今天完成一个画画板。

首先来个布局：

<RelativeLayout 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: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" >

    <ImageView

        android:id="@+id/iv"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world"

        />

	<LinearLayout

	    android:layout_width="match_parent"

	    android:layout_height="wrap_content"

	    android:orientation="horizontal"

	    android:layout_alignParentBottom="true"

	    >

	    <Button

	        android:layout_width="wrap_content"

	        android:layout_height="wrap_content"

	        android:text="红色"

	        android:onClick="red"

	        />

	    <Button

	        android:layout_width="wrap_content"

	        android:layout_height="wrap_content"

	        android:text="绿色"

	        android:onClick="green"

	        />

	    <Button

	        android:layout_width="wrap_content"

	        android:layout_height="wrap_content"

	        android:text="刷子"

	        android:onClick="brush"

	        />

	    <Button

	        android:layout_width="wrap_content"

	        android:layout_height="wrap_content"

	        android:text="保存"

	        android:onClick="save"

	        />

	</LinearLayout>

</RelativeLayout>

可见，要分红绿色，而且还要保存最后画的图片。

看一下主活动代码：

package com.itydl.paintban;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import android.net.Uri;

import android.os.Bundle;

import android.os.Environment;

import android.app.Activity;

import android.content.Intent;

import android.graphics.Bitmap;

import android.graphics.Bitmap.CompressFormat;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Matrix;

import android.graphics.Paint;

import android.view.Menu;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ImageView;

public class MainActivity extends Activity {

	private ImageView iv;

	int startX;

	int startY;

	private Canvas canvas;

	private Paint paint;

	private Bitmap bmCopy;

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		//加载画画板的背景图

		Bitmap bmSrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);

		bmCopy = Bitmap.createBitmap(bmSrc.getWidth(), bmSrc.getHeight(), bmSrc.getConfig());

		paint = new Paint();

		canvas = new Canvas(bmCopy);

		//绘制

		canvas.drawBitmap(bmSrc, new Matrix(), paint);

		iv = (ImageView) findViewById(R.id.iv);

		iv.setImageBitmap(bmCopy);

		//设置触摸侦听

		iv.setOnTouchListener(new OnTouchListener() {

			//触摸屏幕时，触摸事件产生时，此方法调用

			@Override

			public boolean onTouch(View v, MotionEvent event) {

				int action = event.getAction();

				switch (action) {

				//用户手指摸到屏幕

				case MotionEvent.ACTION_DOWN:

					startX = (int) event.getX();

					startY = (int) event.getY();

					break;

				//用户手指正在滑动

				case MotionEvent.ACTION_MOVE:

					int x = (int) event.getX();

					int y = (int) event.getY();

					canvas.drawLine(startX, startY, x, y, paint);

					//每次绘制完毕之后，本次绘制的结束坐标变成下一次绘制的初始坐标

					startX = x;

					startY = y;

					iv.setImageBitmap(bmCopy);

					break;

				//用户手指离开屏幕

				case MotionEvent.ACTION_UP:

					break;

				}

				//true：告诉系统，这个触摸事件由我来处理

				//false：告诉系统，这个触摸事件我不处理，这时系统会把触摸事件传递给imageview的父节点

				return true;

			}

		});

	}

	public void red(View v){

		paint.setColor(Color.RED);

	}

	public void green(View v){

		paint.setColor(Color.GREEN);

	}

	public void brush(View v){

		paint.setStrokeWidth(7);

	}

	public void save(View v){

		File file = new File("sdcard/dazuo.png");

		FileOutputStream fos = null;

		try {

			fos = new FileOutputStream(file);

		} catch (FileNotFoundException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		bmCopy.compress(CompressFormat.PNG, 100, fos);

		//发送sd卡就绪广播

		Intent intent = new Intent();

		intent.setAction(Intent.ACTION_MEDIA_MOUNTED);

		intent.setData(Uri.fromFile(Environment.getExternalStorageDirectory()));

		sendBroadcast(intent);

	}

}

运行看一下结果：

画了个绿帽子，哈哈。欢迎关注本博客点击打开链接  http://blog.csdn.net/qq_32059827，每天花上5分钟，阅读一篇有趣的安卓小文哦。