Android简易实战教程--第二十四话《画画板》

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。