Android 播放 Gif 图片控件

接到个需求要播放一个带 Gif 图片的动画，ios 本身就对 Gif 是支持的，android 需要自己实现，因此需要自己自定义一个控件，废话不多，现在贴上代码如下：

/**
 * 播放 Gif View
 * Created by William on 2017/7/4.
 */

public class UMGifImageView extends View {

    private static final int DEFAULT_VIEW_DURATION = 1000;

    private int mMovieResourceId;
    private Movie mMovie;

    private long mMovieStart;
    private int mCurrentAnimationTime = 0;

    /**
     * Position for drawing animation frames in the center of the view.
     */
    private float mLeft;
    private float mTop;

    /**
     * Scaling factor to fit the animation within view bounds.
     */
    private float mScale;

    /**
     * Scaled movie frames width and height.
     */
    private int mMeasuredMovieWidth;
    private int mMeasuredMovieHeight;

    private volatile boolean mPaused = false;
    private boolean mVisible = true;

    public UMGifImageView(Context context) {
        this(context, null);
    }

    public UMGifImageView(Context context, AttributeSet attrs) {
        this(context, attrs, R.styleable.CustomTheme_GifViewStyle);
    }

    public UMGifImageView(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) {

        /**
         * Starting from HONEYCOMB have to turn off HW acceleration to draw
         * Movie on Canvas.
         */
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        }

        final TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.GifImageView, defStyle,
                R.style.Widget_GifMoviewView);

        mMovieResourceId = array.getResourceId(R.styleable.GifImageView_gif, -1);
        mPaused = array.getBoolean(R.styleable.GifImageView_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;

        /**
         * Calculate new movie start time, so that it resumes from the same
         * frame.
         */
        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();

            /*
             * Calculate horizontal scaling
             */
            float scaleH = 1f;
            int measureModeWidth = MeasureSpec.getMode(widthMeasureSpec);

            if (measureModeWidth != MeasureSpec.UNSPECIFIED) {
                int maximumWidth = MeasureSpec.getSize(widthMeasureSpec);
                if (movieWidth > maximumWidth) {
                    scaleH = (float) movieWidth / (float) maximumWidth;
                }
            }

            /*
             * calculate vertical scaling
             */
            float scaleW = 1f;
            int measureModeHeight = MeasureSpec.getMode(heightMeasureSpec);

            if (measureModeHeight != MeasureSpec.UNSPECIFIED) {
                int maximumHeight = MeasureSpec.getSize(heightMeasureSpec);
                if (movieHeight > maximumHeight) {
                    scaleW = (float) movieHeight / (float) maximumHeight;
                }
            }

            /*
             * calculate overall scale
             */
            mScale = 1f / Math.max(scaleH, scaleW);

            mMeasuredMovieWidth = (int) (movieWidth * mScale);
            mMeasuredMovieHeight = (int) (movieHeight * mScale);

            setMeasuredDimension(mMeasuredMovieWidth, mMeasuredMovieHeight);

        } else {
            /*
             * No movie set, just set minimum available size.
             */
            setMeasuredDimension(getSuggestedMinimumWidth(), getSuggestedMinimumHeight());
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);

        /*
         * Calculate left / top for drawing in center
         */
        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);
            }
        }
    }

    /**
     * Invalidates view only if it is visible.
     * 

     * {@link #postInvalidateOnAnimation()} is used for Jelly Bean and higher.
     */
    @SuppressLint("NewApi")
    private void invalidateView() {
        if (mVisible) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                postInvalidateOnAnimation();
            } else {
                invalidate();
            }
        }
    }

    /**
     * Calculate current animation time
     */
    private void updateAnimationTime() {
        long now = android.os.SystemClock.uptimeMillis();

        if (mMovieStart == 0) {
            mMovieStart = now;
        }

        int dur = mMovie.duration();

        if (dur == 0) {
            dur = DEFAULT_VIEW_DURATION;
        }

        mCurrentAnimationTime = (int) ((now - mMovieStart) % dur);
    }

    /**
     * Draw current GIF frame
     */
    private void drawMovieFrame(Canvas canvas) {

        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();
    }

}

然后还要在 attrs.xml 文件中自定义属性：

最后，就可以在自己的布局文件中直接使用了：

其中 custom:gif 是直接引用 gif 图片，把 gif 图片放在 drawable 文件夹中即可。