public static Spanned fromHtml (String source)

public void setError (CharSequence error)

Added in API level 1

• 在TextView上不太经常使用，很多其它用在EditText上（EditText继承自TextView）提示用户输入非法。还有个多态方法setError(CharSequence error,Drawable icon)来让开发人员自己定义错误提示图片。

效果图：

Sets the right-hand compound drawable of the TextView to the "error" icon and sets an error message that will be displayed in a popup when the TextView has focus. The icon and error message will be reset to null when any key events cause changes to the TextView‘s text. If the error is null, the error message and icon will be cleared.

public static String getStackTraceString (Throwable tr)

Added in API level 1

• 有时候我们希望程序抛出异常时能把异常信息保存到制定文件夹的文件里，getStackTraceString就能够将异常信息转换成字符串的形式。

使用演示样例：

[java] view plain copy

1. try {  
2.         //TODO  
3.     } catch (Exception e) {  
4.         String exceptionStr = Log.getStackTraceString(e);  
5.     }  

Handy function to get a loggable stack trace from a Throwable

Parameters

tr	An exception to log

public static LayoutInflater from (Context context)

Added in API level 1

• 和冗长的getSystemService()说Goodbye。

Obtains the LayoutInflater from the given context.

public abstract File getCacheDir ()

Added in API level 1

• 获取应用默认缓存路径“/data/data/应用包名/cache”

Returns the absolute path to the application specific cache directory on the filesystem. These files will be ones that get deleted first when the device runs low on storage. There is no guarantee when these files will be deleted. Note: you should not rely on the system deleting these files for you; you should always have a reasonable maximum, such as 1 MB, for the amount of space you consume with cache files, and prune those files when exceeding that space.

Returns

• The path of the directory holding application cache files.

public void reverse ()

Added in API level 11

• 由于当调用这种方法时，假设动画正在播放，能够反向播放动画直到回播放的原点。

  所以我喜欢用它来平滑的结束动画的播放。

Plays the ValueAnimator in reverse. If the animation is already running, it will stop itself and play backwards from the point reached when reverse was called. If the animation is not currently running, then it will start from the end and play backwards. This behavior is only set for the current animation; future playing of the animation will use the default behavior of playing forward.

• 将文件的大小由字节转换成KB、MB甚至G。再也不用手动去和1024较真了。

Formats a content size to be in the form of bytes, kilobytes, megabytes, etc

Parameters

Returns

• formatted string with the number

• 能够将TextView中的文字依据设定的mask自己主动设置成超链接。设置超链接的点击事件时会用到LinkMovementMethod。我还用过。大家可參考这篇博文

  Android应用实例之---使用Linkify + 正则式区分微博文本链接及跳转处理

Scans the text of the provided TextView and turns all occurrences of the link types indicated in the mask into clickable links. If matches are found the movement method for the TextView is set to LinkMovementMethod.

• 这个就非经常见了，用于在Activity中拦截返回键事件。（Fragment中可没有这种方法，要想在Fragment中拦截返回键事件请參考我的还有一篇博客优雅的让Fragment监听返回键）

Called when the activity has detected the user‘s press of the back key. The default implementation simply finishes the current activity, but you can override this to do whatever you want.

• 在初始化Fragment时向Fragment传參的一个非常方便的接口，在Fragment中使用getArguments()来接收。

Supply the construction arguments for this fragment. This can only be called before the fragment has been attached to its activity; that is, you should call it immediately after constructing the fragment. The arguments supplied here will be retained across fragment destroy and creation.

• PhoneNumverUtils提供了一系列方法用来格式化电话号码

Breaks the given number down and formats it according to the rules for the country the number is from.

