android glide 加载 apng 图片 android imageloader

转载

mob64ca1418aeab 2024-07-02 20:30:03

文章标签 移动开发 java python android ide 文章分类 Android 移动开发

完整代码在最后，可直接拿去用。

先说一下思路：

ImageLoader类用来控制图片的加载，特别是遇到很多请求的时候，就要对任务进行排队。所以这里就产生两个points，一是imagelodaer要确保使用单例模式，二是要建立合理的线程池来确保众多任务的处理。

所以我们应用的时候，使用静态方法来返回该类的对象，如果没有则new一个返回，如果已经有了，则返回已存在的。

public static ImageLoader getInstance(int threadCount, Type type) {
    if (mInstance == null) {
        synchronized (ImageLoader.class) {
            if (mInstance == null) {
                mInstance = new ImageLoader(threadCount, type);
            }
        }
    }
    return mInstance;
}
public static ImageLoader getInstance(int threadCount, Type type) {
    if (mInstance == null) {
        synchronized (ImageLoader.class) {
            if (mInstance == null) {
                mInstance = new ImageLoader(threadCount, type);
            }
        }
    }
    return mInstance;
}

因为在一开始时，可能多个地方（比如 adapter里getView的时候）同时进行了第一个if判断，所以这里用了两个if来判断是否为空，确保单例。

对于第二个问题，我们在ImageLoader内部建立一个线程池，让其不断轮询，从线程池里取出任务来执行。

实现方法，在Thread里面用Looper，然后每次从线程池里取出一个任务来执行。

// 后台轮询线程
mPoolThread = new Thread() {
    @Override
    public void run() {
        Looper.prepare();
        mPoolThreadHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                // 从线程池取任务并执行。
                mThreadPool.execute(getTask());
                try {
                    mSemaphoreTHreadPool.acquire();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        mSemaphorePoolThreadHandler.release();
        Looper.loop();
    }
};
mPoolThread.start();
// 后台轮询线程
mPoolThread = new Thread() {
    @Override
    public void run() {
        Looper.prepare();
        mPoolThreadHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                // 从线程池取任务并执行。
                mThreadPool.execute(getTask());
                try {
                    mSemaphoreTHreadPool.acquire();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        mSemaphorePoolThreadHandler.release();
        Looper.loop();
    }
};
mPoolThread.start();

然后，任务就是从图片路径来获取图片，然后压缩并为imageview设置图片。

首先，我们需要一块缓存来存储压缩好的图片，节省资源，并防止内存溢出。我们可以用LruCache来实现，我们用图片路径为key，bitmap为value；

int maxMemory = (int) Runtime.getRuntime().maxMemory();// 获取最大可用内存
int cacheMemory = maxMemory / 8; // 设置为最大可用内存的1/8；
mLruCache = new LruCache<String, Bitmap>(cacheMemory) {
    @Override
    protected int sizeOf(String key, Bitmap value) {
        return value.getRowBytes() * value.getHeight();
    }
};
int maxMemory = (int) Runtime.getRuntime().maxMemory();// 获取最大可用内存
int cacheMemory = maxMemory / 8; // 设置为最大可用内存的1/8；
mLruCache = new LruCache<String, Bitmap>(cacheMemory) {
    @Override
    protected int sizeOf(String key, Bitmap value) {
        return value.getRowBytes() * value.getHeight();
    }
};

接下来计算ImageView的大小，在android api 16 以上的版本中，我们可以直接使用imageView.getMaxWidth() getMaxHeight()，但是为了保证兼容性问题，这里利用java的反射机制来实现：

protected ImageSize getImageViewSize(ImageView imageView) {
    ImageSize imageSize = new ImageSize();
    DisplayMetrics displayMetrics = imageView.getContext().getResources().getDisplayMetrics();

    LayoutParams lp = imageView.getLayoutParams();
    int width = imageView.getWidth();
    if (width <= 0) {
        width = lp.width;
    }
    if (width <= 0) {
        // android 16 以上可用
        // width = imageView.getMaxWidth();
        width = getImageViewFieldValue(imageView, "mMaxWidth");
    }
    if (width <= 0) {
        width = displayMetrics.widthPixels;
    }

    int height = imageView.getHeight();
    if (height <= 0) {
        height = lp.height;
    }
    if (height <= 0) {
        height = getImageViewFieldValue(imageView, "mMaxHeight");
    }

    if (height <= 0) {
        height = displayMetrics.heightPixels;
    }

    imageSize.width = width;
    imageSize.height = height;


    return imageSize;
}
protected ImageSize getImageViewSize(ImageView imageView) {
    ImageSize imageSize = new ImageSize();
    DisplayMetrics displayMetrics = imageView.getContext().getResources().getDisplayMetrics();

