动态图片 gif

Movie 类

文档位置：/sdk/docs/reference/android/graphics/Movie.html

官方对这个类连一句介绍都没有，并且所有的方法也没有一行注释，可见多么不受重视！

package android.graphics;

直接继承自Object，直接继承自Object的基本上都是工具类。

Android的ImageView无法直接加载Gif图片，鉴于此，Android社区开发者为解决此问题贡献了很多解决方案，其中一种比较简易的做法是通过Android中的Movie类把一个gif图片当作一个原始的资源加载到Movie，然后Movie将其解析为Movie帧进行加载。

Movie其实管理着GIF动画中的多个帧，只需要通过 setTime() 一下就可以让它在draw()的时候绘出相应的那帧图像，通过当前时间与duration之间的换算关系，便可实现GIF动起来的效果。

对于比较小的gif图片使用此方法还是可以的，要是大的话，建议还是把gif图片转换成一帧一帧的png图片，然后通过animation播放。

简单的利用Movie播放GIF图的控件

setContentView(new CustomGifView(this, R.drawable.ic_launcher)); //显示普通图片
setContentView(new CustomGifView(this, R.drawable.gif1));  //显示gif动图

/**
 * 自定义可以循环播放gif动画的View，可以像使用其他控件一样使用
 * @author 白乾涛
 */
public class CustomGifView extends View {
   private Movie mMovie;
   private long mMovieStart;
   private int resId;
   
   public CustomGifView(Context context, int resId) {
      super(context);
      this.resId = resId;
      setLayerType(View.LAYER_TYPE_SOFTWARE, null);//必须关闭硬件加速
      mMovie = Movie.decodeStream(getResources().openRawResource(resId));//创建Movie对象
   }
   
   public void onDraw(Canvas canvas) {
      long now = SystemClock.uptimeMillis();//系统当前时刻
      //第一次播放 
      if (mMovieStart == 0) mMovieStart = now;//动画开始的时间
      if (mMovie != null) {
         int dur = mMovie.duration();//动画持续的时间，也就是完成一次动画的时间
         if (dur == 0) dur = 1000;
         int relTime = (int) ((now - mMovieStart) % dur);//注意这是取余操作，这才能算出当前这次重复播放的第一帧的时间
         mMovie.setTime(relTime);//设置相对本次播放第一帧时间，根据这个时间来决定显示第几帧
         mMovie.draw(canvas, 0, 0);
         invalidate();
      } else {//如果指定的资源不是gif图片，也就是说是普通的图片，则需要手动绘制此图片
         canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), resId), getMatrix(), new Paint());
      }
   }
}

Movie 类的 API

static Movie decodeByteArray(byte[] data, int offset, int length)
static Movie decodeFile(String pathName)
static Movie decodeStream(InputStream is)
void draw(Canvas canvas, float x, float y, Paint paint)
void draw(Canvas canvas, float x, float y)
int duration()
int height()
boolean isOpaque()
boolean setTime(int relativeMilliseconds)
int width()

开源库 android-gif-drawable

位置：https://github.com/koral--/android-gif-drawable

底层解码使用C实现，极大的提高了解码效率，同时很大程度上避免了OOM。

Views and Drawable for displaying animated GIFs on Android

Bundled GIFLib via JNI is used to render frames. This way should be more efficient than WebView or Movie classes.

Requirements

Android 2.3+ (API level 9+)
for GifTextureView Android 4.0+ (API level 14+) and hardware-accelerated rendering渲染
for GifTexImage2D OpenGL ES 2.0+

Building from source

Android NDK needed to compile native sources

配置build.gradle

Insert the following dependency to build.gradle file of your project.

dependencies {
    compile 'pl.droidsonroids.gif:android-gif-drawable:1.2.6'
}

Note that Maven central repository should be defined eg. in top-level build.gradle like this:

buildscript {
    repositories {
        mavenCentral()
    }
}
allprojects {
    repositories {
        mavenCentral()
    }
}

XML中使用

The simplest way is to use GifImageView or GifImageButton like a normal ImageView:

<pl.droidsonroids.gif.GifImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/gif1"
    android:src="@drawable/gif2"/>

If drawables declared by android:src and/or android:background are GIF files then they will be automatically recognized as GifDrawables and animated. If given drawable is not a GIF then mentioned Views work like plain平常的 ImageView and ImageButton.

GifTextView allows you to use GIFs as compound复合的 drawables and background.

<pl.droidsonroids.gif.GifTextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/gif1"
    android:drawableTop="@drawable/gif2"/>

代码中构造GifDrawable

GifImageView, GifImageButton and GifTextView have also hooks for setters implemented. So animated GIFs can be set by calling setImageResource(int resId) and setBackgroundResource(int resId)

GifDrawable can be constructed directly from various sources:

void constructGifDrawable() throws IOException {
   //asset file
   GifDrawable gifFromAssets = new GifDrawable(getAssets(), "gif1.gif");
   
   //resource (drawable or raw)
   GifDrawable gifFromResource = new GifDrawable(getResources(), R.drawable.gif1);
   
   //Uri
   ContentResolver contentResolver = null; //can be null for file:// Uris
   GifDrawable gifFromUri = new GifDrawable(contentResolver, null);//gifUri
   
   //byte array
   byte[] rawGifBytes = null;
   GifDrawable gifFromBytes = new GifDrawable(rawGifBytes);
   