Parameters

Returns

• A locally acceptable formatting of the input, or the raw input if formatting rules aren‘t known for the number

Genymotion

• 一个比較好用的安卓模拟器。分为免费版、个人版和商业版。当中免费版提供了从2.3到4.4版本号的SDK，并带有GPS和摄像头功能。

  我常常使用这个模拟器做博客Demo的gif图。

  免费版百度网盘链接：http://pan.baidu.com/s/1kTj2Nu3

• 经常使用于屏幕方法改变时的逻辑处理，但我还没用到过，所以具体介绍还是挪步到

  Activity.isChangingConfigurations()

Check to see whether this activity is in the process of being destroyed in order to be recreated with a new configuration. This is often used in onStop() to determine whether the state needs to be cleaned up or will be passed on to the next instance of the activity via onRetainNonConfigurationInstance().

Returns

• If the activity is being torn down in order to be recreated with a new configuration, returns true; else returns false.

• 假设想实现一个Button。宽度占领屏幕宽度的50%怎么办？代码动态计算？尝试结合使用android:weightSum和android:layout_weight吧。參考博客：合用weightSum属性和layout_weight属性

Defines the maximum weight sum. If unspecified, the sum is computed by adding the layout_weight of all of the children. This can be used for instance to give a single child 50% of the total available space by giving it a layout_weight of 0.5 and setting the weightSum to 1.0.

Must be a floating point value, such as "1.2".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol weightSum.

• 设置这个属性后子控件就能够在父控件的范围之外进行绘制了，编写动画时再也不用一层多余的FrameLayout。

Defines whether a child is limited to draw inside of its bounds or not. This is useful with animations that scale the size of the children to more than 100% for instance. In such a case, this property should be set to false to allow the children to draw outside of their bounds. The default value of this property is true.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?

[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol clipChildren.

Related Methods

• setClipChildren(boolean)

• 当开发人员须要设置一个内容不足以填充整个屏幕的ScrollView全屏时，设置fill_parent是不起作用的，那么使用这个属性吧。

Defines whether the scrollview should stretch its content to fill the viewport.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol fillViewport.

• 用来设置Bitmap显示方式。有平铺、反复等。比如设置反复显示

[html] view plain copy

1. <bitmap     
2.     xmlns:android="http://schemas.android.com/apk/res/android"     
3.     android:src="@drawable/repeatimg"     
4.     android:tileMode="repeat"     
5.     android:dither="true" />  

Defines the tile mode. When the tile mode is enabled, the bitmap is repeated. Gravity is ignored when the tile mode is enabled. Default value is "disabled".

Must be one of the following constant values.

This corresponds to the global attribute resource symbol tileMode.

• 为selector设置渐变效果。演示样例：

[html] view plain copy

1. <?xml version="1.0" encoding="utf-8"?>  
2.   
3. <selector xmlns:android="http://schemas.android.com/apk/res/android"  
4.     android:enterFadeDuration="500"  
5.     android:exitFadeDuration="500">  
6.   
7.     <item android:state_focused="true"  
8.         android:drawable="@color/press"/>  
9.     <item  
10.         android:state_pressed="true"  
11.         android:drawable="@color/press"/>  
12.     <item  
13.         android:drawable="@color/normal"/>  
14. </selector>  

Amount of time (in milliseconds) to fade out an old state drawable.

Must be an integer value, such as "100".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

• 经经常使用到的设置图片在ImageView中的展示样式。

  參考演示样例请挪步：ImageView.ScaleType设置图解

Controls how the image should be resized or moved to match the size of this ImageView.

Must be one of the following constant values.

This corresponds to the global attribute resource symbol scaleType.

• 使用这种方法能够开启和禁用四大组件。開始我非常纳闷为什么要禁用组件？后来通过查看android 禁用和开启四大组件的方法博文，发现这种方法能够作为后期性能优化方法之中的一个。

Set the enabled setting for a package component (activity, receiver, service, provider). This setting will override any enabled state which may have been set by the component in its manifest.

Parameters

• 不知道大家有没有注意到startActivity(Intent,Bundle)，那么ActivityOptions就是这个Bundle的原型。负责Activity跳转时的动画。