Android----EdgeEffect类边缘效果的实现

package sample.edward.com.normalsample.edge;

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Build;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.EdgeEffect;

/**
* Created by edward.ma on 2016/5/12.
*/
public class EdgeView extends View {
private EdgeEffect mRightEffect;
private int mTouchSlop;
private int mLastMotionX, mLastMotionY;
private boolean mIsShownEdge = false;

public EdgeView(Context context) {
super(context);
init(context);
}

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

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private void init(Context context) {
mRightEffect = new EdgeEffect(context);
mRightEffect.setColor(Color.RED);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getActionMasked();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastMotionX = (int) event.getX();
mLastMotionY = (int) event.getY();
mIsShownEdge = false;
break;
case MotionEvent.ACTION_MOVE:
int x = (int) event.getX();
int y = (int) event.getY();
int deltax = x - mLastMotionX;
int deltay = y - mLastMotionY;
if (!mIsShownEdge) {
if (Math.abs(deltax) > mTouchSlop && deltax < 0 && Math.abs(deltax) > Math.abs(deltay)) {
mIsShownEdge = true;
mLastMotionX = x;
mLastMotionY = y;
}
}
if (mIsShownEdge) {
if (deltax < 0) {
// 这个方法确定每次拉伸边缘需要更新的参数
// 第一个参数：每次拉伸增加的距离（0——1）叠加的 ex：第一次传入0.1， 第二次传入0.2的话，总距离就会叠加0.1+0.2 = 0.3
// 第二个参数：边缘圆的位置，上下拉动时边缘鼓起的最大位置的坐标就是这个参数决定的，默认是0.5
mRightEffect.onPull((float) Math.abs(deltax) / getMeasuredWidth());
//mRightEffect.onPull((float)Math.abs(deltax) / getMeasuredWidth(), 0.2f);
//更新后刷新view
postInvalidateOnAnimation();
}
}
break;
case MotionEvent.ACTION_UP:
mIsShownEdge = false;
mRightEffect.onRelease();
postInvalidateOnAnimation();
break;
default:
break;
}
return true;
}

@Override
public void draw(Canvas canvas) {
super.draw(canvas);
// 默认边缘是画在最上面，在画图时需要对画布进行平移和旋转
// 具体可参照listview的上下边缘和viewpager的左右边缘的实现方法。
// 这里实现的是右边缘
if (!mRightEffect.isFinished()) {
int count = canvas.save();
canvas.rotate(90);
canvas.translate(0, -getMeasuredWidth());
mRightEffect.setSize(getMeasuredHeight(), getMeasuredWidth());
if (mRightEffect.draw(canvas)) {
postInvalidateOnAnimation();
}
canvas.restoreToCount(count);
} else {
mRightEffect.finish();
}
}
}