如果你有这样的需求：用户进入你的app以后，所有的操作都是你的app中设定的，用户不可以拥有系统设置等行为的能力。然而，Android系统，可以通过从顶部往下拉，从而得到一个通知和快速系统设置的页面：
因此，现在你想禁止它弹出，怎么办呢？
我不知道在app中怎么做，但是如果你们的处境像我一样:android系统是一个针对特殊平台定制的，它一旦启动就进入特定的功能页面，并且不允许用户有进入系统设置的能力，那么您可以像下面这样，直接在系统代码中进行修改。
分析如何解决问题
使用Android device monitor工具，我们可以看到Android 状态栏的布局，我们会发现，平时我们看到的状态栏（如下图所示）是由PhoneStatusBarView负责绘制个管理的：
结合我们的操作，当我们点击状态栏或者下拉的时候，都会出现通知界面。而点击和下拉都是触摸事件，因此，理所当然的，我们会想到在PhoneStatusBarView的onTouchEvent中处理相应的逻辑。onTouchEvent定义在frameworks\base\packages\SystemUI\src\com\android\systemui\statusbar\phone\PhoneStatusBarView.Java中：
@Override public boolean onTouchEvent(MotionEvent event) { boolean barConsumedEvent = mBar.interceptTouchEvent(event); if (DEBUG_GESTURES) { if (event.getActionMasked() != MotionEvent.ACTION_MOVE) { EventLog.writeEvent(EventLogTags.SYSUI_PANELBAR_TOUCH, event.getActionMasked(), (int) event.getX(), (int) event.getY(), barConsumedEvent ? 1 : 0); } } return barConsumedEvent || super.onTouchEvent(event); }
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它似乎什么都没有做…然而不要忽视了，它调用了super.onTouchEvent(event)方法。PhoneStatusBarView继承了PanelBar类，这个类继承自PanelBar类。因此，super.onTouchEvent就是调用PanelBar中的onTouchEvent方法，PanelBar也在frameworks\base\packages\SystemUI\src\com\android\systemui\statusbar\phone\目录下：
@Override public boolean onTouchEvent(MotionEvent event) { // Allow subclasses to implement enable/disable semantics if (!panelsEnabled()) { if (event.getAction() == MotionEvent.ACTION_DOWN) { Log.v(TAG, String.format("onTouch: all panels disabled, ignoring touch at (%d,%d)", (int) event.getX(), (int) event.getY())); } return false; } // figure out which panel needs to be talked to here if (event.getAction() == MotionEvent.ACTION_DOWN) { final PanelView panel = selectPanelForTouch(event); if (panel == null) { // panel is not there, so we'll eat the gesture Log.v(TAG, String.format("onTouch: no panel for touch at (%d,%d)", (int) event.getX(), (int) event.getY())); mTouchingPanel = null; return true; } boolean enabled = panel.isEnabled(); if (DEBUG) LOG("PanelBar.onTouch: state=%d ACTION_DOWN: panel %s %s", mState, panel, (enabled ? "" : " (disabled)")); if (!enabled) { // panel is disabled, so we'll eat the gesture Log.v(TAG, String.format( "onTouch: panel (%s) is disabled, ignoring touch at (%d,%d)", panel, (int) event.getX(), (int) event.getY())); mTouchingPanel = null; return true; } startOpeningPanel(panel); } final boolean result = mTouchingPanel != null ? mTouchingPanel.onTouchEvent(event) : true; return result; }
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从函数的名字猜测，startOpeningPanel方法似乎就是弹出下拉菜单的入口，把它注释掉，重新编译SystemUI模块，然后替换/system/priv-app/SystemUI/SystemUI.apk，重启系统，就发现无论你是点击还是下拉屏幕顶部，都不会出现下拉也面了。
我们不妨简单分析下这里：
startOpeningPanel接收一个panel作为参数，而这个panel则是selectPanelForTouch(event);方法返回的。
PhoneStatusBarView中覆写了该方法：
@Override public PanelView selectPanelForTouch(MotionEvent touch) { // No double swiping. If either panel is open, nothing else can be pulled down. return mNotificationPanel.getExpandedHeight() > 0 ? null : mNotificationPanel; }
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可以看到，这里返回的是mNotificationPanel。是的它就是下面的样子：
既然我们在这里得到了这个页面，startOpeningPanel应该就是将这个页面呈现出来吧。
startOpeningPanel如下：
// called from PanelView when self-expanding, too public void startOpeningPanel(PanelView panel) { if (DEBUG) LOG("startOpeningPanel: " + panel); mTouchingPanel = panel; mPanelHolder.setSelectedPanel(mTouchingPanel); for (PanelView pv : mPanels) { if (pv != panel) { pv.collapse(false /* delayed */); } } }
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对所有的PanelView ，调用它的collapse方法，改方法如下：
public void collapse(boolean delayed) { if (DEBUG) logf("collapse: " + this); if (mPeekPending || mPeekAnimator != null) { mCollapseAfterPeek = true; if (mPeekPending) { // We know that the whole gesture is just a peek triggered by a simple click, so // better start it now. removeCallbacks(mPeekRunnable); mPeekRunnable.run(); } } else if (!isFullyCollapsed() && !mTracking && !mClosing) { cancelHeightAnimator(); mClosing = true; notifyExpandingStarted(); if (delayed) { postDelayed(mFlingCollapseRunnable, 120); } else { fling(0, false /* expand */); } } }
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如果我们正在下拉，同时下拉的动画不为空，那么会调用mPeekRunnable.run();
private Runnable mPeekRunnable = new Runnable() { @Override public void run() { mPeekPending = false; runPeekAnimation(); } };
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调用runPeekAnimation：
private void runPeekAnimation() { mPeekHeight = getPeekHeight(); if (DEBUG) logf("peek to height=%.1f", mPeekHeight); if (mHeightAnimator != null) { return; } mPeekAnimator = ObjectAnimator.ofFloat(this, "expandedHeight", mPeekHeight) .setDuration(250); mPeekAnimator.setInterpolator(mLinearOutSlowInInterpolator); mPeekAnimator.addListener(new AnimatorListenerAdapter() { private boolean mCancelled; @Override public void onAnimationCancel(Animator animation) { mCancelled = true; } @Override public void onAnimationEnd(Animator animation) { mPeekAnimator = null; if (mCollapseAfterPeek && !mCancelled) { postOnAnimation(new Runnable() { @Override public void run() { collapse(false /* delayed */); } }); } mCollapseAfterPeek = false; } }); notifyExpandingStarted(); mPeekAnimator.start(); mJustPeeked = true; }
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这里使用了属性动画将它移动到指定的高度上。