一个电话拨号不需通过拨号用户界面需要用户确认(Allows an application to initiate a phone call without going through the Dialer user interface for the user to confirm the call being placed.)

android.permission.CALL_PRIVILEGED
允 许一个程序拨打任何号码，包含紧急号码无需通过拨号用户界面需要用户确认(Allows an application to call any phone number, including emergency numbers, without going through the Dialer user interface for the user to confirm the call being placed)

android.permission.CAMERA
请求访问使用照相设备(Required to be able to access the camera device. )

android.permission.CHANGE_COMPONENT_ENABLED_STATE
允 许一个程序是否改变一个组件或其他的启用或禁用(Allows an application to change whether an application component (other than its own) is enabled or not. )

android.permission.CHANGE_CONFIGURATION
允许一个程序修改当前设置，如本地化(Allows an application to modify the current configuration, such as locale. )

android.permission.CHANGE_NETWORK_STATE
允许程序改变网络连接状态(Allows applications to change network connectivity state)

android.permission.CHANGE_WIFI_STATE
允许程序改变Wi-Fi连接状态(Allows applications to change Wi-Fi connectivity state)

android.permission.CLEAR_APP_CACHE
允许一个程序清楚缓存从所有安装的程序在设备中(Allows an application to clear the caches of all installed applications on the device. )

android.permission.CLEAR_APP_USER_DATA
允许一个程序清除用户设置(Allows an application to clear user data)

android.permission.CONTROL_LOCATION_UPDATES
允许启用禁止位置更新提示从无线模块(Allows enabling/disabling location update notifications from the radio. )

android.permission.DELETE_CACHE_FILES
允许程序删除缓存文件(Allows an application to delete cache files)

android.permission.DELETE_PACKAGES
允许一个程序删除包(Allows an application to delete packages)

android.permission.DEVICE_POWER
允许访问底层电源管理(Allows low-level access to power management)

android.permission.DIAGNOSTIC
允许程序RW诊断资源(Allows applications to RW to diagnostic resources. )

android.permission.DISABLE_KEYGUARD
允许程序禁用键盘锁(Allows applications to disable the keyguard )

android.permission.DUMP
允许程序返回状态抓取信息从系统服务(Allows an application to retrieve state dump information from system services.)

android.permission.EXPAND_STATUS_BAR
允许一个程序扩展收缩在状态栏,android开发网提示应该是一个类似Windows Mobile中的托盘程序(Allows an application to expand or collapse the status bar. )

android.permission.FACTORY_TEST
作为一个工厂测试程序，运行在root用户(Run as a manufacturer test application, running as the root user. )

android.permission.FLASHLIGHT
访问闪光灯,android开发网提示HTC Dream不包含闪光灯(Allows access to the flashlight )

android.permission.FORCE_BACK
允许程序强行一个后退操作是否在顶层activities(Allows an application to force a BACK operation on whatever is the top activity. )

android.permission.FOTA_UPDATE
暂时不了解这是做什么使用的，android开发网分析可能是一个预留权限.

android.permission.GET_ACCOUNTS
访问一个帐户列表在Accounts Service中(Allows access to the list of accounts in the Accounts Service)

android.permission.GET_PACKAGE_SIZE
允许一个程序获取任何package占用空间容量(Allows an application to find out the space used by any package. )

android.permission.GET_TASKS
允 许一个程序获取信息有关当前或最近运行的任务，一个缩略的任务状态，是否活动等等(Allows an application to get information about the currently or recently running tasks: a thumbnail representation of the tasks, what activities are running in it, etc.)

android.permission.HARDWARE_TEST
允许访问硬件(Allows access to hardware peripherals. )

android.permission.INJECT_EVENTS
允 许一个程序截获用户事件如按键、触摸、轨迹球等等到一个时间流，android 开发网提醒算是hook技术吧(Allows an application to inject user events (keys, touch, trackball) into the event stream and deliver them to ANY window.)

android.permission.INSTALL_PACKAGES
允许一个程序安装packages(Allows an application to install packages. )

android.permission.INTERNAL_SYSTEM_WINDOW
允许打开窗口使用系统用户界面(Allows an application to open windows that are for use by parts of the system user interface. )

android.permission.INTERNET
允许程序打开网络套接字(Allows applications to open network sockets)

android.permission.MANAGE_APP_TOKENS
允 许程序管理(创建、催后、 z- order默认向z轴推移)程序引用在窗口管理器中(Allows an application to manage (create, destroy, Z-order) application tokens in the window manager. )

android.permission.MASTER_CLEAR

目前还没有明确的解释，android开发网分析可能是清除一切数据，类似硬格机

android.permission.MODIFY_AUDIO_SETTINGS
允许程序修改全局音频设置(Allows an application to modify global audio settings)

android.permission.MODIFY_PHONE_STATE
允许修改话机状态，如电源，人机接口等(Allows modification of the telephony state – power on, mmi, etc. )

android.permission.MOUNT_UNMOUNT_FILESYSTEMS
允许挂载和反挂载文件系统可移动存储(Allows mounting and unmounting file systems for removable storage. )

android.permission.PERSISTENT_ACTIVITY
允许一个程序设置他的activities显示(Allow an application to make its activities persistent. )

android.permission.PROCESS_OUTGOING_CALLS
允许程序监视、修改有关播出电话(Allows an application to monitor, modify, or abort outgoing calls)

android.permission.READ_CALENDAR
允许程序读取用户日历数据(Allows an application to read the user’s calendar data.)

