Android的简单图形和view刷新

最新推荐文章于 2023-04-01 19:13:34 发布

原创最新推荐文章于 2023-04-01 19:13:34 发布 · 1.1k 阅读

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文章标签：

#android #图形 #constructor #float #import #class

本文介绍了一个简单的自定义View绘制实例，通过Android提供的Canvas API实现了矩形、椭圆、圆及线条等基本图形的绘制，并展示了如何在独立线程中不断刷新View以实现动态效果。

创建View:

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.view.View;

public class MyView extends View{

private Paint paint;

public MyView(Context context) {
  super(context);
  // TODO Auto-generated constructor stub

  paint = new Paint();
  //设置画笔无锯齿(如果不设置可以看到效果很差)
  paint.setAntiAlias(true);
  //设置背景常亮
  this.setKeepScreenOn(true);
  //设置画笔颜色
  paint.setColor(Color.RED);
}

@Override
protected void onDraw(Canvas canvas) {
  // TODO Auto-generated method stub
  super.onDraw(canvas);

  //设置刷屏颜色
  canvas.drawColor(Color.WHITE);
  //这里前两个参数意思是矩形左上角坐标
  //后两个参数意思是矩形右下角坐标
  Rect rect = new Rect(30,30,50,50);
  //绘制矩形
  canvas.drawRect(rect, paint);
  //RectF 只是矩形 float形式只是跟Rect精确度不一样
  RectF rectF = new RectF(70f,30f,90f,90f);
  //绘制椭圆
        canvas.drawArc(rectF, 0, 360, true, paint);
        //绘制圆，第三个参数为半径
        canvas.drawCircle(150, 30, 20, paint);
        float[] points =new float[]{200f,10f,200f,40f,300f,30f,400f,70f};
        canvas.drawLines(points, paint);
      //选取特定点数组中两点来画出一条直线
//      canvas.drawLines(points, 1, 4, paint);
        canvas.drawText("Hello world", 230, 30, paint);
}
}

使用view：

import android.app.Activity;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import com.main.MyView;

public class SimpleGraph extends Activity {

private boolean iIsStart = true;
private MyView myView;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        myView = new MyView(this);

        setContentView(myView);

        //刷新View
        new Thread(new Runnable() {

   @Override
   public void run() {
    // TODO Auto-generated method stub
    while(iIsStart)
    {
     try {
      Thread.sleep(1000);
     } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();

      System.out.println(e.toString());
     }

     //使用postInvalidate可以直接在线程中更新界面