1.Toast的用法
Toast.makeText(this, "Toast", Toast.LENGTH_SHORT).show()
2.makeText入手
public static Toast makeText(Context context, CharSequence text, @Duration int duration) {
Toast result = new Toast(context)
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)
result.mNextView = v
result.mDuration = duration
return result
}
只是加载了一个布局。接下来我们看show方法
3.Toast#show
public void show() {
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 {
service.enqueueToast(pkg, tn, mDuration);
} catch (RemoteException e) {
}
}
如果mNextView==null，抛出异常
获取INotificationManager
static private INotificationManager getService() {
if (sService != null) {
return sService;
}
sService = INotificationManager.Stub.asInterface(ServiceManager.getService("notification"));
return sService;
}
* 这里的INotificationManager，是在启动的时候加载到ServiceManager的mCache里的，关于如何加载的这里略过，对应的服务端实现在NotificationManagerService里 *
4.NotificationManagerService里的enqueueToast方法。
@Override
public void enqueueToast(String pkg, ITransientNotification callback, int duration)
{
final boolean isSystemToast = isCallerSystem() || ("android".equals(pkg));
synchronized (mToastQueue) {
int callingPid = Binder.getCallingPid();
long callingId = Binder.clearCallingIdentity();
try {
ToastRecord record;
int index = indexOfToastLocked(pkg, callback);
if (index >= 0) {
record = mToastQueue.get(index);
record.update(duration);
} else {
if (!isSystemToast) {
int count = 0;
final int N = mToastQueue.size();
for (int i=0; i
= MAX_PACKAGE_NOTIFICATIONS) { Slog.e(TAG, "Package has already posted " + count + " toasts. Not showing more. Package=" + pkg); return; } } } } record = new ToastRecord(callingPid, pkg, callback, duration); mToastQueue.add(record); index = mToastQueue.size() - 1; keepProcessAliveLocked(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); } } }
代码略长，听我慢慢道来、
算出当前Toast在ToastQueue中的索引，
如果>=0,怎说明已经在队列中，更新时间即可
! >= 0的情况下
如果不是系统Toast，就判断当前包名下，队列中有多少个toast，>=50，直接返回，并更新index
将其包装一下加入队列
设置该Toast所在的进程为前台进程
如果index为0，显示。
5.NotificationManagerService#showNextToastLocked
void showNextToastLocked() {
ToastRecord record = mToastQueue.get(0);
while (record != null) {
if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);
try {
record.callback.show();
scheduleTimeoutLocked(record);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Object died trying to show notification " + record.callback
+ " in package " + record.pkg);
int index = mToastQueue.indexOf(record);
if (index >= 0) {
mToastQueue.remove(index);
}
keepProcessAliveLocked(record.pid);
if (mToastQueue.size() > 0) {
record = mToastQueue.get(0);
} else {
record = null;
}
}
}
}
代码比较简单，调用ToastRecore.callback的show方法去显示，并且发一个延时消息。
private void scheduleTimeoutLocked(ToastRecord r)
{
mHandler.removeCallbacksAndMessages(r);
Message m = Message.obtain(mHandler, MESSAGE_TIMEOUT, r);
long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY;
mHandler.sendMessageDelayed(m, delay);
}
那么，这里的record的callback的show方法是什么呢。record是我们从队列中取出来的，他的初始化方法在enqueueToast方法中。
record = new ToastRecord(callingPid, pkg, callback, duration);
而这里的callback是enqueueToast的参数，也就是说，是我们在Toast中出传入的。Toast中相关代码如下
service.enqueueToast(pkg, tn, mDuration)
这里的tn是在toast初始化的时候初始化的。因此，将会掉TN的show方法。
6.TN#show
@Override
public void show() {
if (localLOGV) Log.v(TAG, "SHOW: " + this);
mHandler.post(mShow);
}
final Runnable mShow = new Runnable() {
@Override
public void run() {
handleShow();
}
};
会看到，最后就会调用handleShow方法。
7.TN#handleShow
public void handleShow() {
if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView
+ " mNextView=" + mNextView)
if (mView != mNextView) {
// remove the old view if necessary
handleHide()
mView = mNextView
Context context = mView.getContext().getApplicationContext()
String packageName = mView.getContext().getOpPackageName()
if (context == null) {
context = mView.getContext()
}
mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE)
// We can resolve the Gravity here by using the Locale for getting
// the layout direction
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
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)
mWM.addView(mView, mParams)
trySendAccessibilityEvent()
}
}
上面的代码很简单，就是设置View的参数，并通过WindowManager添加显示。
8.NotificationManagerService#cancelToastLocked
这个方法中，调用TN的hide方法隐藏当前Toast，并从列表中移除，将下一个Toast所在的进程挂到前台，并显示。
hide方法中，只是调用WindowManager的removeView移除。
大家自己去看源码去吧。