android.permission.READ_CONTACTS
允许程序读取用户联系人数据(Allows an application to read the user’s contacts data.)

android.permission.READ_FRAME_BUFFER
允许程序屏幕波或和更多常规的访问帧缓冲数据(Allows an application to take screen shots and more generally get access to the frame buffer data)

android.permission.READ_INPUT_STATE
允许程序返回当前按键状态(Allows an application to retrieve the current state of keys and switches. )

android.permission.READ_LOGS
允许程序读取底层系统日志文件(Allows an application to read the low-level system log files. )

android.permission.READ_OWNER_DATA
允许程序读取所有者数据(Allows an application to read the owner’s data)

android.permission.READ_SMS
允许程序读取短信息(Allows an application to read SMS messages.)

android.permission.READ_SYNC_SETTINGS
允许程序读取同步设置(Allows applications to read the sync settings)

android.permission.READ_SYNC_STATS
允许程序读取同步状态(Allows applications to read the sync stats)

android.permission.REBOOT
请求能够重新启动设备(Required to be able to reboot the device. )

android.permission.RECEIVE_BOOT_COMPLETED
允 许一个程序接收到 ACTION_BOOT_COMPLETED广播在系统完成启动(Allows an application to receive the ACTION_BOOT_COMPLETED that is broadcast after the system finishes booting. )

android.permission.RECEIVE_MMS
允许一个程序监控将收到MMS彩信,记录或处理(Allows an application to monitor incoming MMS messages, to record or perform processing on them. )

android.permission.RECEIVE_SMS
允许程序监控一个将收到短信息，记录或处理(Allows an application to monitor incoming SMS messages, to record or perform processing on them.)

android.permission.RECEIVE_WAP_PUSH
允许程序监控将收到WAP PUSH信息(Allows an application to monitor incoming WAP push messages. )

android.permission.RECORD_AUDIO
允许程序录制音频(Allows an application to record audio)

android.permission.REORDER_TASKS
允许程序改变Z轴排列任务(Allows an application to change the Z-order of tasks)

android.permission.RESTART_PACKAGES
允许程序重新启动其他程序(Allows an application to restart other applications)

android.permission.SEND_SMS
允许程序发送SMS短信(Allows an application to send SMS messages)

android.permission.SET_ACTIVITY_WATCHER
允许程序监控或控制activities已经启动全局系统中(Allows an application to watch and control how activities are started globally in the system.)

android.permission.SET_ALWAYS_FINISH
允许程序控制是否活动间接完成在处于后台时(Allows an application to control whether activities are immediately finished when put in the background.)

android.permission.SET_ANIMATION_SCALE
修改全局信息比例(Modify the global animation scaling factor.)

android.permission.SET_DEBUG_APP
配置一个程序用于调试(Configure an application for debugging.)

android.permission.SET_ORIENTATION
允许底层访问设置屏幕方向和实际旋转(Allows low-level access to setting the orientation (actually rotation) of the screen.)

android.permission.SET_PREFERRED_APPLICATIONS
允 许一个程序修改列表参数PackageManager.addPackageToPreferred()和 PackageManager.removePackageFromPreferred()方法(Allows an application to modify the list of preferred applications with the PackageManager.addPackageToPreferred() and PackageManager.removePackageFromPreferred() methods.)

android.permission.SET_PROCESS_FOREGROUND
允许程序当前运行程序强行到前台(Allows an application to force any currently running process to be in the foreground.)

android.permission.SET_PROCESS_LIMIT
允许设置最大的运行进程数量(Allows an application to set the maximum number of (not needed) application processes that can be running. )

android.permission.SET_TIME_ZONE
允许程序设置时间区域(Allows applications to set the system time zone)

android.permission.SET_WALLPAPER
允许程序设置壁纸(Allows applications to set the wallpaper )

android.permission.SET_WALLPAPER_HINTS
允许程序设置壁纸hits(Allows applications to set the wallpaper hints)

android.permission.SIGNAL_PERSISTENT_PROCESSES
允许程序请求发送信号到所有显示的进程中(Allow an application to request that a signal be sent to all persistent processes)

android.permission.STATUS_BAR
允许程序打开、关闭或禁用状态栏及图标Allows an application to open, close, or disable the status bar and its icons.

