android简单图形示例

android.graphics.Canvas可用于在android中绘制图形。它提供了绘制椭圆，矩形，图片，文本，线条等的方法。

android.graphics.Paint类与画布一起使用以绘制对象。它包含颜色和样式的信息。

在此示例中，我们将在android中显示2D图形。

activity_main.xml

<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/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" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

活动类

package com.example.simplegraphics;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;

public class MainActivity extends Activity {

	DemoView demoview;
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		demoview = new DemoView(this);
		setContentView(demoview);
	}

	private class DemoView extends View{
		public DemoView(Context context){
			super(context);
		}

		@Override protected void onDraw(Canvas canvas) {
			super.onDraw(canvas);

			// custom drawing code here
			Paint paint = new Paint();
			paint.setStyle(Paint.Style.FILL);

			// make the entire canvas white
			paint.setColor(Color.WHITE);
			canvas.drawPaint(paint);
			
			// draw blue circle with anti aliasing turned off
			paint.setAntiAlias(false);
			paint.setColor(Color.BLUE);
			canvas.drawCircle(20, 20, 15, paint);

			// draw green circle with anti aliasing turned on
			paint.setAntiAlias(true);
			paint.setColor(Color.GREEN);
			canvas.drawCircle(60, 20, 15, paint);

			// draw red rectangle with anti aliasing turned off
			paint.setAntiAlias(false);
			paint.setColor(Color.RED);
			canvas.drawRect(100, 5, 200, 30, paint);
                         
			// draw the rotated text
			canvas.rotate(-45);
		            
			paint.setStyle(Paint.Style.FILL);
			canvas.drawText("Graphics Rotation", 40, 180, paint);
			
			//undo the rotate
			canvas.restore();
		}
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
}

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