    LayoutParams lp = imageView.getLayoutParams();
    int width = imageView.getWidth();
    if (width <= 0) {
        width = lp.width;
    }
    if (width <= 0) {
        // android 16 以上可用
        // width = imageView.getMaxWidth();
        width = getImageViewFieldValue(imageView, "mMaxWidth");
    }
    if (width <= 0) {
        width = displayMetrics.widthPixels;
    }

    int height = imageView.getHeight();
    if (height <= 0) {
        height = lp.height;
    }
    if (height <= 0) {
        height = getImageViewFieldValue(imageView, "mMaxHeight");
    }

    if (height <= 0) {
        height = displayMetrics.heightPixels;
    }

    imageSize.width = width;
    imageSize.height = height;


    return imageSize;
}

我们设置好ImageView的实际大小后，接着来压缩图片，我们使用BitmapFactory来压缩，这里需要两个参数，照片路径和尺寸。

private Bitmap decodeSampledBitMapFromPath(String path, int width, int height) {
    // 获取图片的宽和高，并不把图片加载到内存中
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(path, options);

    options.inSampleSize = caculateSampleSize(options, width, height);

    options.inJustDecodeBounds = false;
    Bitmap bitmap = BitmapFactory.decodeFile(path, options);
    return bitmap;
}
private Bitmap decodeSampledBitMapFromPath(String path, int width, int height) {
    // 获取图片的宽和高，并不把图片加载到内存中
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(path, options);

    options.inSampleSize = caculateSampleSize(options, width, height);

    options.inJustDecodeBounds = false;
    Bitmap bitmap = BitmapFactory.decodeFile(path, options);
    return bitmap;
}

尺寸是指要压缩成的尺寸，这里我们可以根据自己的需要来计算比例

private int caculateSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    int width = options.outWidth;
    int height = options.outHeight;
    int inSampleSize = 1;

    if (width > reqWidth || height > reqHeight) {
        int widthRadio = Math.round(width * 1.0f / reqWidth);
        int heightRadio = Math.round(height * 1.0f / reqHeight);
        inSampleSize = Math.max(widthRadio, heightRadio);
    }

    return inSampleSize;
}
private int caculateSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    int width = options.outWidth;
    int height = options.outHeight;
    int inSampleSize = 1;

    if (width > reqWidth || height > reqHeight) {
        int widthRadio = Math.round(width * 1.0f / reqWidth);
        int heightRadio = Math.round(height * 1.0f / reqHeight);
        inSampleSize = Math.max(widthRadio, heightRadio);
    }

    return inSampleSize;
}

整理思路介绍完了，还有几个要点必须要说一下。

因为使用了线程池，所以我们必须要限制一下线程数，不然照样内存溢出，我们使用锁来确保最大线程数不会超过我们预定的线程数。

使用方法：

ImageLoader.getInstance(maxThreadCount, QueueType).loadImage(path, imageview);
ImageLoader.getInstance(maxThreadCount, QueueType).loadImage(path, imageview);

getInstance第一个参数是设置最大同时进行的线程数，第二个是队列出队方式，上文没有给出说明，可以看代码，很容易理解。loadImage两参数，一是路径，二是ImageView。

最后附完整代码：

package org.out.naruto.utils;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.DisplayMetrics;
import android.util.LruCache;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;

import java.lang.reflect.Field;
import java.util.LinkedList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;


