android中使用imageview显示Gif图片

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http://blog.youkuaiyun.com/riyuegonghe/article/details/9283479

http://weavora.com/blog/2012/02/07/android-how-to-use-animated-gif/

To date Android platform supports a sufficiently large number of media formats. See documentation here. Among the declared graphic formats you’ll find the one we are interested – GIF. Generally speaking this format does not cause any difficulties until you’ll try to use a GIF file with animation. In this case, the standard class ImageViewdisplays GIF file as a usual static image. Doing search you can find forums stating that Android platform doesn’t fully support GIF, that animated GIF files cannot be used. Nevertheless you can still solve this problem and I’ll show you how.

There are at least two ways:

• using class WebView or
• using class Movie

It is difficult to say which solution is better, however there is one important point. Although WebView is a part of any Android SDK, the ability to play animated GIF files only appeared from version Android 2.2 (API level 8). So if you plan support for vide range of devices, then second option is likely more acceptable for you. I’ll further focus on it.

It is not quite fair to say that class Movie is well documented. Otherwise, this article probably would be useless :-) So, let’s try to create a separate component that can play animated GIF files using class Movie.

OK, creating a new class GIFView, inherited from View:

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package com . wvr . widget ; import android.content.Context ; import android.util.AttributeSet ; import android.view.View ;   public class GIFView extends View {       public GIFView ( Context context ) {         super ( context );     }       public GIFView ( Context context , AttributeSet attrs ) {         super ( context , attrs );     }       public GIFView ( Context context , AttributeSet attrs , int defStyle ) {         super ( context , attrs , defStyle );     }   }

view raw GIFView.java hosted with ❤ by  GitHub

Now let’s add new variable of type Movie to our class and initialize it

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package com . wvr . widget ;   import java.io.InputStream ; import com.wvr.example.R ; import android.content.Context ; import android.graphics.Movie ; import android.util.AttributeSet ; import android.view.View ;   public class GIFView extends View {         private Movie mMovie ;       public GIFView ( Context context ) {         super ( context );         initializeView ();     }       public GIFView ( Context context , AttributeSet attrs ) {         super ( context , attrs );         initializeView ();     }       public GIFView ( Context context , AttributeSet attrs , int defStyle ) {         super ( context , attrs , defStyle );         initializeView ();     }       private void initializeView () {         //R.drawable.loader - our animated GIF         InputStream is = getContext (). getResources (). openRawResource ( R . drawable . loader );         mMovie = Movie . decodeStream ( is );     }   }

view raw GIFView2.java hosted with ❤ by  GitHub

OK, now Movie object is initialized and we just need to draw it. We will use onDraw(Canvas) method for this purpose, but before that, we must let Movie object know what exact part of GIF file it should draw. To do this we need a separate variable movieStart of long type, which we assign SystemClock.uptimeMillis() value. In this case we will know when the movie was started and can calculate how much time has passed.

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@Override     protected void onDraw ( Canvas canvas ) {         canvas . drawColor ( Color . TRANSPARENT );         super . onDraw ( canvas );         long now = android . os . SystemClock . uptimeMillis ();         if ( movieStart == 0 ) {             movieStart = now ;         }         if ( movie != null ) {             int relTime = ( int ) (( now - movieStart ) % movie . duration ());             movie . setTime ( relTime );             movie . draw ( canvas , getWidth () - movie . width (), getHeight () - movie . height ());             this . invalidate ();         }     }

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All we need now is initialize GIFView in our Activity class

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public class AnimatedGIFActivity extends Activity {     @Override     public void onCreate ( Bundle savedInstanceState ) {         super . onCreate ( savedInstanceState );         GIFView gifView = new GIFView ( this );         setContentView ( gifView );     } }

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Now let’s add the possibility to pass GIF id as a parameter

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private int gifId ;       public void setGIFResource ( int resId ) {         this . gifId = resId ;         initializeView ();     }       public int getGIFResource () {         return this . gifId ;     }       private void initializeView () {         if ( gifId != 0 ) {             InputStream is = getContext (). getResources (). openRawResource ( gifId );             movie = Movie . decodeStream ( is );             movieStart = 0 ;             this . invalidate ();         }     }

view raw GIF_Param.java hosted with ❤ by  GitHub

Here is how the Activity class should look:

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public void onCreate ( Bundle savedInstanceState ) {         super . onCreate ( savedInstanceState );         GIFView gifView = new GIFView ( this );         gifView . setGIFResource ( R . drawable . loader );         setContentView ( gifView );     }

view raw onCreate.java hosted with ❤ by  GitHub

Another good practice is using components in XML markup. So, let’s also do this. For this purpose I’ll create fileattrs.xml (res/values/attrs.xml) with the following structure:

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<resources>     <declare-styleable name= "GIFView" >         <attr name= "src" format= "reference" />     </declare-styleable> </resources>

view raw attrs.xml hosted with ❤ by  GitHub

Now we just need to read XML-attributes in our GIFView class:

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private void setAttrs ( AttributeSet attrs ) {         if ( attrs != null ) {             TypedArray a = getContext (). obtainStyledAttributes ( attrs , R . styleable . GIFView , 0 , 0 );             String gifSource = a . getString ( R . styleable . GIFView_src );             //little workaround here. Who knows better approach on how to easily get resource id - please share             String sourceName = Uri . parse ( gifSource ). getLastPathSegment (). replace ( ".gif" , "" );             setGIFResource ( getResources (). getIdentifier ( sourceName , "drawable" , getContext (). getPackageName ()));             a . recycle ();         }     }

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After this we are able to use GIFView in XML markup the following way:

main.xml

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<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android= "http://schemas.android.com/apk/res/android"     xmlns:components= "http://schemas.android.com/apk/res/com.wvr.example"     android:layout_width= "fill_parent"     android:layout_height= "fill_parent"     android:orientation= "vertical" >       <com.wvr.widget.GIFView         android:layout_width= "wrap_content"         android:layout_height= "wrap_content"         components:src= "@drawable/loader" /> </LinearLayout>

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Our Activity class looks the following way:

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public class AnimatedGIFActivity extends Activity {     @Override     public void onCreate ( Bundle savedInstanceState ) {         super . onCreate ( savedInstanceState );         setContentView ( R . layout . main );     } }

view raw AnimatedGIFActivity.java hosted with ❤ by  GitHub

That’s it. Have you ever used such approach or maybe you have some better solution – please let us know.

           

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