• 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。

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  • 原文地址:https://www.cnblogs.com/wanghang/p/6299605.html
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