Android 极简反射教程，及应用示例

public class HashMapClass extends HashMap {    public static void main(String[] args) {     Method[] methods = HashMapClass.class.getMethods();      for (Method method : methods) {       System.out.println("method name is " + method.getName());     }   }  }

try {       Class mClass = Class.forName("java.lang.Object");        // 不包含包名前缀的名字       String simpleName = mClass.getSimpleName();        // 类型修饰符, private, protect, static etc.       int modifiers = mClass.getModifiers();       // Modifier 提供的一些用于判读类型的静态方法.       Modifier.isPrivate(modifiers);        // 父类的信息       Class superclass = mClass.getSuperclass();        // 构造函数       Constructor[] constructors = mClass.getConstructors();        // 字段类型       Field[] fields = mClass.getFields();     } catch (ClassNotFoundException e) {       e.printStackTrace();     }

public class Student {    private final String name; private int grade = 1;    public Student(String name) {     this.name = name;   }    public String getName() {     return name;   }    private int getGrade() {     return grade;   }    private void goToSchool() {     System.out.println(name + " go to school!");   } }

try {   Class studentClass = Student.class;    // 参数类型为一个 String 的构造函数   Constructor constructor = studentClass.getConstructor(new Class[]{String.class});    // 实例化 student 对象   Student student = (Student)constructor.newInstance("Li Lei");   System.out.print(student.getName()); } catch (ReflectiveOperationException e) {   e.printStackTrace(); }

try {   Student student = new Student("Han MeiMei");   System.out.println("origin grade is " + student.getGrade());    Class studentClass = Student.class;   // 获取声明的 grade 字段，这里要注意 getField 和 getDeclaredField 的区别   Field gradeField = studentClass.getDeclaredField("grade");    // 如果是 private 或者 package 权限的，一定要赋予其访问权限   gradeField.setAccessible(true);    // 修改 student 对象中的 Grade 字段值   gradeField.set(student, 2);   System.out.println("after reflection grade is " + student.getGrade());  } catch (ReflectiveOperationException e) {   e.printStackTrace(); }

try {   Student student = new Student("Han MeiMei");    // 获取私有方法，同样注意 getMethod 和 getDeclaredMethod 的区别   Method goMethod = Student.class.getDeclaredMethod("goToSchool", null);   // 赋予访问权限   goMethod.setAccessible(true);    // 调用 goToSchool 方法。   goMethod.invoke(student, null);  } catch (ReflectiveOperationException e) {   e.printStackTrace(); }

// we use token to identify this activity without having to send the // activity itself back to the activity manager. (matters more with ipc) @Override public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,         ActivityInfo info, Configuration curConfig, Configuration overrideConfig,         CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,         int procState, Bundle state, PersistableBundle persistentState,         List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,         boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {      updateProcessState(procState, false);      ActivityClientRecord r = new ActivityClientRecord();      r.token = token;     r.ident = ident;     r.intent = intent;     r.referrer = referrer;     r.voiceInteractor = voiceInteractor;     r.activityInfo = info;     r.compatInfo = compatInfo;     r.state = state;     r.persistentState = persistentState;      r.pendingResults = pendingResults;     r.pendingIntents = pendingNewIntents;      r.startsNotResumed = notResumed;     r.isForward = isForward;      r.profilerInfo = profilerInfo;      r.overrideConfig = overrideConfig;     updatePendingConfiguration(curConfig);      sendMessage(H.LAUNCH_ACTIVITY, r); }

private class H extends Handler {     public static final int LAUNCH_ACTIVITY         = 100;     public static final int PAUSE_ACTIVITY          = 101;     public static final int PAUSE_ACTIVITY_FINISHING= 102;     public static final int STOP_ACTIVITY_SHOW      = 103;     public static final int STOP_ACTIVITY_HIDE      = 104;     public static final int SHOW_WINDOW             = 105;     public static final int HIDE_WINDOW             = 106;     public static final int RESUME_ACTIVITY         = 107;     public static final int SEND_RESULT             = 108;     public static final int DESTROY_ACTIVITY        = 109;     public static final int BIND_APPLICATION        = 110;     public static final int EXIT_APPLICATION        = 111;     public static final int NEW_INTENT              = 112;     public static final int RECEIVER                = 113;     public static final int CREATE_SERVICE          = 114;     public static final int SERVICE_ARGS            = 115;     public static final int STOP_SERVICE            = 116;      //......      public void handleMessage(Message msg){      // ...     } }

/**  * Handle system messages here.  */ public void dispatchMessage(Message msg) {     if (msg.callback != null) {         handleCallback(msg);     } else {         if (mCallback != null) {             if (mCallback.handleMessage(msg)) {                 return;             }         }         handleMessage(msg);     } }

public class LaunchCallback implements Handler.Callback {    public static final int LAUNCH_ACTIVITY = 100;    private Handler.Callback originCallback;    public LaunchCallback(Handler.Callback originCallback) {     this.originCallback = originCallback;   }    @Override   public boolean handleMessage(Message msg) {      if (msg.what == LAUNCH_ACTIVITY) {       Toast.makeText(           VApp.getApp().getApplicationContext(),           "activity is going to launch! ", Toast.LENGTH_SHORT).show();     }      return originCallback.handleMessage(msg);   }  }

public class InjectTool {    public static void dexInject() {     try {        // 通过反射调用 ActivityThread 的静态方法, 获取 currentActivityThread       Class<?> activityThreadClass = Class.forName("android.app.ActivityThread");       Method currentActivityThreadMethod = activityThreadClass.getDeclaredMethod("currentActivityThread");       currentActivityThreadMethod.setAccessible(true);       Object currentActivityThread = currentActivityThreadMethod.invoke(null);        // 获取 currentActivityThread 这个示例中的 mH       Field handlerField = activityThreadClass.getDeclaredField("mH");       handlerField.setAccessible(true);       Handler handler = (Handler) handlerField.get(currentActivityThread);        // 修改 mH 中的 callback 字段       Field callbackField = Handler.class.getDeclaredField("mCallback");       callbackField.setAccessible(true);       Handler.Callback callback = (Handler.Callback) callbackField.get(handler);        callbackField.set(handler, new LaunchCallback(callback));     } catch (IllegalArgumentException | NoSuchMethodException | IllegalAccessException         | InvocationTargetException | ClassNotFoundException | NoSuchFieldException e) {       e.printStackTrace();     }   }  }

@Override protected void attachBaseContext(Context base) {     super.attachBaseContext(base);     InjectTool.dexInject(); }