问题
I'm having some troubles with a slideshow I'm building.
I've created 2 animations in xml for fade in and fade out:
fadein.xml
<?xml version="1.0" encoding="UTF-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<alpha android:fromAlpha="0.0" android:toAlpha="1.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:duration="2000"/>
</set>
fadeout.xml
<?xml version="1.0" encoding="UTF-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<alpha android:fromAlpha="1.0" android:toAlpha="0.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:duration="2000"/>
</set>
What Im'trying to do, is to change images from an ImageView using the fade effect, so the currently displayed image will fade out, and another one will fade in. Considering that I have an image already set, I can fadeout this Image without problem, with this:
Animation fadeInAnimation = AnimationUtils.loadAnimation(this, R.anim.your_fade_in_anim);
imageView.startAnimation(fadeoutAnim);
But then, I set the next image to be displayed:
imageView.setImageBitmap(secondImage);
It just shows up in the imageView, and when i set the animation it hides the image, the fade it in... Is there any way to fix that, I mean, when I do imageView.setImageBitmap(secondImage); command, the image do not shows up immediately, and only when the fade in animation is executed?
回答1:
To implement this the way you have started, you'll need to add an AnimationListener so that you can detect the beginning and ending of an animation. When onAnimationEnd() for the fade out is called, you can set the visibility of your ImageView object to View.INVISIBLE, switch the images and start your fade in animation - you'll need another AnimationListener here too. When you receive onAnimationEnd() for your fade in animation, set the ImageView to be View.VISIBLE and that should give you the effect you're looking for.
I've implemented a similar effect before, but I used a ViewSwitcher with 2 ImageViews rather than a single ImageView. You can set the "in" and "out" animations for the ViewSwitcher with your fade in and fade out so it can manage the AnimationListener implementation. Then all you need to do is alternate between the 2 ImageViews.
Edit: To be a bit more useful, here is a quick example of how to use the ViewSwitcher. I have included the full source at https://github.com/aldryd/imageswitcher.
activity_main.xml
<ViewSwitcher
android:id="@+id/switcher"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:inAnimation="@anim/fade_in"
android:outAnimation="@anim/fade_out" >
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="fitCenter"
android:src="@drawable/sunset" />
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="fitCenter"
android:src="@drawable/clouds" />
</ViewSwitcher>
MainActivity.java
// Let the ViewSwitcher do the animation listening for you
((ViewSwitcher) findViewById(R.id.switcher)).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ViewSwitcher switcher = (ViewSwitcher) v;
if (switcher.getDisplayedChild() == 0) {
switcher.showNext();
} else {
switcher.showPrevious();
}
}
});
回答2:
I wanted to achieve the same goal as you, so I wrote the following method which does exactly that if you pass it an ImageView and a list of references to image drawables.
ImageView demoImage = (ImageView) findViewById(R.id.DemoImage);
int imagesToShow[] = { R.drawable.image1, R.drawable.image2,R.drawable.image3 };
animate(demoImage, imagesToShow, 0,false);
private void animate(final ImageView imageView, final int 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.setImageResource(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) {
animate(imageView, images, imageIndex + 1,forever); //Calls itself until it gets to the end of the array
}
else {
if (forever){
animate(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
}
});
}
回答3:
Have you thought of using TransitionDrawable instead of custom animations? https://developer.android.com/reference/android/graphics/drawable/TransitionDrawable.html
One way to achieve what you are looking for is:
// create the transition layers
Drawable[] layers = new Drawable[2];
layers[0] = new BitmapDrawable(getResources(), firstBitmap);
layers[1] = new BitmapDrawable(getResources(), secondBitmap);
TransitionDrawable transitionDrawable = new TransitionDrawable(layers);
imageView.setImageDrawable(transitionDrawable);
transitionDrawable.startTransition(FADE_DURATION);
回答4:
I used used fadeIn animation to replace new image for old one
ObjectAnimator.ofFloat(imageView, View.ALPHA, 0.2f, 1.0f).setDuration(1000).start();
回答5:
Based on Aladin Q's solution, here is a helper function that I wrote, that will change the image in an imageview while running a little fade out / fade in animation:
public static void ImageViewAnimatedChange(Context c, final ImageView v, final Bitmap new_image) {
final Animation anim_out = AnimationUtils.loadAnimation(c, android.R.anim.fade_out);
final Animation anim_in = AnimationUtils.loadAnimation(c, android.R.anim.fade_in);