android.permission.SUBSCRIBED_FEEDS_READ
允许一个程序访问订阅RSS Feed内容提供(Allows an application to allow access the subscribed feeds ContentProvider. )

android.permission.SUBSCRIBED_FEEDS_WRITE
系统暂时保留改设置,android开发网认为未来版本会加入该功能。

android.permission.SYSTEM_ALERT_WINDOW
允 许一个程序打开窗口使用 TYPE_SYSTEM_ALERT，显示在其他所有程序的顶层(Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications. )

android.permission.VIBRATE
允许访问振动设备(Allows access to the vibrator)

android.permission.WAKE_LOCK
允许使用PowerManager的 WakeLocks保持进程在休眠时从屏幕消失( Allows using PowerManager WakeLocks to keep

processor from sleeping or screen from dimming)

android.permission.WRITE_APN_SETTINGS
允许程序写入API设置(Allows applications to write the apn settings)

android.permission.WRITE_CALENDAR
允许一个程序写入但不读取用户日历数据(Allows an application to write (but not read) the user’s calendar data. )

android.permission.WRITE_CONTACTS
允许程序写入但不读取用户联系人数据(Allows an application to write (but not read) the user’s contacts data. )

android.permission.WRITE_GSERVICES
允许程序修改Google服务地图(Allows an application to modify the Google service map. )

android.permission.WRITE_OWNER_DATA
允许一个程序写入但不读取所有者数据(Allows an application to write (but not read) the owner’s data.)

android.permission.WRITE_SETTINGS
允许程序读取或写入系统设置(Allows an application to read or write the system settings. )

android.permission.WRITE_SMS
允许程序写短信(Allows an application to write SMS messages)

android.permission.WRITE_SYNC_SETTINGS
允许程序写入同步设置(Allows applications to write the sync settings)

3.空间置顶：永远保留在最顶层，类似于天天动听的桌面歌词那样，始终在最顶层。
API 中有这样一个常量：WindowManager.LayoutParams.TYPE_SYSTEM_ALERT。文档中对它的的描述为:“Window type: system window, such as low power alert. These windows are always on top of application windows.”也就是说用这个type可以显示在其他application的顶层，但注意：当用到这个常量的时候，要加上相应的权限， 即：<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />。这个权限在文档中的描述为：“Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications. Very few applications should use this permission; these windows are intended for system-level interaction with the user.”
WindowManager mWin = (WindowManager)getSystemService(Context.WINDOW_SERVICE)
然后使用addView的方法创建窗体，这样的窗体时凌驾于任何程序之上的。

4.设置全屏和无标题：在实际的应用程序开发中，我们有时需要把 Activity 设置成全屏显示，一般情况下，可以通过两种方式来设置全屏显示效果。其一，通过在代码中可以设置，其二，通过manifest配置文件来设置全屏。
其一：在代码中设置(如下)

 public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
          
        //设置无标题  
        requestWindowFeature(Window.FEATURE_NO_TITLE);  
        //设置全屏  
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);  
          
        setContentView(R.layout.main);  
 }  
 但要注意的是：在代码中设置的话，设置无标题和设置全屏的两段代码要放置在 setContentView(R.layout.main); 这段代码的前面。要不然会报错。

    其二：在manifest配置文件中设置
 <?xml version="1.0" encoding="utf-8"?>  
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
      package="com.andyidea"  
      android:versionCode="1"  
      android:versionName="1.0">  
    <uses-sdk android:minSdkVersion="8" />  
    <application android:icon="@drawable/icon" android:label="@string/app_name">  
        <activity android:name=".login.LoginActivity"   
                  android:theme="@android:style/android.NoTitleBar.Fullscreen"  
                  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>
  在相应的Activity中节点中添加属 性：android:theme="@android:style/Theme.NoTitleBar.Fullscreen" 即可以设置某个Activity全屏显示。若设置成         android:theme="@android:style/Theme.NoTitleBar" 即是只是设置成无标题状态。

5.在代码中设置背景：
　　Resources res = getResources();
      Drawable drawable = res.getDrawable(R.drawable.bkcolor);
      this.getWindow().setBackgroundDrawable(drawable);
　　需要在value目录下的string.xml文件中加入一段代码，如<drawable name="bkcolor">#ff00ff</drawable>

6.在ondraw中获取text文本的长和宽：
  1）字符串宽度 Paint.measureText 方法，这个方法很简单。
  2）字符高度使用 FontMetrics 类：
　　Paint pFont = new Paint();
　　Rect rect = new Rect();
　　//返回包围整个字符串的最小的一个Rect区域
　　pFont.getTextBounds(str, 0, 1, rect);
　　strwid = rect.width();
　　strhei = rect.height();

7.抗锯齿：在画图时，由于旋转或者缩放后，会产生锯齿，可以通过这样解决。
　　1）直接在paint上加上抗锯齿
　　     paint.setAntiAlias(true);
　　2）在不能给paint加抗锯齿的地方，可以直接给canvas加抗锯齿
　　　　canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG));