Android6.0 源碼修改之 仿IOS添加全屏可拖拽浮窗返回按鈕
前言
之前寫過屏蔽系統導航欄功能的文章，具體可看Android6.0 源碼修改之屏蔽導航欄虛擬按鍵（Home和RecentAPP）/動態顯示和隱藏NavigationBar

在某些特殊定制的版本中要求完全去掉導航欄，那么當用戶點進一些系統自帶的應用界面如設置、聯系人等，就沒法退出了，雖然可以在actionBar中添加back按鈕，但總不能每一個app都去添加吧。所以靈機一動我們就給系統添加一個全屏可拖拽的浮窗按鈕，點擊的時候處理返回鍵的邏輯。它大概長這樣(審美可能丑了點，你們可以自由發揮)

在這里插入圖片描述
圖1 最終效果圖

思路分析
通過分析之前的NavigationBar代碼，發現系統是通過WindowManager添加View的方式來實現，此處我們也可以模擬這種方法來添加
添加懸浮窗以后監聽觸摸事件，跟隨手指移動重新修改view的layoutParam
松手后獲取當前X坐標，小于屏幕width的一半則平移歸位至屏幕左邊
添加系統的返回按鍵功能
一、添加懸浮窗
private void showFloatingWindow() {

DisplayMetrics outMetrics = new DisplayMetrics(); mWindowManager.getDefaultDisplay().getMetrics(outMetrics); screenWidth = outMetrics.widthPixels; screenHeight = outMetrics.heightPixels;layoutParams = new WindowManager.LayoutParams(); layoutParams.type = WindowManager.LayoutParams.TYPE_PHONE; layoutParams.format = PixelFormat.RGBA_8888; layoutParams.gravity = Gravity.LEFT | Gravity.TOP; layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE; layoutParams.width = 100; layoutParams.height = 100; layoutParams.x = 200; layoutParams.y = 200;button = new ImageButton(mContext); button.setBackground(mContext.getResources().getDrawable(R.drawable.fab_background));//系統通訊錄里的藍色圓形圖標 button.setImageResource(R.drawable.ic_sysbar_back);//系統本身的back圖標 mWindowManager.addView(button, layoutParams); isShowFloatingView = true;

}
代碼很簡單，就是通過windowManager添加一個ImageButton，寬高都是100的，位置在屏幕左上角為原點的200,200。需要注意的是因為我們是在源碼里添加，而且是M的版本，所以type為WindowManager.LayoutParams.TYPE_PHONE。如果是在普通的app里注意事項可參考這篇

二、添加觸摸事件監聽
button.setOnTouchListener(new FloatingOnTouchListener());

private class FloatingOnTouchListener implements View.OnTouchListener {

private int lastX; private int lastY;@Override public boolean onTouch(View view, MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:isDrag = false;lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;case MotionEvent.ACTION_MOVE:isDrag = true;int nowX = (int) event.getRawX();int nowY = (int) event.getRawY();int movedX = nowX - lastX;int movedY = nowY - lastY;lastX = nowX;lastY = nowY;layoutParams.x = layoutParams.x + movedX;layoutParams.y = layoutParams.y + movedY;//獲取當前手指移動的x和y，通過updateViewLayout方法將改變后的x和y設置給buttonmWindowManager.updateViewLayout(view, layoutParams);break;case MotionEvent.ACTION_UP:if (isDrag) {log("lastX=" + lastX + " screenWidth=" + screenWidth);//手指抬起時，判斷是需要滑動到屏幕左邊還是屏幕右邊if (lastX >= screenWidth / 2) {setAnimation(view, lastX, screenWidth);} else {setAnimation(view, -lastX, 0);}}break;}//返回true則消費事件，返回false則傳遞事件，此處特殊處理是為了和點擊事件區分return isDrag || view.onTouchEvent(event); }

三、添加抬起滑動歸位動畫
private void setAnimation(final View view, int fromX, int toX) {

final ValueAnimator animator = ValueAnimator.ofInt(fromX, toX);if (Math.abs(fromX) < screenWidth / 4 || fromX > screenWidth * 3 / 4)animator.setDuration(300);elseanimator.setDuration(600);animator.setInterpolator(new LinearInterpolator());animator.addListener(new Animator.AnimatorListener() {@Overridepublic void onAnimationStart(Animator animation) {}@Overridepublic void onAnimationEnd(Animator animation) {log("onAnimationEnd=");savePreValue(layoutParams.x, layoutParams.y);}@Overridepublic void onAnimationCancel(Animator animation) {}@Overridepublic void onAnimationRepeat(Animator animation) {}});animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {int current = (int) animator.getAnimatedValue();log("current=" + current);layoutParams.x = Math.abs(current);mWindowManager.updateViewLayout(view, layoutParams);}});animator.start(); }

