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 {
  /**
   * 默认为1秒
   */
  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));
    }
  }
  /**
   * 设置gif图资源
   *
   * @param movieResId
   */
  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();
  }
  /**
   * 设置暂停
   *
   * @param paused
   */
  public void setPaused(boolean paused) {
    this.mPaused = paused;
    if (!paused) {
      mMovieStart = android.os.SystemClock.uptimeMillis()
          - mCurrentAnimationTime;
    }
    invalidate();
  }
  /**
   * 判断gif图是否停止了
   *
   * @return
   */
  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。