我想用淡入淡出动画切换图像。
我将这段代码用于动画：
package android.infra;
import android.graphics.drawable.Drawable;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.AlphaAnimation;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.AnimationSet;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;
public class AnimationsHelper {
public static void switchImageAnimations(final ImageView imageView, final Drawable images[], final int imageIndex, final boolean forever) {
//imageView <-- The View which displays the images
//images[] <-- Holds R references to the images to display
//imageIndex <-- index of the first image to show in images[]
//forever <-- If equals true then after the last image it starts all over again with the first image resulting in an infinite loop. You have been warned.
int fadeInDuration = 500; // Configure time values here
int timeBetween = 3000;
int fadeOutDuration = 1000;
imageView.setVisibility(View.INVISIBLE); //Visible or invisible by default - this will apply when the animation ends
imageView.setImageDrawable(images[imageIndex]);
Animation fadeIn = new AlphaAnimation(0, 1);
fadeIn.setInterpolator(new DecelerateInterpolator()); // add this
fadeIn.setDuration(fadeInDuration);
Animation fadeOut = new AlphaAnimation(1, 0);
fadeOut.setInterpolator(new AccelerateInterpolator()); // and this
fadeOut.setStartOffset(fadeInDuration + timeBetween);
fadeOut.setDuration(fadeOutDuration);
AnimationSet animation = new AnimationSet(false); // change to false
animation.addAnimation(fadeIn);
animation.addAnimation(fadeOut);
animation.setRepeatCount(1);
imageView.setAnimation(animation);
animation.setAnimationListener(new AnimationListener() {
public void onAnimationEnd(Animation animation) {
if (images.length - 1 > imageIndex) {
switchImageAnimations(imageView, images, imageIndex + 1,forever); //Calls itself until it gets to the end of the array
}
else {
if (forever == true){
switchImageAnimations(imageView, images, 0,forever); //Calls itself to start the animation all over again in a loop if forever = true
}
}
}
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
}
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
}
});
}
}
此代码用于下载图像并显示它们：
package android.infra;
import java.util.Map;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Collections;
import java.util.WeakHashMap;
import java.lang.ref.SoftReference;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.widget.ImageView;
import android.os.Handler;
import android.os.Message;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
public class DrawableBackgroundDownloader {
private final Map<String, SoftReference<Drawable>> mCache = new HashMap<String, SoftReference<Drawable>>();
private final LinkedList <Drawable> mChacheController = new LinkedList <Drawable> ();
private ExecutorService mThreadPool;
private final Map<ImageView, String> mImageViews = Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
public static int MAX_CACHE_SIZE = 80;
public int THREAD_POOL_SIZE = 3;
/**
* Constructor
*/
public DrawableBackgroundDownloader() {
mThreadPool = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
}
/**
* Clears all instance data and stops running threads
*/
public void Reset() {
ExecutorService oldThreadPool = mThreadPool;
mThreadPool = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
oldThreadPool.shutdownNow();
mChacheController.clear();
mCache.clear();
mImageViews.clear();
}
public void loadDrawable(final String url, final ImageView imageView,Drawable placeholder) {
mImageViews.put(imageView, url);
Drawable drawable = getDrawableFromCache(url);
// check in UI thread, so no concurrency issues
if (drawable != null) {
//Log.d(null, "Item loaded from mCache: " + url);
// imageView.setImageDrawable(drawable);
Drawable imagesToShow[] = { drawable };
android.infra.AnimationsHelper.switchImageAnimations(imageView, imagesToShow, 0, false);
} else {
imageView.setImageDrawable(placeholder);
queueJob(url, imageView, placeholder);
}
}
private Drawable getDrawableFromCache(String url) {
if (mCache.containsKey(url)) {
return mCache.get(url).get();
}
return null;
}
private synchronized void putDrawableInCache(String url,Drawable drawable) {
int chacheControllerSize = mChacheController.size();
if (chacheControllerSize > MAX_CACHE_SIZE)
mChacheController.subList(0, MAX_CACHE_SIZE/2).clear();
mChacheController.addLast(drawable);
mCache.put(url, new SoftReference<Drawable>(drawable));
}
private void queueJob(final String url, final ImageView imageView,final Drawable placeholder) {
/* Create handler in UI thread. */
final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
String tag = mImageViews.get(imageView);
if (tag != null && tag.equals(url)) {
if (imageView.isShown())
if (msg.obj != null) {
// imageView.setImageDrawable((Drawable) msg.obj);
Drawable imagesToShow[] = { (Drawable) msg.obj };
android.infra.AnimationsHelper.switchImageAnimations(imageView, imagesToShow, 0, false);
} else {
imageView.setImageDrawable(placeholder);
//Log.d(null, "fail " + url);
}
}
}
};
mThreadPool.submit(new Runnable() {
@Override
public void run() {
final Drawable bmp = downloadDrawable(url);
// if the view is not visible anymore, the image will be ready for next time in cache
if (imageView.isShown())
{
Message message = Message.obtain();
message.obj = bmp;
//Log.d(null, "Item downloaded: " + url);
handler.sendMessage(message);
}
}
});
}
private Drawable downloadDrawable(String url) {
try {
InputStream is = getInputStream(url);
Drawable drawable = Drawable.createFromStream(is, url);
putDrawableInCache(url,drawable);
return drawable;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private InputStream getInputStream(String urlString) throws MalformedURLException, IOException {
URL url = new URL(urlString);
URLConnection connection;
connection = url.openConnection();
connection.setUseCaches(true);
connection.connect();
InputStream response = connection.getInputStream();
return response;
}
}
如您所见，我正在尝试通过以下方式在第二段代码中使用它：
Drawable imagesToShow[] = { (Drawable) msg.obj };
android.infra.AnimationsHelper.switchImageAnimations(imageView, imagesToShow, 0, false);
出于某种原因，我的图像加载（没有任何动画），然后动画执行，我的图像视图由于某种原因变得不可见！
提前致谢。