/**
 * @author Hao_S
 */
public class ImageLoader {

    private static final String TAG = "ImageLoader";
    private static ImageLoader mInstance;

    private LruCache<String, Bitmap> mLruCache;

    private ExecutorService mThreadPool;
    private static final int DEAFUT_THREAD_COUNT = 1;
    /**
     * 队列调度方式
     */
    private Type mType = Type.LIFO;

    private LinkedList<Runnable> mTaskQueue;

    private Thread mPoolThread;
    private Handler mPoolThreadHandler;

    private Handler mUIHandler;

    private Semaphore mSemaphorePoolThreadHandler = new Semaphore(0);
    private Semaphore mSemaphoreTHreadPool;


    public enum Type {
        LIFO, FIFO
    }

    private ImageLoader(int mThreadCount, Type type) {
        init(mThreadCount, type);
    }

    private void init(int threadCount, Type type) {
        // 后台轮询线程
        mPoolThread = new Thread() {
            @Override
            public void run() {
                Looper.prepare();
                mPoolThreadHandler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        // 从线程池取任务并执行。
                        mThreadPool.execute(getTask());
                        try {
                            mSemaphoreTHreadPool.acquire();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                };
                mSemaphorePoolThreadHandler.release();
                Looper.loop();
            }
        };
        mPoolThread.start();

        int maxMemory = (int) Runtime.getRuntime().maxMemory();// 获取最大可用内存
        int cacheMemory = maxMemory / 8; // 设置为最大可用内存的1/8；
        mLruCache = new LruCache<String, Bitmap>(cacheMemory) {
            @Override
            protected int sizeOf(String key, Bitmap value) {
                return value.getRowBytes() * value.getHeight();
            }
        };

        mThreadPool = Executors.newFixedThreadPool(threadCount);
        mTaskQueue = new LinkedList<Runnable>();
        mType = type;

        mSemaphoreTHreadPool = new Semaphore(threadCount);
    }

    private Runnable getTask() {
        if (mType == Type.FIFO) {
            return mTaskQueue.removeFirst();
        } else {
            return mTaskQueue.removeLast();
        }
    }


    /**
     * 单例模式
     */

    public static ImageLoader getInstance(int threadCount, Type type) {
        if (mInstance == null) {
            synchronized (ImageLoader.class) {
                if (mInstance == null) {
                    mInstance = new ImageLoader(threadCount, type);
                }
            }
        }
        return mInstance;
    }

    public void loadImage(final String path, final ImageView imageView) {
        imageView.setTag(path);

        if (mUIHandler == null) {
            mUIHandler = new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    // 获取得到的图片，为ImageView回调设置图片
                    ImgBeanHolder holder = (ImgBeanHolder) msg.obj;
                    Bitmap bm = holder.bitmap;
                    ImageView imageView = holder.imageView;
                    String path = holder.path;
                    if (imageView.getTag().toString().equals(path)) {
                        imageView.setImageBitmap(bm);
                    }
                }
            };
        }
        Bitmap bm = getBitmapFromLruCache(path);
        if (bm != null) {
            refreashBitmap(bm, imageView, path);
        } else {
            addTask(new Runnable() {
                @Override
                public void run() {
                    // 加载图片 压缩
                    ImageSize imageSize = getImageViewSize(imageView);
                    Bitmap bm = decodeSampledBitMapFromPath(path, imageSize.width, imageSize.height);
                    addBitmapToLruCache(path, bm);
                    refreashBitmap(bm, imageView, path);

                    mSemaphoreTHreadPool.release();
                }
            });
        }
    }

    private void refreashBitmap(Bitmap bm, ImageView imageView, String path) {
        Message message = Message.obtain();
        ImgBeanHolder holder = new ImgBeanHolder();
        holder.bitmap = bm;
        holder.imageView = imageView;
        holder.path = path;
        message.obj = holder;
        mUIHandler.sendMessage(message);
    }

    private void addBitmapToLruCache(String path, Bitmap bm) {
        if (getBitmapFromLruCache(path) == null) {
            if (bm != null) {
                mLruCache.put(path, bm);
            }
        }
    }

    private Bitmap decodeSampledBitMapFromPath(String path, int width, int height) {
        // 获取图片的宽和高，并不把图片加载到内存中
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);

        options.inSampleSize = caculateSampleSize(options, width, height);

        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(path, options);
        return bitmap;
    }

    private int caculateSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        int width = options.outWidth;
        int height = options.outHeight;
        int inSampleSize = 1;

        if (width > reqWidth || height > reqHeight) {
            int widthRadio = Math.round(width * 1.0f / reqWidth);
            int heightRadio = Math.round(height * 1.0f / reqHeight);
            inSampleSize = Math.max(widthRadio, heightRadio);
        }

        return inSampleSize;
    }


    protected ImageSize getImageViewSize(ImageView imageView) {
        ImageSize imageSize = new ImageSize();
        DisplayMetrics displayMetrics = imageView.getContext().getResources().getDisplayMetrics();

