Android开发之简易画夹

    我的这个小画板功能有两个方面：改变画笔的颜色和改变画笔的粗细。至于如何实现改变画笔的颜色，我的设想是先通过几个小按钮来控制画笔的颜色，这样我们就可以知道如何在我们编写的画板组件内的线条颜色。之后再改变换画笔颜色的方式（采用拖动条等）。对于画笔的粗细，我是通过一个输入框加一个按钮来确定的。最终的效果如下图：


 


 

 

 
 
 

一、DrewView类；

    这个类是继承View类。其中开放了两个方法，changecolor()和changewidth()。这两个函数分别用于改变画笔的颜色和粗细。

package com.example.study;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

@SuppressLint("ClickableViewAccessibility")
public class Drawview extends View{
	private List<Point> pointall=new ArrayList<Point>();
	int color;
	float width;
	public Drawview(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		super.setBackgroundColor(Color.WHITE);  
        super.setOnTouchListener(new Touch());
        color=Color.BLACK;
	}
	public void changecolor(int color)//修改画笔的颜色
	{
		this.color=color;
	}
	public void changewidth(float width)//修改画笔的粗细
	{
		this.width=width;
	}
	private class Touch implements OnTouchListener{  
		  
        @Override  
        public boolean onTouch(View v, MotionEvent e) {  
            // TODO Auto-generated method stub  
            Point p=new Point((int)e.getX(),(int)e.getY());  
            if(e.getAction()==e.ACTION_DOWN){    //当按下  
                pointall=new ArrayList<Point>();  
                pointall.add(p);  
            }  
            else if(e.getAction()==e.ACTION_UP){//当抬起  
                pointall.add(p);  
                Drawview.this.postInvalidate();   //重绘  
            }  
            else if(e.getAction()==e.ACTION_MOVE){  
                pointall.add(p);                   //移动时候  
                Drawview.this.postInvalidate();   //重绘  
            }  
            return true;  
        }  
          
    }  
    protected void onDraw(Canvas canvas){  
    	Paint p=new Paint();   
    	p.setColor(color);//定义颜色  
    	p.setStrokeWidth(width);
        if(pointall.size()>1){  
            Iterator<Point> iter=pointall.iterator();// 现在有坐标点保存的时候可以开始进行绘图  
            Point first=null;  
            Point last=null;  
            while(iter.hasNext()){  
                if(first==null){  
                    first=(Point)iter.next();  
                }  
                else{   
                    if(last!=null){  
                    first=last;    //将下一个坐标点赋给上面的  
                   }  
                last=(Point)iter.next();    //不停下指  
                canvas.drawLine(first.x, first.y, last.x, last.y,p);      
                      
                }  
            }  
        }  
    }  
  
      
}  

 二、activity_home.xml

    这是画板的页面，这里面使用了前面我们新建的drewview类（这是因为drewview是是继承view类的，所以和TextView等使用方法相同）。

<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="com.example.study.Home12" >

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="34dp" >
      
        <TextView 
            android:layout_width="wrap_content"
        	android:layout_height="wrap_content"
            android:text="您所选的颜色："
            />
        <TextView 
            android:id="@+id/test"
            android:layout_width="50dp"
            android:layout_height="fill_parent"
            />
        <Button 
            android:id="@+id/standard_color"
            android:layout_width="wrap_content"
        	android:layout_height="wrap_content"
            android:onClick="chose_color"
            android:text="选择标准颜色"
            />
    </LinearLayout>

    <SeekBar
        android:id="@+id/seekBar1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:max="16777215"
        android:progress="0"
        />
    

<LinearLayout
        android:id="@+id/linearLayout2"
        android:layout_below="@id/linearLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="34dp" >
        <EditText 
            android:id="@+id/width"
        	android:layout_width="200dp"
        	android:layout_height="wrap_content"
        	android:inputType="numberDecimal"
        	android:text="1.0"
        />
        <Button 
            android:id="@+id/changewidth"
            android:text="@string/width"
            android:layout_width="wrap_content"
        	android:layout_height="wrap_content"
            android:onClick="width"
            android:textSize="12sp"
            />
</LinearLayout>

    <com.example.study.Drawview
        android:id="@+id/paintview"
        android:layout_width="fill_parent"
        android:layout_height="500dp"
        android:layout_below="@id/linearLayout2" />

</RelativeLayout>

 三、home12.java

     这是和activity_home.xml相匹配的activity。

package com.example.study;

import com.example.study.Drawview;
import com.example.study.R;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import android.widget.Toast;

public class Home12 extends Activity {
	Drawview dv=null;//用来存放画布视图变量
	EditText wid=null;
	SeekBar sb=null;
	TextView test=null;
	int color=0x00000000;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_home);
		dv=(Drawview)super.findViewById(R.id.paintview);//获取画布视图
		wid=(EditText)super.findViewById(R.id.width);//获取输入的画笔宽度值
		sb=(SeekBar)super.findViewById(R.id.seekBar1);//获取拖动条视图
		sb.setOnSeekBarChangeListener(new seekbar());//为拖动条视图添加监听
		//test=(TextView)super.findViewById(R.id.test);
	}
	private class seekbar implements OnSeekBarChangeListener
	{

		@Override
		public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
			// TODO Auto-generated method stub
			dv.changecolor(progress+0xff000000);
			test.setBackgroundColor(progress+0xff000000);
		}

		@Override
		public void onStartTrackingTouch(SeekBar seekBar) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public void onStopTrackingTouch(SeekBar seekBar) {
			// TODO Auto-generated method stub
			
		}
		
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.home, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
	public void width(View view)
	{
		float width;
		
		if(wid.getText()!=null)
			{
			width=Float.parseFloat(wid.getText().toString().trim());
			dv.changewidth(width);
			}
	}
	public void chose_color(View view)
	{
		String[] items={"黑色","红色","绿色","蓝色"};
		AlertDialog.Builder builder=new AlertDialog.Builder(this);
		builder.setTitle("选择标准颜色");
		builder.setIcon(R.drawable.ic_launcher);
		builder.setItems(items, new OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				// TODO Auto-generated method stub
				int color=0x000000;
				switch(which)
				{
				case 0:
					color=0;
					break;
				case 1:
					color=16711680;
					break;
				case 2:
					color=65280;
					break;
				case 3:
					color=255;
					break;
				}
				dv.changecolor(color+0xff000000);
				test.setBackgroundColor(color+0xff000000);
				sb.setProgress(color);
				Toast t=Toast.makeText(Home12.this, "color is:"+color, Toast.LENGTH_SHORT);
				t.show();
			}
		});
		builder.setPositiveButton("yes", new OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				// TODO Auto-generated method stub
				
			}
		});
		builder.setNeutralButton("temp2", new OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				// TODO Auto-generated method stub
				
			}
		});
		builder.setNegativeButton("no", new OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				// TODO Auto-generated method stub
				
			}
		});
		//setPositiveButton(builder);
		builder.show();
	}
}