anim_out.setAnimationListener(new AnimationListener()
{
@Override public void onAnimationStart(Animation animation) {}
@Override public void onAnimationRepeat(Animation animation) {}
@Override public void onAnimationEnd(Animation animation)
{
v.setImageBitmap(new_image);
anim_in.setAnimationListener(new AnimationListener() {
@Override public void onAnimationStart(Animation animation) {}
@Override public void onAnimationRepeat(Animation animation) {}
@Override public void onAnimationEnd(Animation animation) {}
});
v.startAnimation(anim_in);
}
});
v.startAnimation(anim_out);
}
回答6:
you can do it by two simple point and change in your code
1.In your xml in anim folder of your project, Set the fade in and fade out duration time not equal
2.In you java class before the start of fade out animation, set second imageView visibility Gone then after fade out animation started set second imageView visibility which you want to fade in visible
fadeout.xml
<alpha
android:duration="4000"
android:fromAlpha="1.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:toAlpha="0.0" />
fadein.xml
<alpha
android:duration="6000"
android:fromAlpha="0.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:toAlpha="1.0" />
In you java class
Animation animFadeOut = AnimationUtils.loadAnimation(this, R.anim.fade_out);
ImageView iv = (ImageView) findViewById(R.id.imageView1);
ImageView iv2 = (ImageView) findViewById(R.id.imageView2);
iv.setVisibility(View.VISIBLE);
iv2.setVisibility(View.GONE);
animFadeOut.reset();
iv.clearAnimation();
iv.startAnimation(animFadeOut);
Animation animFadeIn = AnimationUtils.loadAnimation(this, R.anim.fade_in);
iv2.setVisibility(View.VISIBLE);
animFadeIn.reset();
iv2.clearAnimation();
iv2.startAnimation(animFadeIn);
回答7:
For infinite Fade In and Out
AlphaAnimation fadeIn=new AlphaAnimation(0,1);
AlphaAnimation fadeOut=new AlphaAnimation(1,0);
final AnimationSet set = new AnimationSet(false);
set.addAnimation(fadeIn);
set.addAnimation(fadeOut);
fadeOut.setStartOffset(2000);
set.setDuration(2000);
imageView.startAnimation(set);
set.setAnimationListener(new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) { }
@Override
public void onAnimationRepeat(Animation animation) { }
@Override
public void onAnimationEnd(Animation animation) {
imageView.startAnimation(set);
}
});
回答8:
I'm using this kind of routine for programmatically chaining animations.
final Animation anim_out = AnimationUtils.loadAnimation(context, android.R.anim.fade_out);
final Animation anim_in = AnimationUtils.loadAnimation(context, android.R.anim.fade_in);
anim_out.setAnimationListener(new AnimationListener()
{
@Override
public void onAnimationStart(Animation animation) {}
@Override
public void onAnimationRepeat(Animation animation) {}
@Override
public void onAnimationEnd(Animation animation)
{
////////////////////////////////////////
// HERE YOU CHANGE YOUR IMAGE CONTENT //
////////////////////////////////////////
//ui_image.setImage...
anim_in.setAnimationListener(new AnimationListener()
{
@Override
public void onAnimationStart(Animation animation) {}
@Override
public void onAnimationRepeat(Animation animation) {}
@Override
public void onAnimationEnd(Animation animation) {}
});
ui_image.startAnimation(anim_in);
}
});
ui_image.startAnimation(anim_out);
回答9:
The best and the easiest way, for me was this..
->Simply create a thread with Handler containing sleep().
private ImageView myImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shape_count); myImageView= (ImageView)findViewById(R.id.shape1);
Animation myFadeInAnimation = AnimationUtils.loadAnimation(this, R.anim.fadein);
myImageView.startAnimation(myFadeInAnimation);
new Thread(new Runnable() {
private Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
Log.w("hendler", "recived");
Animation myFadeOutAnimation = AnimationUtils.loadAnimation(getBaseContext(), R.anim.fadeout);
myImageView.startAnimation(myFadeOutAnimation);
myImageView.setVisibility(View.INVISIBLE);
}
};
@Override
public void run() {
try{
Thread.sleep(2000); // your fadein duration
}catch (Exception e){
}
handler.sendEmptyMessage(1);
}
}).start();
}
回答10:
This is probably the best solution you'll get. Simple and Easy. I learned it on udemy.
Suppose you have two images having image id's id1 and id2 respectively and currently the image view is set as id1 and you want to change it to the other image everytime someone clicks in. So this is the basic code in MainActivity.java File
int clickNum=0;
public void click(View view){
clickNum++;
ImageView a=(ImageView)findViewById(R.id.id1);
ImageView b=(ImageView)findViewById(R.id.id2);
if(clickNum%2==1){
a.animate().alpha(0f).setDuration(2000); //alpha controls the transpiracy
}
else if(clickNum%2==0){
b.animate().alpha(0f).setDuration(2000); //alpha controls the transpiracy
}
}
I hope this will surely help
来源：https://stackoverflow.com/questions/8720626/android-fade-in-and-fade-out-with-imageview