        LayoutParams lp = imageView.getLayoutParams();
        int width = imageView.getWidth();
        if (width <= 0) {
            width = lp.width;
        }
        if (width <= 0) {
            // android 16 以上可用
            // width = imageView.getMaxWidth();
            width = getImageViewFieldValue(imageView, "mMaxWidth");
        }
        if (width <= 0) {
            width = displayMetrics.widthPixels;
        }

        int height = imageView.getHeight();
        if (height <= 0) {
            height = lp.height;
        }
        if (height <= 0) {
            height = getImageViewFieldValue(imageView, "mMaxHeight");
        }

        if (height <= 0) {
            height = displayMetrics.heightPixels;
        }

        imageSize.width = width;
        imageSize.height = height;


        return imageSize;
    }

    private static int getImageViewFieldValue(Object object, String fieldName) {
        int value = 0;
        Field field = null;
        try {
            field = ImageView.class.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        field.setAccessible(true);

        try {
            int fieldValue = field.getInt(object);
            if (fieldValue > 0 && fieldValue < Integer.MAX_VALUE) {
                value = fieldValue;
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return value;
    }

    private synchronized void addTask(Runnable runnable) {
        mTaskQueue.add(runnable);
        try {
            if (mPoolThreadHandler == null)
                mSemaphorePoolThreadHandler.acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        mPoolThreadHandler.sendEmptyMessage(0X110);
    }


    private class ImageSize {
        int width;
        int height;
    }

    private Bitmap getBitmapFromLruCache(String key) {
        return mLruCache.get(key);
    }

    private class ImgBeanHolder {
        ImageView imageView;
        Bitmap bitmap;
        String path;
    }

}
package org.out.naruto.utils;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.DisplayMetrics;
import android.util.LruCache;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;

import java.lang.reflect.Field;
import java.util.LinkedList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;


/**
 * @author Hao_S
 */
public class ImageLoader {

    private static final String TAG = "ImageLoader";
    private static ImageLoader mInstance;

    private LruCache<String, Bitmap> mLruCache;

    private ExecutorService mThreadPool;
    private static final int DEAFUT_THREAD_COUNT = 1;
    /**
     * 队列调度方式
     */
    private Type mType = Type.LIFO;

    private LinkedList<Runnable> mTaskQueue;

    private Thread mPoolThread;
    private Handler mPoolThreadHandler;

    private Handler mUIHandler;

    private Semaphore mSemaphorePoolThreadHandler = new Semaphore(0);
    private Semaphore mSemaphoreTHreadPool;


    public enum Type {
        LIFO, FIFO
    }

    private ImageLoader(int mThreadCount, Type type) {
        init(mThreadCount, type);
    }

    private void init(int threadCount, Type type) {
        // 后台轮询线程
        mPoolThread = new Thread() {
            @Override
            public void run() {
                Looper.prepare();
                mPoolThreadHandler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        // 从线程池取任务并执行。
                        mThreadPool.execute(getTask());
                        try {
                            mSemaphoreTHreadPool.acquire();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                };
                mSemaphorePoolThreadHandler.release();
                Looper.loop();
            }
        };
        mPoolThread.start();

        int maxMemory = (int) Runtime.getRuntime().maxMemory();// 获取最大可用内存
        int cacheMemory = maxMemory / 8; // 设置为最大可用内存的1/8；
        mLruCache = new LruCache<String, Bitmap>(cacheMemory) {
            @Override
            protected int sizeOf(String key, Bitmap value) {
                return value.getRowBytes() * value.getHeight();
            }
        };

        mThreadPool = Executors.newFixedThreadPool(threadCount);
        mTaskQueue = new LinkedList<Runnable>();
        mType = type;

        mSemaphoreTHreadPool = new Semaphore(threadCount);
    }

    private Runnable getTask() {
        if (mType == Type.FIFO) {
            return mTaskQueue.removeFirst();
        } else {
            return mTaskQueue.removeLast();
        }
    }


