Android RAM 过度使用

Question

我遇到了一个让我抓狂的问题所以:

这是我实现的 ViewPager(我知道这很糟糕)，它具有视差效果(移动背景)并且工作正常。

package com.breadwallet.tools.adapter;

/**
 * Created by Mihail on 6/29/15.
 */

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.Log;

import com.breadwallet.presenter.activities.MainActivity;
import com.breadwallet.tools.animation.FragmentAnimator;
import com.breadwallet.tools.animation.SpringAnimator;


@SuppressLint("NewApi")
public class ParallaxViewPager extends ViewPager {


    public static final int FIT_WIDTH = 0;
    public static final int FIT_HEIGHT = 1;
    public static final float OVERLAP_FULL = 1f;
    public static final float OVERLAP_HALF = 0.5f;
    public static final float OVERLAP_QUARTER = 0.25f;
    private static final float CORRECTION_PERCENTAGE = 0.01f;
    public Bitmap bitmap;
    private Rect source, destination;
    private int scaleType;
    private int chunkWidth;
    private int projectedWidth;
    private float overlap;
    private OnPageChangeListener secondOnPageChangeListener;
    private MainActivity app;


    public ParallaxViewPager(Context context) {
        super(context);
        init();
        app = MainActivity.getApp();
    }


    public ParallaxViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
        app = MainActivity.getApp();
    }


    private void init() {
        source = new Rect();
        destination = new Rect();
        scaleType = FIT_HEIGHT;
        overlap = OVERLAP_HALF;


        setOnPageChangeListener(new OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                if (bitmap != null) {
                    source.left = (int) Math.floor((position + positionOffset - CORRECTION_PERCENTAGE) * chunkWidth);
                    source.right = (int) Math.ceil((position + positionOffset + CORRECTION_PERCENTAGE) * chunkWidth + projectedWidth);
                    destination.left = (int) Math.floor((position + positionOffset - CORRECTION_PERCENTAGE) * getWidth());
                    destination.right = (int) Math.ceil((position + positionOffset + 1 + CORRECTION_PERCENTAGE) * getWidth());
                    invalidate();
                }

                if (secondOnPageChangeListener != null) {
                    secondOnPageChangeListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
                }
            }


            @Override
            public void onPageSelected(int position) {
                if (secondOnPageChangeListener != null) {
                    secondOnPageChangeListener.onPageSelected(position);
                }
                app.setPagerIndicator(position);
                if (FragmentAnimator.level == 0) {
                    if (position == 1) {
                        new Handler().postDelayed(new Runnable() {

                            @Override
                            public void run() {
                                SpringAnimator.showBouncySlide(getRootView(), SpringAnimator.TO_RIGHT);
                            }
                        }, 80);
                    } else if (position == 0) {
                        new Handler().postDelayed(new Runnable() {

                            @Override
                            public void run() {
                                SpringAnimator.showBouncySlide(getRootView(), SpringAnimator.TO_LEFT);
                            }
                        }, 80);
                    }
                }

                Log.e("AdapterParalax", "Showing animation!!!!!");
            }

            @Override
            public void onPageScrollStateChanged(int state) {
                if (secondOnPageChangeListener != null) {
                    secondOnPageChangeListener.onPageScrollStateChanged(state);
                }
            }
        });
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        destination.top = 0;
        destination.bottom = h;
        if (getAdapter() != null && bitmap != null)
            calculateParallaxParameters();
    }

    private void calculateParallaxParameters() {
        if (bitmap.getWidth() < getWidth() && bitmap.getWidth() < bitmap.getHeight() && scaleType == FIT_HEIGHT) {
            Log.w(ParallaxViewPager.class.getName(), "Invalid bitmap bounds for the current device, parallax effect will not work.");
        }


        final float ratio = (float) getHeight() / bitmap.getHeight();
        if (ratio != 1) {
            switch (scaleType) {
                case FIT_WIDTH:
                    source.top = (int) ((bitmap.getHeight() - bitmap.getHeight() / ratio) / 2);
                    source.bottom = bitmap.getHeight() - source.top;
                    chunkWidth = (int) Math.ceil((float) bitmap.getWidth() / (float) getAdapter().getCount());
                    projectedWidth = chunkWidth;
                    break;
                case FIT_HEIGHT:
                default:
                    source.top = 0;
                    source.bottom = bitmap.getHeight();
                    projectedWidth = (int) Math.ceil(getWidth() / ratio);
                    chunkWidth = (int) Math.ceil((bitmap.getWidth() - projectedWidth) / (float) getAdapter().getCount() * overlap);
                    break;
            }
        }
    }