   //FileDescriptor
   FileDescriptor fd = new RandomAccessFile("/path/anim.gif", "r").getFD();
   GifDrawable gifFromFd = new GifDrawable(fd);
   
   //file path
   GifDrawable gifFromPath = new GifDrawable("/path/anim.gif");
   
   //file
   File gifFile = new File(getFilesDir(), "gif1.gif");
   GifDrawable gifFromFile = new GifDrawable(gifFile);
   
   //AssetFileDescriptor
   AssetFileDescriptor afd = getAssets().openFd("gif1.gif");
   GifDrawable gifFromAfd = new GifDrawable(afd);
   
   //InputStream (it must support marking)
   InputStream sourceIs = null;
   BufferedInputStream bis = new BufferedInputStream(sourceIs, 1024);//GIF_LENGTH
   GifDrawable gifFromStream = new GifDrawable(bis);
   
   //direct ByteBuffer
   ByteBuffer rawGifByteBuffer = null;
   GifDrawable gifFromByteBuffer = new GifDrawable(rawGifByteBuffer);
}

InputStreams are closed automatically in finalizer if GifDrawable is no longer needed so you don't need to explicitly明确的 close them. Calling recycle() will also close underlying潜在的 input source.

Note that all input sources need to have ability to rewind倒回 to the beginning. It is required to correctly play animated GIFs (where animation is repeatable) since subsequent随后的 frames are decoded on demand from source.

动画过程控制 Animation control

GifDrawable implements an Animatable and MediaPlayerControl so you can use its methods and more:

stop() - stops the animation, can be called from any thread
start() - starts the animation, can be called from any thread
isRunning() - returns whether animation is currently running or not
reset() - rewinds the animation, does not restart stopped one
setSpeed(float factor) - sets new animation speed factor, eg. passing 2.0f will double the animation speed
seekTo(int position) - seeks animation (within current loop) to given position (in milliseconds)
getDuration() - returns duration of one loop of the animation
getCurrentPosition() - returns elapsed time from the beginning of a current loop of animation

使用 MediaPlayerControl

Standard controls for a MediaPlayer (like in VideoView) can be used to control GIF animation and show its current progress.

Just set GifDrawable as MediaPlayer on your MediaController like this:

@BindView(R.id.gif) GifImageView gifView;
android.widget.MediaController mc;

mc = new MediaController(this);
mc.setMediaPlayer((pl.droidsonroids.gif.GifDrawable) gifView.getDrawable());
mc.setAnchorView(gifView);

mc.show();

获取GIF元数据

Retrieving GIF metadata

getLoopCount() - returns a loop count as defined in NETSCAPE 2.0 extension
getNumberOfFrames() - returns number of frames (at least 1)
getComment() - returns comment text (null if GIF has no comment)
getFrameByteCount() - returns minimum number of bytes that can be used to store pixels of the single frame
getAllocationByteCount() - returns size (in bytes) of the allocated memory used to store pixels of given GifDrawable
getInputSourceByteCount() - returns length (in bytes) of the backing input data
toString() - returns human readable information about image size and number of frames (intended for debugging purpose)

一个GifDrawable用在多个View上

Associating single GifDrawable instance with multiple Views：

Normally single GifDrawable instance associated with multiple Views will animate only on the last one. To solve that create MultiCallback instance, add Views to it and set callback for given drawable, eg.:

MultiCallback multiCallback = new MultiCallback();
imageView.setImageDrawable(gifDrawable);
multiCallback.addView(imageView);
anotherImageView.setImageDrawable(gifDrawable);
multiCallback.addView(anotherImageView);

gifDrawable.setCallback(multiCallback);

高级API

Advanced

recycle() - provided to speed up freeing memory (like in android.graphics.Bitmap)

isRecycled() - checks whether drawable is recycled

getError() - returns last error details

开源库 Cutta/GifView

位置：https://github.com/Cutta/GifView

Library for playing gifs on Android

Simple android view to display gifs efficiently高效的. You can start, pause and stop gifView.

Inspired by灵感来自 sbakhtiarov/gif-movie-view

这个自定义的View其实主要还是使用了 android.graphics.Movie 这个类。

去看源码时，发现就一个独杆司令GifView，API也就下面几个：

AS中使用

Add these lines on top-level build file

// Top-level build file where you can add configuration options common to all sub-projects/modules.
repositories {
    maven {
        url "https://jitpack.io"
    }
}

On app's build.gradle

compile 'com.github.Cutta:GifView:1.1'

布局和代码中设置：

xmlns:custom="http://schemas.android.com/apk/res-auto"

<com.cunoraz.gifview.library.GifView
    android:id="@+id/gif"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:layout_centerInParent="true"
    custom:gif="@drawable/gif1"/>

GifView gifView = (GifView) view.findViewById(R.id.gif);
gifView.pause(); //默认为自动播放，可以手动设置 custom:paused="true"

Eclipse中使用

1、把独杆司令GifView拷到项目中

2、把自定义属性拷到attrs.xml中

<declare-styleable name="GifView">
	<attr name="gif" format="reference" />
	<attr name="paused" format="boolean" />
</declare-styleable>

3、在布局和代码中使用

xmlns:custom="http://schemas.android.com/apk/res/com.bqt"

<com.bqt.GifView
	android:id="@+id/gif"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	custom:gif="@drawable/gif" />

没啥好说的，简单实用。

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