    /**
     * 单例模式
     */

    public static ImageLoader getInstance(int threadCount, Type type) {
        if (mInstance == null) {
            synchronized (ImageLoader.class) {
                if (mInstance == null) {
                    mInstance = new ImageLoader(threadCount, type);
                }
            }
        }
        return mInstance;
    }

    public void loadImage(final String path, final ImageView imageView) {
        imageView.setTag(path);

        if (mUIHandler == null) {
            mUIHandler = new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    // 获取得到的图片，为ImageView回调设置图片
                    ImgBeanHolder holder = (ImgBeanHolder) msg.obj;
                    Bitmap bm = holder.bitmap;
                    ImageView imageView = holder.imageView;
                    String path = holder.path;
                    if (imageView.getTag().toString().equals(path)) {
                        imageView.setImageBitmap(bm);
                    }
                }
            };
        }
        Bitmap bm = getBitmapFromLruCache(path);
        if (bm != null) {
            refreashBitmap(bm, imageView, path);
        } else {
            addTask(new Runnable() {
                @Override
                public void run() {
                    // 加载图片 压缩
                    ImageSize imageSize = getImageViewSize(imageView);
                    Bitmap bm = decodeSampledBitMapFromPath(path, imageSize.width, imageSize.height);
                    addBitmapToLruCache(path, bm);
                    refreashBitmap(bm, imageView, path);

                    mSemaphoreTHreadPool.release();
                }
            });
        }
    }

    private void refreashBitmap(Bitmap bm, ImageView imageView, String path) {
        Message message = Message.obtain();
        ImgBeanHolder holder = new ImgBeanHolder();
        holder.bitmap = bm;
        holder.imageView = imageView;
        holder.path = path;
        message.obj = holder;
        mUIHandler.sendMessage(message);
    }

    private void addBitmapToLruCache(String path, Bitmap bm) {
        if (getBitmapFromLruCache(path) == null) {
            if (bm != null) {
                mLruCache.put(path, bm);
            }
        }
    }

    private Bitmap decodeSampledBitMapFromPath(String path, int width, int height) {
        // 获取图片的宽和高，并不把图片加载到内存中
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);

        options.inSampleSize = caculateSampleSize(options, width, height);

        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile(path, options);
        return bitmap;
    }

    private int caculateSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        int width = options.outWidth;
        int height = options.outHeight;
        int inSampleSize = 1;

        if (width > reqWidth || height > reqHeight) {
            int widthRadio = Math.round(width * 1.0f / reqWidth);
            int heightRadio = Math.round(height * 1.0f / reqHeight);
            inSampleSize = Math.max(widthRadio, heightRadio);
        }

        return inSampleSize;
    }


    protected ImageSize getImageViewSize(ImageView imageView) {
        ImageSize imageSize = new ImageSize();
        DisplayMetrics displayMetrics = imageView.getContext().getResources().getDisplayMetrics();

        LayoutParams lp = imageView.getLayoutParams();
        int width = imageView.getWidth();
        if (width <= 0) {
            width = lp.width;
        }
        if (width <= 0) {
            // android 16 以上可用
            // width = imageView.getMaxWidth();
            width = getImageViewFieldValue(imageView, "mMaxWidth");
        }
        if (width <= 0) {
            width = displayMetrics.widthPixels;
        }

        int height = imageView.getHeight();
        if (height <= 0) {
            height = lp.height;
        }
        if (height <= 0) {
            height = getImageViewFieldValue(imageView, "mMaxHeight");
        }

        if (height <= 0) {
            height = displayMetrics.heightPixels;
        }

        imageSize.width = width;
        imageSize.height = height;


        return imageSize;
    }

    private static int getImageViewFieldValue(Object object, String fieldName) {
        int value = 0;
        Field field = null;
        try {
            field = ImageView.class.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        field.setAccessible(true);

        try {
            int fieldValue = field.getInt(object);
            if (fieldValue > 0 && fieldValue < Integer.MAX_VALUE) {
                value = fieldValue;
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return value;
    }

    private synchronized void addTask(Runnable runnable) {
        mTaskQueue.add(runnable);
        try {
            if (mPoolThreadHandler == null)
                mSemaphorePoolThreadHandler.acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        mPoolThreadHandler.sendEmptyMessage(0X110);
    }


    private class ImageSize {
        int width;
        int height;
    }

    private Bitmap getBitmapFromLruCache(String key) {
        return mLruCache.get(key);
    }

    private class ImgBeanHolder {
        ImageView imageView;
        Bitmap bitmap;
        String path;
    }

}

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