}
同樣是通過改變button的x和y值來達到滑動效果，只不過我只需要x平移，y為0，需要斜著滑的你們可自由發揮，為了使滑動看上去平滑，給動畫添加了一個線性插值器，設置滑動時間，監聽返回插值進度，這樣動態設置給button。為了保存button的最終位置，添加了一個動畫完成監聽，并將x和y寫入到SharedPreferences中保存。

四、添加點擊返回功能
通過打印日志分析，系統導航欄的返回按鍵，發現其原理是通過KeyButtonView的觸摸事件發送一個KeyEvent事件給系統來實現返回功能

源碼位置frameworksbasepackagesSystemUIsrccomandroidsystemuistatusbarpolicyKeyButtonView.java

public boolean onTouchEvent(MotionEvent ev) {

final int action = ev.getAction(); int x, y; if (action == MotionEvent.ACTION_DOWN) {mGestureAborted = false; } if (mGestureAborted) {return false; }switch (action) {case MotionEvent.ACTION_DOWN://按下的時間mDownTime = SystemClock.uptimeMillis();setPressed(true);if (mCode != 0) {//按下事件sendEvent(KeyEvent.ACTION_DOWN, 0, mDownTime);} else {// Provide the same haptic feedback that the system offers for virtual keys.performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY);}removeCallbacks(mCheckLongPress);postDelayed(mCheckLongPress, ViewConfiguration.getLongPressTimeout());break;case MotionEvent.ACTION_MOVE:x = (int)ev.getX();y = (int)ev.getY();setPressed(x >= -mTouchSlop&& x < getWidth() + mTouchSlop&& y >= -mTouchSlop&& y < getHeight() + mTouchSlop);break;case MotionEvent.ACTION_CANCEL:setPressed(false);if (mCode != 0) {sendEvent(KeyEvent.ACTION_UP, KeyEvent.FLAG_CANCELED);}removeCallbacks(mCheckLongPress);break;case MotionEvent.ACTION_UP:final boolean doIt = isPressed();setPressed(false);if (mCode != 0) {if (doIt) {//抬起事件sendEvent(KeyEvent.ACTION_UP, 0);sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);playSoundEffect(SoundEffectConstants.CLICK);} else {sendEvent(KeyEvent.ACTION_UP, KeyEvent.FLAG_CANCELED);}} else {// no key code, just a regular ImageViewif (doIt) {performClick();}}removeCallbacks(mCheckLongPress);break; }return true;

}

//以下為我們給button添加的點擊事件
private void sendEvent(int action, int flags, long when) {

int mCode = 4; Log.e(TAG, "mCode="+mCode + " flags="+flags); final int repeatCount = (flags & KeyEvent.FLAG_LONG_PRESS) != 0 ? 1 : 0; final KeyEvent ev = new KeyEvent(when - 100, when, action, mCode, repeatCount,0, KeyCharacterMap.VIRTUAL_KEYBOARD, 0,flags | KeyEvent.FLAG_FROM_SYSTEM | KeyEvent.FLAG_VIRTUAL_HARD_KEY,InputDevice.SOURCE_KEYBOARD); InputManager.getInstance().injectInputEvent(ev,InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);

}

button.setOnClickListener(new View.OnClickListener() {

@Overridepublic void onClick(View v) {Log.e(TAG,"click dragButton ...");final long mDownTime = SystemClock.uptimeMillis();//onBackPressed();sendEvent(KeyEvent.ACTION_DOWN, 0, mDownTime);new Handler().postDelayed(new Runnable() {@Overridepublic void run() {sendEvent(KeyEvent.ACTION_UP, 0, SystemClock.uptimeMillis());}}, 300);} });

需要注意的地方，系統返回鍵對應的code為4，所以mCode=4，KeyButtonView的觸摸事件包含按下和抬起，所以我們只需模擬發送按下和抬起事件，可以看到抬起事件加了300ms的延時發送，這是關鍵不然系統不會處理。
原文地址https://www.cnblogs.com/cczheng-666/p/10741082.html

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