在Android中画线必须由一个载体，要么是一个控件，要么是一个布局，其实他们都是继承自View，通过自定义控件或布局的方式画线是最常见的。下面的小例子实现了在自定义RelativeLayout中画网格线

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自定义控件代码：

package layout.layout.ex;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.widget.RelativeLayout;

public class GridRelativeLayout extends RelativeLayout {
	private Canvas myCanvas;
	private int horGrid = 100, verGrid = 100;//水平网格和竖直网格
	private int screenW, screenH;//屏幕宽和高
	private boolean initOver = false;//初始化标签

	public GridRelativeLayout(Context context) {
		super(context);
		setWillNotDraw(false);
	}

	public GridRelativeLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
		setWillNotDraw(false);
	}

	public GridRelativeLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		setWillNotDraw(false);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		this.myCanvas = canvas;
		Paint paint = new Paint();
		paint.setColor(android.graphics.Color.YELLOW);//颜色
		paint.setStrokeWidth(3);//线宽
		int verNum = (int)(screenH / verGrid) + 1;
		int horNum = (int)(screenW / horGrid) + 1;
		if (initOver) {
			for (int i = 0; i < verNum; i++) {
				canvas.drawLine(0, i * verGrid - 1, screenW, i * verGrid - 1,
						paint);
			}
			for (int i = 0; i < horNum; i++) {
				canvas.drawLine(i * horGrid - 1, 0, i * horGrid - 1, screenH,
						paint);
			}
		}
	}

	/**设置网格线参数**/
	public void setInf(int vergrid, int horgrid, int screenW, int screenH) {
		this.verGrid = vergrid;
		this.horGrid = horgrid;
		this.screenW = screenW;
		this.screenH = screenH;
		initOver = true;
		postInvalidate();
	}
	
	/**擦除网格线**/
	public void clearLine()
	{
		initOver = false;
		postInvalidate();
	}
}

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package com.example.test005;

import layout.layout.ex.GridRelativeLayout;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
private GridRelativeLayout rl;
private Button btnDraw,btnClear;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		rl=(GridRelativeLayout)findViewById(R.id.rl);
		btnDraw=(Button)findViewById(R.id.button1);
		btnClear=(Button)findViewById(R.id.button2);
		btnDraw.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				rl.setInf(100, 100, 1280, 720);//画网格线
			}
		});
		btnClear.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				rl.clearLine();//擦除网格线
			}
		});
		
		
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

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