Lazy measurement with Probe (Experimental)

LazyMeasurementInterceptor.java

/*
 * Copyright (C) 2014 Lucas Rocha
 *
 * 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 org.lucasr.probe.interceptors;

import android.util.Log;
import android.util.LongSparseArray;
import android.view.View;

import org.lucasr.probe.Interceptor;

import static android.os.Build.VERSION.SDK_INT;
import static android.os.Build.VERSION_CODES.KITKAT;

public class LazyMeasurementInterceptor extends Interceptor {
    private static final String LOGTAG = "LazyMeasurement";

    private static final boolean POST_KITKAT = (SDK_INT >= KITKAT);

    private static class MeasureState {
        final LongSparseArray<Long> cache;
        boolean needsOnMeasureBeforeLayout;
        int lastWidthMeasureSpec;
        int lastHeightMeasureSpec;

        public MeasureState() {
            cache = new LongSparseArray<Long>(2);
        }

        void clear() {
            cache.clear();
            needsOnMeasureBeforeLayout = false;
            lastWidthMeasureSpec = 0;
            lastHeightMeasureSpec = 0;
        }
    }

    private void clearMeasureState(View view) {
        final MeasureState measureState = (MeasureState) view.getTag(R.id.measure_state);
        if (measureState != null) {
            measureState.clear();
        }
    }

    @Override
    public void onMeasure(View view, int widthMeasureSpec, int heightMeasureSpec) {
        if (POST_KITKAT) {
            Log.d(LOGTAG, "Post-KitKat, onMeasure() on " + view.getTag());
            super.onMeasure(view, widthMeasureSpec, heightMeasureSpec);
            return;
        }

        MeasureState measureState = (MeasureState) view.getTag(R.id.measure_state);
        if (measureState== null) {
            measureState = new MeasureState();
            view.setTag(R.id.measure_state, measureState);
        }

        final long key = (long) widthMeasureSpec << 32 | (long) heightMeasureSpec & 0xffffffffL;
        final int cacheIndex = measureState.cache.indexOfKey(key);
        if (cacheIndex < 0) {
            Log.d(LOGTAG, "Pre-KitKat, onMeasure() on " + view.getTag());
            super.onMeasure(view, widthMeasureSpec, heightMeasureSpec);
            measureState.needsOnMeasureBeforeLayout = false;
        } else {
            final long value = measureState.cache.valueAt(cacheIndex);
            setMeasuredDimension(view, (int) (value >> 32), (int) value);
            measureState.needsOnMeasureBeforeLayout = true;
        }

        measureState.lastWidthMeasureSpec = widthMeasureSpec;
        measureState.lastHeightMeasureSpec = heightMeasureSpec;

        measureState.cache.put(key, ((long) view.getMeasuredWidth()) << 32 |
                (long) view.getMeasuredHeight() & 0xffffffffL);
    }

    @Override
    public void onLayout(View view, boolean changed, int l, int t, int r, int b) {
        if (POST_KITKAT) {
            super.onLayout(view, changed, l, t, r, b);
            return;
        }

        final MeasureState measureState = (MeasureState) view.getTag(R.id.measure_state);
        if (measureState.needsOnMeasureBeforeLayout) {
            invokeOnMeasure(view, measureState.lastWidthMeasureSpec,
                    measureState.lastHeightMeasureSpec);
            measureState.needsOnMeasureBeforeLayout = false;
        }

        super.onLayout(view, changed, l, t, r, b);
    }

    @Override
    public void requestLayout(View view) {
        if (!POST_KITKAT) {
            clearMeasureState(view);
        }

        super.requestLayout(view);
    }

    @Override
    public void forceLayout(View view) {
        if (!POST_KITKAT) {
            clearMeasureState(view);
        }

        super.forceLayout(view);
    }
}