NMS Toast
Posted ttdevs
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0x00 NMS Toast
Toast.makeText(Context, "Toast message content.", Toast.LENGTH_SHORT).show();
以下代码分析基于android 8.1.0
0x01 Toast
Toast类只有500多行，逻辑比较简单，主要有三部分组成： Toast，INotificationManager和TN。Toast类负责构造Toast对象；NotificationManager 负责与 NotificationManagerService交互；TN负责Toast最终的显示。
首先构建一个Toast对象：
public static Toast makeText(@NonNull Context context, @Nullable Looper looper,
@NonNull CharSequence text, @Duration int duration)
// 创建一个Toast对象
Toast result = new Toast(context, looper);
// 加载布局，设置Toast要显示的内容
LayoutInflater inflate = (LayoutInflater)
context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);
TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);
tv.setText(text);
// 将加载的View设给Toast
result.mNextView = v;
result.mDuration = duration;
return result;
调用Toast.show()方法：
public void show()
// mNextView为最终要展示的View，不能为null，Toast创建的时候默认创建一个，也可通过Toast.setView(View view)设置
if (mNextView == null)
throw new RuntimeException("setView must have been called");
INotificationManager service = getService();
String pkg = mContext.getOpPackageName();
TN tn = mTN;
tn.mNextView = mNextView;
try
// 将TN发给NotificationManagerService
service.enqueueToast(pkg, tn, mDuration);
catch (RemoteException e)
// Empty
几行代码，获取 INotificationManager 服务。
// =======================================================================================
// All the gunk below is the interaction with the Notification Service, which handles
// the proper ordering of these system-wide.
// =======================================================================================
private static INotificationManager sService;
static private INotificationManager getService()
if (sService != null)
return sService;
sService = INotificationManager.Stub.asInterface(ServiceManager.getService("notification"));
return sService;
看到 INotificationManager.Stub.asInterface() 很自然的会去搜 NotificationManagerService，嗯嗯，AOSP
中全局搜索就可以了。至此，Toast的工作做完一半，下来的工作进入 NotificationManagerService。
0x02 NotificationManagerService
frameworks/base/services/core/java/com/android/server/notification/NotificationManagerService.java
我们来看enqueueToast()：
...
final ArrayList<ToastRecord> mToastQueue = new ArrayList<>();
...
private final IBinder mService = new INotificationManager.Stub()
// Toasts
// ============================================================================
@Override
public void enqueueToast(String pkg, ITransientNotification callback, int duration)
if (DBG)
Slog.i(TAG, "enqueueToast pkg=" + pkg + " callback=" + callback
+ " duration=" + duration);
if (pkg == null || callback == null)
Slog.e(TAG, "Not doing toast. pkg=" + pkg + " callback=" + callback);
return ;
final boolean isSystemToast = isCallerSystemOrPhone() || ("android".equals(pkg));
final boolean isPackageSuspended =
isPackageSuspendedForUser(pkg, Binder.getCallingUid());
if (ENABLE_BLOCKED_TOASTS && !isSystemToast &&
(!areNotificationsEnabledForPackage(pkg, Binder.getCallingUid())
|| isPackageSuspended))
Slog.e(TAG, "Suppressing toast from package " + pkg
+ (isPackageSuspended
? " due to package suspended by administrator."
: " by user request."));
return;
synchronized (mToastQueue)
int callingPid = Binder.getCallingPid();
long callingId = Binder.clearCallingIdentity();
try
ToastRecord record;
int index;
// All packages aside from the android package can enqueue one toast at a time
if (!isSystemToast)
index = indexOfToastPackageLocked(pkg);
else
index = indexOfToastLocked(pkg, callback);
// If the package already has a toast, we update its toast
// in the queue, we don't move it to the end of the queue.
if (index >= 0)
// Toast已经存在
record = mToastQueue.get(index);
record.update(duration);
record.update(callback);
else
// Toast不存在
Binder token = new Binder();
// 将这个token添加到系统，否则无法正常显示
mWindowManagerInternal.addWindowToken(token, TYPE_TOAST, DEFAULT_DISPLAY);
record = new ToastRecord(callingPid, pkg, callback, duration, token);
// 添加到队列，接下来我们去跟踪这个队列的出口
mToastQueue.add(record);
index = mToastQueue.size() - 1;
keepProcessAliveIfNeededLocked(callingPid);
// If it's at index 0, it's the current toast. It doesn't matter if it's
// new or just been updated. Call back and tell it to show itself.
// If the callback fails, this will remove it from the list, so don't
// assume that it's valid after this.
if (index == 0)
showNextToastLocked();
finally
Binder.restoreCallingIdentity(callingId);
@GuardedBy("mToastQueue")
void showNextToastLocked()
// 获取要展示的Toast
ToastRecord record = mToastQueue.get(0);
while (record != null)
if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);
try
// 显示Toast，这个callback是上面的TN对象，可以看到，这个时候又调回了Toast.TN.show(IBinder windowToken)
record.callback.show(record.token);
// 处理Toast显示时间
scheduleTimeoutLocked(record);
return;
catch (RemoteException e)
Slog.w(TAG, "Object died trying to show notification " + record.callback
+ " in package " + record.pkg);
// remove it from the list and let the process die
int index = mToastQueue.indexOf(record);
if (index >= 0)
mToastQueue.remove(index);
keepProcessAliveIfNeededLocked(record.pid);
if (mToastQueue.size() > 0)
record = mToastQueue.get(0);
else
record = null;
@GuardedBy("mToastQueue")
private void scheduleTimeoutLocked(ToastRecord r)
// 从这里可以看到，是依赖Handler实现的
mHandler.removeCallbacksAndMessages(r);
Message m = Message.obtain(mHandler, MESSAGE_TIMEOUT, r);
// 这里定义Toast的显示时间，LONG:3.5s, SHORT:2s。注意区分显示时的hideTimeoutMilliseconds
long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY;
mHandler.sendMessageDelayed(m, delay);
...
