services/core/java/com/android/server/wm/DragInputEventReceiver.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.wm;

import static android.view.InputDevice.SOURCE_CLASS_POINTER;
import static android.view.MotionEvent.ACTION_CANCEL;
import static android.view.MotionEvent.ACTION_DOWN;
import static android.view.MotionEvent.ACTION_MOVE;
import static android.view.MotionEvent.ACTION_UP;
import static android.view.MotionEvent.BUTTON_STYLUS_PRIMARY;
import static com.android.server.wm.WindowManagerDebugConfig.DEBUG_DRAG;
import static com.android.server.wm.WindowManagerDebugConfig.TAG_WM;

import android.os.Looper;
import android.util.Slog;
import android.view.InputChannel;
import android.view.InputDevice;
import android.view.InputEvent;
import android.view.InputEventReceiver;
import android.view.MotionEvent;

/**
 * Input receiver for drag and drop
 */
class DragInputEventReceiver extends InputEventReceiver {
    private final DragDropController mDragDropController;

    // Set, if stylus button was down at the start of the drag.
    private boolean mStylusButtonDownAtStart;
    // Indicates the first event to check for button state.
    private boolean mIsStartEvent = true;
    // Set to true to ignore input events after the drag gesture is complete but the drag events
    // are still being dispatched.
    private boolean mMuteInput = false;

    DragInputEventReceiver(InputChannel inputChannel, Looper looper,
            DragDropController controller) {
        super(inputChannel, looper);
        mDragDropController = controller;
    }

    @Override
    public void onInputEvent(InputEvent event) {
        boolean handled = false;
        try {
            if (!(event instanceof MotionEvent)
                    || (event.getSource() & SOURCE_CLASS_POINTER) == 0
                    || mMuteInput) {
                return;
            }
            final MotionEvent motionEvent = (MotionEvent) event;
            final float newX = motionEvent.getRawX();
            final float newY = motionEvent.getRawY();
            final boolean isStylusButtonDown =
                    (motionEvent.getButtonState() & BUTTON_STYLUS_PRIMARY) != 0;

            if (mIsStartEvent) {
                // First event and the button was down, check for the button being
                // lifted in the future, if that happens we'll drop the item.
                mStylusButtonDownAtStart = isStylusButtonDown;
                mIsStartEvent = false;
            }

            switch (motionEvent.getAction()) {
                case ACTION_DOWN:
                    if (DEBUG_DRAG) Slog.w(TAG_WM, "Unexpected ACTION_DOWN in drag layer");
                    return;
                case ACTION_MOVE:
                    if (mStylusButtonDownAtStart && !isStylusButtonDown) {
                        if (DEBUG_DRAG) {
                            Slog.d(TAG_WM, "Button no longer pressed; dropping at " + newX + ","
                                    + newY);
                        }
                        mMuteInput = true;
                    }
                    break;
                case ACTION_UP:
                    if (DEBUG_DRAG) {
                        Slog.d(TAG_WM, "Got UP on move channel; dropping at " + newX + "," + newY);
                    }
                    mMuteInput = true;
                    break;
                case ACTION_CANCEL:
                    if (DEBUG_DRAG) Slog.d(TAG_WM, "Drag cancelled!");
                    mMuteInput = true;
                    break;
                default:
                    return;
            }

            mDragDropController.handleMotionEvent(!mMuteInput /* keepHandling */, newX, newY);
            handled = true;
        } catch (Exception e) {
            Slog.e(TAG_WM, "Exception caught by drag handleMotion", e);
        } finally {
            finishInputEvent(event, handled);
        }
    }
}