Toast 源码分析

分析下Toast源码

我们常用Toast.makeText()方法创建Toast对象

    public static Toast makeText(Context context, CharSequence text, @Duration int duration) {
        Toast result = new Toast(context);

        //创建系统默认的Toast布局
        LayoutInflater inflate = (LayoutInflater)
                context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);
        //布局中的TextView
        TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);
        tv.setText(text);
        
        //view和duration赋值给Toast的全局变量
        result.mNextView = v;
        result.mDuration = duration;

        return result;
    }

    //重载方法，可传字符串资源
    public static Toast makeText(Context context, @StringRes int resId, @Duration int duration)
                                throws Resources.NotFoundException {
        return makeText(context, context.getResources().getText(resId), duration);
    }

Toast构造方法

    final Context mContext;
    final TN mTN;
    int mDuration;
    View mNextView;

    public Toast(Context context) {
        mContext = context;
        mTN = new TN();
        mTN.mY = context.getResources().getDimensionPixelSize(
                com.android.internal.R.dimen.toast_y_offset);
        mTN.mGravity = context.getResources().getInteger(
                com.android.internal.R.integer.config_toastDefaultGravity);
    }

TN是Toast的静态内部类，继承自ITransientNotification.Stub用于IPC

private static class TN extends ITransientNotification.Stub{

}

通过makeText()方法创建Toast对象后调用show()方法显示

    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 {
            //重点
            service.enqueueToast(pkg, tn, mDuration);
        } catch (RemoteException e) {
            // Empty
        }
    }

    private static INotificationManager sService;

    static private INotificationManager getService() {
        if (sService != null) {
            return sService;
        }
        //AIDL 获取服务端代理对象
        sService = INotificationManager.Stub.asInterface(ServiceManager.getService("notification"));
        return sService;
    }

NotificationManagerService中INotificationManager.Stub.enqueueToast()

        //callback即TN
        @Override
        public void enqueueToast(String pkg, ITransientNotification callback, int duration)
        {
            ...
            synchronized (mToastQueue) {
                int callingPid = Binder.getCallingPid();
                long callingId = Binder.clearCallingIdentity();
                try {
                    ToastRecord record;
                    int index;
                    
                    if (!isSystemToast) {
                        index = indexOfToastPackageLocked(pkg);
                    } else {
                        index = indexOfToastLocked(pkg, callback);
                    }

                    if (index >= 0) {
                        record = mToastQueue.get(index);
                        record.update(duration);
                        try {
                            record.callback.hide();
                        } catch (RemoteException e) {
                        }
                        record.update(callback);
                    } else {
                        Binder token = new Binder();
                        mWindowManagerInternal.addWindowToken(token, TYPE_TOAST, DEFAULT_DISPLAY);
                        record = new ToastRecord(callingPid, pkg, callback, duration, token);
                        mToastQueue.add(record);
                        index = mToastQueue.size() - 1;
                    }
                    keepProcessAliveIfNeededLocked(callingPid);
                    if (index == 0) {
                        //重点
                        showNextToastLocked();
                    }
                } finally {
                    Binder.restoreCallingIdentity(callingId);
                }
            }
        }

NotificationManagerService.ToastRecord TN的包装类

    private static final class ToastRecord
    {
        //进程id
        final int pid;
        //包名
        final String pkg;
        //TN
        ITransientNotification callback;
        //显示时长
        int duration;
        //token
        Binder token;

        ToastRecord(int pid, String pkg, ITransientNotification callback, int duration,
                    Binder token) {
            this.pid = pid;
            this.pkg = pkg;
            this.callback = callback;
            this.duration = duration;
            this.token = token;
        }

        void update(int duration) {
            this.duration = duration;
        }

        void update(ITransientNotification callback) {
            this.callback = callback;
        }

        void dump(PrintWriter pw, String prefix, DumpFilter filter) {
            if (filter != null && !filter.matches(pkg)) return;
            pw.println(prefix + this);
        }

        @Override
        public final String toString()
        {
            return "ToastRecord{"
                + Integer.toHexString(System.identityHashCode(this))
                + " pkg=" + pkg
                + " callback=" + callback
                + " duration=" + duration;
        }
    }

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 {
                //重点，最终还是调用TN.Show()
                record.callback.show(record.token);
                //显示duration时长后取消Toast
                scheduleDurationReachedLocked(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);
                }
                keepProcessAliveIfNeededLocked(record.pid);
                if (mToastQueue.size() > 0) {
                    record = mToastQueue.get(0);
                } else {
                    record = null;
                }
            }
        }
    }

NotificationManagerService.scheduleDurationReachedLocked()

    private void scheduleDurationReachedLocked(ToastRecord r)
    {
        mHandler.removeCallbacksAndMessages(r);
        Message m = Message.obtain(mHandler, MESSAGE_DURATION_REACHED, r);
        long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY;
        mHandler.sendMessageDelayed(m, delay);
    }

mHandler是WorkerHandler
WorkerHandler.handleMessage()

        public void handleMessage(Message msg)
        {
            switch (msg.what)
            {
                case MESSAGE_DURATION_REACHED:
                    handleDurationReached((ToastRecord)msg.obj);
                    break;
                ...
            }
        }

NotificationManagerService.handleDurationReached()

    private void handleDurationReached(ToastRecord record)
    {
        if (DBG) Slog.d(TAG, "Timeout pkg=" + record.pkg + " callback=" + record.callback);
        synchronized (mToastQueue) {
            int index = indexOfToastLocked(record.pkg, record.callback);
            if (index >= 0) {
                cancelToastLocked(index);
            }
        }
    }

NotificationManagerService.cancelToastLocked()

    void cancelToastLocked(int index) {
        ToastRecord record = mToastQueue.get(index);
        try {
            //最终调用TN.hide()
            record.callback.hide();
        } catch (RemoteException e) {
            Slog.w(TAG, "Object died trying to hide notification " + record.callback
                    + " in package " + record.pkg);
        }
        ...
    }

Toast.show()方法通过binder机制获取NMS代理对象，然后调用服务端enqueueToast()方法将Toast内部类TN做为回调对象传入。NMS经过一系列调用最终回调到TN.show()方法显示Toast，并在显示Duration时长后回调TN.hide()方法取消Toast。

接下来看TN.show()

        final Handler mHandler = new Handler();

        public void show() {
            mHandler.post(mShow);
        }

        public void hide() {
            mHandler.post(mHide);
        }

        final Runnable mShow = new Runnable() {
            @Override
            public void run() {
                handleShow();
            }
        };

        final Runnable mHide = new Runnable() {
            @Override
            public void run() {
                handleHide();
                mNextView = null;
            }
        };

TN.handleShow() 这里只贴重点

        public void handleShow() {
            if (mView != mNextView) {
                // remove the old view if necessary
                handleHide();
                mView = mNextView;
                mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
                mWM.addView(mView, mParams);
            }
        }

通过WindowManager.addView()来显示View。流程前面有讲Android Activity、Window、View

TN.handleHide()

        public void handleHide() {
            if (mView != null) {
                if (mView.getParent() != null) {
                    mWM.removeView(mView);
                }
                mView = null;
            }
        }

通过WindowManager.removeView()取消显示。流程前面有讲Dialog 源码分析

自定义Toast

        Toast toast = new Toast(context);
        View view = LayoutInflater.from(context).inflate(R.layout.toast, null);

        TextView tvContent = (TextView) view.findViewById(R.id.tvContentToast);
        tvContent.setText(msg);

        toast.setView(view);
        toast.setDuration(Toast.LENGTH_SHORT);
        toast.setGravity(Gravity.CENTER, 0, 0);
        toast.show();