Analysis of Java reflection mechanism + application examples

Analysis of Java reflection mechanism + application examples

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Introduction to this section:

In fact, a long time ago, I wanted to generalize about this reflection mechanism in Java, a few days ago, I saw a reflection mechanism of the network

Video tutorials Feel good, and review a bit, today interview for an afternoon, come back don't want to write code, write about Java

A summary of the reflection, write some simple examples of use, and finally found 2 examples of application of the reflection mechanism in Android, respectively, is

The older SDK uses the Aidl + Java reflection mechanism to answer and hang up the phone and use the reflection mechanism to close it via a button

dialog box, follow-up if used to the other summary ~

The text of this section:

1. Reflection of the relevant concept map:

2. Simple Use Example:

We write a simple example to understand the use of the Java reflection mechanism, in fact, through the class of related methods to implement it!

Let's start by defining a class to do a demonstration: Test.java:

Package Com.jay.test;public class Test {private String s1;public int i1;public static float PI = 3.14159f;public Test () {S Ystem.out.println ("I am a constructive method without reference");} Public Test (String s1) {super (); this.s1 = S1; System.out.println ("I am a constructor with a parameter");} Public Test (String s1,int i1) {System.out.println ("I am a constructor with two parameters");} public void sum (int a,int b) {System.out.println ("a+b =" + (a+b));}}

① gets information about a class:

public static void Gettheclass () {Class Class1 = Test.class; System.out.println (Class1.getname ()); System.out.println (Class1.getsimplename ());}

Run:

② Get constructed method:

Get the construction method by Constructor this API:

Provides four ways to call:

Constructor getconstructor (class[] params) --Get a public constructor that uses a special parameter type,

constructor[] GetConstructors () --Get all public constructors for the class

Constructor getdeclaredconstructor (class[] params) --Get constructors that use specific parameter types (regardless of access level)

constructor[] getdeclaredconstructors () --Get all constructors for the class (regardless of access level)

code example:

public static void GetConstructor () {Class Class1 = Test.class; Constructor[] cs = class1.getdeclaredconstructors (); for (Constructor Constructor:cs) {System.out.print ( Constructor.getname () + "(");//Gets the corresponding data type of the constructor's parameter list: class[] paramtypes = Constructor.getparametertypes (); for (Class Class2:paramtypes) {System.out.print (Class2.getsimplename () + ",");} System.out.println (")");}}

Run:

③ Get member variables:

To get the relevant member variable, you need to use the Field API:

There are also four methods available for invocation:

Field GetField (String name) --Get a named public field

field[] GetFields () --Get all public fields of the class

Field Getdeclaredfield (String name) --Get the named field of the class declaration

field[] Getdeclaredfields () --Get all the fields of the class declaration

code example:

public static void GetField () {Class Class1 = Test.class; field[] field = Class1.getfields (); for (Field field:fields) {//Gets the data type of the member variable class FieldType = Field.gettype (); String TypeName = Fieldtype.getname ();//Gets the parameter name of the member variable string filedname = Field.getname (); System.out.println (typename+ "" +filedname);}

Run:

④ Get the relevant method:

The method API is used to get the related methods in the class:

There are also four methods available for invocation:

Method GetMethod (String name, class[] params) --Use a specific parameter type to get a named public method

method[] GetMethods () --Get all public methods of the class

Method Getdeclaredmethod (String name, class[] params) --Use a close-up parameter type to get a naming method for class declarations

method[] Getdeclaredmethods () --Get all the methods of class declaration without permission

code example:

① get all the public methods in the class:

public static void GetMethod () {Class Class1 = Test.class; Method[] methods = Class1.getmethods (); for (int i = 0;i < methods.length;i++) {//Get method return value class ReturnType = methods[i].ge Treturntype (); System.out.print (Returntype.getname () + "");//Get Method name System.out.print (methods[i].getname () + "(");//Get parameter list class[] Paramtypes = Methods[i].getparametertypes (); for (Class class2:paramtypes) {System.out.print (Class2.getname () + ",");} System.out.println (")");}}

Run:

In addition to our custom methods, we have seen some other methods, which are some of the methods provided by the parent class ~

② uses reflection to invoke related methods:

code example:

public static void Usemethod () throws exception{test test = new test (); Class Class1 = Test.getclass (); method = Class1.getmethod ("sum", Int.class,int.class), Object object = Method.invoke (test, New object[]{11,22});

Run:

Of course, do not forget to catch the exception when calling this method!

using Reflection instances in 3.Android:

Some examples of the reflection mechanism in Android, such as: Android after the 1.1 version of the answer and hang off the API to hide

, we can invoke the relevant method in Itelephony by Aidl + reflection mechanism, in view of space, the time relationship here

For an example of the reflection mechanism in Android, refer to the following information :

①android answer and hang-up phone implementation:

Http://blog.sina.com.cn/s/blog_5da93c8f0101g4wb.html

② use the reflection mechanism to close the dialog box by using the button:

http://blog.csdn.net/nokiaguy/article/details/5770263

PS: In addition, seemingly Android 4.1 after the answer to the call method is not possible, the high version of the solution is as follows:

Http://bbs.51cto.com/thread-1078059-1.html

Well, about the Java reflection briefly understand here, follow-up encounter related re-mark~

Analysis of Java reflection mechanism + application examples