理论背景

当我们在分析android的键盘记录的时候就不得不和input进行打交道，那么input在系统中是怎么进行实现的？
Android手机中默认携带input子系统，并且开在机就会产生默认的mouse和keyboard事件，这样使得用户开机就可以触屏点击和使用按键。
android中键盘实现的系统源码位置\source\frameworks\base\cmds\input\src\com\android\commands\input\Input.java

关键代码实现解析：java层代码

Input类定义

public class Input {
    //用于定义打印调试信息
    private static final String TAG = "Input";
    private static final String INVALID_ARGUMENTS = "Error: Invalid arguments for command: ";
    //用map方式实现关键字和标识对应
    private static final Map<String, Integer> SOURCES = new HashMap<String, Integer>() {{
        put("keyboard", InputDevice.SOURCE_KEYBOARD);
        put("dpad", InputDevice.SOURCE_DPAD);
        put("gamepad", InputDevice.SOURCE_GAMEPAD);
        put("touchscreen", InputDevice.SOURCE_TOUCHSCREEN);
        put("mouse", InputDevice.SOURCE_MOUSE);
        put("stylus", InputDevice.SOURCE_STYLUS);
        put("trackball", InputDevice.SOURCE_TRACKBALL);
        put("touchpad", InputDevice.SOURCE_TOUCHPAD);
        put("touchnavigation", InputDevice.SOURCE_TOUCH_NAVIGATION);
        put("joystick", InputDevice.SOURCE_JOYSTICK);
    }};

sendKeyEvent 函数定义

//函数功能：发送键盘事件
  private void sendKeyEvent(int inputSource, int keyCode, boolean longpress) {
       //获取从开机到现在的毫秒数
       long now = SystemClock.uptimeMillis();
       //注入键盘事件
        injectKeyEvent(new KeyEvent(now, now, KeyEvent.ACTION_DOWN, keyCode, 0, 0,
                KeyCharacterMap.VIRTUAL_KEYBOARD, 0, 0, inputSource));
        if (longpress) {
            injectKeyEvent(new KeyEvent(now, now, KeyEvent.ACTION_DOWN, keyCode, 1, 0,
                    KeyCharacterMap.VIRTUAL_KEYBOARD, 0, KeyEvent.FLAG_LONG_PRESS,
                    inputSource));
        }
        injectKeyEvent(new KeyEvent(now, now, KeyEvent.ACTION_UP, keyCode, 0, 0,
                KeyCharacterMap.VIRTUAL_KEYBOARD, 0, 0, inputSource));
    }

sendSwipe 函数定义

//函数功能：实现滑屏操作
 private void sendSwipe(int inputSource, float x1, float y1, float x2, float y2, int duration) {
        if (duration < 0) {
            duration = 300;
        }
            //获取从开机到现在的毫秒数
        long now = SystemClock.uptimeMillis();
        //注入触摸事件
        injectMotionEvent(inputSource, MotionEvent.ACTION_DOWN, now, x1, y1, 1.0f);
        //计算开始时间和结束时间
        long startTime = now;
        long endTime = startTime + duration;
        while (now < endTime) {
            long elapsedTime = now - startTime;
            float alpha = (float) elapsedTime / duration;
            injectMotionEvent(inputSource, MotionEvent.ACTION_MOVE, now, lerp(x1, x2, alpha),
                    lerp(y1, y2, alpha), 1.0f);
            now = SystemClock.uptimeMillis();
        }
        injectMotionEvent(inputSource, MotionEvent.ACTION_UP, now, x2, y2, 0.0f);
    }

injectKeyEvent 函数定义

//函数功能：注入事件的实现
   private void injectKeyEvent(KeyEvent event) {
       //打印调试信息
        Log.i(TAG, "injectKeyEvent: " + event);
        //获取inputManager的实例事件
        InputManager.getInstance().injectInputEvent(event,
                InputManager.INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH);
    }

injectMotionEvent 函数定义

函数功能：注入触摸事件
 private void injectMotionEvent(int inputSource, int action, long when, float x, float y, float pressure) {
        final float DEFAULT_SIZE = 1.0f;
        final int DEFAULT_META_STATE = 0;
        final float DEFAULT_PRECISION_X = 1.0f;
        final float DEFAULT_PRECISION_Y = 1.0f;
        final int DEFAULT_DEVICE_ID = 0;
        final int DEFAULT_EDGE_FLAGS = 0;
        MotionEvent event = MotionEvent.obtain(when, when, action, x, y, pressure, DEFAULT_SIZE,
                DEFAULT_META_STATE, DEFAULT_PRECISION_X, DEFAULT_PRECISION_Y, DEFAULT_DEVICE_ID,
                DEFAULT_EDGE_FLAGS);
        event.setSource(inputSource);
        Log.i(TAG, "injectMotionEvent: " + event);
        InputManager.getInstance().injectInputEvent(event,
                InputManager.INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH);
    }

sendMove 函数定义

//函数功能：发送移动事件
   private void sendMove(int inputSource, float dx, float dy) {
        //获取时间
        long now = SystemClock.uptimeMillis();
        //调用注入触摸事件
        injectMotionEvent(inputSource, MotionEvent.ACTION_MOVE, now, dx, dy, 0.0f);
    }