    /**
     * Sets the background from a resource file.
     *
     * @param resid
     */
    @Override
    public void setBackgroundResource(int resid) {
        bitmap = BitmapFactory.decodeResource(getResources(), resid);
    }


    /**
     * Sets the background from a Drawable.
     *
     * @param background
     */
    @Override
    public void setBackground(Drawable background) {
        bitmap = ((BitmapDrawable) background).getBitmap();
    }


    /**
     * Deprecated.
     * Sets the background from a Drawable.
     *
     * @param background
     */
    @Override
    public void setBackgroundDrawable(Drawable background) {
        bitmap = ((BitmapDrawable) background).getBitmap();
    }


    /**
     * Sets the background from a bitmap.
     *
     * @param bitmap
     * @return The ParallaxViewPager object itself.
     */
    public ParallaxViewPager setBackground(Bitmap bitmap) {
        this.bitmap = bitmap;
        return this;
    }


    /**
     * Sets how the view should scale the background. The available choices are:
     * <ul>
     * <li>FIT_HEIGHT - the height of the image is resized to matched the height of the View, also stretching the width to keep the aspect ratio. The non-visible part of the bitmap is divided into equal parts, each of them sliding in at the proper position.</li>
     * <li>FIT_WIDTH - the width of the background image is divided into equal chunks, each taking up the whole width of the screen.</li>
     * </ul>
     *
     * @param scaleType
     * @return
     */
    public ParallaxViewPager setScaleType(final int scaleType) {
        if (scaleType != FIT_WIDTH && scaleType != FIT_HEIGHT)
            throw new IllegalArgumentException("Illegal argument: scaleType must be FIT_WIDTH or FIT_HEIGHT");
        this.scaleType = scaleType;
        return this;
    }


    /**
     * Sets the amount of overlapping with the setOverlapPercentage(final float percentage) method. This is a number between 0 and 1, the smaller it is, the slower is the background scrolling.
     *
     * @param percentage
     * @return The ParallaxViewPager object itself.
     */
    public ParallaxViewPager setOverlapPercentage(final float percentage) {
        if (percentage <= 0 || percentage >= 1)
            throw new IllegalArgumentException("Illegal argument: percentage must be between 0 and 1");
        overlap = percentage;
        return this;
    }


    /**
     * Recalculates the parameters of the parallax effect, useful after changes in runtime.
     *
     * @return The ParallaxViewPager object itself.
     */
    public ParallaxViewPager invalidateParallaxParameters() {
        calculateParallaxParameters();
        return this;
    }


    @Override
    protected void onDraw(Canvas canvas) {
        if (bitmap != null)
            canvas.drawBitmap(bitmap, source, destination, null);
    }

    public void addOnPageChangeListener(OnPageChangeListener listener) {
        secondOnPageChangeListener = listener;
    }
}

所以问题是这个家伙占用了多达 40mb 的 RAM，这给了我一个 OutOfMemoryError 这很好，因为我可以简单地向应用程序添加更多内存，但为什么它占用这么多内存？那是正常的吗？我可以做些什么吗，或者这只是 Android 中的正常行为？因为iOS一般不会吃那么多内存。我用作背景的图片只有 27kb。所以我更感兴趣的是一些专家关于我错过或不知道什么的意见。谢谢伙计们。

Answer 1

所以，您使用的位图太宽了。它需要宽度 x 高度 x 4 个字节的 ram。您应该调整位图的大小以适合屏幕，如果不够，您应该考虑减少位数 x 像素(默认情况下为 32)