继承android.view.View自定义view，使用画笔绘制view示例

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/testcontainer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

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

<com.gifor.CustomView
android:id="@+id/customView1"
android:layout_width="100dp"
android:layout_height="100dp" />

</LinearLayout>

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);
LinearLayout ll = (LinearLayout)this.findViewById(R.id.testcontainer);//xml布局方式加载自定义view
ll.addView(new CustomView(this));//代码方式加载自定义view
}

}

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

public class CustomView extends View {
Paint linePaint;

public CustomView(Context context) {
super(context);
/*
*初始化画笔
*/
linePaint = new Paint();
linePaint.setColor(Color.BLUE);//设置画笔颜色
linePaint.setAntiAlias(true);//设置画笔是否抗锯齿
linePaint.setStrokeWidth(10);//设置画笔粗细
}

public CustomView(Context context, AttributeSet attr) {//使用xml布局绘制自定义view必须有此构造方法
super(context, attr);
/*
*初始化画笔
*/
linePaint = new Paint();
linePaint.setColor(Color.BLACK);//设置画笔颜色
linePaint.setAntiAlias(true);//设置画笔是否抗锯齿
linePaint.setStrokeWidth(10);//设置画笔粗细
}

@Override
protected void onDraw(Canvas canvas) {
canvas.drawLine(0, 0, this.getWidth(), this.getHeight(), linePaint);//从view左上角到view右下角画线
canvas.drawLine(this.getWidth(), 0, 0, this.getHeight(), linePaint);//从view右上角到view左下角画线
super.onDraw(canvas);
}
}