transitiondrawable ImageVIew切换动画

一个TransitionDrawable是一个特殊的Drawable对象，可以实现两个drawable资源之间淡入淡出的效果。

<transition>节点下的每个<item>代表一个drawable资源。只能有两个<item>。先前转换调用startTransition()。向后，调用 reverseTransition()。

文件位于：

res/drawable/filename.xml
文件名作为资源ID

编译资源类型：

指向 TransitionDrawable的指针

资源引用：

In Java: R.drawable.filename
In XML: @[package:]drawable/filename

语法：

<?xml version="1.0" encoding="utf-8"?>
<transition
xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
        android:drawable="@[package:]drawable/drawable_resource"
        android:id="@[+][package:]id/resource_name"
        android:top="dimension"
        android:right="dimension"
        android:bottom="dimension"
        android:left="dimension" />
</transition>

元素：

例子：

XML文件保存为：res/drawable/transition.xml：

<?xml version="1.0" encoding="utf-8"?>
<transition xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/on" />
    <item android:drawable="@drawable/off" />
</transition>

在layout文件中使用：

<ImageButton
    android:id="@+id/button"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    android:src="@drawable/transition" />

And the following code performs a 500ms transition from the first item to the second:

ImageButton button = (ImageButton) findViewById(R.id.button);
TransitionDrawable drawable = (TransitionDrawable) button.getDrawable();
drawable.startTransition(500);

参考

TransitionDrawable

下面是实例：

1、xml方式使用

transition.xml：

[java] view plain copy

<?xml version="1.0" encoding="utf-8"?>
<transition xmlns:android="http://schemas.android.com/apk/res/android" >
<item android:drawable="@drawable/image01"/>
<item android:drawable="@drawable/image02"/>
</transition>

在layout中使用：

[java] view plain copy

<ImageView
android:id="@+id/imgView"
android:src="@drawable/transition"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>

在代码中控制：

[java] view plain copy

ImageView imageView = (ImageView) findViewById(R.id.imgView);
TransitionDrawable transitionDrawable = (TransitionDrawable) imageView.getDrawable();
transitionDrawable.startTransition(3000);

下面是一个实例：实现多张图片循环的淡入淡出的效果。

[java] view plain copy

package com.example.drawabletest;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.TransitionDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
public class MainActivity extends Activity {
private int change=0;
private int[] ids = new int[] { R.drawable.image1, R.drawable.image2, R.drawable.image3,
R.drawable.image4, R.drawable.image5 };
private Drawable[] drawables;
private ImageView imageView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.imgView);
/*获得合适的drawable资源*/
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.drawable.image1, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 500 * 500);
opts.inJustDecodeBounds = false;
drawables=new Drawable[ids.length];
try {
for (int i = 0; i < ids.length; i++) {// for循环，加载5个drawable资源
Bitmap bmp = BitmapFactory.decodeResource(getResources(), ids[i], opts);
drawables[i] = new BitmapDrawable(bmp);
}
} catch (Exception e) {
e.printStackTrace();
}
//开启线程，改变transition
new Thread(new MyRunnable()).start();
}
//处理transition的改变
private Handler handler=new Handler(new Handler.Callback() {
public boolean handleMessage(Message msg) {
int duration=msg.arg1;
TransitionDrawable transitionDrawable=null;
transitionDrawable= new TransitionDrawable(new Drawable[] {
drawables[change%ids.length],//实现从0 1 2 3 4 5 0 1 2.。。这样的不停转变
drawables[(change+1)%ids.length] });
change++;
imageView.setImageDrawable(transitionDrawable);
transitionDrawable.startTransition(duration);
return false;
}
});
//线程，去发送消息，让transition一直改变
private class MyRunnable implements Runnable{
public void run() {
while (true) {
int duration=3000;//改变的间隔
Message message=handler.obtainMessage();
message.arg1=duration;
handler.sendMessage(message);
try {
Thread.sleep(duration);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
//计算合适的图片大小
public static int computeSampleSize(BitmapFactory.Options options, int minSideLength,
int maxNumOfPixels) {
int initialSize = computeInitialSampleSize(options, minSideLength, maxNumOfPixels);
int roundedSize;
if (initialSize <= 8) {
roundedSize = 1;
while (roundedSize < initialSize) {
roundedSize <<= 1;
}
} else {
roundedSize = (initialSize + 7) / 8 * 8;
}
return roundedSize;
}
//计算合适的图片大小
private static int computeInitialSampleSize(BitmapFactory.Options options, int minSideLength,
int maxNumOfPixels) {
double w = options.outWidth;
double h = options.outHeight;
int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math.sqrt(w * h
/ maxNumOfPixels));
int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(
Math.floor(w / minSideLength), Math.floor(h / minSideLength));
if (upperBound < lowerBound) {
// return the larger one when there is no overlapping zone.
return lowerBound;
}
if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
return 1;
} else if (minSideLength == -1) {
return lowerBound;
} else {
return upperBound;
}
}
}