;
0x03 Toast.TN
再回到Toast里，这次看里面的TN，从show(IBinder windowToken)开始。
private static class TN extends ITransientNotification.Stub
private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams();
private static final int SHOW = 0;
private static final int HIDE = 1;
private static final int CANCEL = 2;
final Handler mHandler;
int mGravity;
int mX, mY;
float mHorizontalMargin;
float mVerticalMargin;
View mView;
View mNextView;
int mDuration;
WindowManager mWM;
String mPackageName;
// 默认显示时间
static final long SHORT_DURATION_TIMEOUT = 4000;
static final long LONG_DURATION_TIMEOUT = 7000;
TN(String packageName, @Nullable Looper looper)
// XXX This should be changed to use a Dialog, with a Theme.Toast
// defined that sets up the layout params appropriately.
final WindowManager.LayoutParams params = mParams;
params.height = WindowManager.LayoutParams.WRAP_CONTENT;
params.width = WindowManager.LayoutParams.WRAP_CONTENT;
params.format = PixelFormat.TRANSLUCENT;
params.windowAnimations = com.android.internal.R.style.Animation_Toast;
params.type = WindowManager.LayoutParams.TYPE_TOAST;
params.setTitle("Toast");
params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;
mPackageName = packageName;
// 子线程显示Toast就会抛这个异常
if (looper == null)
// Use Looper.myLooper() if looper is not specified.
looper = Looper.myLooper();
if (looper == null)
throw new RuntimeException(
"Can't toast on a thread that has not called Looper.prepare()");
mHandler = new Handler(looper, null)
@Override
public void handleMessage(Message msg)
switch (msg.what)
case SHOW:
// (2) 拿到token，展示
IBinder token = (IBinder) msg.obj;
handleShow(token);
break;
case HIDE:
handleHide();
// Don't do this in handleHide() because it is also invoked by
// handleShow()
mNextView = null;
break;
case CANCEL:
handleHide();
// Don't do this in handleHide() because it is also invoked by
// handleShow()
mNextView = null;
try
getService().cancelToast(mPackageName, TN.this);
catch (RemoteException e)
break;
;
/**
* (1) schedule handleShow into the right thread
*/
@Override
public void show(IBinder windowToken)
if (localLOGV) Log.v(TAG, "SHOW: " + this);
// 发送显示Toast的Message
mHandler.obtainMessage(SHOW, windowToken).sendToTarget();
/**
* schedule handleHide into the right thread
*/
@Override
public void hide()
if (localLOGV) Log.v(TAG, "HIDE: " + this);
mHandler.obtainMessage(HIDE).sendToTarget();
/**
* hide 和 cancel逻辑相同
*/
public void cancel()
if (localLOGV) Log.v(TAG, "CANCEL: " + this);
mHandler.obtainMessage(CANCEL).sendToTarget();
/**
* (3)真正展示Toast的地方，最终还是WindowManager.addView()
* @param windowToken 展示Toast的token
*/
public void handleShow(IBinder windowToken)
if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView
+ " mNextView=" + mNextView);
// If a cancel/hide is pending - no need to show - at this point
// the window token is already invalid and no need to do any work.
if (mHandler.hasMessages(CANCEL) || mHandler.hasMessages(HIDE))
return;
// Toast没有显示过或者当前不再显示状态
if (mView != mNextView)
// remove the old view if necessary
// 移除之前的View
handleHide();
mView = mNextView;
Context context = mView.getContext().getApplicationContext();
String packageName = mView.getContext().getOpPackageName();
if (context == null)
context = mView.getContext();
// 世界的本源
mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
// We can resolve the Gravity here by using the Locale for getting
// the layout direction
// 以下配置Toast的显示参数
final Configuration config = mView.getContext().getResources().getConfiguration();
final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());
mParams.gravity = gravity;
if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL)
mParams.horizontalWeight = 1.0f;
if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL)
mParams.verticalWeight = 1.0f;
mParams.x = mX;
mParams.y = mY;
mParams.verticalMargin = mVerticalMargin;
mParams.horizontalMargin = mHorizontalMargin;
mParams.packageName = packageName;
// 显示超时时间
mParams.hideTimeoutMilliseconds = mDuration ==
Toast.LENGTH_LONG ? LONG_DURATION_TIMEOUT : SHORT_DURATION_TIMEOUT;
// 要显示，token是必须的
mParams.token = windowToken;
// 这种方法可以判断当前View是否正在显示，如果显示就remove掉
if (mView.getParent() != null)
if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);
mWM.removeView(mView);
if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this);
// Since the notification manager service cancels the token right
// after it notifies us to cancel the toast there is an inherent
// race and we may attempt to add a window after the token has been
// invalidated. Let us hedge against that.
try
// 好了，真正的开始显示了
mWM.addView(mView, mParams);
trySendAccessibilityEvent();
catch (WindowManager.BadTokenException e)
/* ignore */
private void trySendAccessibilityEvent()
AccessibilityManager accessibilityManager =
AccessibilityManager.getInstance(mView.getContext());
if (!accessibilityManager.isEnabled())
return;
// treat toasts as notifications since they are used to
// announce a transient piece of information to the user
AccessibilityEvent event = AccessibilityEvent.<以上是关于NMS Toast的主要内容，如果未能解决你的问题，请参考以下文章