显示刀锋的View

package com.wbhuang.myninjia;

import java.util.ArrayList;

import java.util.List;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.util.DisplayMetrics;

import android.view.MotionEvent;

import android.view.View;

import android.view.WindowManager;

/**

* @author wbhuang

* 20130821

*/

public class ShadeView extends View {

static final int MAX_POINTS_NUM = 10;

static final float CENTER_RATIO = 0.5f;

static final float SHAPE_RATIO = 0.02f;

//点类

static class Vertex {

public float x;

public float y;

public Vertex() {}

public Vertex(float x, float y) {

this.x = x;

this.y = y;

}

}

List leftVertexs = new ArrayList(MAX_POINTS_NUM);//刀锋上边线点集

List rightVertexs = new ArrayList(MAX_POINTS_NUM);//刀锋下边线点集

List sampleVertexs = new ArrayList(MAX_POINTS_NUM);//刀锋路径的点集

float shape_width = 10;

private Paint paint;

private static final int gestureColor = Color.rgb(153, 153, 153);

private static final int alpha = 220;

private static final int alpha_full = 255;

private static long last_time;

private static final int MIN_TIME_INTERVAL = 10;

public ShadeView(Context context) {

super(context);

paint = new Paint();

paint.setStyle(Paint.Style.FILL);

DisplayMetrics metric = new DisplayMetrics();

((WindowManager)context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getMetrics(metric);

int width = metric.widthPixels;

shape_width = width * SHAPE_RATIO;//刀锋长度

}

//计算路径上面和下面的点集

private void calcVertexs() {

int len = sampleVertexs.size();

leftVertexs.clear();

rightVertexs.clear();

for (int i = 1; i < len; i++) {

Vertex cur = sampleVertexs.get(i);

Vertex pre = sampleVertexs.get(i-1);

Vertex center = new Vertex();

center.x = cur.x - (cur.x - pre.x) * CENTER_RATIO;

center.y = cur.y - (cur.y - pre.y) * CENTER_RATIO;

float w = cur.x - pre.x;

float h = cur.y - pre.y;

double angle = Math.atan(h/w);

Vertex leftVertex = new Vertex();

Vertex rightVertex = new Vertex();

float centerShapeWidth = shape_width * i / len;

if (i == (len - 2))

centerShapeWidth = shape_width;

if (cur.x > pre.x) {

leftVertex.x = (float) (center.x + Math.sin(angle) * centerShapeWidth);

leftVertex.y = (float) (center.y - Math.cos(angle) * centerShapeWidth);

rightVertex.x = (float) (center.x - Math.sin(angle) * centerShapeWidth);

rightVertex.y = (float) (center.y + Math.cos(angle) * centerShapeWidth);

} else {

rightVertex.x = (float) (center.x + Math.sin(angle) * centerShapeWidth);

rightVertex.y = (float) (center.y - Math.cos(angle) * centerShapeWidth);

leftVertex.x = (float) (center.x - Math.sin(angle) * centerShapeWidth);

leftVertex.y = (float) (center.y + Math.cos(angle) * centerShapeWidth);

}

leftVertexs.add(leftVertex);

rightVertexs.add(rightVertex);

}

}

@Override

public void onDraw(Canvas canvas) {

Path path = new Path();

if (sampleVertexs.size() > 1) {

calcVertexs();

Vertex begin = sampleVertexs.get(0);

Vertex end = sampleVertexs.get(sampleVertexs.size()-1);

path.moveTo(begin.x, begin.y);

for (int i= 0; i < leftVertexs.size(); i++) {

Vertex vertex = leftVertexs.get(i);

path.lineTo(vertex.x, vertex.y);

}

path.lineTo(end.x, end.y);

for (int i = rightVertexs.size() - 1; i > 0; i--) {

Vertex vertex = rightVertexs.get(i);

path.lineTo(vertex.x, vertex.y);

}

paint.setColor(Color.WHITE);

paint.setAlpha(alpha_full);

canvas.drawPath(path, paint);

}

super.onDraw(canvas);

}

@Override

public boolean onTouchEvent(android.view.MotionEvent event) {

if(event.getPointerCount() == 1){

int action = event.getAction();

if (MotionEvent.ACTION_DOWN == action) {

leftVertexs.clear();

rightVertexs.clear();

sampleVertexs.clear();

} else if (MotionEvent.ACTION_MOVE == action) {

//if (event.getEventTime() - last_time > MIN_TIME_INTERVAL) {

last_time = event.getEventTime();

if (sampleVertexs.size() > MAX_POINTS_NUM) {

sampleVertexs.remove(0);

}

Vertex vertex = new Vertex(event.getX(), event.getY());

sampleVertexs.add(vertex);

//}

} else if (MotionEvent.ACTION_UP == action) {

leftVertexs.clear();

rightVertexs.clear();

sampleVertexs.clear();

}

this.invalidate();

}

return true;

}

}

package com.wbhuang.myninjia;

import android.app.Activity;

import android.os.Bundle;

public class NinjiaActivity extends Activity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(new ShadeView(this));

}

}