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这个是developer.android.com的demo,初学android,做下笔记.
目的: 实现点击缩略图,动画放大为大图,点击大图,反向动画为缩略图.
思路: 最外层用 FrameLayout,便于将加载大图的ImageView覆盖在缩略图之上,先将此imageView隐藏,动画时再显示.
layout
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp">
<TextView style="?android:textAppearanceSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/message_zoom_touch_expand" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:orientation="horizontal">
<!-- TouchHighlightImageButton是一个自定义ImageButton,点击时盖上一层半透明图层,以标识focused 和 pressed 状态-->
<com.example.android.animationsdemo.TouchHighlightImageButton
android:id="@+id/thumb_button_1"
android:layout_width="100dp"
android:layout_height="75dp"
android:layout_marginRight="1dp"
android:src="@drawable/thumb1"
android:scaleType="centerCrop"
android:contentDescription="@string/description_image_1" />
<com.example.android.animationsdemo.TouchHighlightImageButton
android:id="@+id/thumb_button_2"
android:layout_width="100dp"
android:layout_height="75dp"
android:src="@drawable/thumb2"
android:scaleType="centerCrop"
android:contentDescription="@string/description_image_2" />
</LinearLayout>
</LinearLayout>
<ImageView
android:id="@+id/expanded_image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="invisible"
android:contentDescription="@string/description_zoom_touch_close" />
</FrameLayout>
ZoomActivity
package com.example.android.animationsdemo;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.content.Intent;
import android.graphics.Point;
import android.graphics.Rect;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.NavUtils;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;
public class ZoomActivity extends FragmentActivity {
/**
* 存放属性动画对象,方便后面中途取消动画时用.
*/
private Animator mCurrentAnimator;
/**
* 动画过场时间
*/
private int mShortAnimationDuration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_zoom);
//这里没什么好说的,thumb1View ,thumb2View 2个缩略图
final View thumb1View = findViewById(R.id.thumb_button_1);
thumb1View.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
zoomImageFromThumb(thumb1View, R.drawable.image1);
}
});
final View thumb2View = findViewById(R.id.thumb_button_2);
thumb2View.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
zoomImageFromThumb(thumb2View, R.drawable.image2);
}
});
mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);
// mShortAnimationDuration = 2000; 可以改长一点观察动画的详细过程
}
//无关,不解释
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
/*
* @param thumbView 要放大的缩略图View.
* @param imageResId 大图Id.
*/
private void zoomImageFromThumb(final View thumbView, int imageResId) {
// 如果动画正在执行,立马中断它,重新开始
if (mCurrentAnimator != null) {
mCurrentAnimator.cancel();
}
//载入大图
final ImageView expandedImageView = (ImageView) findViewById(R.id.expanded_image);
expandedImageView.setImageResource(imageResId);
//重点开始: 计算动画的开始和结束边界,其实就是计算2个矩形
final Rect startBounds = new Rect();
final Rect finalBounds = new Rect();
final Point globalOffset = new Point();
// 获得缩略图的矩形,注意:使用的是绝对坐标,相对于全屏
thumbView.getGlobalVisibleRect(startBounds);
//获得大图的(这里是放置大图的FrameLayout,一回事)的矩形,和偏移量
//所谓"偏移量",指绝对坐标和相对坐标之差,之于为什么要这么干,因为属性动画中用的全是相对坐标
findViewById(R.id.container).getGlobalVisibleRect(finalBounds, globalOffset);
//用偏移量修正2个矩形
startBounds.offset(-globalOffset.x, -globalOffset.y);
finalBounds.offset(-globalOffset.x, -globalOffset.y);
// 1.计算高和宽的Scale,
// 2.如果缩略图和大图的高宽比不一样,先在startBounds中修正它
// 因为动画过程中出现拉伸的状况就不美了,我没测试过
float startScale;
if ((float) finalBounds.width() / finalBounds.height()
> (float) startBounds.width() / startBounds.height()) {
// Extend start bounds horizontally
startScale = (float) startBounds.height() / finalBounds.height();
float startWidth = startScale * finalBounds.width();
float deltaWidth = (startWidth - startBounds.width()) / 2;
startBounds.left -= deltaWidth;
startBounds.right += deltaWidth;
} else {
// Extend start bounds vertically
startScale = (float) startBounds.width() / finalBounds.width();
float startHeight = startScale * finalBounds.height();
float deltaHeight = (startHeight - startBounds.height()) / 2;
startBounds.top -= deltaHeight;
startBounds.bottom += deltaHeight;
}
// 准备开场,先将缩略图隐藏,接下来是大图的动画,跟它无关了.
thumbView.setAlpha(0f);
expandedImageView.setVisibility(View.VISIBLE);
// 设置动画开始的SCALE_X 和SCALE_Y变化的左上角原点,如果不设置的话默认从View的center开始
expandedImageView.setPivotX(0f);
expandedImageView.setPivotY(0f);
// 到这就没啥好说的了
AnimatorSet set = new AnimatorSet();
set
.play(ObjectAnimator.ofFloat(expandedImageView, View.X, startBounds.left,
finalBounds.left))
.with(ObjectAnimator.ofFloat(expandedImageView, View.Y, startBounds.top,
finalBounds.top))
.with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X, startScale, 1f))//最后的Scale肯定是1
.with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_Y, startScale, 1f));
set.setDuration(mShortAnimationDuration);
set.setInterpolator(new DecelerateInterpolator());//用了个加速度插值器
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mCurrentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
mCurrentAnimator = null;
}
});
set.start();
mCurrentAnimator = set;
//放大后再点击,缩回原状
final float startScaleFinal = startScale;
expandedImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (mCurrentAnimator != null) {
mCurrentAnimator.cancel();
}
AnimatorSet set = new AnimatorSet();
set
.play(ObjectAnimator.ofFloat(expandedImageView, View.X, startBounds.left))
.with(ObjectAnimator.ofFloat(expandedImageView, View.Y, startBounds.top))
.with(ObjectAnimator
.ofFloat(expandedImageView, View.SCALE_X, startScaleFinal))
.with(ObjectAnimator
.ofFloat(expandedImageView, View.SCALE_Y, startScaleFinal));
set.setDuration(mShortAnimationDuration);
set.setInterpolator(new DecelerateInterpolator());
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
thumbView.setAlpha(1f);
expandedImageView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
thumbView.setAlpha(1f);
expandedImageView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
});
set.start();
mCurrentAnimator = set;
}
});
}
}主要知识点:
1. 绝对坐标及相对坐标的获取和转换, getGlobalVisibleRect(Rect r, Point offset);
2. 属性动画使用的一些注意点,比如 SCALE_X 和SCALE_Y变化原点的设置等.
附上一个效果图
