Android异步任务框架动画

Question

首先，我尝试了很多在Android中制作流畅动画的方法，而我最好的选择可能就是使用AnimationDrawable.。一切都很完美，直到我走出了旧设备上的异常记忆。原因很明显是帧数，在我的例子中是75帧。这就是我如何使用Thread.sleep()、、AsyncTask、和来动画帧的方法。为了避免动画滞后，我使用了Stack，在其中我预加载了前10帧，然后弹出使用过的帧，然后推送一个新的，直到没有更多的帧。一切都比我预期的要好，但唯一的问题是，在动画结束时，最后一帧消失了，我一整天都在敲击我的头，以理解为什么会发生这种情况，但显然没有成功。下面是我调用动画的活动和动画代码所在的文件中的代码。

SplashActivity.java

private void startAnimation() {
        gifImageView = (LogoAnimImageView) findViewById(R.id.gifImageView);
        gifImageView.setSplashActivityContext(this);
        gifImageView.setBackgroundResource(R.drawable.logo_frame_0);
        gifImageView.setAnimImageViewListener(new LogoAnimImageView.LogoAnimImageViewInterface() {
            @Override
            public void animationEnd() {
                mAnimationFinished = true;
                LoadNextActivity();

            }
        });
        gifImageView.startLogoAnimation();

    }

LogoAnimImageView.java

public class LogoAnimImageView extends ImageView {

    public interface LogoAnimImageViewInterface {
        void animationEnd();
    }

    final Handler mHandler = new Handler();

    private Stack<Drawable> mImageStack;

    private SplashActivity mSplashActivity;

    private LogoAnimImageViewInterface mListener;

    private int mFrameIndex;

    private int[] mResources = {R.drawable.logo_frame_0,R.drawable.logo_frame_1,R.drawable.logo_frame_2,R.drawable.logo_frame_3,
            R.drawable.logo_frame_4,R.drawable.logo_frame_5,R.drawable.logo_frame_6,
            R.drawable.logo_frame_7,R.drawable.logo_frame_8,R.drawable.logo_frame_9,R.drawable.logo_frame_10,
            R.drawable.logo_frame_11,R.drawable.logo_frame_12,R.drawable.logo_frame_13,R.drawable.logo_frame_14,
            R.drawable.logo_frame_15,R.drawable.logo_frame_16,R.drawable.logo_frame_17,R.drawable.logo_frame_18,
            R.drawable.logo_frame_19,R.drawable.logo_frame_20,R.drawable.logo_frame_21,R.drawable.logo_frame_22,
            R.drawable.logo_frame_23,R.drawable.logo_frame_24,R.drawable.logo_frame_25,R.drawable.logo_frame_26,
            R.drawable.logo_frame_27,R.drawable.logo_frame_28,R.drawable.logo_frame_29,R.drawable.logo_frame_30,
            R.drawable.logo_frame_31,R.drawable.logo_frame_32,R.drawable.logo_frame_33,R.drawable.logo_frame_34,
            R.drawable.logo_frame_35,R.drawable.logo_frame_36,R.drawable.logo_frame_37,R.drawable.logo_frame_38,
            R.drawable.logo_frame_39,R.drawable.logo_frame_40,R.drawable.logo_frame_41,R.drawable.logo_frame_42,
            R.drawable.logo_frame_43,R.drawable.logo_frame_44,R.drawable.logo_frame_45,R.drawable.logo_frame_46,
            R.drawable.logo_frame_47,R.drawable.logo_frame_48,R.drawable.logo_frame_49,R.drawable.logo_frame_50,
            R.drawable.logo_frame_51,R.drawable.logo_frame_52,R.drawable.logo_frame_53,R.drawable.logo_frame_54,
            R.drawable.logo_frame_55,R.drawable.logo_frame_56,R.drawable.logo_frame_57,R.drawable.logo_frame_58,
            R.drawable.logo_frame_59,R.drawable.logo_frame_60,R.drawable.logo_frame_61,R.drawable.logo_frame_62,
            R.drawable.logo_frame_63,R.drawable.logo_frame_64,R.drawable.logo_frame_65,R.drawable.logo_frame_66,
            R.drawable.logo_frame_67,R.drawable.logo_frame_68,R.drawable.logo_frame_69,R.drawable.logo_frame_70,
            R.drawable.logo_frame_71,R.drawable.logo_frame_72,R.drawable.logo_frame_73,R.drawable.logo_frame_74

    };

    public LogoAnimImageView(Context context) {
        super(context);
    }

    public LogoAnimImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public LogoAnimImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public void startLogoAnimation() {

        mFrameIndex = 10;
        mImageStack = new Stack<Drawable>();
        for (int i=1;i<=mFrameIndex;i++) {
            Drawable drawable = getDrawable(mResources[i]);
            mImageStack.push(drawable);
        }
        mFrameIndex++;
        mSplashActivity.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                new LogoAnimOperation().execute((Object)null);
            }
        });



