Android中显示GIF动画的实现代码

本文实例讲述了Android中显示GIF动画的实现代码。分享给大家供大家参考，具体如下：

gif图动画在android中还是比较常用的，比如像新浪微博中，有很多gif图片，而且展示非常好，所以我也想弄一个。经过我多方的搜索资料和整理，终于弄出来了，其实GitHub上有很多开源的gif的展示代码，我下载过几个，但是都不是很理想，不是我完全想要的。所以有时候就得自己学会总结，把开源的东西整理成自己的，现在无聊，也正好有朋友需要，所以现在整理了一下，留着以后备用！

废话不多说，直接上图：

在这里主要用的是：android中的android.graphics.Movie 这个类，这是android提供给我们的一个非常方便的工具。

首先，重写控件View,自定义一个展示gif图的GifView，代码如下：

package net.loonggg.gif.view; 
import net.loonggg.gif.R; 
import android.annotation.SuppressLint; 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.graphics.canvas; 
import android.graphics.Movie; 
import android.os.Build; 
import android.util.AttributeSet; 
import android.view.View; 
public class GifView extends View { 
   
  private static final int DEFAULT_MOVIE_DURATION = 1000; 
  private int mMovieResourceId; 
  private Movie mMovie; 
  private long mMovieStart; 
  private int mCurrentAnimationTime = 0; 
  private float mLeft; 
  private float mTop; 
  private float mScale; 
  private int mMeasuredMovieWidth; 
  private int mMeasuredMovieHeight; 
  private boolean mVisible = true; 
  private volatile boolean mPaused = false; 
  public GifView(Context context) { 
    this(context, null); 
  } 
  public GifView(Context context, AttributeSet attrs) { 
    this(context, attrs, R.styleable.CustomTheme_gifViewStyle); 
  } 
  public GifView(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
    setViewAttributes(context, attrs, defStyle); 
  } 
  @SuppressLint("Newapi") 
  private void setViewAttributes(Context context, AttributeSet attrs, 
      int defStyle) { 
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) { 
      setLayerType(View.LAYER_TYPE_SOFTWARE, null); 
    } 
    // 从描述文件中读出gif的值，创建出Movie实例 
    final TypedArray array = context.obtainStyledAttributes(attrs, 
        R.styleable.GifView, defStyle, R.style.Widget_GifView); 
    mMovieResourceId = array.getResourceId(R.styleable.GifView_gif, -1); 
    mPaused = array.getBoolean(R.styleable.GifView_paused, false); 
    array.recycle(); 
    if (mMovieResourceId != -1) { 
      mMovie = Movie.decodeStream(getResources().openRawResource( 
          mMovieResourceId)); 
    } 
  } 
   
  public void setMovieResource(int movieResId) { 
    this.mMovieResourceId = movieResId; 
    mMovie = Movie.decodeStream(getResources().openRawResource( 
        mMovieResourceId)); 
    requestLayout(); 
  } 
  public void setMovie(Movie movie) { 
    this.mMovie = movie; 
    requestLayout(); 
  } 
  public Movie getMovie() { 
    return mMovie; 
  } 
  public void setMovieTime(int time) { 
    mCurrentAnimationTime = time; 
    invalidate(); 
  } 
   
  public void setPaused(boolean paused) { 
    this.mPaused = paused; 
    if (!paused) { 
      mMovieStart = android.os.SystemClock.uptimeMillis() 
          - mCurrentAnimationTime; 
    } 
    invalidate(); 
  } 
   
