Android画板

Android画板：

本案例是一个简单的Android小应用，仅供大家学习

MyView.java

package com.example.drawboard;

import android.R.color;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;


public class MyView extends SurfaceView implements Callback,OnTouchListener{
	private Paint paint = new Paint();//创建一个画笔对象
	private Path path = new Path();//创建一个路径对象
	public MyView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		getHolder().addCallback(this);//添加回调函数
		paint.setColor(Color.RED);//设置画笔颜色
		paint.setTextSize(10);//设置画笔粗细
		paint.setAntiAlias(true);//清理锯齿
		paint.setStyle(Style.STROKE);//设置画笔为空心
		setOnTouchListener(this);//添加触摸监听事件
	}
	//定义绘画方法
	public void draw() {
		//添加画布并且锁定
		Canvas canvas = getHolder().lockCanvas();
		canvas.drawColor(Color.WHITE);//初始化画布的颜色为白色
		canvas.drawPath(path, paint);
		
		//清理画布
		getHolder().unlockCanvasAndPost(canvas);
		
		
		
	}
	//定义清除画布方法
	public void clear() {
		path.reset();//路径重置，清除画布
		draw();//如果不再次调用此方法，则清除画布之后，将不能再绘画
	}
	@Override
	public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void surfaceCreated(SurfaceHolder arg0) {
		// TODO Auto-generated method stub
		draw();
	}

	@Override
	public void surfaceDestroyed(SurfaceHolder arg0) {
		// TODO Auto-generated method stub
		
	}
	@Override
	public boolean onTouch(View arg0, MotionEvent event) {
		// TODO Auto-generated method stub
		//判断动作事件
		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN://按下事件
			path.moveTo(event.getX(), event.getY());//获取X和Y坐标
			draw();//开始绘制
			break;

		case MotionEvent.ACTION_MOVE://移动事件
			path.lineTo(event.getX(), event.getY());//获取移动时的x和y坐标
			draw();//开始绘制
			break;
		}
		return true;
	}

}

MainActivity.java

package com.example.drawboard;

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

public class MainActivity extends Activity {
	private Button btn;
	private MyView view;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		btn = (Button)findViewById(R.id.btn);
		view = (MyView)findViewById(R.id.draw);
		btn.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				view.clear();
			}
		});
	}

}

activity_main.xml

<pre name="code" class="java"><LinearLayout xmlns:android="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:orientation="vertical"
    tools:context=".MainActivity" >

    <com.example.drawboard.MyView
        android:id="@+id/draw"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />
    <Button
        android:id="@+id/btn"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="清理画布"/>

</LinearLayout>

运行之后如图：

点击清理画布可以清除所画内容