android画等边三角形

运行截图如下图所示

1.画三角形类

import ;
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public class Triangle extends View {
 private int mStartX;
 private int mStartY;
 private Path mPath;
 private Paint mPaint;
 private float point_x_3;
 private float point_y_3;
 private float point_x_2;
 private float point_y_2;
 int VIEW_WIDTH = 1280;
 int VIEW_HEIGHT = 750;
 // 定义一个内存中的图片，该图片将作为缓冲区
 Bitmap cacheBitmap ;
 // 定义cacheBitmap上的Canvas对象
 Canvas cacheCanvas = null;

 public Triangle(Context context, AttributeSet attrs) {
  super(context, attrs);
  
  mPath = new Path();
  mPaint = new Paint();
  
  cacheBitmap = (VIEW_WIDTH, VIEW_HEIGHT,
    Config.ARGB_8888);
  cacheCanvas = new Canvas();
  
  //设置画笔的颜色
  ();
  //设置背景色
  ();
  
  // 设置cacheCanvas将会绘制到内存中的cacheBitmap上
  (cacheBitmap, VIEW_WIDTH, VIEW_HEIGHT, null);
  (10);
  (true);
  // 设置Paint的样式
  ();
  // 设置结合处为圆弧
  ();
  // 设置画笔样式为圆弧
  ();
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {

  switch (()) {
  case MotionEvent.ACTION_DOWN:
   mStartX = (int) ();
   mStartY = (int) ();
   break;
  case MotionEvent.ACTION_MOVE:
   float x = ();
   float y = ();
   float deltaX = x - mStartX;
   float deltaY = y - mStartY;
   float frac = (float) (3) / 2;
   point_x_2 = x;
   point_y_2 = y;
   point_x_3 = mStartX + (float) ((1 - (frac, 2)) * deltaX - frac * deltaY);
   point_y_3 = mStartY + (float) ((1 - (frac, 2)) * deltaY + frac * deltaX);
   break;
  case MotionEvent.ACTION_UP:
   (); 
   (mStartX, mStartY);
   (point_x_2, point_y_2);
   (point_x_3, point_y_3);
   ();
   
   break;
  default:
   break;
  }
  invalidate();
  return true;
 }

 @Override
 protected void onDraw(Canvas canvas) {
  (mPath, mPaint);
 }
}

 

类

import ;
import ;
import ;

public class MainActivity extends Activity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  (savedInstanceState);
  setContentView(.activity_main);
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(, menu);
  return true;
 }

}

3.布局文件

<RelativeLayout xmlns:androaa">/apk/res/android"
    xmlns:tools="/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >
 
    <
        android:layout_height="fill_parent"
        android:layout_width="fill_parent"
        android:width="1280dp"
  android:height="1280dp"
        />
</RelativeLayout>