  public boolean isPaused() { 
    return this.mPaused; 
  } 
  @Override 
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
    if (mMovie != null) { 
      int movieWidth = mMovie.width(); 
      int movieHeight = mMovie.height(); 
      int maximumWidth = MeasureSpec.getSize(widthMeasureSpec); 
      float scaleW = (float) movieWidth / (float) maximumWidth; 
      mScale = 1f / scaleW; 
      mMeasuredMovieWidth = maximumWidth; 
      mMeasuredMovieHeight = (int) (movieHeight * mScale); 
      setMeasuredDimension(mMeasuredMovieWidth, mMeasuredMovieHeight); 
    } else { 
      setMeasuredDimension(getSuggestedMinimumWidth(), 
          getSuggestedMinimumHeight()); 
    } 
  } 
  @Override 
  protected void onLayout(boolean changed, int l, int t, int r, int b) { 
    super.onLayout(changed, l, t, r, b); 
    mLeft = (getWidth() - mMeasuredMovieWidth) / 2f; 
    mTop = (getHeight() - mMeasuredMovieHeight) / 2f; 
    mVisible = getVisibility() == View.VISIBLE; 
  } 
  @Override 
  protected void onDraw(Canvas canvas) { 
    if (mMovie != null) { 
      if (!mPaused) { 
        updateAnimationTime(); 
        drawMovieFrame(canvas); 
        invalidateView(); 
      } else { 
        drawMovieFrame(canvas); 
      } 
    } 
  } 
  @SuppressLint("NewApi") 
  private void invalidateView() { 
    if (mVisible) { 
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) { 
        postInvalidateOnAnimation(); 
      } else { 
        invalidate(); 
      } 
    } 
  } 
  private void updateAnimationTime() { 
    long now = android.os.SystemClock.uptimeMillis(); 
    // 如果第一帧，记录起始时间 
    if (mMovieStart == 0) { 
      mMovieStart = now; 
    } 
    // 取出动画的时长 
    int dur = mMovie.duration(); 
    if (dur == 0) { 
      dur = DEFAULT_MOVIE_DURATION; 
    } 
    // 算出需要显示第几帧 
    mCurrentAnimationTime = (int) ((now - mMovieStart) % dur); 
  } 
  private void drawMovieFrame(Canvas canvas) { 
    // 设置要显示的帧，绘制即可 
    mMovie.setTime(mCurrentAnimationTime); 
    canvas.save(Canvas.MATRIX_SAVE_FLAG); 
    canvas.scale(mScale, mScale); 
    mMovie.draw(canvas, mLeft / mScale, mTop / mScale); 
    canvas.restore(); 
  } 
  @SuppressLint("NewApi") 
  @Override 
  public void onScreenStateChanged(int screenState) { 
    super.onScreenStateChanged(screenState); 
    mVisible = screenState == SCREEN_STATE_ON; 
    invalidateView(); 
  } 
  @SuppressLint("NewApi") 
  @Override 
  protected void onVisibilityChanged(View changedView, int visibility) { 
    super.onVisibilityChanged(changedView, visibility); 
    mVisible = visibility == View.VISIBLE; 
    invalidateView(); 
  } 
  @Override 
  protected void onWindowVisibilityChanged(int visibility) { 
    super.onWindowVisibilityChanged(visibility); 
    mVisible = visibility == View.VISIBLE; 
    invalidateView(); 
  } 
}

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，是很容易实现GIF动起来的效果。

其次，在xml布局文件中，把这个view定义进去，代码如下：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="Http://schemas.android.com/apk/res/android" 
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent" 
  android:orientation="vertical" > 
  <net.loonggg.gif.view.GifView 
    android:id="@+id/gif1" 
    android:layout_width="100dp" 
    android:layout_height="100dp" 
    android:layout_gravity="center_horizontal" 
    android:enabled="false" /> 
  <net.loonggg.gif.view.GifView 
    android:id="@+id/gif2" 
    android:layout_width="200dp" 
    android:layout_height="200dp" 
    android:layout_gravity="center_horizontal" 
    android:enabled="false" /> 
</LinearLayout>

最后，在MainActivity中的使用，代码如下：

package net.loonggg.gif; 
import net.loonggg.gif.view.GifView; 
import android.app.Activity; 
import android.os.Bundle; 
public class Gif extends Activity { 
  private GifView gif1, gif2; 
  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    gif1 = (GifView) findViewById(R.id.gif1); 
    // 设置背景gif图片资源 
    gif1.setMovieResource(R.raw.kitty); 
    gif2 = (GifView) findViewById(R.id.gif2); 
    gif2.setMovieResource(R.raw.b); 
    // 设置暂停 
    // gif2.setPaused(true); 
  } 
}

注意：与ImageView和其他View唯一的区别在于我加了一个gif属性。

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
  <declare-styleable name="GifView"> 
    <attr name="gif" fORMat="reference" /> 
    <attr name="paused" format="boolean" /> 
  </declare-styleable> 
  <declare-styleable name="CustomTheme"> 
    <attr name="gifViewStyle" format="reference" /> 
  </declare-styleable> 
</resources>

这个代码已经非常好了，使用也非常方便，其实不懂代码是什么意思也可以很好的用，只需要懂得我写注释的那几行和Activity里面的那几行代码就可以了！

希望本文所述对大家Android程序设计有所帮助。

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