    }

    public void setSplashActivityContext(SplashActivity splashActivity) {
        this.mSplashActivity = splashActivity;
    }

    public void setAnimImageViewListener(LogoAnimImageViewInterface listener) {
        this.mListener = listener;
    }

    private Drawable getDrawable(int id) {
        Drawable drawable;
        if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP){
            drawable = mSplashActivity.getDrawable(id);
        } else {
            drawable = mSplashActivity.getResources().getDrawable(id);
        }
        return drawable;
    }

    private class LogoAnimOperation extends AsyncTask<Object,Void,String> {

        @Override
        protected String doInBackground(Object... params) {
            int number=1;
            while (mImageStack.size() > 1) {
                try {
                    Thread.sleep(40);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                final Drawable drawable = mImageStack.pop();
                mSplashActivity.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {

                        if(android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                            LogoAnimImageView.this.setBackground(drawable);
                        }
                        else {
                            LogoAnimImageView.this.setBackgroundDrawable(drawable);
                        }
                        if (mFrameIndex < mResources.length) {
                            Drawable newDrawable = getDrawable(mResources[mFrameIndex]);
                            mImageStack.push(newDrawable);
                            mFrameIndex++;
                        }

                    }
                });

            }

            return "";
        }

        @Override
        protected void onPostExecute(String s) {
            mSplashActivity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Drawable drawable = getDrawable(R.drawable.logo_frame_74);
                    if(android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                        LogoAnimImageView.this.setBackground(drawable);
                    }
                    else {
                        LogoAnimImageView.this.setBackgroundDrawable(drawable);
                    }
                }
            });
            mListener.animationEnd();
            super.onPostExecute(s);
        }
    }

}

Answer 1

...but，唯一的问题是，在动画结束时，最后一帧消失了，我一整天都在敲我的头，以理解为什么会发生这种情况，而且显然没有成功。

问题可能在于你的AsyncTask's onPostExecute(String)

@Override
protected void onPostExecute(String s) {
    mSplashActivity.runOnUiThread(new Runnable() {
        @Override
        public void run() {
            Drawable drawable = getDrawable(R.drawable.logo_frame_74);
            if(android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                LogoAnimImageView.this.setBackground(drawable);
            } else {
                LogoAnimImageView.this.setBackgroundDrawable(drawable);
            }
        }
    });
    mListener.animationEnd();
    super.onPostExecute(s);
}

1. onPostExecute(String)将始终在UI线程上被调用。因此，mSplashActivity.runOnUiThread(....)是多余的。
2. 通过使用runOnUiThread(Runnable)，您将发送到UI线程的事件队列。所以，当轮到它时，运行程序就会被执行。但是，mSplashActivity.runOnUiThread(....)调用后的代码可能会在可运行之前执行。因此，在您的mListener.animationEnd()有机会显示R.drawable.logo_frame_74之前，可能会调用R.drawable.logo_frame_74。

但是，这不应该发生在你的情况下。如果从UI线程(它是这样的)调用runOnUiThread(Runnable)，则不会将Runnable提交到事件队列，而是立即执行。

我怀疑这里真正的问题是动画(R.drawable.logo_frame_74)的最后一帧和下一个活动的启动之间没有任何延迟。也许您可以注释掉对mListener.animationEnd()的调用，以检查动画是在最后一帧还是第二帧结束。

虽然这是一种有趣的方法，也是我以前从未见过的一种方法，但我不得不说，您处理的线程太多了。如果您试图在需要时加载Drawables，有一种更简单的方法：

public class LogoAnimImageView extends ImageView {

    ....
    ....

    // flag to indicate whether `mNextFrameDrawable` should continue loading the next frame
    private boolean mStopAnimating;

    // loads the next frame, and calls back to activity when done
    private Runnable mNextFrameRunnable = new Runnable() {
        @Override
        public void run() {
            if (!mStopAnimating) {
                if (isFinishedAnimating() && mListener != null) {
                    mListener.animationEnd();
                } else { // Load next frame
                    setViewBg(getNextFrameDrawable());
                    // Will load the next frame in 40 ms
                    postDelayed(this, 40L);
                }
            }
        }
    };    

    // This method can be set `public static` and placed in a separate `Utils` class
    private void setViewBg(Drawable d) {
        if(android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            setBackground(drawable);
        } else {
            setBackgroundDrawable(drawable);
        }
    }   

    private Boolean isFinishedAnimating() {
        return mFrameIndex >= mResources.length; 
    } 

    // returns the next frame's drawable and increments the `mFrameIndex` pointer
    private Drawable getNextFrameDrawable() {
        return getDrawable(mResources[mFrameIndex++]);
    }

    // start animating
    public void startLogoAnimation() {
        mFrameIndex = 0;
        mStopAnimating = false;
        post(mNextFrameRunnable);
    }

    // stop animating
    public void stopLogoAnimation() {
        mStopAnimating = true;
        removeCallbacks(mNextFrameRunnable);
    }

    ....
    ....
}

AsyncTask既不需要，也不适合处理这样的场景。