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package com.android.mail.utils;
import android.os.Handler;
import android.view.View;
import android.view.ViewTreeObserver;
/**
* Given a View to monitor draws on, an instance of this class will notify a listener of state
* changes between {@link #STATE_ACTIVE} and {@link #STATE_IDLE}.
* <p>
* Any drawing will instantly trigger {@link #STATE_ACTIVE}. {@link #STATE_IDLE} is only
* subsequently triggered if {@link #IDLE_WINDOW_MS} continuous milliseconds elapse with zero draws.
*/
public class DrawIdler {
public static final int STATE_IDLE = 0;
public static final int STATE_ACTIVE = 1;
private static final int IDLE_WINDOW_MS = 100;
private int mState = STATE_IDLE;
private View mRoot;
private IdleListener mListener;
private final IdleReader mIdleReader = new IdleReader();
private final Handler mHandler = new Handler();
public interface IdleListener {
void onStateChanged(DrawIdler idler, int newState);
}
public void setListener(IdleListener listener) {
mListener = listener;
if (mListener != null) {
mListener.onStateChanged(this, mState);
}
}
public void setRootView(View rootView) {
if (mRoot == rootView) {
return;
} else if (mRoot != null) {
mRoot.getViewTreeObserver().removeOnPreDrawListener(mIdleReader);
}
mRoot = rootView;
if (mRoot != null) {
mRoot.getViewTreeObserver().addOnPreDrawListener(mIdleReader);
}
}
public int getCurrentState() {
return mState;
}
private void setState(int newState) {
if (mState == newState) {
return;
}
mState = newState;
if (mListener != null) {
mListener.onStateChanged(this, newState);
}
}
// this inner class keeps implementation details private
// (we use OnPreDrawListener instead of OnDrawListener because the latter is only JB+)
private class IdleReader implements Runnable, ViewTreeObserver.OnPreDrawListener {
@Override
public void run() {
setState(STATE_IDLE);
}
@Override
public boolean onPreDraw() {
setState(STATE_ACTIVE);
mHandler.removeCallbacks(this);
mHandler.postDelayed(this, IDLE_WINDOW_MS);
return true; // always allow the draw; we're only here to observe
}
}
}
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